From 73b350be53c62112b809fd7691f85beb857dfc11 Mon Sep 17 00:00:00 2001
From: weru <onewesh@gmail.com>
Date: Wed, 04 Nov 2020 15:40:27 +0000
Subject: [PATCH] update lunr js version

---
 assets/js/lunr.js | 3476 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 3,475 insertions(+), 1 deletions(-)

diff --git a/assets/js/lunr.js b/assets/js/lunr.js
index fa6842a..f1f1e4d 100644
--- a/assets/js/lunr.js
+++ b/assets/js/lunr.js
@@ -1 +1,3475 @@
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Current version of lunr '"+z.version+"' does not match serialized index '"+e.version+"'");for(var u=0;u<i.length;u++){var l=(h=i[u])[0],c=h[1];r[l]=new z.Vector(c)}for(u=0;u<s.length;u++){var h,d=(h=s[u])[0],f=h[1];o.insert(d),n[d]=f}return o.finish(),t.fields=e.fields,t.fieldVectors=r,t.invertedIndex=n,t.tokenSet=o.root,t.pipeline=a,new z.Index(t)},z.Builder=function(){this._ref="id",this._fields=Object.create(null),this._documents=Object.create(null),this.invertedIndex=Object.create(null),this.fieldTermFrequencies={},this.fieldLengths={},this.tokenizer=z.tokenizer,this.pipeline=new z.Pipeline,this.searchPipeline=new z.Pipeline,this.documentCount=0,this._b=.75,this._k1=1.2,this.termIndex=0,this.metadataWhitelist=[]},z.Builder.prototype.ref=function(e){this._ref=e},z.Builder.prototype.field=function(e,t){if(/\//.test(e))throw new RangeError("Field '"+e+"' contains illegal character '/'");this._fields[e]=t||{}},z.Builder.prototype.b=function(e){this._b=e<0?0:1<e?1:e},z.Builder.prototype.k1=function(e){this._k1=e},z.Builder.prototype.add=function(e,t){var r=e[this._ref],i=Object.keys(this._fields);this._documents[r]=t||{},this.documentCount+=1;for(var n=0;n<i.length;n++){var s=i[n],o=this._fields[s].extractor,a=o?o(e):e[s],u=this.tokenizer(a,{fields:[s]}),l=this.pipeline.run(u),c=new z.FieldRef(r,s),h=Object.create(null);this.fieldTermFrequencies[c]=h,this.fieldLengths[c]=0,this.fieldLengths[c]+=l.length;for(var d=0;d<l.length;d++){var f=l[d];if(null==h[f]&&(h[f]=0),h[f]+=1,null==this.invertedIndex[f]){var p=Object.create(null);p._index=this.termIndex,this.termIndex+=1;for(var y=0;y<i.length;y++)p[i[y]]=Object.create(null);this.invertedIndex[f]=p}null==this.invertedIndex[f][s][r]&&(this.invertedIndex[f][s][r]=Object.create(null));for(var m=0;m<this.metadataWhitelist.length;m++){var g=this.metadataWhitelist[m],x=f.metadata[g];null==this.invertedIndex[f][s][r][g]&&(this.invertedIndex[f][s][r][g]=[]),this.invertedIndex[f][s][r][g].push(x)}}}},z.Builder.prototype.calculateAverageFieldLengths=function(){for(var e=Object.keys(this.fieldLengths),t=e.length,r={},i={},n=0;n<t;n++){var s=z.FieldRef.fromString(e[n]),o=s.fieldName;i[o]||(i[o]=0),i[o]+=1,r[o]||(r[o]=0),r[o]+=this.fieldLengths[s]}var a=Object.keys(this._fields);for(n=0;n<a.length;n++){var u=a[n];r[u]=r[u]/i[u]}this.averageFieldLength=r},z.Builder.prototype.createFieldVectors=function(){for(var e={},t=Object.keys(this.fieldTermFrequencies),r=t.length,i=Object.create(null),n=0;n<r;n++){for(var s=z.FieldRef.fromString(t[n]),o=s.fieldName,a=this.fieldLengths[s],u=new z.Vector,l=this.fieldTermFrequencies[s],c=Object.keys(l),h=c.length,d=this._fields[o].boost||1,f=this._documents[s.docRef].boost||1,p=0;p<h;p++){var y,m,g,x=c[p],v=l[x],w=this.invertedIndex[x]._index;void 0===i[x]?(y=z.idf(this.invertedIndex[x],this.documentCount),i[x]=y):y=i[x],m=y*((this._k1+1)*v)/(this._k1*(1-this._b+this._b*(a/this.averageFieldLength[o]))+v),m*=d,m*=f,g=Math.round(1e3*m)/1e3,u.insert(w,g)}e[s]=u}this.fieldVectors=e},z.Builder.prototype.createTokenSet=function(){this.tokenSet=z.TokenSet.fromArray(Object.keys(this.invertedIndex).sort())},z.Builder.prototype.build=function(){return this.calculateAverageFieldLengths(),this.createFieldVectors(),this.createTokenSet(),new z.Index({invertedIndex:this.invertedIndex,fieldVectors:this.fieldVectors,tokenSet:this.tokenSet,fields:Object.keys(this._fields),pipeline:this.searchPipeline})},z.Builder.prototype.use=function(e){var t=Array.prototype.slice.call(arguments,1);t.unshift(this),e.apply(this,t)},z.MatchData=function(e,t,r){for(var i=Object.create(null),n=Object.keys(r||{}),s=0;s<n.length;s++){var o=n[s];i[o]=r[o].slice()}this.metadata=Object.create(null),void 0!==e&&(this.metadata[e]=Object.create(null),this.metadata[e][t]=i)},z.MatchData.prototype.combine=function(e){for(var t=Object.keys(e.metadata),r=0;r<t.length;r++){var i=t[r],n=Object.keys(e.metadata[i]);null==this.metadata[i]&&(this.metadata[i]=Object.create(null));for(var s=0;s<n.length;s++){var o=n[s],a=Object.keys(e.metadata[i][o]);null==this.metadata[i][o]&&(this.metadata[i][o]=Object.create(null));for(var u=0;u<a.length;u++){var l=a[u];null==this.metadata[i][o][l]?this.metadata[i][o][l]=e.metadata[i][o][l]:this.metadata[i][o][l]=this.metadata[i][o][l].concat(e.metadata[i][o][l])}}}},z.MatchData.prototype.add=function(e,t,r){if(!(e in this.metadata))return this.metadata[e]=Object.create(null),void(this.metadata[e][t]=r);if(t in this.metadata[e])for(var i=Object.keys(r),n=0;n<i.length;n++){var s=i[n];s in this.metadata[e][t]?this.metadata[e][t][s]=this.metadata[e][t][s].concat(r[s]):this.metadata[e][t][s]=r[s]}else this.metadata[e][t]=r},z.Query=function(e){this.clauses=[],this.allFields=e},z.Query.wildcard=new String("*"),z.Query.wildcard.NONE=0,z.Query.wildcard.LEADING=1,z.Query.wildcard.TRAILING=2,z.Query.presence={OPTIONAL:1,REQUIRED:2,PROHIBITED:3},z.Query.prototype.clause=function(e){return"fields"in e||(e.fields=this.allFields),"boost"in e||(e.boost=1),"usePipeline"in e||(e.usePipeline=!0),"wildcard"in e||(e.wildcard=z.Query.wildcard.NONE),e.wildcard&z.Query.wildcard.LEADING&&e.term.charAt(0)!=z.Query.wildcard&&(e.term="*"+e.term),e.wildcard&z.Query.wildcard.TRAILING&&e.term.slice(-1)!=z.Query.wildcard&&(e.term=e.term+"*"),"presence"in e||(e.presence=z.Query.presence.OPTIONAL),this.clauses.push(e),this},z.Query.prototype.isNegated=function(){for(var e=0;e<this.clauses.length;e++)if(this.clauses[e].presence!=z.Query.presence.PROHIBITED)return!1;return!0},z.Query.prototype.term=function(e,t){if(Array.isArray(e))return e.forEach(function(e){this.term(e,z.utils.clone(t))},this),this;var r=t||{};return r.term=e.toString(),this.clause(r),this},z.QueryParseError=function(e,t,r){this.name="QueryParseError",this.message=e,this.start=t,this.end=r},z.QueryParseError.prototype=new Error,z.QueryLexer=function(e){this.lexemes=[],this.str=e,this.length=e.length,this.pos=0,this.start=0,this.escapeCharPositions=[]},z.QueryLexer.prototype.run=function(){for(var e=z.QueryLexer.lexText;e;)e=e(this)},z.QueryLexer.prototype.sliceString=function(){for(var e=[],t=this.start,r=this.pos,i=0;i<this.escapeCharPositions.length;i++)r=this.escapeCharPositions[i],e.push(this.str.slice(t,r)),t=r+1;return e.push(this.str.slice(t,this.pos)),this.escapeCharPositions.length=0,e.join("")},z.QueryLexer.prototype.emit=function(e){this.lexemes.push({type:e,str:this.sliceString(),start:this.start,end:this.pos}),this.start=this.pos},z.QueryLexer.prototype.escapeCharacter=function(){this.escapeCharPositions.push(this.pos-1),this.pos+=1},z.QueryLexer.prototype.next=function(){if(this.pos>=this.length)return z.QueryLexer.EOS;var e=this.str.charAt(this.pos);return this.pos+=1,e},z.QueryLexer.prototype.width=function(){return this.pos-this.start},z.QueryLexer.prototype.ignore=function(){this.start==this.pos&&(this.pos+=1),this.start=this.pos},z.QueryLexer.prototype.backup=function(){--this.pos},z.QueryLexer.prototype.acceptDigitRun=function(){for(var e,t;47<(t=(e=this.next()).charCodeAt(0))&&t<58;);e!=z.QueryLexer.EOS&&this.backup()},z.QueryLexer.prototype.more=function(){return this.pos<this.length},z.QueryLexer.EOS="EOS",z.QueryLexer.FIELD="FIELD",z.QueryLexer.TERM="TERM",z.QueryLexer.EDIT_DISTANCE="EDIT_DISTANCE",z.QueryLexer.BOOST="BOOST",z.QueryLexer.PRESENCE="PRESENCE",z.QueryLexer.lexField=function(e){return e.backup(),e.emit(z.QueryLexer.FIELD),e.ignore(),z.QueryLexer.lexText},z.QueryLexer.lexTerm=function(e){if(1<e.width()&&(e.backup(),e.emit(z.QueryLexer.TERM)),e.ignore(),e.more())return z.QueryLexer.lexText},z.QueryLexer.lexEditDistance=function(e){return e.ignore(),e.acceptDigitRun(),e.emit(z.QueryLexer.EDIT_DISTANCE),z.QueryLexer.lexText},z.QueryLexer.lexBoost=function(e){return e.ignore(),e.acceptDigitRun(),e.emit(z.QueryLexer.BOOST),z.QueryLexer.lexText},z.QueryLexer.lexEOS=function(e){0<e.width()&&e.emit(z.QueryLexer.TERM)},z.QueryLexer.termSeparator=z.tokenizer.separator,z.QueryLexer.lexText=function(e){for(;;){var t=e.next();if(t==z.QueryLexer.EOS)return z.QueryLexer.lexEOS;if(92!=t.charCodeAt(0)){if(":"==t)return z.QueryLexer.lexField;if("~"==t)return e.backup(),0<e.width()&&e.emit(z.QueryLexer.TERM),z.QueryLexer.lexEditDistance;if("^"==t)return e.backup(),0<e.width()&&e.emit(z.QueryLexer.TERM),z.QueryLexer.lexBoost;if("+"==t&&1===e.width())return e.emit(z.QueryLexer.PRESENCE),z.QueryLexer.lexText;if("-"==t&&1===e.width())return e.emit(z.QueryLexer.PRESENCE),z.QueryLexer.lexText;if(t.match(z.QueryLexer.termSeparator))return z.QueryLexer.lexTerm}else e.escapeCharacter()}},z.QueryParser=function(e,t){this.lexer=new z.QueryLexer(e),this.query=t,this.currentClause={},this.lexemeIdx=0},z.QueryParser.prototype.parse=function(){this.lexer.run(),this.lexemes=this.lexer.lexemes;for(var e=z.QueryParser.parseClause;e;)e=e(this);return this.query},z.QueryParser.prototype.peekLexeme=function(){return this.lexemes[this.lexemeIdx]},z.QueryParser.prototype.consumeLexeme=function(){var e=this.peekLexeme();return this.lexemeIdx+=1,e},z.QueryParser.prototype.nextClause=function(){var e=this.currentClause;this.query.clause(e),this.currentClause={}},z.QueryParser.parseClause=function(e){var t=e.peekLexeme();if(null!=t)switch(t.type){case z.QueryLexer.PRESENCE:return z.QueryParser.parsePresence;case z.QueryLexer.FIELD:return z.QueryParser.parseField;case z.QueryLexer.TERM:return z.QueryParser.parseTerm;default:var r="expected either a field or a term, found "+t.type;throw 1<=t.str.length&&(r+=" with value '"+t.str+"'"),new z.QueryParseError(r,t.start,t.end)}},z.QueryParser.parsePresence=function(e){var t=e.consumeLexeme();if(null!=t){switch(t.str){case"-":e.currentClause.presence=z.Query.presence.PROHIBITED;break;case"+":e.currentClause.presence=z.Query.presence.REQUIRED;break;default:var r="unrecognised presence operator'"+t.str+"'";throw new z.QueryParseError(r,t.start,t.end)}var i=e.peekLexeme();if(null==i){r="expecting term or field, found nothing";throw new z.QueryParseError(r,t.start,t.end)}switch(i.type){case z.QueryLexer.FIELD:return z.QueryParser.parseField;case z.QueryLexer.TERM:return z.QueryParser.parseTerm;default:r="expecting term or field, found '"+i.type+"'";throw new z.QueryParseError(r,i.start,i.end)}}},z.QueryParser.parseField=function(e){var t=e.consumeLexeme();if(null!=t){if(-1==e.query.allFields.indexOf(t.str)){var r=e.query.allFields.map(function(e){return"'"+e+"'"}).join(", "),i="unrecognised field '"+t.str+"', possible fields: "+r;throw new z.QueryParseError(i,t.start,t.end)}e.currentClause.fields=[t.str];var n=e.peekLexeme();if(null==n){i="expecting term, found nothing";throw new z.QueryParseError(i,t.start,t.end)}switch(n.type){case z.QueryLexer.TERM:return z.QueryParser.parseTerm;default:i="expecting term, found '"+n.type+"'";throw new z.QueryParseError(i,n.start,n.end)}}},z.QueryParser.parseTerm=function(e){var t=e.consumeLexeme();if(null!=t){e.currentClause.term=t.str.toLowerCase(),-1!=t.str.indexOf("*")&&(e.currentClause.usePipeline=!1);var r=e.peekLexeme();if(null!=r)switch(r.type){case z.QueryLexer.TERM:return e.nextClause(),z.QueryParser.parseTerm;case z.QueryLexer.FIELD:return e.nextClause(),z.QueryParser.parseField;case z.QueryLexer.EDIT_DISTANCE:return z.QueryParser.parseEditDistance;case z.QueryLexer.BOOST:return z.QueryParser.parseBoost;case z.QueryLexer.PRESENCE:return e.nextClause(),z.QueryParser.parsePresence;default:var i="Unexpected lexeme type '"+r.type+"'";throw new z.QueryParseError(i,r.start,r.end)}else e.nextClause()}},z.QueryParser.parseEditDistance=function(e){var t=e.consumeLexeme();if(null!=t){var r=parseInt(t.str,10);if(isNaN(r)){var i="edit distance must be numeric";throw new z.QueryParseError(i,t.start,t.end)}e.currentClause.editDistance=r;var n=e.peekLexeme();if(null!=n)switch(n.type){case z.QueryLexer.TERM:return e.nextClause(),z.QueryParser.parseTerm;case z.QueryLexer.FIELD:return e.nextClause(),z.QueryParser.parseField;case z.QueryLexer.EDIT_DISTANCE:return z.QueryParser.parseEditDistance;case z.QueryLexer.BOOST:return z.QueryParser.parseBoost;case z.QueryLexer.PRESENCE:return e.nextClause(),z.QueryParser.parsePresence;default:i="Unexpected lexeme type '"+n.type+"'";throw new z.QueryParseError(i,n.start,n.end)}else e.nextClause()}},z.QueryParser.parseBoost=function(e){var t=e.consumeLexeme();if(null!=t){var r=parseInt(t.str,10);if(isNaN(r)){var i="boost must be numeric";throw new z.QueryParseError(i,t.start,t.end)}e.currentClause.boost=r;var n=e.peekLexeme();if(null!=n)switch(n.type){case z.QueryLexer.TERM:return e.nextClause(),z.QueryParser.parseTerm;case z.QueryLexer.FIELD:return e.nextClause(),z.QueryParser.parseField;case z.QueryLexer.EDIT_DISTANCE:return z.QueryParser.parseEditDistance;case z.QueryLexer.BOOST:return z.QueryParser.parseBoost;case z.QueryLexer.PRESENCE:return e.nextClause(),z.QueryParser.parsePresence;default:i="Unexpected lexeme type '"+n.type+"'";throw new z.QueryParseError(i,n.start,n.end)}else e.nextClause()}},i=this,n=function(){return z},"function"==typeof define&&define.amd?define(n):"object"==typeof exports?module.exports=n():i.lunr=n()}();
+/**
+ * lunr - http://lunrjs.com - A bit like Solr, but much smaller and not as bright - 2.3.9
+ * Copyright (C) 2020 Oliver Nightingale
+ * @license MIT
+ */
+
+;(function(){
+
+  /**
+   * A convenience function for configuring and constructing
+   * a new lunr Index.
+   *
+   * A lunr.Builder instance is created and the pipeline setup
+   * with a trimmer, stop word filter and stemmer.
+   *
+   * This builder object is yielded to the configuration function
+   * that is passed as a parameter, allowing the list of fields
+   * and other builder parameters to be customised.
+   *
+   * All documents _must_ be added within the passed config function.
+   *
+   * @example
+   * var idx = lunr(function () {
+   *   this.field('title')
+   *   this.field('body')
+   *   this.ref('id')
+   *
+   *   documents.forEach(function (doc) {
+   *     this.add(doc)
+   *   }, this)
+   * })
+   *
+   * @see {@link lunr.Builder}
+   * @see {@link lunr.Pipeline}
+   * @see {@link lunr.trimmer}
+   * @see {@link lunr.stopWordFilter}
+   * @see {@link lunr.stemmer}
+   * @namespace {function} lunr
+   */
+  var lunr = function (config) {
+    var builder = new lunr.Builder
+
+    builder.pipeline.add(
+      lunr.trimmer,
+      lunr.stopWordFilter,
+      lunr.stemmer
+    )
+
+    builder.searchPipeline.add(
+      lunr.stemmer
+    )
+
+    config.call(builder, builder)
+    return builder.build()
+  }
+
+  lunr.version = "2.3.9"
+  /*!
+   * lunr.utils
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * A namespace containing utils for the rest of the lunr library
+   * @namespace lunr.utils
+   */
+  lunr.utils = {}
+
+  /**
+   * Print a warning message to the console.
+   *
+   * @param {String} message The message to be printed.
+   * @memberOf lunr.utils
+   * @function
+   */
+  lunr.utils.warn = (function (global) {
+    /* eslint-disable no-console */
+    return function (message) {
+      if (global.console && console.warn) {
+        console.warn(message)
+      }
+    }
+    /* eslint-enable no-console */
+  })(this)
+
+  /**
+   * Convert an object to a string.
+   *
+   * In the case of `null` and `undefined` the function returns
+   * the empty string, in all other cases the result of calling
+   * `toString` on the passed object is returned.
+   *
+   * @param {Any} obj The object to convert to a string.
+   * @return {String} string representation of the passed object.
+   * @memberOf lunr.utils
+   */
+  lunr.utils.asString = function (obj) {
+    if (obj === void 0 || obj === null) {
+      return ""
+    } else {
+      return obj.toString()
+    }
+  }
+
+  /**
+   * Clones an object.
+   *
+   * Will create a copy of an existing object such that any mutations
+   * on the copy cannot affect the original.
+   *
+   * Only shallow objects are supported, passing a nested object to this
+   * function will cause a TypeError.
+   *
+   * Objects with primitives, and arrays of primitives are supported.
+   *
+   * @param {Object} obj The object to clone.
+   * @return {Object} a clone of the passed object.
+   * @throws {TypeError} when a nested object is passed.
+   * @memberOf Utils
+   */
+  lunr.utils.clone = function (obj) {
+    if (obj === null || obj === undefined) {
+      return obj
+    }
+
+    var clone = Object.create(null),
+        keys = Object.keys(obj)
+
+    for (var i = 0; i < keys.length; i++) {
+      var key = keys[i],
+          val = obj[key]
+
+      if (Array.isArray(val)) {
+        clone[key] = val.slice()
+        continue
+      }
+
+      if (typeof val === 'string' ||
+          typeof val === 'number' ||
+          typeof val === 'boolean') {
+        clone[key] = val
+        continue
+      }
+
+      throw new TypeError("clone is not deep and does not support nested objects")
+    }
+
+    return clone
+  }
+  lunr.FieldRef = function (docRef, fieldName, stringValue) {
+    this.docRef = docRef
+    this.fieldName = fieldName
+    this._stringValue = stringValue
+  }
+
+  lunr.FieldRef.joiner = "/"
+
+  lunr.FieldRef.fromString = function (s) {
+    var n = s.indexOf(lunr.FieldRef.joiner)
+
+    if (n === -1) {
+      throw "malformed field ref string"
+    }
+
+    var fieldRef = s.slice(0, n),
+        docRef = s.slice(n + 1)
+
+    return new lunr.FieldRef (docRef, fieldRef, s)
+  }
+
+  lunr.FieldRef.prototype.toString = function () {
+    if (this._stringValue == undefined) {
+      this._stringValue = this.fieldName + lunr.FieldRef.joiner + this.docRef
+    }
+
+    return this._stringValue
+  }
+  /*!
+   * lunr.Set
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * A lunr set.
+   *
+   * @constructor
+   */
+  lunr.Set = function (elements) {
+    this.elements = Object.create(null)
+
+    if (elements) {
+      this.length = elements.length
+
+      for (var i = 0; i < this.length; i++) {
+        this.elements[elements[i]] = true
+      }
+    } else {
+      this.length = 0
+    }
+  }
+
+  /**
+   * A complete set that contains all elements.
+   *
+   * @static
+   * @readonly
+   * @type {lunr.Set}
+   */
+  lunr.Set.complete = {
+    intersect: function (other) {
+      return other
+    },
+
+    union: function () {
+      return this
+    },
+
+    contains: function () {
+      return true
+    }
+  }
+
+  /**
+   * An empty set that contains no elements.
+   *
+   * @static
+   * @readonly
+   * @type {lunr.Set}
+   */
+  lunr.Set.empty = {
+    intersect: function () {
+      return this
+    },
+
+    union: function (other) {
+      return other
+    },
+
+    contains: function () {
+      return false
+    }
+  }
+
+  /**
+   * Returns true if this set contains the specified object.
+   *
+   * @param {object} object - Object whose presence in this set is to be tested.
+   * @returns {boolean} - True if this set contains the specified object.
+   */
+  lunr.Set.prototype.contains = function (object) {
+    return !!this.elements[object]
+  }
+
+  /**
+   * Returns a new set containing only the elements that are present in both
+   * this set and the specified set.
+   *
+   * @param {lunr.Set} other - set to intersect with this set.
+   * @returns {lunr.Set} a new set that is the intersection of this and the specified set.
+   */
+
+  lunr.Set.prototype.intersect = function (other) {
+    var a, b, elements, intersection = []
+
+    if (other === lunr.Set.complete) {
+      return this
+    }
+
+    if (other === lunr.Set.empty) {
+      return other
+    }
+
+    if (this.length < other.length) {
+      a = this
+      b = other
+    } else {
+      a = other
+      b = this
+    }
+
+    elements = Object.keys(a.elements)
+
+    for (var i = 0; i < elements.length; i++) {
+      var element = elements[i]
+      if (element in b.elements) {
+        intersection.push(element)
+      }
+    }
+
+    return new lunr.Set (intersection)
+  }
+
+  /**
+   * Returns a new set combining the elements of this and the specified set.
+   *
+   * @param {lunr.Set} other - set to union with this set.
+   * @return {lunr.Set} a new set that is the union of this and the specified set.
+   */
+
+  lunr.Set.prototype.union = function (other) {
+    if (other === lunr.Set.complete) {
+      return lunr.Set.complete
+    }
+
+    if (other === lunr.Set.empty) {
+      return this
+    }
+
+    return new lunr.Set(Object.keys(this.elements).concat(Object.keys(other.elements)))
+  }
+  /**
+   * A function to calculate the inverse document frequency for
+   * a posting. This is shared between the builder and the index
+   *
+   * @private
+   * @param {object} posting - The posting for a given term
+   * @param {number} documentCount - The total number of documents.
+   */
+  lunr.idf = function (posting, documentCount) {
+    var documentsWithTerm = 0
+
+    for (var fieldName in posting) {
+      if (fieldName == '_index') continue // Ignore the term index, its not a field
+      documentsWithTerm += Object.keys(posting[fieldName]).length
+    }
+
+    var x = (documentCount - documentsWithTerm + 0.5) / (documentsWithTerm + 0.5)
+
+    return Math.log(1 + Math.abs(x))
+  }
+
+  /**
+   * A token wraps a string representation of a token
+   * as it is passed through the text processing pipeline.
+   *
+   * @constructor
+   * @param {string} [str=''] - The string token being wrapped.
+   * @param {object} [metadata={}] - Metadata associated with this token.
+   */
+  lunr.Token = function (str, metadata) {
+    this.str = str || ""
+    this.metadata = metadata || {}
+  }
+
+  /**
+   * Returns the token string that is being wrapped by this object.
+   *
+   * @returns {string}
+   */
+  lunr.Token.prototype.toString = function () {
+    return this.str
+  }
+
+  /**
+   * A token update function is used when updating or optionally
+   * when cloning a token.
+   *
+   * @callback lunr.Token~updateFunction
+   * @param {string} str - The string representation of the token.
+   * @param {Object} metadata - All metadata associated with this token.
+   */
+
+  /**
+   * Applies the given function to the wrapped string token.
+   *
+   * @example
+   * token.update(function (str, metadata) {
+   *   return str.toUpperCase()
+   * })
+   *
+   * @param {lunr.Token~updateFunction} fn - A function to apply to the token string.
+   * @returns {lunr.Token}
+   */
+  lunr.Token.prototype.update = function (fn) {
+    this.str = fn(this.str, this.metadata)
+    return this
+  }
+
+  /**
+   * Creates a clone of this token. Optionally a function can be
+   * applied to the cloned token.
+   *
+   * @param {lunr.Token~updateFunction} [fn] - An optional function to apply to the cloned token.
+   * @returns {lunr.Token}
+   */
+  lunr.Token.prototype.clone = function (fn) {
+    fn = fn || function (s) { return s }
+    return new lunr.Token (fn(this.str, this.metadata), this.metadata)
+  }
+  /*!
+   * lunr.tokenizer
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * A function for splitting a string into tokens ready to be inserted into
+   * the search index. Uses `lunr.tokenizer.separator` to split strings, change
+   * the value of this property to change how strings are split into tokens.
+   *
+   * This tokenizer will convert its parameter to a string by calling `toString` and
+   * then will split this string on the character in `lunr.tokenizer.separator`.
+   * Arrays will have their elements converted to strings and wrapped in a lunr.Token.
+   *
+   * Optional metadata can be passed to the tokenizer, this metadata will be cloned and
+   * added as metadata to every token that is created from the object to be tokenized.
+   *
+   * @static
+   * @param {?(string|object|object[])} obj - The object to convert into tokens
+   * @param {?object} metadata - Optional metadata to associate with every token
+   * @returns {lunr.Token[]}
+   * @see {@link lunr.Pipeline}
+   */
+  lunr.tokenizer = function (obj, metadata) {
+    if (obj == null || obj == undefined) {
+      return []
+    }
+
+    if (Array.isArray(obj)) {
+      return obj.map(function (t) {
+        return new lunr.Token(
+          lunr.utils.asString(t).toLowerCase(),
+          lunr.utils.clone(metadata)
+        )
+      })
+    }
+
+    var str = obj.toString().toLowerCase(),
+        len = str.length,
+        tokens = []
+
+    for (var sliceEnd = 0, sliceStart = 0; sliceEnd <= len; sliceEnd++) {
+      var char = str.charAt(sliceEnd),
+          sliceLength = sliceEnd - sliceStart
+
+      if ((char.match(lunr.tokenizer.separator) || sliceEnd == len)) {
+
+        if (sliceLength > 0) {
+          var tokenMetadata = lunr.utils.clone(metadata) || {}
+          tokenMetadata["position"] = [sliceStart, sliceLength]
+          tokenMetadata["index"] = tokens.length
+
+          tokens.push(
+            new lunr.Token (
+              str.slice(sliceStart, sliceEnd),
+              tokenMetadata
+            )
+          )
+        }
+
+        sliceStart = sliceEnd + 1
+      }
+
+    }
+
+    return tokens
+  }
+
+  /**
+   * The separator used to split a string into tokens. Override this property to change the behaviour of
+   * `lunr.tokenizer` behaviour when tokenizing strings. By default this splits on whitespace and hyphens.
+   *
+   * @static
+   * @see lunr.tokenizer
+   */
+  lunr.tokenizer.separator = /[\s\-]+/
+  /*!
+   * lunr.Pipeline
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * lunr.Pipelines maintain an ordered list of functions to be applied to all
+   * tokens in documents entering the search index and queries being ran against
+   * the index.
+   *
+   * An instance of lunr.Index created with the lunr shortcut will contain a
+   * pipeline with a stop word filter and an English language stemmer. Extra
+   * functions can be added before or after either of these functions or these
+   * default functions can be removed.
+   *
+   * When run the pipeline will call each function in turn, passing a token, the
+   * index of that token in the original list of all tokens and finally a list of
+   * all the original tokens.
+   *
+   * The output of functions in the pipeline will be passed to the next function
+   * in the pipeline. To exclude a token from entering the index the function
+   * should return undefined, the rest of the pipeline will not be called with
+   * this token.
+   *
+   * For serialisation of pipelines to work, all functions used in an instance of
+   * a pipeline should be registered with lunr.Pipeline. Registered functions can
+   * then be loaded. If trying to load a serialised pipeline that uses functions
+   * that are not registered an error will be thrown.
+   *
+   * If not planning on serialising the pipeline then registering pipeline functions
+   * is not necessary.
+   *
+   * @constructor
+   */
+  lunr.Pipeline = function () {
+    this._stack = []
+  }
+
+  lunr.Pipeline.registeredFunctions = Object.create(null)
+
+  /**
+   * A pipeline function maps lunr.Token to lunr.Token. A lunr.Token contains the token
+   * string as well as all known metadata. A pipeline function can mutate the token string
+   * or mutate (or add) metadata for a given token.
+   *
+   * A pipeline function can indicate that the passed token should be discarded by returning
+   * null, undefined or an empty string. This token will not be passed to any downstream pipeline
+   * functions and will not be added to the index.
+   *
+   * Multiple tokens can be returned by returning an array of tokens. Each token will be passed
+   * to any downstream pipeline functions and all will returned tokens will be added to the index.
+   *
+   * Any number of pipeline functions may be chained together using a lunr.Pipeline.
+   *
+   * @interface lunr.PipelineFunction
+   * @param {lunr.Token} token - A token from the document being processed.
+   * @param {number} i - The index of this token in the complete list of tokens for this document/field.
+   * @param {lunr.Token[]} tokens - All tokens for this document/field.
+   * @returns {(?lunr.Token|lunr.Token[])}
+   */
+
+  /**
+   * Register a function with the pipeline.
+   *
+   * Functions that are used in the pipeline should be registered if the pipeline
+   * needs to be serialised, or a serialised pipeline needs to be loaded.
+   *
+   * Registering a function does not add it to a pipeline, functions must still be
+   * added to instances of the pipeline for them to be used when running a pipeline.
+   *
+   * @param {lunr.PipelineFunction} fn - The function to check for.
+   * @param {String} label - The label to register this function with
+   */
+  lunr.Pipeline.registerFunction = function (fn, label) {
+    if (label in this.registeredFunctions) {
+      lunr.utils.warn('Overwriting existing registered function: ' + label)
+    }
+
+    fn.label = label
+    lunr.Pipeline.registeredFunctions[fn.label] = fn
+  }
+
+  /**
+   * Warns if the function is not registered as a Pipeline function.
+   *
+   * @param {lunr.PipelineFunction} fn - The function to check for.
+   * @private
+   */
+  lunr.Pipeline.warnIfFunctionNotRegistered = function (fn) {
+    var isRegistered = fn.label && (fn.label in this.registeredFunctions)
+
+    if (!isRegistered) {
+      lunr.utils.warn('Function is not registered with pipeline. This may cause problems when serialising the index.\n', fn)
+    }
+  }
+
+  /**
+   * Loads a previously serialised pipeline.
+   *
+   * All functions to be loaded must already be registered with lunr.Pipeline.
+   * If any function from the serialised data has not been registered then an
+   * error will be thrown.
+   *
+   * @param {Object} serialised - The serialised pipeline to load.
+   * @returns {lunr.Pipeline}
+   */
+  lunr.Pipeline.load = function (serialised) {
+    var pipeline = new lunr.Pipeline
+
+    serialised.forEach(function (fnName) {
+      var fn = lunr.Pipeline.registeredFunctions[fnName]
+
+      if (fn) {
+        pipeline.add(fn)
+      } else {
+        throw new Error('Cannot load unregistered function: ' + fnName)
+      }
+    })
+
+    return pipeline
+  }
+
+  /**
+   * Adds new functions to the end of the pipeline.
+   *
+   * Logs a warning if the function has not been registered.
+   *
+   * @param {lunr.PipelineFunction[]} functions - Any number of functions to add to the pipeline.
+   */
+  lunr.Pipeline.prototype.add = function () {
+    var fns = Array.prototype.slice.call(arguments)
+
+    fns.forEach(function (fn) {
+      lunr.Pipeline.warnIfFunctionNotRegistered(fn)
+      this._stack.push(fn)
+    }, this)
+  }
+
+  /**
+   * Adds a single function after a function that already exists in the
+   * pipeline.
+   *
+   * Logs a warning if the function has not been registered.
+   *
+   * @param {lunr.PipelineFunction} existingFn - A function that already exists in the pipeline.
+   * @param {lunr.PipelineFunction} newFn - The new function to add to the pipeline.
+   */
+  lunr.Pipeline.prototype.after = function (existingFn, newFn) {
+    lunr.Pipeline.warnIfFunctionNotRegistered(newFn)
+
+    var pos = this._stack.indexOf(existingFn)
+    if (pos == -1) {
+      throw new Error('Cannot find existingFn')
+    }
+
+    pos = pos + 1
+    this._stack.splice(pos, 0, newFn)
+  }
+
+  /**
+   * Adds a single function before a function that already exists in the
+   * pipeline.
+   *
+   * Logs a warning if the function has not been registered.
+   *
+   * @param {lunr.PipelineFunction} existingFn - A function that already exists in the pipeline.
+   * @param {lunr.PipelineFunction} newFn - The new function to add to the pipeline.
+   */
+  lunr.Pipeline.prototype.before = function (existingFn, newFn) {
+    lunr.Pipeline.warnIfFunctionNotRegistered(newFn)
+
+    var pos = this._stack.indexOf(existingFn)
+    if (pos == -1) {
+      throw new Error('Cannot find existingFn')
+    }
+
+    this._stack.splice(pos, 0, newFn)
+  }
+
+  /**
+   * Removes a function from the pipeline.
+   *
+   * @param {lunr.PipelineFunction} fn The function to remove from the pipeline.
+   */
+  lunr.Pipeline.prototype.remove = function (fn) {
+    var pos = this._stack.indexOf(fn)
+    if (pos == -1) {
+      return
+    }
+
+    this._stack.splice(pos, 1)
+  }
+
+  /**
+   * Runs the current list of functions that make up the pipeline against the
+   * passed tokens.
+   *
+   * @param {Array} tokens The tokens to run through the pipeline.
+   * @returns {Array}
+   */
+  lunr.Pipeline.prototype.run = function (tokens) {
+    var stackLength = this._stack.length
+
+    for (var i = 0; i < stackLength; i++) {
+      var fn = this._stack[i]
+      var memo = []
+
+      for (var j = 0; j < tokens.length; j++) {
+        var result = fn(tokens[j], j, tokens)
+
+        if (result === null || result === void 0 || result === '') continue
+
+        if (Array.isArray(result)) {
+          for (var k = 0; k < result.length; k++) {
+            memo.push(result[k])
+          }
+        } else {
+          memo.push(result)
+        }
+      }
+
+      tokens = memo
+    }
+
+    return tokens
+  }
+
+  /**
+   * Convenience method for passing a string through a pipeline and getting
+   * strings out. This method takes care of wrapping the passed string in a
+   * token and mapping the resulting tokens back to strings.
+   *
+   * @param {string} str - The string to pass through the pipeline.
+   * @param {?object} metadata - Optional metadata to associate with the token
+   * passed to the pipeline.
+   * @returns {string[]}
+   */
+  lunr.Pipeline.prototype.runString = function (str, metadata) {
+    var token = new lunr.Token (str, metadata)
+
+    return this.run([token]).map(function (t) {
+      return t.toString()
+    })
+  }
+
+  /**
+   * Resets the pipeline by removing any existing processors.
+   *
+   */
+  lunr.Pipeline.prototype.reset = function () {
+    this._stack = []
+  }
+
+  /**
+   * Returns a representation of the pipeline ready for serialisation.
+   *
+   * Logs a warning if the function has not been registered.
+   *
+   * @returns {Array}
+   */
+  lunr.Pipeline.prototype.toJSON = function () {
+    return this._stack.map(function (fn) {
+      lunr.Pipeline.warnIfFunctionNotRegistered(fn)
+
+      return fn.label
+    })
+  }
+  /*!
+   * lunr.Vector
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * A vector is used to construct the vector space of documents and queries. These
+   * vectors support operations to determine the similarity between two documents or
+   * a document and a query.
+   *
+   * Normally no parameters are required for initializing a vector, but in the case of
+   * loading a previously dumped vector the raw elements can be provided to the constructor.
+   *
+   * For performance reasons vectors are implemented with a flat array, where an elements
+   * index is immediately followed by its value. E.g. [index, value, index, value]. This
+   * allows the underlying array to be as sparse as possible and still offer decent
+   * performance when being used for vector calculations.
+   *
+   * @constructor
+   * @param {Number[]} [elements] - The flat list of element index and element value pairs.
+   */
+  lunr.Vector = function (elements) {
+    this._magnitude = 0
+    this.elements = elements || []
+  }
+
+
+  /**
+   * Calculates the position within the vector to insert a given index.
+   *
+   * This is used internally by insert and upsert. If there are duplicate indexes then
+   * the position is returned as if the value for that index were to be updated, but it
+   * is the callers responsibility to check whether there is a duplicate at that index
+   *
+   * @param {Number} insertIdx - The index at which the element should be inserted.
+   * @returns {Number}
+   */
+  lunr.Vector.prototype.positionForIndex = function (index) {
+    // For an empty vector the tuple can be inserted at the beginning
+    if (this.elements.length == 0) {
+      return 0
+    }
+
+    var start = 0,
+        end = this.elements.length / 2,
+        sliceLength = end - start,
+        pivotPoint = Math.floor(sliceLength / 2),
+        pivotIndex = this.elements[pivotPoint * 2]
+
+    while (sliceLength > 1) {
+      if (pivotIndex < index) {
+        start = pivotPoint
+      }
+
+      if (pivotIndex > index) {
+        end = pivotPoint
+      }
+
+      if (pivotIndex == index) {
+        break
+      }
+
+      sliceLength = end - start
+      pivotPoint = start + Math.floor(sliceLength / 2)
+      pivotIndex = this.elements[pivotPoint * 2]
+    }
+
+    if (pivotIndex == index) {
+      return pivotPoint * 2
+    }
+
+    if (pivotIndex > index) {
+      return pivotPoint * 2
+    }
+
+    if (pivotIndex < index) {
+      return (pivotPoint + 1) * 2
+    }
+  }
+
+  /**
+   * Inserts an element at an index within the vector.
+   *
+   * Does not allow duplicates, will throw an error if there is already an entry
+   * for this index.
+   *
+   * @param {Number} insertIdx - The index at which the element should be inserted.
+   * @param {Number} val - The value to be inserted into the vector.
+   */
+  lunr.Vector.prototype.insert = function (insertIdx, val) {
+    this.upsert(insertIdx, val, function () {
+      throw "duplicate index"
+    })
+  }
+
+  /**
+   * Inserts or updates an existing index within the vector.
+   *
+   * @param {Number} insertIdx - The index at which the element should be inserted.
+   * @param {Number} val - The value to be inserted into the vector.
+   * @param {function} fn - A function that is called for updates, the existing value and the
+   * requested value are passed as arguments
+   */
+  lunr.Vector.prototype.upsert = function (insertIdx, val, fn) {
+    this._magnitude = 0
+    var position = this.positionForIndex(insertIdx)
+
+    if (this.elements[position] == insertIdx) {
+      this.elements[position + 1] = fn(this.elements[position + 1], val)
+    } else {
+      this.elements.splice(position, 0, insertIdx, val)
+    }
+  }
+
+  /**
+   * Calculates the magnitude of this vector.
+   *
+   * @returns {Number}
+   */
+  lunr.Vector.prototype.magnitude = function () {
+    if (this._magnitude) return this._magnitude
+
+    var sumOfSquares = 0,
+        elementsLength = this.elements.length
+
+    for (var i = 1; i < elementsLength; i += 2) {
+      var val = this.elements[i]
+      sumOfSquares += val * val
+    }
+
+    return this._magnitude = Math.sqrt(sumOfSquares)
+  }
+
+  /**
+   * Calculates the dot product of this vector and another vector.
+   *
+   * @param {lunr.Vector} otherVector - The vector to compute the dot product with.
+   * @returns {Number}
+   */
+  lunr.Vector.prototype.dot = function (otherVector) {
+    var dotProduct = 0,
+        a = this.elements, b = otherVector.elements,
+        aLen = a.length, bLen = b.length,
+        aVal = 0, bVal = 0,
+        i = 0, j = 0
+
+    while (i < aLen && j < bLen) {
+      aVal = a[i], bVal = b[j]
+      if (aVal < bVal) {
+        i += 2
+      } else if (aVal > bVal) {
+        j += 2
+      } else if (aVal == bVal) {
+        dotProduct += a[i + 1] * b[j + 1]
+        i += 2
+        j += 2
+      }
+    }
+
+    return dotProduct
+  }
+
+  /**
+   * Calculates the similarity between this vector and another vector.
+   *
+   * @param {lunr.Vector} otherVector - The other vector to calculate the
+   * similarity with.
+   * @returns {Number}
+   */
+  lunr.Vector.prototype.similarity = function (otherVector) {
+    return this.dot(otherVector) / this.magnitude() || 0
+  }
+
+  /**
+   * Converts the vector to an array of the elements within the vector.
+   *
+   * @returns {Number[]}
+   */
+  lunr.Vector.prototype.toArray = function () {
+    var output = new Array (this.elements.length / 2)
+
+    for (var i = 1, j = 0; i < this.elements.length; i += 2, j++) {
+      output[j] = this.elements[i]
+    }
+
+    return output
+  }
+
+  /**
+   * A JSON serializable representation of the vector.
+   *
+   * @returns {Number[]}
+   */
+  lunr.Vector.prototype.toJSON = function () {
+    return this.elements
+  }
+  /* eslint-disable */
+  /*!
+   * lunr.stemmer
+   * Copyright (C) 2020 Oliver Nightingale
+   * Includes code from - http://tartarus.org/~martin/PorterStemmer/js.txt
+   */
+
+  /**
+   * lunr.stemmer is an english language stemmer, this is a JavaScript
+   * implementation of the PorterStemmer taken from http://tartarus.org/~martin
+   *
+   * @static
+   * @implements {lunr.PipelineFunction}
+   * @param {lunr.Token} token - The string to stem
+   * @returns {lunr.Token}
+   * @see {@link lunr.Pipeline}
+   * @function
+   */
+  lunr.stemmer = (function(){
+    var step2list = {
+        "ational" : "ate",
+        "tional" : "tion",
+        "enci" : "ence",
+        "anci" : "ance",
+        "izer" : "ize",
+        "bli" : "ble",
+        "alli" : "al",
+        "entli" : "ent",
+        "eli" : "e",
+        "ousli" : "ous",
+        "ization" : "ize",
+        "ation" : "ate",
+        "ator" : "ate",
+        "alism" : "al",
+        "iveness" : "ive",
+        "fulness" : "ful",
+        "ousness" : "ous",
+        "aliti" : "al",
+        "iviti" : "ive",
+        "biliti" : "ble",
+        "logi" : "log"
+      },
+
+      step3list = {
+        "icate" : "ic",
+        "ative" : "",
+        "alize" : "al",
+        "iciti" : "ic",
+        "ical" : "ic",
+        "ful" : "",
+        "ness" : ""
+      },
+
+      c = "[^aeiou]",          // consonant
+      v = "[aeiouy]",          // vowel
+      C = c + "[^aeiouy]*",    // consonant sequence
+      V = v + "[aeiou]*",      // vowel sequence
+
+      mgr0 = "^(" + C + ")?" + V + C,               // [C]VC... is m>0
+      meq1 = "^(" + C + ")?" + V + C + "(" + V + ")?$",  // [C]VC[V] is m=1
+      mgr1 = "^(" + C + ")?" + V + C + V + C,       // [C]VCVC... is m>1
+      s_v = "^(" + C + ")?" + v;                   // vowel in stem
+
+    var re_mgr0 = new RegExp(mgr0);
+    var re_mgr1 = new RegExp(mgr1);
+    var re_meq1 = new RegExp(meq1);
+    var re_s_v = new RegExp(s_v);
+
+    var re_1a = /^(.+?)(ss|i)es$/;
+    var re2_1a = /^(.+?)([^s])s$/;
+    var re_1b = /^(.+?)eed$/;
+    var re2_1b = /^(.+?)(ed|ing)$/;
+    var re_1b_2 = /.$/;
+    var re2_1b_2 = /(at|bl|iz)$/;
+    var re3_1b_2 = new RegExp("([^aeiouylsz])\\1$");
+    var re4_1b_2 = new RegExp("^" + C + v + "[^aeiouwxy]$");
+
+    var re_1c = /^(.+?[^aeiou])y$/;
+    var re_2 = /^(.+?)(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$/;
+
+    var re_3 = /^(.+?)(icate|ative|alize|iciti|ical|ful|ness)$/;
+
+    var re_4 = /^(.+?)(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize)$/;
+    var re2_4 = /^(.+?)(s|t)(ion)$/;
+
+    var re_5 = /^(.+?)e$/;
+    var re_5_1 = /ll$/;
+    var re3_5 = new RegExp("^" + C + v + "[^aeiouwxy]$");
+
+    var porterStemmer = function porterStemmer(w) {
+      var stem,
+        suffix,
+        firstch,
+        re,
+        re2,
+        re3,
+        re4;
+
+      if (w.length < 3) { return w; }
+
+      firstch = w.substr(0,1);
+      if (firstch == "y") {
+        w = firstch.toUpperCase() + w.substr(1);
+      }
+
+      // Step 1a
+      re = re_1a
+      re2 = re2_1a;
+
+      if (re.test(w)) { w = w.replace(re,"$1$2"); }
+      else if (re2.test(w)) { w = w.replace(re2,"$1$2"); }
+
+      // Step 1b
+      re = re_1b;
+      re2 = re2_1b;
+      if (re.test(w)) {
+        var fp = re.exec(w);
+        re = re_mgr0;
+        if (re.test(fp[1])) {
+          re = re_1b_2;
+          w = w.replace(re,"");
+        }
+      } else if (re2.test(w)) {
+        var fp = re2.exec(w);
+        stem = fp[1];
+        re2 = re_s_v;
+        if (re2.test(stem)) {
+          w = stem;
+          re2 = re2_1b_2;
+          re3 = re3_1b_2;
+          re4 = re4_1b_2;
+          if (re2.test(w)) { w = w + "e"; }
+          else if (re3.test(w)) { re = re_1b_2; w = w.replace(re,""); }
+          else if (re4.test(w)) { w = w + "e"; }
+        }
+      }
+
+      // Step 1c - replace suffix y or Y by i if preceded by a non-vowel which is not the first letter of the word (so cry -> cri, by -> by, say -> say)
+      re = re_1c;
+      if (re.test(w)) {
+        var fp = re.exec(w);
+        stem = fp[1];
+        w = stem + "i";
+      }
+
+      // Step 2
+      re = re_2;
+      if (re.test(w)) {
+        var fp = re.exec(w);
+        stem = fp[1];
+        suffix = fp[2];
+        re = re_mgr0;
+        if (re.test(stem)) {
+          w = stem + step2list[suffix];
+        }
+      }
+
+      // Step 3
+      re = re_3;
+      if (re.test(w)) {
+        var fp = re.exec(w);
+        stem = fp[1];
+        suffix = fp[2];
+        re = re_mgr0;
+        if (re.test(stem)) {
+          w = stem + step3list[suffix];
+        }
+      }
+
+      // Step 4
+      re = re_4;
+      re2 = re2_4;
+      if (re.test(w)) {
+        var fp = re.exec(w);
+        stem = fp[1];
+        re = re_mgr1;
+        if (re.test(stem)) {
+          w = stem;
+        }
+      } else if (re2.test(w)) {
+        var fp = re2.exec(w);
+        stem = fp[1] + fp[2];
+        re2 = re_mgr1;
+        if (re2.test(stem)) {
+          w = stem;
+        }
+      }
+
+      // Step 5
+      re = re_5;
+      if (re.test(w)) {
+        var fp = re.exec(w);
+        stem = fp[1];
+        re = re_mgr1;
+        re2 = re_meq1;
+        re3 = re3_5;
+        if (re.test(stem) || (re2.test(stem) && !(re3.test(stem)))) {
+          w = stem;
+        }
+      }
+
+      re = re_5_1;
+      re2 = re_mgr1;
+      if (re.test(w) && re2.test(w)) {
+        re = re_1b_2;
+        w = w.replace(re,"");
+      }
+
+      // and turn initial Y back to y
+
+      if (firstch == "y") {
+        w = firstch.toLowerCase() + w.substr(1);
+      }
+
+      return w;
+    };
+
+    return function (token) {
+      return token.update(porterStemmer);
+    }
+  })();
+
+  lunr.Pipeline.registerFunction(lunr.stemmer, 'stemmer')
+  /*!
+   * lunr.stopWordFilter
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * lunr.generateStopWordFilter builds a stopWordFilter function from the provided
+   * list of stop words.
+   *
+   * The built in lunr.stopWordFilter is built using this generator and can be used
+   * to generate custom stopWordFilters for applications or non English languages.
+   *
+   * @function
+   * @param {Array} token The token to pass through the filter
+   * @returns {lunr.PipelineFunction}
+   * @see lunr.Pipeline
+   * @see lunr.stopWordFilter
+   */
+  lunr.generateStopWordFilter = function (stopWords) {
+    var words = stopWords.reduce(function (memo, stopWord) {
+      memo[stopWord] = stopWord
+      return memo
+    }, {})
+
+    return function (token) {
+      if (token && words[token.toString()] !== token.toString()) return token
+    }
+  }
+
+  /**
+   * lunr.stopWordFilter is an English language stop word list filter, any words
+   * contained in the list will not be passed through the filter.
+   *
+   * This is intended to be used in the Pipeline. If the token does not pass the
+   * filter then undefined will be returned.
+   *
+   * @function
+   * @implements {lunr.PipelineFunction}
+   * @params {lunr.Token} token - A token to check for being a stop word.
+   * @returns {lunr.Token}
+   * @see {@link lunr.Pipeline}
+   */
+  lunr.stopWordFilter = lunr.generateStopWordFilter([
+    'a',
+    'able',
+    'about',
+    'across',
+    'after',
+    'all',
+    'almost',
+    'also',
+    'am',
+    'among',
+    'an',
+    'and',
+    'any',
+    'are',
+    'as',
+    'at',
+    'be',
+    'because',
+    'been',
+    'but',
+    'by',
+    'can',
+    'cannot',
+    'could',
+    'dear',
+    'did',
+    'do',
+    'does',
+    'either',
+    'else',
+    'ever',
+    'every',
+    'for',
+    'from',
+    'get',
+    'got',
+    'had',
+    'has',
+    'have',
+    'he',
+    'her',
+    'hers',
+    'him',
+    'his',
+    'how',
+    'however',
+    'i',
+    'if',
+    'in',
+    'into',
+    'is',
+    'it',
+    'its',
+    'just',
+    'least',
+    'let',
+    'like',
+    'likely',
+    'may',
+    'me',
+    'might',
+    'most',
+    'must',
+    'my',
+    'neither',
+    'no',
+    'nor',
+    'not',
+    'of',
+    'off',
+    'often',
+    'on',
+    'only',
+    'or',
+    'other',
+    'our',
+    'own',
+    'rather',
+    'said',
+    'say',
+    'says',
+    'she',
+    'should',
+    'since',
+    'so',
+    'some',
+    'than',
+    'that',
+    'the',
+    'their',
+    'them',
+    'then',
+    'there',
+    'these',
+    'they',
+    'this',
+    'tis',
+    'to',
+    'too',
+    'twas',
+    'us',
+    'wants',
+    'was',
+    'we',
+    'were',
+    'what',
+    'when',
+    'where',
+    'which',
+    'while',
+    'who',
+    'whom',
+    'why',
+    'will',
+    'with',
+    'would',
+    'yet',
+    'you',
+    'your'
+  ])
+
+  lunr.Pipeline.registerFunction(lunr.stopWordFilter, 'stopWordFilter')
+  /*!
+   * lunr.trimmer
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * lunr.trimmer is a pipeline function for trimming non word
+   * characters from the beginning and end of tokens before they
+   * enter the index.
+   *
+   * This implementation may not work correctly for non latin
+   * characters and should either be removed or adapted for use
+   * with languages with non-latin characters.
+   *
+   * @static
+   * @implements {lunr.PipelineFunction}
+   * @param {lunr.Token} token The token to pass through the filter
+   * @returns {lunr.Token}
+   * @see lunr.Pipeline
+   */
+  lunr.trimmer = function (token) {
+    return token.update(function (s) {
+      return s.replace(/^\W+/, '').replace(/\W+$/, '')
+    })
+  }
+
+  lunr.Pipeline.registerFunction(lunr.trimmer, 'trimmer')
+  /*!
+   * lunr.TokenSet
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * A token set is used to store the unique list of all tokens
+   * within an index. Token sets are also used to represent an
+   * incoming query to the index, this query token set and index
+   * token set are then intersected to find which tokens to look
+   * up in the inverted index.
+   *
+   * A token set can hold multiple tokens, as in the case of the
+   * index token set, or it can hold a single token as in the
+   * case of a simple query token set.
+   *
+   * Additionally token sets are used to perform wildcard matching.
+   * Leading, contained and trailing wildcards are supported, and
+   * from this edit distance matching can also be provided.
+   *
+   * Token sets are implemented as a minimal finite state automata,
+   * where both common prefixes and suffixes are shared between tokens.
+   * This helps to reduce the space used for storing the token set.
+   *
+   * @constructor
+   */
+  lunr.TokenSet = function () {
+    this.final = false
+    this.edges = {}
+    this.id = lunr.TokenSet._nextId
+    lunr.TokenSet._nextId += 1
+  }
+
+  /**
+   * Keeps track of the next, auto increment, identifier to assign
+   * to a new tokenSet.
+   *
+   * TokenSets require a unique identifier to be correctly minimised.
+   *
+   * @private
+   */
+  lunr.TokenSet._nextId = 1
+
+  /**
+   * Creates a TokenSet instance from the given sorted array of words.
+   *
+   * @param {String[]} arr - A sorted array of strings to create the set from.
+   * @returns {lunr.TokenSet}
+   * @throws Will throw an error if the input array is not sorted.
+   */
+  lunr.TokenSet.fromArray = function (arr) {
+    var builder = new lunr.TokenSet.Builder
+
+    for (var i = 0, len = arr.length; i < len; i++) {
+      builder.insert(arr[i])
+    }
+
+    builder.finish()
+    return builder.root
+  }
+
+  /**
+   * Creates a token set from a query clause.
+   *
+   * @private
+   * @param {Object} clause - A single clause from lunr.Query.
+   * @param {string} clause.term - The query clause term.
+   * @param {number} [clause.editDistance] - The optional edit distance for the term.
+   * @returns {lunr.TokenSet}
+   */
+  lunr.TokenSet.fromClause = function (clause) {
+    if ('editDistance' in clause) {
+      return lunr.TokenSet.fromFuzzyString(clause.term, clause.editDistance)
+    } else {
+      return lunr.TokenSet.fromString(clause.term)
+    }
+  }
+
+  /**
+   * Creates a token set representing a single string with a specified
+   * edit distance.
+   *
+   * Insertions, deletions, substitutions and transpositions are each
+   * treated as an edit distance of 1.
+   *
+   * Increasing the allowed edit distance will have a dramatic impact
+   * on the performance of both creating and intersecting these TokenSets.
+   * It is advised to keep the edit distance less than 3.
+   *
+   * @param {string} str - The string to create the token set from.
+   * @param {number} editDistance - The allowed edit distance to match.
+   * @returns {lunr.Vector}
+   */
+  lunr.TokenSet.fromFuzzyString = function (str, editDistance) {
+    var root = new lunr.TokenSet
+
+    var stack = [{
+      node: root,
+      editsRemaining: editDistance,
+      str: str
+    }]
+
+    while (stack.length) {
+      var frame = stack.pop()
+
+      // no edit
+      if (frame.str.length > 0) {
+        var char = frame.str.charAt(0),
+            noEditNode
+
+        if (char in frame.node.edges) {
+          noEditNode = frame.node.edges[char]
+        } else {
+          noEditNode = new lunr.TokenSet
+          frame.node.edges[char] = noEditNode
+        }
+
+        if (frame.str.length == 1) {
+          noEditNode.final = true
+        }
+
+        stack.push({
+          node: noEditNode,
+          editsRemaining: frame.editsRemaining,
+          str: frame.str.slice(1)
+        })
+      }
+
+      if (frame.editsRemaining == 0) {
+        continue
+      }
+
+      // insertion
+      if ("*" in frame.node.edges) {
+        var insertionNode = frame.node.edges["*"]
+      } else {
+        var insertionNode = new lunr.TokenSet
+        frame.node.edges["*"] = insertionNode
+      }
+
+      if (frame.str.length == 0) {
+        insertionNode.final = true
+      }
+
+      stack.push({
+        node: insertionNode,
+        editsRemaining: frame.editsRemaining - 1,
+        str: frame.str
+      })
+
+      // deletion
+      // can only do a deletion if we have enough edits remaining
+      // and if there are characters left to delete in the string
+      if (frame.str.length > 1) {
+        stack.push({
+          node: frame.node,
+          editsRemaining: frame.editsRemaining - 1,
+          str: frame.str.slice(1)
+        })
+      }
+
+      // deletion
+      // just removing the last character from the str
+      if (frame.str.length == 1) {
+        frame.node.final = true
+      }
+
+      // substitution
+      // can only do a substitution if we have enough edits remaining
+      // and if there are characters left to substitute
+      if (frame.str.length >= 1) {
+        if ("*" in frame.node.edges) {
+          var substitutionNode = frame.node.edges["*"]
+        } else {
+          var substitutionNode = new lunr.TokenSet
+          frame.node.edges["*"] = substitutionNode
+        }
+
+        if (frame.str.length == 1) {
+          substitutionNode.final = true
+        }
+
+        stack.push({
+          node: substitutionNode,
+          editsRemaining: frame.editsRemaining - 1,
+          str: frame.str.slice(1)
+        })
+      }
+
+      // transposition
+      // can only do a transposition if there are edits remaining
+      // and there are enough characters to transpose
+      if (frame.str.length > 1) {
+        var charA = frame.str.charAt(0),
+            charB = frame.str.charAt(1),
+            transposeNode
+
+        if (charB in frame.node.edges) {
+          transposeNode = frame.node.edges[charB]
+        } else {
+          transposeNode = new lunr.TokenSet
+          frame.node.edges[charB] = transposeNode
+        }
+
+        if (frame.str.length == 1) {
+          transposeNode.final = true
+        }
+
+        stack.push({
+          node: transposeNode,
+          editsRemaining: frame.editsRemaining - 1,
+          str: charA + frame.str.slice(2)
+        })
+      }
+    }
+
+    return root
+  }
+
+  /**
+   * Creates a TokenSet from a string.
+   *
+   * The string may contain one or more wildcard characters (*)
+   * that will allow wildcard matching when intersecting with
+   * another TokenSet.
+   *
+   * @param {string} str - The string to create a TokenSet from.
+   * @returns {lunr.TokenSet}
+   */
+  lunr.TokenSet.fromString = function (str) {
+    var node = new lunr.TokenSet,
+        root = node
+
+    /*
+     * Iterates through all characters within the passed string
+     * appending a node for each character.
+     *
+     * When a wildcard character is found then a self
+     * referencing edge is introduced to continually match
+     * any number of any characters.
+     */
+    for (var i = 0, len = str.length; i < len; i++) {
+      var char = str[i],
+          final = (i == len - 1)
+
+      if (char == "*") {
+        node.edges[char] = node
+        node.final = final
+
+      } else {
+        var next = new lunr.TokenSet
+        next.final = final
+
+        node.edges[char] = next
+        node = next
+      }
+    }
+
+    return root
+  }
+
+  /**
+   * Converts this TokenSet into an array of strings
+   * contained within the TokenSet.
+   *
+   * This is not intended to be used on a TokenSet that
+   * contains wildcards, in these cases the results are
+   * undefined and are likely to cause an infinite loop.
+   *
+   * @returns {string[]}
+   */
+  lunr.TokenSet.prototype.toArray = function () {
+    var words = []
+
+    var stack = [{
+      prefix: "",
+      node: this
+    }]
+
+    while (stack.length) {
+      var frame = stack.pop(),
+          edges = Object.keys(frame.node.edges),
+          len = edges.length
+
+      if (frame.node.final) {
+        /* In Safari, at this point the prefix is sometimes corrupted, see:
+         * https://github.com/olivernn/lunr.js/issues/279 Calling any
+         * String.prototype method forces Safari to "cast" this string to what
+         * it's supposed to be, fixing the bug. */
+        frame.prefix.charAt(0)
+        words.push(frame.prefix)
+      }
+
+      for (var i = 0; i < len; i++) {
+        var edge = edges[i]
+
+        stack.push({
+          prefix: frame.prefix.concat(edge),
+          node: frame.node.edges[edge]
+        })
+      }
+    }
+
+    return words
+  }
+
+  /**
+   * Generates a string representation of a TokenSet.
+   *
+   * This is intended to allow TokenSets to be used as keys
+   * in objects, largely to aid the construction and minimisation
+   * of a TokenSet. As such it is not designed to be a human
+   * friendly representation of the TokenSet.
+   *
+   * @returns {string}
+   */
+  lunr.TokenSet.prototype.toString = function () {
+    // NOTE: Using Object.keys here as this.edges is very likely
+    // to enter 'hash-mode' with many keys being added
+    //
+    // avoiding a for-in loop here as it leads to the function
+    // being de-optimised (at least in V8). From some simple
+    // benchmarks the performance is comparable, but allowing
+    // V8 to optimize may mean easy performance wins in the future.
+
+    if (this._str) {
+      return this._str
+    }
+
+    var str = this.final ? '1' : '0',
+        labels = Object.keys(this.edges).sort(),
+        len = labels.length
+
+    for (var i = 0; i < len; i++) {
+      var label = labels[i],
+          node = this.edges[label]
+
+      str = str + label + node.id
+    }
+
+    return str
+  }
+
+  /**
+   * Returns a new TokenSet that is the intersection of
+   * this TokenSet and the passed TokenSet.
+   *
+   * This intersection will take into account any wildcards
+   * contained within the TokenSet.
+   *
+   * @param {lunr.TokenSet} b - An other TokenSet to intersect with.
+   * @returns {lunr.TokenSet}
+   */
+  lunr.TokenSet.prototype.intersect = function (b) {
+    var output = new lunr.TokenSet,
+        frame = undefined
+
+    var stack = [{
+      qNode: b,
+      output: output,
+      node: this
+    }]
+
+    while (stack.length) {
+      frame = stack.pop()
+
+      // NOTE: As with the #toString method, we are using
+      // Object.keys and a for loop instead of a for-in loop
+      // as both of these objects enter 'hash' mode, causing
+      // the function to be de-optimised in V8
+      var qEdges = Object.keys(frame.qNode.edges),
+          qLen = qEdges.length,
+          nEdges = Object.keys(frame.node.edges),
+          nLen = nEdges.length
+
+      for (var q = 0; q < qLen; q++) {
+        var qEdge = qEdges[q]
+
+        for (var n = 0; n < nLen; n++) {
+          var nEdge = nEdges[n]
+
+          if (nEdge == qEdge || qEdge == '*') {
+            var node = frame.node.edges[nEdge],
+                qNode = frame.qNode.edges[qEdge],
+                final = node.final && qNode.final,
+                next = undefined
+
+            if (nEdge in frame.output.edges) {
+              // an edge already exists for this character
+              // no need to create a new node, just set the finality
+              // bit unless this node is already final
+              next = frame.output.edges[nEdge]
+              next.final = next.final || final
+
+            } else {
+              // no edge exists yet, must create one
+              // set the finality bit and insert it
+              // into the output
+              next = new lunr.TokenSet
+              next.final = final
+              frame.output.edges[nEdge] = next
+            }
+
+            stack.push({
+              qNode: qNode,
+              output: next,
+              node: node
+            })
+          }
+        }
+      }
+    }
+
+    return output
+  }
+  lunr.TokenSet.Builder = function () {
+    this.previousWord = ""
+    this.root = new lunr.TokenSet
+    this.uncheckedNodes = []
+    this.minimizedNodes = {}
+  }
+
+  lunr.TokenSet.Builder.prototype.insert = function (word) {
+    var node,
+        commonPrefix = 0
+
+    if (word < this.previousWord) {
+      throw new Error ("Out of order word insertion")
+    }
+
+    for (var i = 0; i < word.length && i < this.previousWord.length; i++) {
+      if (word[i] != this.previousWord[i]) break
+      commonPrefix++
+    }
+
+    this.minimize(commonPrefix)
+
+    if (this.uncheckedNodes.length == 0) {
+      node = this.root
+    } else {
+      node = this.uncheckedNodes[this.uncheckedNodes.length - 1].child
+    }
+
+    for (var i = commonPrefix; i < word.length; i++) {
+      var nextNode = new lunr.TokenSet,
+          char = word[i]
+
+      node.edges[char] = nextNode
+
+      this.uncheckedNodes.push({
+        parent: node,
+        char: char,
+        child: nextNode
+      })
+
+      node = nextNode
+    }
+
+    node.final = true
+    this.previousWord = word
+  }
+
+  lunr.TokenSet.Builder.prototype.finish = function () {
+    this.minimize(0)
+  }
+
+  lunr.TokenSet.Builder.prototype.minimize = function (downTo) {
+    for (var i = this.uncheckedNodes.length - 1; i >= downTo; i--) {
+      var node = this.uncheckedNodes[i],
+          childKey = node.child.toString()
+
+      if (childKey in this.minimizedNodes) {
+        node.parent.edges[node.char] = this.minimizedNodes[childKey]
+      } else {
+        // Cache the key for this node since
+        // we know it can't change anymore
+        node.child._str = childKey
+
+        this.minimizedNodes[childKey] = node.child
+      }
+
+      this.uncheckedNodes.pop()
+    }
+  }
+  /*!
+   * lunr.Index
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * An index contains the built index of all documents and provides a query interface
+   * to the index.
+   *
+   * Usually instances of lunr.Index will not be created using this constructor, instead
+   * lunr.Builder should be used to construct new indexes, or lunr.Index.load should be
+   * used to load previously built and serialized indexes.
+   *
+   * @constructor
+   * @param {Object} attrs - The attributes of the built search index.
+   * @param {Object} attrs.invertedIndex - An index of term/field to document reference.
+   * @param {Object<string, lunr.Vector>} attrs.fieldVectors - Field vectors
+   * @param {lunr.TokenSet} attrs.tokenSet - An set of all corpus tokens.
+   * @param {string[]} attrs.fields - The names of indexed document fields.
+   * @param {lunr.Pipeline} attrs.pipeline - The pipeline to use for search terms.
+   */
+  lunr.Index = function (attrs) {
+    this.invertedIndex = attrs.invertedIndex
+    this.fieldVectors = attrs.fieldVectors
+    this.tokenSet = attrs.tokenSet
+    this.fields = attrs.fields
+    this.pipeline = attrs.pipeline
+  }
+
+  /**
+   * A result contains details of a document matching a search query.
+   * @typedef {Object} lunr.Index~Result
+   * @property {string} ref - The reference of the document this result represents.
+   * @property {number} score - A number between 0 and 1 representing how similar this document is to the query.
+   * @property {lunr.MatchData} matchData - Contains metadata about this match including which term(s) caused the match.
+   */
+
+  /**
+   * Although lunr provides the ability to create queries using lunr.Query, it also provides a simple
+   * query language which itself is parsed into an instance of lunr.Query.
+   *
+   * For programmatically building queries it is advised to directly use lunr.Query, the query language
+   * is best used for human entered text rather than program generated text.
+   *
+   * At its simplest queries can just be a single term, e.g. `hello`, multiple terms are also supported
+   * and will be combined with OR, e.g `hello world` will match documents that contain either 'hello'
+   * or 'world', though those that contain both will rank higher in the results.
+   *
+   * Wildcards can be included in terms to match one or more unspecified characters, these wildcards can
+   * be inserted anywhere within the term, and more than one wildcard can exist in a single term. Adding
+   * wildcards will increase the number of documents that will be found but can also have a negative
+   * impact on query performance, especially with wildcards at the beginning of a term.
+   *
+   * Terms can be restricted to specific fields, e.g. `title:hello`, only documents with the term
+   * hello in the title field will match this query. Using a field not present in the index will lead
+   * to an error being thrown.
+   *
+   * Modifiers can also be added to terms, lunr supports edit distance and boost modifiers on terms. A term
+   * boost will make documents matching that term score higher, e.g. `foo^5`. Edit distance is also supported
+   * to provide fuzzy matching, e.g. 'hello~2' will match documents with hello with an edit distance of 2.
+   * Avoid large values for edit distance to improve query performance.
+   *
+   * Each term also supports a presence modifier. By default a term's presence in document is optional, however
+   * this can be changed to either required or prohibited. For a term's presence to be required in a document the
+   * term should be prefixed with a '+', e.g. `+foo bar` is a search for documents that must contain 'foo' and
+   * optionally contain 'bar'. Conversely a leading '-' sets the terms presence to prohibited, i.e. it must not
+   * appear in a document, e.g. `-foo bar` is a search for documents that do not contain 'foo' but may contain 'bar'.
+   *
+   * To escape special characters the backslash character '\' can be used, this allows searches to include
+   * characters that would normally be considered modifiers, e.g. `foo\~2` will search for a term "foo~2" instead
+   * of attempting to apply a boost of 2 to the search term "foo".
+   *
+   * @typedef {string} lunr.Index~QueryString
+   * @example <caption>Simple single term query</caption>
+   * hello
+   * @example <caption>Multiple term query</caption>
+   * hello world
+   * @example <caption>term scoped to a field</caption>
+   * title:hello
+   * @example <caption>term with a boost of 10</caption>
+   * hello^10
+   * @example <caption>term with an edit distance of 2</caption>
+   * hello~2
+   * @example <caption>terms with presence modifiers</caption>
+   * -foo +bar baz
+   */
+
+  /**
+   * Performs a search against the index using lunr query syntax.
+   *
+   * Results will be returned sorted by their score, the most relevant results
+   * will be returned first.  For details on how the score is calculated, please see
+   * the {@link https://lunrjs.com/guides/searching.html#scoring|guide}.
+   *
+   * For more programmatic querying use lunr.Index#query.
+   *
+   * @param {lunr.Index~QueryString} queryString - A string containing a lunr query.
+   * @throws {lunr.QueryParseError} If the passed query string cannot be parsed.
+   * @returns {lunr.Index~Result[]}
+   */
+  lunr.Index.prototype.search = function (queryString) {
+    return this.query(function (query) {
+      var parser = new lunr.QueryParser(queryString, query)
+      parser.parse()
+    })
+  }
+
+  /**
+   * A query builder callback provides a query object to be used to express
+   * the query to perform on the index.
+   *
+   * @callback lunr.Index~queryBuilder
+   * @param {lunr.Query} query - The query object to build up.
+   * @this lunr.Query
+   */
+
+  /**
+   * Performs a query against the index using the yielded lunr.Query object.
+   *
+   * If performing programmatic queries against the index, this method is preferred
+   * over lunr.Index#search so as to avoid the additional query parsing overhead.
+   *
+   * A query object is yielded to the supplied function which should be used to
+   * express the query to be run against the index.
+   *
+   * Note that although this function takes a callback parameter it is _not_ an
+   * asynchronous operation, the callback is just yielded a query object to be
+   * customized.
+   *
+   * @param {lunr.Index~queryBuilder} fn - A function that is used to build the query.
+   * @returns {lunr.Index~Result[]}
+   */
+  lunr.Index.prototype.query = function (fn) {
+    // for each query clause
+    // * process terms
+    // * expand terms from token set
+    // * find matching documents and metadata
+    // * get document vectors
+    // * score documents
+
+    var query = new lunr.Query(this.fields),
+        matchingFields = Object.create(null),
+        queryVectors = Object.create(null),
+        termFieldCache = Object.create(null),
+        requiredMatches = Object.create(null),
+        prohibitedMatches = Object.create(null)
+
+    /*
+     * To support field level boosts a query vector is created per
+     * field. An empty vector is eagerly created to support negated
+     * queries.
+     */
+    for (var i = 0; i < this.fields.length; i++) {
+      queryVectors[this.fields[i]] = new lunr.Vector
+    }
+
+    fn.call(query, query)
+
+    for (var i = 0; i < query.clauses.length; i++) {
+      /*
+       * Unless the pipeline has been disabled for this term, which is
+       * the case for terms with wildcards, we need to pass the clause
+       * term through the search pipeline. A pipeline returns an array
+       * of processed terms. Pipeline functions may expand the passed
+       * term, which means we may end up performing multiple index lookups
+       * for a single query term.
+       */
+      var clause = query.clauses[i],
+          terms = null,
+          clauseMatches = lunr.Set.empty
+
+      if (clause.usePipeline) {
+        terms = this.pipeline.runString(clause.term, {
+          fields: clause.fields
+        })
+      } else {
+        terms = [clause.term]
+      }
+
+      for (var m = 0; m < terms.length; m++) {
+        var term = terms[m]
+
+        /*
+         * Each term returned from the pipeline needs to use the same query
+         * clause object, e.g. the same boost and or edit distance. The
+         * simplest way to do this is to re-use the clause object but mutate
+         * its term property.
+         */
+        clause.term = term
+
+        /*
+         * From the term in the clause we create a token set which will then
+         * be used to intersect the indexes token set to get a list of terms
+         * to lookup in the inverted index
+         */
+        var termTokenSet = lunr.TokenSet.fromClause(clause),
+            expandedTerms = this.tokenSet.intersect(termTokenSet).toArray()
+
+        /*
+         * If a term marked as required does not exist in the tokenSet it is
+         * impossible for the search to return any matches. We set all the field
+         * scoped required matches set to empty and stop examining any further
+         * clauses.
+         */
+        if (expandedTerms.length === 0 && clause.presence === lunr.Query.presence.REQUIRED) {
+          for (var k = 0; k < clause.fields.length; k++) {
+            var field = clause.fields[k]
+            requiredMatches[field] = lunr.Set.empty
+          }
+
+          break
+        }
+
+        for (var j = 0; j < expandedTerms.length; j++) {
+          /*
+           * For each term get the posting and termIndex, this is required for
+           * building the query vector.
+           */
+          var expandedTerm = expandedTerms[j],
+              posting = this.invertedIndex[expandedTerm],
+              termIndex = posting._index
+
+          for (var k = 0; k < clause.fields.length; k++) {
+            /*
+             * For each field that this query term is scoped by (by default
+             * all fields are in scope) we need to get all the document refs
+             * that have this term in that field.
+             *
+             * The posting is the entry in the invertedIndex for the matching
+             * term from above.
+             */
+            var field = clause.fields[k],
+                fieldPosting = posting[field],
+                matchingDocumentRefs = Object.keys(fieldPosting),
+                termField = expandedTerm + "/" + field,
+                matchingDocumentsSet = new lunr.Set(matchingDocumentRefs)
+
+            /*
+             * if the presence of this term is required ensure that the matching
+             * documents are added to the set of required matches for this clause.
+             *
+             */
+            if (clause.presence == lunr.Query.presence.REQUIRED) {
+              clauseMatches = clauseMatches.union(matchingDocumentsSet)
+
+              if (requiredMatches[field] === undefined) {
+                requiredMatches[field] = lunr.Set.complete
+              }
+            }
+
+            /*
+             * if the presence of this term is prohibited ensure that the matching
+             * documents are added to the set of prohibited matches for this field,
+             * creating that set if it does not yet exist.
+             */
+            if (clause.presence == lunr.Query.presence.PROHIBITED) {
+              if (prohibitedMatches[field] === undefined) {
+                prohibitedMatches[field] = lunr.Set.empty
+              }
+
+              prohibitedMatches[field] = prohibitedMatches[field].union(matchingDocumentsSet)
+
+              /*
+               * Prohibited matches should not be part of the query vector used for
+               * similarity scoring and no metadata should be extracted so we continue
+               * to the next field
+               */
+              continue
+            }
+
+            /*
+             * The query field vector is populated using the termIndex found for
+             * the term and a unit value with the appropriate boost applied.
+             * Using upsert because there could already be an entry in the vector
+             * for the term we are working with. In that case we just add the scores
+             * together.
+             */
+            queryVectors[field].upsert(termIndex, clause.boost, function (a, b) { return a + b })
+
+            /**
+             * If we've already seen this term, field combo then we've already collected
+             * the matching documents and metadata, no need to go through all that again
+             */
+            if (termFieldCache[termField]) {
+              continue
+            }
+
+            for (var l = 0; l < matchingDocumentRefs.length; l++) {
+              /*
+               * All metadata for this term/field/document triple
+               * are then extracted and collected into an instance
+               * of lunr.MatchData ready to be returned in the query
+               * results
+               */
+              var matchingDocumentRef = matchingDocumentRefs[l],
+                  matchingFieldRef = new lunr.FieldRef (matchingDocumentRef, field),
+                  metadata = fieldPosting[matchingDocumentRef],
+                  fieldMatch
+
+              if ((fieldMatch = matchingFields[matchingFieldRef]) === undefined) {
+                matchingFields[matchingFieldRef] = new lunr.MatchData (expandedTerm, field, metadata)
+              } else {
+                fieldMatch.add(expandedTerm, field, metadata)
+              }
+
+            }
+
+            termFieldCache[termField] = true
+          }
+        }
+      }
+
+      /**
+       * If the presence was required we need to update the requiredMatches field sets.
+       * We do this after all fields for the term have collected their matches because
+       * the clause terms presence is required in _any_ of the fields not _all_ of the
+       * fields.
+       */
+      if (clause.presence === lunr.Query.presence.REQUIRED) {
+        for (var k = 0; k < clause.fields.length; k++) {
+          var field = clause.fields[k]
+          requiredMatches[field] = requiredMatches[field].intersect(clauseMatches)
+        }
+      }
+    }
+
+    /**
+     * Need to combine the field scoped required and prohibited
+     * matching documents into a global set of required and prohibited
+     * matches
+     */
+    var allRequiredMatches = lunr.Set.complete,
+        allProhibitedMatches = lunr.Set.empty
+
+    for (var i = 0; i < this.fields.length; i++) {
+      var field = this.fields[i]
+
+      if (requiredMatches[field]) {
+        allRequiredMatches = allRequiredMatches.intersect(requiredMatches[field])
+      }
+
+      if (prohibitedMatches[field]) {
+        allProhibitedMatches = allProhibitedMatches.union(prohibitedMatches[field])
+      }
+    }
+
+    var matchingFieldRefs = Object.keys(matchingFields),
+        results = [],
+        matches = Object.create(null)
+
+    /*
+     * If the query is negated (contains only prohibited terms)
+     * we need to get _all_ fieldRefs currently existing in the
+     * index. This is only done when we know that the query is
+     * entirely prohibited terms to avoid any cost of getting all
+     * fieldRefs unnecessarily.
+     *
+     * Additionally, blank MatchData must be created to correctly
+     * populate the results.
+     */
+    if (query.isNegated()) {
+      matchingFieldRefs = Object.keys(this.fieldVectors)
+
+      for (var i = 0; i < matchingFieldRefs.length; i++) {
+        var matchingFieldRef = matchingFieldRefs[i]
+        var fieldRef = lunr.FieldRef.fromString(matchingFieldRef)
+        matchingFields[matchingFieldRef] = new lunr.MatchData
+      }
+    }
+
+    for (var i = 0; i < matchingFieldRefs.length; i++) {
+      /*
+       * Currently we have document fields that match the query, but we
+       * need to return documents. The matchData and scores are combined
+       * from multiple fields belonging to the same document.
+       *
+       * Scores are calculated by field, using the query vectors created
+       * above, and combined into a final document score using addition.
+       */
+      var fieldRef = lunr.FieldRef.fromString(matchingFieldRefs[i]),
+          docRef = fieldRef.docRef
+
+      if (!allRequiredMatches.contains(docRef)) {
+        continue
+      }
+
+      if (allProhibitedMatches.contains(docRef)) {
+        continue
+      }
+
+      var fieldVector = this.fieldVectors[fieldRef],
+          score = queryVectors[fieldRef.fieldName].similarity(fieldVector),
+          docMatch
+
+      if ((docMatch = matches[docRef]) !== undefined) {
+        docMatch.score += score
+        docMatch.matchData.combine(matchingFields[fieldRef])
+      } else {
+        var match = {
+          ref: docRef,
+          score: score,
+          matchData: matchingFields[fieldRef]
+        }
+        matches[docRef] = match
+        results.push(match)
+      }
+    }
+
+    /*
+     * Sort the results objects by score, highest first.
+     */
+    return results.sort(function (a, b) {
+      return b.score - a.score
+    })
+  }
+
+  /**
+   * Prepares the index for JSON serialization.
+   *
+   * The schema for this JSON blob will be described in a
+   * separate JSON schema file.
+   *
+   * @returns {Object}
+   */
+  lunr.Index.prototype.toJSON = function () {
+    var invertedIndex = Object.keys(this.invertedIndex)
+      .sort()
+      .map(function (term) {
+        return [term, this.invertedIndex[term]]
+      }, this)
+
+    var fieldVectors = Object.keys(this.fieldVectors)
+      .map(function (ref) {
+        return [ref, this.fieldVectors[ref].toJSON()]
+      }, this)
+
+    return {
+      version: lunr.version,
+      fields: this.fields,
+      fieldVectors: fieldVectors,
+      invertedIndex: invertedIndex,
+      pipeline: this.pipeline.toJSON()
+    }
+  }
+
+  /**
+   * Loads a previously serialized lunr.Index
+   *
+   * @param {Object} serializedIndex - A previously serialized lunr.Index
+   * @returns {lunr.Index}
+   */
+  lunr.Index.load = function (serializedIndex) {
+    var attrs = {},
+        fieldVectors = {},
+        serializedVectors = serializedIndex.fieldVectors,
+        invertedIndex = Object.create(null),
+        serializedInvertedIndex = serializedIndex.invertedIndex,
+        tokenSetBuilder = new lunr.TokenSet.Builder,
+        pipeline = lunr.Pipeline.load(serializedIndex.pipeline)
+
+    if (serializedIndex.version != lunr.version) {
+      lunr.utils.warn("Version mismatch when loading serialised index. Current version of lunr '" + lunr.version + "' does not match serialized index '" + serializedIndex.version + "'")
+    }
+
+    for (var i = 0; i < serializedVectors.length; i++) {
+      var tuple = serializedVectors[i],
+          ref = tuple[0],
+          elements = tuple[1]
+
+      fieldVectors[ref] = new lunr.Vector(elements)
+    }
+
+    for (var i = 0; i < serializedInvertedIndex.length; i++) {
+      var tuple = serializedInvertedIndex[i],
+          term = tuple[0],
+          posting = tuple[1]
+
+      tokenSetBuilder.insert(term)
+      invertedIndex[term] = posting
+    }
+
+    tokenSetBuilder.finish()
+
+    attrs.fields = serializedIndex.fields
+
+    attrs.fieldVectors = fieldVectors
+    attrs.invertedIndex = invertedIndex
+    attrs.tokenSet = tokenSetBuilder.root
+    attrs.pipeline = pipeline
+
+    return new lunr.Index(attrs)
+  }
+  /*!
+   * lunr.Builder
+   * Copyright (C) 2020 Oliver Nightingale
+   */
+
+  /**
+   * lunr.Builder performs indexing on a set of documents and
+   * returns instances of lunr.Index ready for querying.
+   *
+   * All configuration of the index is done via the builder, the
+   * fields to index, the document reference, the text processing
+   * pipeline and document scoring parameters are all set on the
+   * builder before indexing.
+   *
+   * @constructor
+   * @property {string} _ref - Internal reference to the document reference field.
+   * @property {string[]} _fields - Internal reference to the document fields to index.
+   * @property {object} invertedIndex - The inverted index maps terms to document fields.
+   * @property {object} documentTermFrequencies - Keeps track of document term frequencies.
+   * @property {object} documentLengths - Keeps track of the length of documents added to the index.
+   * @property {lunr.tokenizer} tokenizer - Function for splitting strings into tokens for indexing.
+   * @property {lunr.Pipeline} pipeline - The pipeline performs text processing on tokens before indexing.
+   * @property {lunr.Pipeline} searchPipeline - A pipeline for processing search terms before querying the index.
+   * @property {number} documentCount - Keeps track of the total number of documents indexed.
+   * @property {number} _b - A parameter to control field length normalization, setting this to 0 disabled normalization, 1 fully normalizes field lengths, the default value is 0.75.
+   * @property {number} _k1 - A parameter to control how quickly an increase in term frequency results in term frequency saturation, the default value is 1.2.
+   * @property {number} termIndex - A counter incremented for each unique term, used to identify a terms position in the vector space.
+   * @property {array} metadataWhitelist - A list of metadata keys that have been whitelisted for entry in the index.
+   */
+  lunr.Builder = function () {
+    this._ref = "id"
+    this._fields = Object.create(null)
+    this._documents = Object.create(null)
+    this.invertedIndex = Object.create(null)
+    this.fieldTermFrequencies = {}
+    this.fieldLengths = {}
+    this.tokenizer = lunr.tokenizer
+    this.pipeline = new lunr.Pipeline
+    this.searchPipeline = new lunr.Pipeline
+    this.documentCount = 0
+    this._b = 0.75
+    this._k1 = 1.2
+    this.termIndex = 0
+    this.metadataWhitelist = []
+  }
+
+  /**
+   * Sets the document field used as the document reference. Every document must have this field.
+   * The type of this field in the document should be a string, if it is not a string it will be
+   * coerced into a string by calling toString.
+   *
+   * The default ref is 'id'.
+   *
+   * The ref should _not_ be changed during indexing, it should be set before any documents are
+   * added to the index. Changing it during indexing can lead to inconsistent results.
+   *
+   * @param {string} ref - The name of the reference field in the document.
+   */
+  lunr.Builder.prototype.ref = function (ref) {
+    this._ref = ref
+  }
+
+  /**
+   * A function that is used to extract a field from a document.
+   *
+   * Lunr expects a field to be at the top level of a document, if however the field
+   * is deeply nested within a document an extractor function can be used to extract
+   * the right field for indexing.
+   *
+   * @callback fieldExtractor
+   * @param {object} doc - The document being added to the index.
+   * @returns {?(string|object|object[])} obj - The object that will be indexed for this field.
+   * @example <caption>Extracting a nested field</caption>
+   * function (doc) { return doc.nested.field }
+   */
+
+  /**
+   * Adds a field to the list of document fields that will be indexed. Every document being
+   * indexed should have this field. Null values for this field in indexed documents will
+   * not cause errors but will limit the chance of that document being retrieved by searches.
+   *
+   * All fields should be added before adding documents to the index. Adding fields after
+   * a document has been indexed will have no effect on already indexed documents.
+   *
+   * Fields can be boosted at build time. This allows terms within that field to have more
+   * importance when ranking search results. Use a field boost to specify that matches within
+   * one field are more important than other fields.
+   *
+   * @param {string} fieldName - The name of a field to index in all documents.
+   * @param {object} attributes - Optional attributes associated with this field.
+   * @param {number} [attributes.boost=1] - Boost applied to all terms within this field.
+   * @param {fieldExtractor} [attributes.extractor] - Function to extract a field from a document.
+   * @throws {RangeError} fieldName cannot contain unsupported characters '/'
+   */
+  lunr.Builder.prototype.field = function (fieldName, attributes) {
+    if (/\//.test(fieldName)) {
+      throw new RangeError ("Field '" + fieldName + "' contains illegal character '/'")
+    }
+
+    this._fields[fieldName] = attributes || {}
+  }
+
+  /**
+   * A parameter to tune the amount of field length normalisation that is applied when
+   * calculating relevance scores. A value of 0 will completely disable any normalisation
+   * and a value of 1 will fully normalise field lengths. The default is 0.75. Values of b
+   * will be clamped to the range 0 - 1.
+   *
+   * @param {number} number - The value to set for this tuning parameter.
+   */
+  lunr.Builder.prototype.b = function (number) {
+    if (number < 0) {
+      this._b = 0
+    } else if (number > 1) {
+      this._b = 1
+    } else {
+      this._b = number
+    }
+  }
+
+  /**
+   * A parameter that controls the speed at which a rise in term frequency results in term
+   * frequency saturation. The default value is 1.2. Setting this to a higher value will give
+   * slower saturation levels, a lower value will result in quicker saturation.
+   *
+   * @param {number} number - The value to set for this tuning parameter.
+   */
+  lunr.Builder.prototype.k1 = function (number) {
+    this._k1 = number
+  }
+
+  /**
+   * Adds a document to the index.
+   *
+   * Before adding fields to the index the index should have been fully setup, with the document
+   * ref and all fields to index already having been specified.
+   *
+   * The document must have a field name as specified by the ref (by default this is 'id') and
+   * it should have all fields defined for indexing, though null or undefined values will not
+   * cause errors.
+   *
+   * Entire documents can be boosted at build time. Applying a boost to a document indicates that
+   * this document should rank higher in search results than other documents.
+   *
+   * @param {object} doc - The document to add to the index.
+   * @param {object} attributes - Optional attributes associated with this document.
+   * @param {number} [attributes.boost=1] - Boost applied to all terms within this document.
+   */
+  lunr.Builder.prototype.add = function (doc, attributes) {
+    var docRef = doc[this._ref],
+        fields = Object.keys(this._fields)
+
+    this._documents[docRef] = attributes || {}
+    this.documentCount += 1
+
+    for (var i = 0; i < fields.length; i++) {
+      var fieldName = fields[i],
+          extractor = this._fields[fieldName].extractor,
+          field = extractor ? extractor(doc) : doc[fieldName],
+          tokens = this.tokenizer(field, {
+            fields: [fieldName]
+          }),
+          terms = this.pipeline.run(tokens),
+          fieldRef = new lunr.FieldRef (docRef, fieldName),
+          fieldTerms = Object.create(null)
+
+      this.fieldTermFrequencies[fieldRef] = fieldTerms
+      this.fieldLengths[fieldRef] = 0
+
+      // store the length of this field for this document
+      this.fieldLengths[fieldRef] += terms.length
+
+      // calculate term frequencies for this field
+      for (var j = 0; j < terms.length; j++) {
+        var term = terms[j]
+
+        if (fieldTerms[term] == undefined) {
+          fieldTerms[term] = 0
+        }
+
+        fieldTerms[term] += 1
+
+        // add to inverted index
+        // create an initial posting if one doesn't exist
+        if (this.invertedIndex[term] == undefined) {
+          var posting = Object.create(null)
+          posting["_index"] = this.termIndex
+          this.termIndex += 1
+
+          for (var k = 0; k < fields.length; k++) {
+            posting[fields[k]] = Object.create(null)
+          }
+
+          this.invertedIndex[term] = posting
+        }
+
+        // add an entry for this term/fieldName/docRef to the invertedIndex
+        if (this.invertedIndex[term][fieldName][docRef] == undefined) {
+          this.invertedIndex[term][fieldName][docRef] = Object.create(null)
+        }
+
+        // store all whitelisted metadata about this token in the
+        // inverted index
+        for (var l = 0; l < this.metadataWhitelist.length; l++) {
+          var metadataKey = this.metadataWhitelist[l],
+              metadata = term.metadata[metadataKey]
+
+          if (this.invertedIndex[term][fieldName][docRef][metadataKey] == undefined) {
+            this.invertedIndex[term][fieldName][docRef][metadataKey] = []
+          }
+
+          this.invertedIndex[term][fieldName][docRef][metadataKey].push(metadata)
+        }
+      }
+
+    }
+  }
+
+  /**
+   * Calculates the average document length for this index
+   *
+   * @private
+   */
+  lunr.Builder.prototype.calculateAverageFieldLengths = function () {
+
+    var fieldRefs = Object.keys(this.fieldLengths),
+        numberOfFields = fieldRefs.length,
+        accumulator = {},
+        documentsWithField = {}
+
+    for (var i = 0; i < numberOfFields; i++) {
+      var fieldRef = lunr.FieldRef.fromString(fieldRefs[i]),
+          field = fieldRef.fieldName
+
+      documentsWithField[field] || (documentsWithField[field] = 0)
+      documentsWithField[field] += 1
+
+      accumulator[field] || (accumulator[field] = 0)
+      accumulator[field] += this.fieldLengths[fieldRef]
+    }
+
+    var fields = Object.keys(this._fields)
+
+    for (var i = 0; i < fields.length; i++) {
+      var fieldName = fields[i]
+      accumulator[fieldName] = accumulator[fieldName] / documentsWithField[fieldName]
+    }
+
+    this.averageFieldLength = accumulator
+  }
+
+  /**
+   * Builds a vector space model of every document using lunr.Vector
+   *
+   * @private
+   */
+  lunr.Builder.prototype.createFieldVectors = function () {
+    var fieldVectors = {},
+        fieldRefs = Object.keys(this.fieldTermFrequencies),
+        fieldRefsLength = fieldRefs.length,
+        termIdfCache = Object.create(null)
+
+    for (var i = 0; i < fieldRefsLength; i++) {
+      var fieldRef = lunr.FieldRef.fromString(fieldRefs[i]),
+          fieldName = fieldRef.fieldName,
+          fieldLength = this.fieldLengths[fieldRef],
+          fieldVector = new lunr.Vector,
+          termFrequencies = this.fieldTermFrequencies[fieldRef],
+          terms = Object.keys(termFrequencies),
+          termsLength = terms.length
+
+
+      var fieldBoost = this._fields[fieldName].boost || 1,
+          docBoost = this._documents[fieldRef.docRef].boost || 1
+
+      for (var j = 0; j < termsLength; j++) {
+        var term = terms[j],
+            tf = termFrequencies[term],
+            termIndex = this.invertedIndex[term]._index,
+            idf, score, scoreWithPrecision
+
+        if (termIdfCache[term] === undefined) {
+          idf = lunr.idf(this.invertedIndex[term], this.documentCount)
+          termIdfCache[term] = idf
+        } else {
+          idf = termIdfCache[term]
+        }
+
+        score = idf * ((this._k1 + 1) * tf) / (this._k1 * (1 - this._b + this._b * (fieldLength / this.averageFieldLength[fieldName])) + tf)
+        score *= fieldBoost
+        score *= docBoost
+        scoreWithPrecision = Math.round(score * 1000) / 1000
+        // Converts 1.23456789 to 1.234.
+        // Reducing the precision so that the vectors take up less
+        // space when serialised. Doing it now so that they behave
+        // the same before and after serialisation. Also, this is
+        // the fastest approach to reducing a number's precision in
+        // JavaScript.
+
+        fieldVector.insert(termIndex, scoreWithPrecision)
+      }
+
+      fieldVectors[fieldRef] = fieldVector
+    }
+
+    this.fieldVectors = fieldVectors
+  }
+
+  /**
+   * Creates a token set of all tokens in the index using lunr.TokenSet
+   *
+   * @private
+   */
+  lunr.Builder.prototype.createTokenSet = function () {
+    this.tokenSet = lunr.TokenSet.fromArray(
+      Object.keys(this.invertedIndex).sort()
+    )
+  }
+
+  /**
+   * Builds the index, creating an instance of lunr.Index.
+   *
+   * This completes the indexing process and should only be called
+   * once all documents have been added to the index.
+   *
+   * @returns {lunr.Index}
+   */
+  lunr.Builder.prototype.build = function () {
+    this.calculateAverageFieldLengths()
+    this.createFieldVectors()
+    this.createTokenSet()
+
+    return new lunr.Index({
+      invertedIndex: this.invertedIndex,
+      fieldVectors: this.fieldVectors,
+      tokenSet: this.tokenSet,
+      fields: Object.keys(this._fields),
+      pipeline: this.searchPipeline
+    })
+  }
+
+  /**
+   * Applies a plugin to the index builder.
+   *
+   * A plugin is a function that is called with the index builder as its context.
+   * Plugins can be used to customise or extend the behaviour of the index
+   * in some way. A plugin is just a function, that encapsulated the custom
+   * behaviour that should be applied when building the index.
+   *
+   * The plugin function will be called with the index builder as its argument, additional
+   * arguments can also be passed when calling use. The function will be called
+   * with the index builder as its context.
+   *
+   * @param {Function} plugin The plugin to apply.
+   */
+  lunr.Builder.prototype.use = function (fn) {
+    var args = Array.prototype.slice.call(arguments, 1)
+    args.unshift(this)
+    fn.apply(this, args)
+  }
+  /**
+   * Contains and collects metadata about a matching document.
+   * A single instance of lunr.MatchData is returned as part of every
+   * lunr.Index~Result.
+   *
+   * @constructor
+   * @param {string} term - The term this match data is associated with
+   * @param {string} field - The field in which the term was found
+   * @param {object} metadata - The metadata recorded about this term in this field
+   * @property {object} metadata - A cloned collection of metadata associated with this document.
+   * @see {@link lunr.Index~Result}
+   */
+  lunr.MatchData = function (term, field, metadata) {
+    var clonedMetadata = Object.create(null),
+        metadataKeys = Object.keys(metadata || {})
+
+    // Cloning the metadata to prevent the original
+    // being mutated during match data combination.
+    // Metadata is kept in an array within the inverted
+    // index so cloning the data can be done with
+    // Array#slice
+    for (var i = 0; i < metadataKeys.length; i++) {
+      var key = metadataKeys[i]
+      clonedMetadata[key] = metadata[key].slice()
+    }
+
+    this.metadata = Object.create(null)
+
+    if (term !== undefined) {
+      this.metadata[term] = Object.create(null)
+      this.metadata[term][field] = clonedMetadata
+    }
+  }
+
+  /**
+   * An instance of lunr.MatchData will be created for every term that matches a
+   * document. However only one instance is required in a lunr.Index~Result. This
+   * method combines metadata from another instance of lunr.MatchData with this
+   * objects metadata.
+   *
+   * @param {lunr.MatchData} otherMatchData - Another instance of match data to merge with this one.
+   * @see {@link lunr.Index~Result}
+   */
+  lunr.MatchData.prototype.combine = function (otherMatchData) {
+    var terms = Object.keys(otherMatchData.metadata)
+
+    for (var i = 0; i < terms.length; i++) {
+      var term = terms[i],
+          fields = Object.keys(otherMatchData.metadata[term])
+
+      if (this.metadata[term] == undefined) {
+        this.metadata[term] = Object.create(null)
+      }
+
+      for (var j = 0; j < fields.length; j++) {
+        var field = fields[j],
+            keys = Object.keys(otherMatchData.metadata[term][field])
+
+        if (this.metadata[term][field] == undefined) {
+          this.metadata[term][field] = Object.create(null)
+        }
+
+        for (var k = 0; k < keys.length; k++) {
+          var key = keys[k]
+
+          if (this.metadata[term][field][key] == undefined) {
+            this.metadata[term][field][key] = otherMatchData.metadata[term][field][key]
+          } else {
+            this.metadata[term][field][key] = this.metadata[term][field][key].concat(otherMatchData.metadata[term][field][key])
+          }
+
+        }
+      }
+    }
+  }
+
+  /**
+   * Add metadata for a term/field pair to this instance of match data.
+   *
+   * @param {string} term - The term this match data is associated with
+   * @param {string} field - The field in which the term was found
+   * @param {object} metadata - The metadata recorded about this term in this field
+   */
+  lunr.MatchData.prototype.add = function (term, field, metadata) {
+    if (!(term in this.metadata)) {
+      this.metadata[term] = Object.create(null)
+      this.metadata[term][field] = metadata
+      return
+    }
+
+    if (!(field in this.metadata[term])) {
+      this.metadata[term][field] = metadata
+      return
+    }
+
+    var metadataKeys = Object.keys(metadata)
+
+    for (var i = 0; i < metadataKeys.length; i++) {
+      var key = metadataKeys[i]
+
+      if (key in this.metadata[term][field]) {
+        this.metadata[term][field][key] = this.metadata[term][field][key].concat(metadata[key])
+      } else {
+        this.metadata[term][field][key] = metadata[key]
+      }
+    }
+  }
+  /**
+   * A lunr.Query provides a programmatic way of defining queries to be performed
+   * against a {@link lunr.Index}.
+   *
+   * Prefer constructing a lunr.Query using the {@link lunr.Index#query} method
+   * so the query object is pre-initialized with the right index fields.
+   *
+   * @constructor
+   * @property {lunr.Query~Clause[]} clauses - An array of query clauses.
+   * @property {string[]} allFields - An array of all available fields in a lunr.Index.
+   */
+  lunr.Query = function (allFields) {
+    this.clauses = []
+    this.allFields = allFields
+  }
+
+  /**
+   * Constants for indicating what kind of automatic wildcard insertion will be used when constructing a query clause.
+   *
+   * This allows wildcards to be added to the beginning and end of a term without having to manually do any string
+   * concatenation.
+   *
+   * The wildcard constants can be bitwise combined to select both leading and trailing wildcards.
+   *
+   * @constant
+   * @default
+   * @property {number} wildcard.NONE - The term will have no wildcards inserted, this is the default behaviour
+   * @property {number} wildcard.LEADING - Prepend the term with a wildcard, unless a leading wildcard already exists
+   * @property {number} wildcard.TRAILING - Append a wildcard to the term, unless a trailing wildcard already exists
+   * @see lunr.Query~Clause
+   * @see lunr.Query#clause
+   * @see lunr.Query#term
+   * @example <caption>query term with trailing wildcard</caption>
+   * query.term('foo', { wildcard: lunr.Query.wildcard.TRAILING })
+   * @example <caption>query term with leading and trailing wildcard</caption>
+   * query.term('foo', {
+   *   wildcard: lunr.Query.wildcard.LEADING | lunr.Query.wildcard.TRAILING
+   * })
+   */
+
+  lunr.Query.wildcard = new String ("*")
+  lunr.Query.wildcard.NONE = 0
+  lunr.Query.wildcard.LEADING = 1
+  lunr.Query.wildcard.TRAILING = 2
+
+  /**
+   * Constants for indicating what kind of presence a term must have in matching documents.
+   *
+   * @constant
+   * @enum {number}
+   * @see lunr.Query~Clause
+   * @see lunr.Query#clause
+   * @see lunr.Query#term
+   * @example <caption>query term with required presence</caption>
+   * query.term('foo', { presence: lunr.Query.presence.REQUIRED })
+   */
+  lunr.Query.presence = {
+    /**
+     * Term's presence in a document is optional, this is the default value.
+     */
+    OPTIONAL: 1,
+
+    /**
+     * Term's presence in a document is required, documents that do not contain
+     * this term will not be returned.
+     */
+    REQUIRED: 2,
+
+    /**
+     * Term's presence in a document is prohibited, documents that do contain
+     * this term will not be returned.
+     */
+    PROHIBITED: 3
+  }
+
+  /**
+   * A single clause in a {@link lunr.Query} contains a term and details on how to
+   * match that term against a {@link lunr.Index}.
+   *
+   * @typedef {Object} lunr.Query~Clause
+   * @property {string[]} fields - The fields in an index this clause should be matched against.
+   * @property {number} [boost=1] - Any boost that should be applied when matching this clause.
+   * @property {number} [editDistance] - Whether the term should have fuzzy matching applied, and how fuzzy the match should be.
+   * @property {boolean} [usePipeline] - Whether the term should be passed through the search pipeline.
+   * @property {number} [wildcard=lunr.Query.wildcard.NONE] - Whether the term should have wildcards appended or prepended.
+   * @property {number} [presence=lunr.Query.presence.OPTIONAL] - The terms presence in any matching documents.
+   */
+
+  /**
+   * Adds a {@link lunr.Query~Clause} to this query.
+   *
+   * Unless the clause contains the fields to be matched all fields will be matched. In addition
+   * a default boost of 1 is applied to the clause.
+   *
+   * @param {lunr.Query~Clause} clause - The clause to add to this query.
+   * @see lunr.Query~Clause
+   * @returns {lunr.Query}
+   */
+  lunr.Query.prototype.clause = function (clause) {
+    if (!('fields' in clause)) {
+      clause.fields = this.allFields
+    }
+
+    if (!('boost' in clause)) {
+      clause.boost = 1
+    }
+
+    if (!('usePipeline' in clause)) {
+      clause.usePipeline = true
+    }
+
+    if (!('wildcard' in clause)) {
+      clause.wildcard = lunr.Query.wildcard.NONE
+    }
+
+    if ((clause.wildcard & lunr.Query.wildcard.LEADING) && (clause.term.charAt(0) != lunr.Query.wildcard)) {
+      clause.term = "*" + clause.term
+    }
+
+    if ((clause.wildcard & lunr.Query.wildcard.TRAILING) && (clause.term.slice(-1) != lunr.Query.wildcard)) {
+      clause.term = "" + clause.term + "*"
+    }
+
+    if (!('presence' in clause)) {
+      clause.presence = lunr.Query.presence.OPTIONAL
+    }
+
+    this.clauses.push(clause)
+
+    return this
+  }
+
+  /**
+   * A negated query is one in which every clause has a presence of
+   * prohibited. These queries require some special processing to return
+   * the expected results.
+   *
+   * @returns boolean
+   */
+  lunr.Query.prototype.isNegated = function () {
+    for (var i = 0; i < this.clauses.length; i++) {
+      if (this.clauses[i].presence != lunr.Query.presence.PROHIBITED) {
+        return false
+      }
+    }
+
+    return true
+  }
+
+  /**
+   * Adds a term to the current query, under the covers this will create a {@link lunr.Query~Clause}
+   * to the list of clauses that make up this query.
+   *
+   * The term is used as is, i.e. no tokenization will be performed by this method. Instead conversion
+   * to a token or token-like string should be done before calling this method.
+   *
+   * The term will be converted to a string by calling `toString`. Multiple terms can be passed as an
+   * array, each term in the array will share the same options.
+   *
+   * @param {object|object[]} term - The term(s) to add to the query.
+   * @param {object} [options] - Any additional properties to add to the query clause.
+   * @returns {lunr.Query}
+   * @see lunr.Query#clause
+   * @see lunr.Query~Clause
+   * @example <caption>adding a single term to a query</caption>
+   * query.term("foo")
+   * @example <caption>adding a single term to a query and specifying search fields, term boost and automatic trailing wildcard</caption>
+   * query.term("foo", {
+   *   fields: ["title"],
+   *   boost: 10,
+   *   wildcard: lunr.Query.wildcard.TRAILING
+   * })
+   * @example <caption>using lunr.tokenizer to convert a string to tokens before using them as terms</caption>
+   * query.term(lunr.tokenizer("foo bar"))
+   */
+  lunr.Query.prototype.term = function (term, options) {
+    if (Array.isArray(term)) {
+      term.forEach(function (t) { this.term(t, lunr.utils.clone(options)) }, this)
+      return this
+    }
+
+    var clause = options || {}
+    clause.term = term.toString()
+
+    this.clause(clause)
+
+    return this
+  }
+  lunr.QueryParseError = function (message, start, end) {
+    this.name = "QueryParseError"
+    this.message = message
+    this.start = start
+    this.end = end
+  }
+
+  lunr.QueryParseError.prototype = new Error
+  lunr.QueryLexer = function (str) {
+    this.lexemes = []
+    this.str = str
+    this.length = str.length
+    this.pos = 0
+    this.start = 0
+    this.escapeCharPositions = []
+  }
+
+  lunr.QueryLexer.prototype.run = function () {
+    var state = lunr.QueryLexer.lexText
+
+    while (state) {
+      state = state(this)
+    }
+  }
+
+  lunr.QueryLexer.prototype.sliceString = function () {
+    var subSlices = [],
+        sliceStart = this.start,
+        sliceEnd = this.pos
+
+    for (var i = 0; i < this.escapeCharPositions.length; i++) {
+      sliceEnd = this.escapeCharPositions[i]
+      subSlices.push(this.str.slice(sliceStart, sliceEnd))
+      sliceStart = sliceEnd + 1
+    }
+
+    subSlices.push(this.str.slice(sliceStart, this.pos))
+    this.escapeCharPositions.length = 0
+
+    return subSlices.join('')
+  }
+
+  lunr.QueryLexer.prototype.emit = function (type) {
+    this.lexemes.push({
+      type: type,
+      str: this.sliceString(),
+      start: this.start,
+      end: this.pos
+    })
+
+    this.start = this.pos
+  }
+
+  lunr.QueryLexer.prototype.escapeCharacter = function () {
+    this.escapeCharPositions.push(this.pos - 1)
+    this.pos += 1
+  }
+
+  lunr.QueryLexer.prototype.next = function () {
+    if (this.pos >= this.length) {
+      return lunr.QueryLexer.EOS
+    }
+
+    var char = this.str.charAt(this.pos)
+    this.pos += 1
+    return char
+  }
+
+  lunr.QueryLexer.prototype.width = function () {
+    return this.pos - this.start
+  }
+
+  lunr.QueryLexer.prototype.ignore = function () {
+    if (this.start == this.pos) {
+      this.pos += 1
+    }
+
+    this.start = this.pos
+  }
+
+  lunr.QueryLexer.prototype.backup = function () {
+    this.pos -= 1
+  }
+
+  lunr.QueryLexer.prototype.acceptDigitRun = function () {
+    var char, charCode
+
+    do {
+      char = this.next()
+      charCode = char.charCodeAt(0)
+    } while (charCode > 47 && charCode < 58)
+
+    if (char != lunr.QueryLexer.EOS) {
+      this.backup()
+    }
+  }
+
+  lunr.QueryLexer.prototype.more = function () {
+    return this.pos < this.length
+  }
+
+  lunr.QueryLexer.EOS = 'EOS'
+  lunr.QueryLexer.FIELD = 'FIELD'
+  lunr.QueryLexer.TERM = 'TERM'
+  lunr.QueryLexer.EDIT_DISTANCE = 'EDIT_DISTANCE'
+  lunr.QueryLexer.BOOST = 'BOOST'
+  lunr.QueryLexer.PRESENCE = 'PRESENCE'
+
+  lunr.QueryLexer.lexField = function (lexer) {
+    lexer.backup()
+    lexer.emit(lunr.QueryLexer.FIELD)
+    lexer.ignore()
+    return lunr.QueryLexer.lexText
+  }
+
+  lunr.QueryLexer.lexTerm = function (lexer) {
+    if (lexer.width() > 1) {
+      lexer.backup()
+      lexer.emit(lunr.QueryLexer.TERM)
+    }
+
+    lexer.ignore()
+
+    if (lexer.more()) {
+      return lunr.QueryLexer.lexText
+    }
+  }
+
+  lunr.QueryLexer.lexEditDistance = function (lexer) {
+    lexer.ignore()
+    lexer.acceptDigitRun()
+    lexer.emit(lunr.QueryLexer.EDIT_DISTANCE)
+    return lunr.QueryLexer.lexText
+  }
+
+  lunr.QueryLexer.lexBoost = function (lexer) {
+    lexer.ignore()
+    lexer.acceptDigitRun()
+    lexer.emit(lunr.QueryLexer.BOOST)
+    return lunr.QueryLexer.lexText
+  }
+
+  lunr.QueryLexer.lexEOS = function (lexer) {
+    if (lexer.width() > 0) {
+      lexer.emit(lunr.QueryLexer.TERM)
+    }
+  }
+
+  // This matches the separator used when tokenising fields
+  // within a document. These should match otherwise it is
+  // not possible to search for some tokens within a document.
+  //
+  // It is possible for the user to change the separator on the
+  // tokenizer so it _might_ clash with any other of the special
+  // characters already used within the search string, e.g. :.
+  //
+  // This means that it is possible to change the separator in
+  // such a way that makes some words unsearchable using a search
+  // string.
+  lunr.QueryLexer.termSeparator = lunr.tokenizer.separator
+
+  lunr.QueryLexer.lexText = function (lexer) {
+    while (true) {
+      var char = lexer.next()
+
+      if (char == lunr.QueryLexer.EOS) {
+        return lunr.QueryLexer.lexEOS
+      }
+
+      // Escape character is '\'
+      if (char.charCodeAt(0) == 92) {
+        lexer.escapeCharacter()
+        continue
+      }
+
+      if (char == ":") {
+        return lunr.QueryLexer.lexField
+      }
+
+      if (char == "~") {
+        lexer.backup()
+        if (lexer.width() > 0) {
+          lexer.emit(lunr.QueryLexer.TERM)
+        }
+        return lunr.QueryLexer.lexEditDistance
+      }
+
+      if (char == "^") {
+        lexer.backup()
+        if (lexer.width() > 0) {
+          lexer.emit(lunr.QueryLexer.TERM)
+        }
+        return lunr.QueryLexer.lexBoost
+      }
+
+      // "+" indicates term presence is required
+      // checking for length to ensure that only
+      // leading "+" are considered
+      if (char == "+" && lexer.width() === 1) {
+        lexer.emit(lunr.QueryLexer.PRESENCE)
+        return lunr.QueryLexer.lexText
+      }
+
+      // "-" indicates term presence is prohibited
+      // checking for length to ensure that only
+      // leading "-" are considered
+      if (char == "-" && lexer.width() === 1) {
+        lexer.emit(lunr.QueryLexer.PRESENCE)
+        return lunr.QueryLexer.lexText
+      }
+
+      if (char.match(lunr.QueryLexer.termSeparator)) {
+        return lunr.QueryLexer.lexTerm
+      }
+    }
+  }
+
+  lunr.QueryParser = function (str, query) {
+    this.lexer = new lunr.QueryLexer (str)
+    this.query = query
+    this.currentClause = {}
+    this.lexemeIdx = 0
+  }
+
+  lunr.QueryParser.prototype.parse = function () {
+    this.lexer.run()
+    this.lexemes = this.lexer.lexemes
+
+    var state = lunr.QueryParser.parseClause
+
+    while (state) {
+      state = state(this)
+    }
+
+    return this.query
+  }
+
+  lunr.QueryParser.prototype.peekLexeme = function () {
+    return this.lexemes[this.lexemeIdx]
+  }
+
+  lunr.QueryParser.prototype.consumeLexeme = function () {
+    var lexeme = this.peekLexeme()
+    this.lexemeIdx += 1
+    return lexeme
+  }
+
+  lunr.QueryParser.prototype.nextClause = function () {
+    var completedClause = this.currentClause
+    this.query.clause(completedClause)
+    this.currentClause = {}
+  }
+
+  lunr.QueryParser.parseClause = function (parser) {
+    var lexeme = parser.peekLexeme()
+
+    if (lexeme == undefined) {
+      return
+    }
+
+    switch (lexeme.type) {
+      case lunr.QueryLexer.PRESENCE:
+        return lunr.QueryParser.parsePresence
+      case lunr.QueryLexer.FIELD:
+        return lunr.QueryParser.parseField
+      case lunr.QueryLexer.TERM:
+        return lunr.QueryParser.parseTerm
+      default:
+        var errorMessage = "expected either a field or a term, found " + lexeme.type
+
+        if (lexeme.str.length >= 1) {
+          errorMessage += " with value '" + lexeme.str + "'"
+        }
+
+        throw new lunr.QueryParseError (errorMessage, lexeme.start, lexeme.end)
+    }
+  }
+
+  lunr.QueryParser.parsePresence = function (parser) {
+    var lexeme = parser.consumeLexeme()
+
+    if (lexeme == undefined) {
+      return
+    }
+
+    switch (lexeme.str) {
+      case "-":
+        parser.currentClause.presence = lunr.Query.presence.PROHIBITED
+        break
+      case "+":
+        parser.currentClause.presence = lunr.Query.presence.REQUIRED
+        break
+      default:
+        var errorMessage = "unrecognised presence operator'" + lexeme.str + "'"
+        throw new lunr.QueryParseError (errorMessage, lexeme.start, lexeme.end)
+    }
+
+    var nextLexeme = parser.peekLexeme()
+
+    if (nextLexeme == undefined) {
+      var errorMessage = "expecting term or field, found nothing"
+      throw new lunr.QueryParseError (errorMessage, lexeme.start, lexeme.end)
+    }
+
+    switch (nextLexeme.type) {
+      case lunr.QueryLexer.FIELD:
+        return lunr.QueryParser.parseField
+      case lunr.QueryLexer.TERM:
+        return lunr.QueryParser.parseTerm
+      default:
+        var errorMessage = "expecting term or field, found '" + nextLexeme.type + "'"
+        throw new lunr.QueryParseError (errorMessage, nextLexeme.start, nextLexeme.end)
+    }
+  }
+
+  lunr.QueryParser.parseField = function (parser) {
+    var lexeme = parser.consumeLexeme()
+
+    if (lexeme == undefined) {
+      return
+    }
+
+    if (parser.query.allFields.indexOf(lexeme.str) == -1) {
+      var possibleFields = parser.query.allFields.map(function (f) { return "'" + f + "'" }).join(', '),
+          errorMessage = "unrecognised field '" + lexeme.str + "', possible fields: " + possibleFields
+
+      throw new lunr.QueryParseError (errorMessage, lexeme.start, lexeme.end)
+    }
+
+    parser.currentClause.fields = [lexeme.str]
+
+    var nextLexeme = parser.peekLexeme()
+
+    if (nextLexeme == undefined) {
+      var errorMessage = "expecting term, found nothing"
+      throw new lunr.QueryParseError (errorMessage, lexeme.start, lexeme.end)
+    }
+
+    switch (nextLexeme.type) {
+      case lunr.QueryLexer.TERM:
+        return lunr.QueryParser.parseTerm
+      default:
+        var errorMessage = "expecting term, found '" + nextLexeme.type + "'"
+        throw new lunr.QueryParseError (errorMessage, nextLexeme.start, nextLexeme.end)
+    }
+  }
+
+  lunr.QueryParser.parseTerm = function (parser) {
+    var lexeme = parser.consumeLexeme()
+
+    if (lexeme == undefined) {
+      return
+    }
+
+    parser.currentClause.term = lexeme.str.toLowerCase()
+
+    if (lexeme.str.indexOf("*") != -1) {
+      parser.currentClause.usePipeline = false
+    }
+
+    var nextLexeme = parser.peekLexeme()
+
+    if (nextLexeme == undefined) {
+      parser.nextClause()
+      return
+    }
+
+    switch (nextLexeme.type) {
+      case lunr.QueryLexer.TERM:
+        parser.nextClause()
+        return lunr.QueryParser.parseTerm
+      case lunr.QueryLexer.FIELD:
+        parser.nextClause()
+        return lunr.QueryParser.parseField
+      case lunr.QueryLexer.EDIT_DISTANCE:
+        return lunr.QueryParser.parseEditDistance
+      case lunr.QueryLexer.BOOST:
+        return lunr.QueryParser.parseBoost
+      case lunr.QueryLexer.PRESENCE:
+        parser.nextClause()
+        return lunr.QueryParser.parsePresence
+      default:
+        var errorMessage = "Unexpected lexeme type '" + nextLexeme.type + "'"
+        throw new lunr.QueryParseError (errorMessage, nextLexeme.start, nextLexeme.end)
+    }
+  }
+
+  lunr.QueryParser.parseEditDistance = function (parser) {
+    var lexeme = parser.consumeLexeme()
+
+    if (lexeme == undefined) {
+      return
+    }
+
+    var editDistance = parseInt(lexeme.str, 10)
+
+    if (isNaN(editDistance)) {
+      var errorMessage = "edit distance must be numeric"
+      throw new lunr.QueryParseError (errorMessage, lexeme.start, lexeme.end)
+    }
+
+    parser.currentClause.editDistance = editDistance
+
+    var nextLexeme = parser.peekLexeme()
+
+    if (nextLexeme == undefined) {
+      parser.nextClause()
+      return
+    }
+
+    switch (nextLexeme.type) {
+      case lunr.QueryLexer.TERM:
+        parser.nextClause()
+        return lunr.QueryParser.parseTerm
+      case lunr.QueryLexer.FIELD:
+        parser.nextClause()
+        return lunr.QueryParser.parseField
+      case lunr.QueryLexer.EDIT_DISTANCE:
+        return lunr.QueryParser.parseEditDistance
+      case lunr.QueryLexer.BOOST:
+        return lunr.QueryParser.parseBoost
+      case lunr.QueryLexer.PRESENCE:
+        parser.nextClause()
+        return lunr.QueryParser.parsePresence
+      default:
+        var errorMessage = "Unexpected lexeme type '" + nextLexeme.type + "'"
+        throw new lunr.QueryParseError (errorMessage, nextLexeme.start, nextLexeme.end)
+    }
+  }
+
+  lunr.QueryParser.parseBoost = function (parser) {
+    var lexeme = parser.consumeLexeme()
+
+    if (lexeme == undefined) {
+      return
+    }
+
+    var boost = parseInt(lexeme.str, 10)
+
+    if (isNaN(boost)) {
+      var errorMessage = "boost must be numeric"
+      throw new lunr.QueryParseError (errorMessage, lexeme.start, lexeme.end)
+    }
+
+    parser.currentClause.boost = boost
+
+    var nextLexeme = parser.peekLexeme()
+
+    if (nextLexeme == undefined) {
+      parser.nextClause()
+      return
+    }
+
+    switch (nextLexeme.type) {
+      case lunr.QueryLexer.TERM:
+        parser.nextClause()
+        return lunr.QueryParser.parseTerm
+      case lunr.QueryLexer.FIELD:
+        parser.nextClause()
+        return lunr.QueryParser.parseField
+      case lunr.QueryLexer.EDIT_DISTANCE:
+        return lunr.QueryParser.parseEditDistance
+      case lunr.QueryLexer.BOOST:
+        return lunr.QueryParser.parseBoost
+      case lunr.QueryLexer.PRESENCE:
+        parser.nextClause()
+        return lunr.QueryParser.parsePresence
+      default:
+        var errorMessage = "Unexpected lexeme type '" + nextLexeme.type + "'"
+        throw new lunr.QueryParseError (errorMessage, nextLexeme.start, nextLexeme.end)
+    }
+  }
+
+    /**
+     * export the module via AMD, CommonJS or as a browser global
+     * Export code from https://github.com/umdjs/umd/blob/master/returnExports.js
+     */
+    ;(function (root, factory) {
+      if (typeof define === 'function' && define.amd) {
+        // AMD. Register as an anonymous module.
+        define(factory)
+      } else if (typeof exports === 'object') {
+        /**
+         * Node. Does not work with strict CommonJS, but
+         * only CommonJS-like enviroments that support module.exports,
+         * like Node.
+         */
+        module.exports = factory()
+      } else {
+        // Browser globals (root is window)
+        root.lunr = factory()
+      }
+    }(this, function () {
+      /**
+       * Just return a value to define the module export.
+       * This example returns an object, but the module
+       * can return a function as the exported value.
+       */
+      return lunr
+    }))
+  })();

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