/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE
 * or https://OpenDS.dev.java.net/OpenDS.LICENSE.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE.  If applicable,
 * add the following below this CDDL HEADER, with the fields enclosed
 * by brackets "[]" replaced with your own identifying information:
 *      Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 *
 *
 *      Copyright 2009 Sun Microsystems, Inc.
 */
package org.opends.sdk;



import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.logging.Level;

import com.sun.opends.sdk.util.StaticUtils;



/**
 * A mutable sequence of bytes backed by a byte array.
 */
public final class ByteStringBuilder implements ByteSequence
{

  /**
   * A sub-sequence of the parent byte string builder. The sub-sequence
   * will be robust against all updates to the byte string builder
   * except for invocations of the method {@code clear()}.
   */
  private final class SubSequence implements ByteSequence
  {

    // The length of the sub-sequence.
    private final int subLength;

    // The offset of the sub-sequence.
    private final int subOffset;



    /**
     * Creates a new sub-sequence.
     * 
     * @param offset
     *          The offset of the sub-sequence.
     * @param length
     *          The length of the sub-sequence.
     */
    private SubSequence(int offset, int length)
    {
      this.subOffset = offset;
      this.subLength = length;
    }



    /**
     * {@inheritDoc}
     */
    public ByteSequenceReader asReader()
    {
      return new ByteSequenceReader(this);
    }



    /**
     * {@inheritDoc}
     */
    public byte byteAt(int index) throws IndexOutOfBoundsException
    {
      if (index >= subLength || index < 0)
      {
        throw new IndexOutOfBoundsException();
      }

      // Protect against reallocation: use builder's buffer.
      return buffer[subOffset + index];
    }



    /**
     * {@inheritDoc}
     */
    public int compareTo(byte[] b, int offset, int length)
        throws IndexOutOfBoundsException
    {
      ByteString.checkArrayBounds(b, offset, length);

      // Protect against reallocation: use builder's buffer.
      return ByteString.compareTo(buffer, subOffset, subLength, b,
          offset, length);
    }



    /**
     * {@inheritDoc}
     */
    public int compareTo(ByteSequence o)
    {
      if (this == o)
      {
        return 0;
      }

      // Protect against reallocation: use builder's buffer.
      return -o.compareTo(buffer, subOffset, subLength);
    }



    /**
     * {@inheritDoc}
     */
    public byte[] copyTo(byte[] b)
    {
      copyTo(b, 0);
      return b;
    }



    /**
     * {@inheritDoc}
     */
    public byte[] copyTo(byte[] b, int offset)
        throws IndexOutOfBoundsException
    {
      if (offset < 0)
      {
        throw new IndexOutOfBoundsException();
      }

      // Protect against reallocation: use builder's buffer.
      System.arraycopy(buffer, subOffset, b, offset, Math.min(
          subLength, b.length - offset));
      return b;
    }



    /**
     * {@inheritDoc}
     */
    public ByteStringBuilder copyTo(ByteStringBuilder builder)
    {
      // Protect against reallocation: use builder's buffer.
      return builder.append(buffer, subOffset, subLength);
    }



    /**
     * {@inheritDoc}
     */
    public OutputStream copyTo(OutputStream stream) throws IOException
    {
      // Protect against reallocation: use builder's buffer.
      stream.write(buffer, subOffset, subLength);
      return stream;
    }



    /**
     * {@inheritDoc}
     */
    public boolean equals(byte[] b, int offset, int length)
        throws IndexOutOfBoundsException
    {
      ByteString.checkArrayBounds(b, offset, length);

      // Protect against reallocation: use builder's buffer.
      return ByteString.equals(buffer, subOffset, subLength, b, offset,
          length);
    }



    /**
     * {@inheritDoc}
     */
    @Override
    public boolean equals(Object o)
    {
      if (this == o)
      {
        return true;
      }
      else if (o instanceof ByteSequence)
      {
        final ByteSequence other = (ByteSequence) o;

        // Protect against reallocation: use builder's buffer.
        return other.equals(buffer, subOffset, subLength);
      }
      else
      {
        return false;
      }
    }



    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode()
    {
      // Protect against reallocation: use builder's buffer.
      return ByteString.hashCode(buffer, subOffset, subLength);
    }



    /**
     * {@inheritDoc}
     */
    public int length()
    {
      return subLength;
    }



    /**
     * {@inheritDoc}
     */
    public ByteSequence subSequence(int start, int end)
        throws IndexOutOfBoundsException
    {
      if (start < 0 || start > end || end > subLength)
      {
        throw new IndexOutOfBoundsException();
      }

      return new SubSequence(subOffset + start, end - start);
    }



    /**
     * {@inheritDoc}
     */
    public byte[] toByteArray()
    {
      return copyTo(new byte[subLength]);
    }



    /**
     * {@inheritDoc}
     */
    public ByteString toByteString()
    {
      // Protect against reallocation: use builder's buffer.
      final byte[] b = new byte[subLength];
      System.arraycopy(buffer, subOffset, b, 0, subLength);
      return ByteString.wrap(b);
    }



    /**
     * {@inheritDoc}
     */
    @Override
    public String toString()
    {
      // Protect against reallocation: use builder's buffer.
      return ByteString.toString(buffer, subOffset, subLength);
    }
  }

  // These are package private so that compression and crypto
  // functionality may directly access the fields.

  // The buffer where data is stored.
  byte[] buffer;

  // The number of bytes to expose from the buffer.
  int length;



  /**
   * Creates a new byte string builder with an initial capacity of 32
   * bytes.
   */
  public ByteStringBuilder()
  {
    // Initially create a 32 byte buffer.
    this(32);
  }



  /**
   * Creates a new byte string builder with the specified initial
   * capacity.
   * 
   * @param capacity
   *          The initial capacity.
   * @throws IllegalArgumentException
   *           If the {@code capacity} is negative.
   */
  public ByteStringBuilder(int capacity)
      throws IllegalArgumentException
  {
    if (capacity < 0)
    {
      throw new IllegalArgumentException();
    }

    this.buffer = new byte[capacity];
    this.length = 0;
  }



  /**
   * Appends the provided byte to this byte string builder.
   * 
   * @param b
   *          The byte to be appended to this byte string builder.
   * @return This byte string builder.
   */
  public ByteStringBuilder append(byte b)
  {
    ensureAdditionalCapacity(1);
    buffer[length++] = b;
    return this;
  }



  /**
   * Appends the provided byte array to this byte string builder.
   * <p>
   * An invocation of the form:
   * 
   * <pre>
   * src.append(b)
   * </pre>
   * 
   * Behaves in exactly the same way as the invocation:
   * 
   * <pre>
   * src.append(b, 0, b.length);
   * </pre>
   * 
   * @param b
   *          The byte array to be appended to this byte string builder.
   * @return This byte string builder.
   */
  public ByteStringBuilder append(byte[] b)
  {
    return append(b, 0, b.length);
  }



  /**
   * Appends the provided byte array to this byte string builder.
   * 
   * @param b
   *          The byte array to be appended to this byte string builder.
   * @param offset
   *          The offset of the byte array to be used; must be
   *          non-negative and no larger than {@code b.length} .
   * @param length
   *          The length of the byte array to be used; must be
   *          non-negative and no larger than {@code b.length - offset}.
   * @return This byte string builder.
   * @throws IndexOutOfBoundsException
   *           If {@code offset} is negative or if {@code length} is
   *           negative or if {@code offset + length} is greater than
   *           {@code b.length}.
   */
  public ByteStringBuilder append(byte[] b, int offset, int length)
      throws IndexOutOfBoundsException
  {
    ByteString.checkArrayBounds(b, offset, length);

    if (length != 0)
    {
      ensureAdditionalCapacity(length);
      System.arraycopy(b, offset, buffer, this.length, length);
      this.length += length;
    }

    return this;
  }



  /**
   * Appends the provided {@code ByteBuffer} to this byte string
   * builder.
   * 
   * @param buffer
   *          The byte buffer to be appended to this byte string
   *          builder.
   * @param length
   *          The number of bytes to be appended from {@code buffer}.
   * @return This byte string builder.
   * @throws IndexOutOfBoundsException
   *           If {@code length} is less than zero or greater than
   *           {@code buffer.remaining()}.
   */
  public ByteStringBuilder append(ByteBuffer buffer, int length)
      throws IndexOutOfBoundsException
  {
    if (length < 0 || length > buffer.remaining())
    {
      throw new IndexOutOfBoundsException();
    }

    if (length != 0)
    {
      ensureAdditionalCapacity(length);
      buffer.get(this.buffer, this.length, length);
      this.length += length;
    }

    return this;
  }



  /**
   * Appends the provided {@link ByteSequence} to this byte string
   * builder.
   * 
   * @param bytes
   *          The byte sequence to be appended to this byte string
   *          builder.
   * @return This byte string builder.
   */
  public ByteStringBuilder append(ByteSequence bytes)
  {
    return bytes.copyTo(this);
  }



  /**
   * Appends the provided {@link ByteSequenceReader} to this byte string
   * builder.
   * 
   * @param reader
   *          The byte sequence reader to be appended to this byte
   *          string builder.
   * @param length
   *          The number of bytes to be appended from {@code reader}.
   * @return This byte string builder.
   * @throws IndexOutOfBoundsException
   *           If {@code length} is less than zero or greater than
   *           {@code reader.remaining()}.
   */
  public ByteStringBuilder append(ByteSequenceReader reader, int length)
      throws IndexOutOfBoundsException
  {
    if (length < 0 || length > reader.remaining())
    {
      throw new IndexOutOfBoundsException();
    }

    if (length != 0)
    {
      ensureAdditionalCapacity(length);
      reader.get(buffer, this.length, length);
      this.length += length;
    }

    return this;
  }



  /**
   * Appends the provided {@code InputStream} to this byte string
   * builder.
   * 
   * @param stream
   *          The input stream to be appended to this byte string
   *          builder.
   * @param length
   *          The maximum number of bytes to be appended from {@code
   *          buffer}.
   * @return The number of bytes read from the input stream, or {@code
   *         -1} if the end of the input stream has been reached.
   * @throws IndexOutOfBoundsException
   *           If {@code length} is less than zero.
   * @throws IOException
   *           If an I/O error occurs.
   */
  public int append(InputStream stream, int length)
      throws IndexOutOfBoundsException, IOException
  {
    if (length < 0)
    {
      throw new IndexOutOfBoundsException();
    }

    ensureAdditionalCapacity(length);
    final int bytesRead = stream.read(buffer, this.length, length);
    if (bytesRead > 0)
    {
      this.length += bytesRead;
    }

    return bytesRead;
  }



  /**
   * Appends the big-endian encoded bytes of the provided integer to
   * this byte string builder.
   * 
   * @param i
   *          The integer whose big-endian encoding is to be appended to
   *          this byte string builder.
   * @return This byte string builder.
   */
  public ByteStringBuilder append(int i)
  {
    ensureAdditionalCapacity(4);
    for (int j = length + 3; j >= length; j--)
    {
      buffer[j] = (byte) (i & 0xFF);
      i >>>= 8;
    }
    length += 4;
    return this;
  }



  /**
   * Appends the big-endian encoded bytes of the provided long to this
   * byte string builder.
   * 
   * @param l
   *          The long whose big-endian encoding is to be appended to
   *          this byte string builder.
   * @return This byte string builder.
   */
  public ByteStringBuilder append(long l)
  {
    ensureAdditionalCapacity(8);
    for (int i = length + 7; i >= length; i--)
    {
      buffer[i] = (byte) (l & 0xFF);
      l >>>= 8;
    }
    length += 8;
    return this;
  }



  /**
   * Appends the big-endian encoded bytes of the provided short to this
   * byte string builder.
   * 
   * @param i
   *          The short whose big-endian encoding is to be appended to
   *          this byte string builder.
   * @return This byte string builder.
   */
  public ByteStringBuilder append(short i)
  {
    ensureAdditionalCapacity(2);
    for (int j = length + 1; j >= length; j--)
    {
      buffer[j] = (byte) (i & 0xFF);
      i >>>= 8;
    }
    length += 2;
    return this;
  }



  /**
   * Appends the UTF-8 encoded bytes of the provided string to this byte
   * string builder.
   * 
   * @param s
   *          The string whose UTF-8 encoding is to be appended to this
   *          byte string builder.
   * @return This byte string builder.
   */
  public ByteStringBuilder append(String s)
  {
    if (s == null)
    {
      return this;
    }

    // Assume that each char is 1 byte
    final int len = s.length();
    ensureAdditionalCapacity(len);

    for (int i = 0; i < len; i++)
    {
      final char c = s.charAt(i);
      final byte b = (byte) (c & 0x0000007F);

      if (c == b)
      {
        buffer[this.length + i] = b;
      }
      else
      {
        // There is a multi-byte char. Defer to JDK
        try
        {
          return append(s.getBytes("UTF-8"));
        }
        catch (final Exception e)
        {
          if (StaticUtils.DEBUG_LOG.isLoggable(Level.WARNING))
          {
            StaticUtils.DEBUG_LOG.warning("Unable to encode String "
                + "to UTF-8 bytes: " + e.toString());
          }

          return append(s.getBytes());
        }
      }
    }

    // The 1 byte char assumption was correct
    this.length += len;
    return this;
  }



  /**
   * Appends the ASN.1 BER length encoding representation of the
   * provided integer to this byte string builder.
   * 
   * @param length
   *          The value to encode using the BER length encoding rules.
   * @return This byte string builder.
   */
  public ByteStringBuilder appendBERLength(int length)
  {
    if ((length & 0x0000007F) == length)
    {
      ensureAdditionalCapacity(1);

      buffer[this.length++] = (byte) (length & 0xFF);
    }
    else if ((length & 0x000000FF) == length)
    {
      ensureAdditionalCapacity(2);

      buffer[this.length++] = (byte) 0x81;
      buffer[this.length++] = (byte) (length & 0xFF);
    }
    else if ((length & 0x0000FFFF) == length)
    {
      ensureAdditionalCapacity(3);

      buffer[this.length++] = (byte) 0x82;
      buffer[this.length++] = (byte) (length >> 8 & 0xFF);
      buffer[this.length++] = (byte) (length & 0xFF);
    }
    else if ((length & 0x00FFFFFF) == length)
    {
      ensureAdditionalCapacity(4);

      buffer[this.length++] = (byte) 0x83;
      buffer[this.length++] = (byte) (length >> 16 & 0xFF);
      buffer[this.length++] = (byte) (length >> 8 & 0xFF);
      buffer[this.length++] = (byte) (length & 0xFF);
    }
    else
    {
      ensureAdditionalCapacity(5);

      buffer[this.length++] = (byte) 0x84;
      buffer[this.length++] = (byte) (length >> 24 & 0xFF);
      buffer[this.length++] = (byte) (length >> 16 & 0xFF);
      buffer[this.length++] = (byte) (length >> 8 & 0xFF);
      buffer[this.length++] = (byte) (length & 0xFF);
    }
    return this;
  }



  /**
   * Returns a {@link ByteSequenceReader} which can be used to
   * incrementally read and decode data from this byte string builder.
   * <p>
   * <b>NOTE:</b> all concurrent updates to this byte string builder are
   * supported with the exception of {@link #clear()}. Any invocations
   * of {@link #clear()} must be accompanied by a subsequent call to
   * {@code ByteSequenceReader.rewind()}.
   * 
   * @return The {@link ByteSequenceReader} which can be used to
   *         incrementally read and decode data from this byte string
   *         builder.
   * @see #clear()
   */
  public ByteSequenceReader asReader()
  {
    return new ByteSequenceReader(this);
  }



  /**
   * {@inheritDoc}
   */
  public byte byteAt(int index) throws IndexOutOfBoundsException
  {
    if (index >= length || index < 0)
    {
      throw new IndexOutOfBoundsException();
    }
    return buffer[index];
  }



  /**
   * Sets the length of this byte string builder to zero.
   * <p>
   * <b>NOTE:</b> if this method is called, then {@code
   * ByteSequenceReader.rewind()} must also be called on any associated
   * byte sequence readers in order for them to remain valid.
   * 
   * @return This byte string builder.
   * @see #asReader()
   */
  public ByteStringBuilder clear()
  {
    length = 0;
    return this;
  }



  /**
   * {@inheritDoc}
   */
  public int compareTo(byte[] b, int offset, int length)
      throws IndexOutOfBoundsException
  {
    ByteString.checkArrayBounds(b, offset, length);
    return ByteString.compareTo(this.buffer, 0, this.length, b, offset,
        length);
  }



  /**
   * {@inheritDoc}
   */
  public int compareTo(ByteSequence o)
  {
    if (this == o)
    {
      return 0;
    }
    return -o.compareTo(buffer, 0, length);
  }



  /**
   * {@inheritDoc}
   */
  public byte[] copyTo(byte[] b)
  {
    copyTo(b, 0);
    return b;
  }



  /**
   * {@inheritDoc}
   */
  public byte[] copyTo(byte[] b, int offset)
      throws IndexOutOfBoundsException
  {
    if (offset < 0)
    {
      throw new IndexOutOfBoundsException();
    }
    System.arraycopy(buffer, 0, b, offset, Math.min(length, b.length
        - offset));
    return b;
  }



  /**
   * {@inheritDoc}
   */
  public ByteStringBuilder copyTo(ByteStringBuilder builder)
  {
    builder.append(buffer, 0, length);
    return builder;
  }



  /**
   * {@inheritDoc}
   */
  public OutputStream copyTo(OutputStream stream) throws IOException
  {
    stream.write(buffer, 0, length);
    return stream;
  }



  /**
   * Ensures that the specified number of additional bytes will fit in
   * this byte string builder and resizes it if necessary.
   * 
   * @param size
   *          The number of additional bytes.
   * @return This byte string builder.
   */
  public ByteStringBuilder ensureAdditionalCapacity(int size)
  {
    final int newCount = this.length + size;
    if (newCount > buffer.length)
    {
      final byte[] newbuffer =
          new byte[Math.max(buffer.length << 1, newCount)];
      System.arraycopy(buffer, 0, newbuffer, 0, buffer.length);
      buffer = newbuffer;
    }
    return this;
  }



  /**
   * {@inheritDoc}
   */
  public boolean equals(byte[] b, int offset, int length)
      throws IndexOutOfBoundsException
  {
    ByteString.checkArrayBounds(b, offset, length);
    return ByteString.equals(this.buffer, 0, this.length, b, offset,
        length);
  }



  /**
   * Indicates whether the provided object is equal to this byte string
   * builder. In order for it to be considered equal, the provided
   * object must be a byte sequence containing the same bytes in the
   * same order.
   * 
   * @param o
   *          The object for which to make the determination.
   * @return {@code true} if the provided object is a byte sequence
   *         whose content is equal to that of this byte string builder,
   *         or {@code false} if not.
   */
  @Override
  public boolean equals(Object o)
  {
    if (this == o)
    {
      return true;
    }
    else if (o instanceof ByteSequence)
    {
      final ByteSequence other = (ByteSequence) o;
      return other.equals(buffer, 0, length);
    }
    else
    {
      return false;
    }
  }



  /**
   * Returns the byte array that backs this byte string builder.
   * Modifications to this byte string builder's content may cause the
   * returned array's content to be modified, and vice versa.
   * <p>
   * Note that the length of the returned array is only guaranteed to be
   * the same as the length of this byte string builder immediately
   * after a call to {@link #trimToSize()}.
   * <p>
   * In addition, subsequent modifications to this byte string builder
   * may cause the backing byte array to be reallocated thus decoupling
   * the returned byte array from this byte string builder.
   * 
   * @return The byte array that backs this byte string builder.
   */
  public byte[] getBackingArray()
  {
    return buffer;
  }



  /**
   * Returns a hash code for this byte string builder. It will be the
   * sum of all of the bytes contained in the byte string builder.
   * <p>
   * <b>NOTE:</b> subsequent changes to this byte string builder will
   * invalidate the returned hash code.
   * 
   * @return A hash code for this byte string builder.
   */
  @Override
  public int hashCode()
  {
    return ByteString.hashCode(buffer, 0, length);
  }



  /**
   * {@inheritDoc}
   */
  public int length()
  {
    return length;
  }



  /**
   * Sets the length of this byte string builder.
   * <p>
   * If the <code>newLength</code> argument is less than the current
   * length, the length is changed to the specified length.
   * <p>
   * If the <code>newLength</code> argument is greater than or equal to
   * the current length, then the capacity is increased and sufficient
   * null bytes are appended so that length becomes the
   * <code>newLength</code> argument.
   * <p>
   * The <code>newLength</code> argument must be greater than or equal
   * to <code>0</code>.
   * 
   * @param newLength
   *          The new length.
   * @return This byte string builder.
   * @throws IndexOutOfBoundsException
   *           If the <code>newLength</code> argument is negative.
   */
  public ByteStringBuilder setLength(int newLength)
  {
    if (newLength < 0)
    {
      throw new IndexOutOfBoundsException("Negative newLength: "
          + newLength);
    }

    if (newLength > length)
    {
      ensureAdditionalCapacity(newLength - length);

      // Pad with zeros.
      for (int i = length; i < newLength; i++)
      {
        buffer[i] = 0;
      }
    }
    length = newLength;

    return this;
  }



  /**
   * Returns a new byte sequence that is a subsequence of this byte
   * sequence.
   * <p>
   * The subsequence starts with the byte value at the specified {@code
   * start} index and ends with the byte value at index {@code end - 1}.
   * The length (in bytes) of the returned sequence is {@code end -
   * start}, so if {@code start == end} then an empty sequence is
   * returned.
   * <p>
   * <b>NOTE:</b> the returned sub-sequence will be robust against all
   * updates to the byte string builder except for invocations of the
   * method {@link #clear()}. If a permanent immutable byte sequence is
   * required then callers should invoke {@code toByteString()} on the
   * returned byte sequence.
   * 
   * @param start
   *          The start index, inclusive.
   * @param end
   *          The end index, exclusive.
   * @return The newly created byte subsequence.
   * @throws IndexOutOfBoundsException
   *           If {@code start} or {@code end} are negative, if {@code
   *           end} is greater than {@code length()}, or if {@code
   *           start} is greater than {@code end}.
   */
  public ByteSequence subSequence(int start, int end)
      throws IndexOutOfBoundsException
  {
    if (start < 0 || start > end || end > length)
    {
      throw new IndexOutOfBoundsException();
    }

    return new SubSequence(start, end - start);
  }



  /**
   * {@inheritDoc}
   */
  public byte[] toByteArray()
  {
    return copyTo(new byte[length]);
  }



  /**
   * Returns the {@link ByteString} representation of this byte string
   * builder. Subsequent changes to this byte string builder will not
   * modify the returned {@link ByteString}.
   * 
   * @return The {@link ByteString} representation of this byte
   *         sequence.
   */
  public ByteString toByteString()
  {
    final byte[] b = new byte[length];
    System.arraycopy(buffer, 0, b, 0, length);
    return ByteString.wrap(b);
  }



  /**
   * {@inheritDoc}
   */
  @Override
  public String toString()
  {
    return ByteString.toString(buffer, 0, length);
  }



  /**
   * Attempts to reduce storage used for this byte string builder. If
   * the buffer is larger than necessary to hold its current sequence of
   * bytes, then it may be resized to become more space efficient.
   * 
   * @return This byte string builder.
   */
  public ByteStringBuilder trimToSize()
  {
    if (buffer.length > length)
    {
      final byte[] newBuffer = new byte[length];
      System.arraycopy(buffer, 0, newBuffer, 0, length);
      buffer = newBuffer;
    }
    return this;
  }
}