/*
 * 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 2006-2008 Sun Microsystems, Inc.
 */

package org.opends.sdk.asn1;



import static com.sun.opends.sdk.messages.Messages.*;
import static org.opends.sdk.asn1.ASN1Constants.*;

import java.io.IOException;
import java.io.InputStream;
import java.util.LinkedList;
import java.util.logging.Level;

import org.opends.sdk.ByteString;
import org.opends.sdk.ByteStringBuilder;
import org.opends.sdk.DecodeException;
import org.opends.sdk.LocalizableMessage;

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



/**
 * An ASN1Reader that reads from an input stream.
 */
final class ASN1InputStreamReader extends AbstractASN1Reader implements
    ASN1Reader
{
  private int state = ELEMENT_READ_STATE_NEED_TYPE;

  private byte peekType = 0;

  private int peekLength = -1;

  private int lengthBytesNeeded = 0;

  private final int maxElementSize;

  private InputStream in;

  private final LinkedList<InputStream> streamStack;

  private byte[] buffer;



  /**
   * Creates a new ASN1 reader whose source is the provided input stream
   * and having a user defined maximum BER element size.
   *
   * @param stream
   *          The input stream to be read.
   * @param maxElementSize
   *          The maximum BER element size, or <code>0</code> to
   *          indicate that there is no limit.
   */
  ASN1InputStreamReader(InputStream stream, int maxElementSize)
  {
    this.in = stream;
    this.streamStack = new LinkedList<InputStream>();
    this.buffer = new byte[512];
    this.maxElementSize = maxElementSize;
  }



  /**
   * {@inheritDoc}
   */
  public void close() throws IOException
  {
    // Calling close of SizeLimitInputStream should close the parent
    // stream.
    in.close();
    streamStack.clear();
  }



  /**
   * {@inheritDoc}
   */
  public boolean elementAvailable() throws IOException
  {
    if ((state == ELEMENT_READ_STATE_NEED_TYPE)
        && !needTypeState(false, false))
    {
      return false;
    }
    if ((state == ELEMENT_READ_STATE_NEED_FIRST_LENGTH_BYTE)
        && !needFirstLengthByteState(false, false))
    {
      return false;
    }
    if ((state == ELEMENT_READ_STATE_NEED_ADDITIONAL_LENGTH_BYTES)
        && !needAdditionalLengthBytesState(false, false))
    {
      return false;
    }

    return peekLength <= in.available();
  }



  /**
   * {@inheritDoc}
   */
  public boolean hasNextElement() throws IOException
  {
    if (!streamStack.isEmpty())
    {
      // We are reading a sub sequence. Return true as long as we
      // haven't exhausted the size limit for the sub sequence sub input
      // stream.
      SizeLimitInputStream subSq = (SizeLimitInputStream) in;
      return (subSq.getSizeLimit() - subSq.getBytesRead() > 0);
    }

    return (state != ELEMENT_READ_STATE_NEED_TYPE)
        || needTypeState(true, false);
  }



  /**
   * {@inheritDoc}
   */
  public int peekLength() throws IOException
  {
    peekType();

    switch (state)
    {
    case ELEMENT_READ_STATE_NEED_FIRST_LENGTH_BYTE:
      needFirstLengthByteState(true, true);
      break;

    case ELEMENT_READ_STATE_NEED_ADDITIONAL_LENGTH_BYTES:
      needAdditionalLengthBytesState(true, true);
    }

    return peekLength;
  }



  /**
   * {@inheritDoc}
   */
  public byte peekType() throws IOException
  {
    if (state == ELEMENT_READ_STATE_NEED_TYPE)
    {
      needTypeState(true, true);
    }

    return peekType;
  }



  /**
   * {@inheritDoc}
   */
  public boolean readBoolean() throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    if (peekLength != 1)
    {
      LocalizableMessage message = ERR_ASN1_BOOLEAN_INVALID_LENGTH.get(peekLength);
      throw DecodeException.fatalError(message);
    }

    int readByte = in.read();
    if (readByte == -1)
    {
      LocalizableMessage message = ERR_ASN1_BOOLEAN_TRUNCATED_VALUE
          .get(peekLength);
      throw DecodeException.fatalError(message);
    }

    if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINEST))
    {
      StaticUtils.DEBUG_LOG.finest(String.format(
          "READ ASN.1 BOOLEAN(type=0x%x, length=%d, value=%s)",
          peekType, peekLength, String.valueOf(readByte != 0x00)));
    }

    state = ELEMENT_READ_STATE_NEED_TYPE;
    return readByte != 0x00;
  }



  /**
   * {@inheritDoc}
   */
  public void readEndSequence() throws IOException,
      IllegalStateException
  {
    if (streamStack.isEmpty())
    {
      LocalizableMessage message = ERR_ASN1_SEQUENCE_READ_NOT_STARTED.get();
      throw new IllegalStateException(message.toString());
    }

    // Ignore all unused trailing components.
    SizeLimitInputStream subSq = (SizeLimitInputStream) in;
    if (subSq.getSizeLimit() - subSq.getBytesRead() > 0)
    {
      if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINE))
      {
        StaticUtils.DEBUG_LOG.fine(String.format(
            "Ignoring %d unused trailing bytes in ASN.1 SEQUENCE",
            subSq.getSizeLimit() - subSq.getBytesRead()));
      }

      subSq.skip(subSq.getSizeLimit() - subSq.getBytesRead());

    }

    if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINEST))
    {
      StaticUtils.DEBUG_LOG.finest(String
          .format("READ ASN.1 END SEQUENCE"));
    }

    in = streamStack.removeFirst();

    // Reset the state
    state = ELEMENT_READ_STATE_NEED_TYPE;
  }



  /**
   * {@inheritDoc}
   */
  public void readEndSet() throws IOException
  {
    // From an implementation point of view, a set is equivalent to a
    // sequence.
    readEndSequence();
  }



  /**
   * {@inheritDoc}
   */
  public int readEnumerated() throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    if ((peekLength < 1) || (peekLength > 4))
    {
      LocalizableMessage message = ERR_ASN1_INTEGER_INVALID_LENGTH.get(peekLength);
      throw DecodeException.fatalError(message);
    }

    // From an implementation point of view, an enumerated value is
    // equivalent to an integer.
    return (int) readInteger();
  }



  /**
   * {@inheritDoc}
   */
  public long readInteger() throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    if ((peekLength < 1) || (peekLength > 8))
    {
      LocalizableMessage message = ERR_ASN1_INTEGER_INVALID_LENGTH.get(peekLength);
      throw DecodeException.fatalError(message);
    }

    if (peekLength > 4)
    {
      long longValue = 0;
      for (int i = 0; i < peekLength; i++)
      {
        int readByte = in.read();
        if (readByte == -1)
        {
          LocalizableMessage message = ERR_ASN1_INTEGER_TRUNCATED_VALUE
              .get(peekLength);
          throw DecodeException.fatalError(message);
        }
        if ((i == 0) && (((byte) readByte) < 0))
        {
          longValue = 0xFFFFFFFFFFFFFFFFL;
        }
        longValue = (longValue << 8) | (readByte & 0xFF);
      }

      state = ELEMENT_READ_STATE_NEED_TYPE;
      return longValue;
    }
    else
    {
      int intValue = 0;
      for (int i = 0; i < peekLength; i++)
      {
        int readByte = in.read();
        if (readByte == -1)
        {
          LocalizableMessage message = ERR_ASN1_INTEGER_TRUNCATED_VALUE
              .get(peekLength);
          throw DecodeException.fatalError(message);
        }
        if ((i == 0) && (((byte) readByte) < 0))
        {
          intValue = 0xFFFFFFFF;
        }
        intValue = (intValue << 8) | (readByte & 0xFF);
      }

      if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINEST))
      {
        StaticUtils.DEBUG_LOG.finest(String.format(
            "READ ASN.1 INTEGER(type=0x%x, length=%d, value=%d)",
            peekType, peekLength, intValue));
      }

      state = ELEMENT_READ_STATE_NEED_TYPE;
      return intValue;
    }
  }



  /**
   * {@inheritDoc}
   */
  public void readNull() throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    // Make sure that the decoded length is exactly zero byte.
    if (peekLength != 0)
    {
      LocalizableMessage message = ERR_ASN1_NULL_INVALID_LENGTH.get(peekLength);
      throw DecodeException.fatalError(message);
    }

    if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINEST))
    {
      StaticUtils.DEBUG_LOG.finest(String
          .format("READ ASN.1 NULL(type=0x%x, length=%d)", peekType,
              peekLength));
    }

    state = ELEMENT_READ_STATE_NEED_TYPE;
  }



  /**
   * {@inheritDoc}
   */
  public ByteString readOctetString() throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    if (peekLength == 0)
    {
      state = ELEMENT_READ_STATE_NEED_TYPE;
      return ByteString.empty();
    }

    // Copy the value and construct the element to return.
    byte[] value = new byte[peekLength];
    int bytesNeeded = peekLength;
    int bytesRead;
    while (bytesNeeded > 0)
    {
      bytesRead = in.read(value, peekLength - bytesNeeded, bytesNeeded);
      if (bytesRead < 0)
      {
        LocalizableMessage message = ERR_ASN1_OCTET_STRING_TRUNCATED_VALUE
            .get(peekLength);
        throw DecodeException.fatalError(message);
      }

      bytesNeeded -= bytesRead;
    }

    if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINEST))
    {
      StaticUtils.DEBUG_LOG.finest(String.format(
          "READ ASN.1 OCTETSTRING(type=0x%x, length=%d)", peekType,
          peekLength));
    }

    state = ELEMENT_READ_STATE_NEED_TYPE;
    return ByteString.wrap(value);
  }



  /**
   * {@inheritDoc}
   */
  public ByteStringBuilder readOctetString(ByteStringBuilder builder)
      throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    if (peekLength == 0)
    {
      state = ELEMENT_READ_STATE_NEED_TYPE;
      return builder;
    }

    // Copy the value and construct the element to return.
    int bytesNeeded = peekLength;
    int bytesRead;
    while (bytesNeeded > 0)
    {
      bytesRead = builder.append(in, bytesNeeded);
      if (bytesRead < 0)
      {
        LocalizableMessage message = ERR_ASN1_OCTET_STRING_TRUNCATED_VALUE
            .get(peekLength);
        throw DecodeException.fatalError(message);
      }
      bytesNeeded -= bytesRead;
    }

    if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINEST))
    {
      StaticUtils.DEBUG_LOG.finest(String.format(
          "READ ASN.1 OCTETSTRING(type=0x%x, length=%d)", peekType,
          peekLength));
    }

    state = ELEMENT_READ_STATE_NEED_TYPE;
    return builder;
  }



  /**
   * {@inheritDoc}
   */
  public String readOctetStringAsString() throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    if (peekLength == 0)
    {
      state = ELEMENT_READ_STATE_NEED_TYPE;
      return "";
    }

    // Resize the temp buffer if needed
    if (peekLength > buffer.length)
    {
      buffer = new byte[peekLength];
    }

    int bytesNeeded = peekLength;
    int bytesRead;
    while (bytesNeeded > 0)
    {
      bytesRead = in
          .read(buffer, peekLength - bytesNeeded, bytesNeeded);
      if (bytesRead < 0)
      {
        LocalizableMessage message = ERR_ASN1_OCTET_STRING_TRUNCATED_VALUE
            .get(peekLength);
        throw DecodeException.fatalError(message);
      }
      bytesNeeded -= bytesRead;
    }

    state = ELEMENT_READ_STATE_NEED_TYPE;

    String str;
    try
    {
      str = new String(buffer, 0, peekLength, "UTF-8");
    }
    catch (Exception e)
    {
      if (StaticUtils.DEBUG_LOG.isLoggable(Level.WARNING))
      {
        StaticUtils.DEBUG_LOG
            .warning("Unable to decode ASN.1 OCTETSTRING "
                + "bytes as UTF-8 string: " + e.toString());
      }

      str = new String(buffer, 0, peekLength);
    }

    if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINEST))
    {
      StaticUtils.DEBUG_LOG.finest(String.format(
          "READ ASN.1 OCTETSTRING(type=0x%x, length=%d, value=%s)",
          peekType, peekLength, str));
    }

    return str;
  }



  /**
   * {@inheritDoc}
   */
  public void readStartSequence() throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    SizeLimitInputStream subStream = new SizeLimitInputStream(in,
        peekLength);

    if (StaticUtils.DEBUG_LOG.isLoggable(Level.FINEST))
    {
      StaticUtils.DEBUG_LOG.finest(String.format(
          "READ ASN.1 START SEQUENCE(type=0x%x, length=%d)", peekType,
          peekLength));
    }

    streamStack.addFirst(in);
    in = subStream;

    // Reset the state
    state = ELEMENT_READ_STATE_NEED_TYPE;
  }



  /**
   * {@inheritDoc}
   */
  public void readStartSet() throws IOException
  {
    // From an implementation point of view, a set is equivalent to a
    // sequence.
    readStartSequence();
  }



  /**
   * {@inheritDoc}
   */
  public ASN1Reader skipElement() throws IOException
  {
    // Read the header if haven't done so already
    peekLength();

    long bytesSkipped = in.skip(peekLength);
    if (bytesSkipped != peekLength)
    {
      LocalizableMessage message = ERR_ASN1_SKIP_TRUNCATED_VALUE.get(peekLength);
      throw DecodeException.fatalError(message);
    }
    state = ELEMENT_READ_STATE_NEED_TYPE;
    return this;
  }



  /**
   * Internal helper method reading the additional ASN.1 length bytes
   * and transition to the next state if successful.
   *
   * @param isBlocking
   *          <code>true</code> to block if the type byte is not
   *          available or <code>false</code> to check for availability
   *          first.
   * @param throwEofException
   *          <code>true</code> to throw an exception when an EOF is
   *          encountered or <code>false</code> to return false.
   * @return <code>true</code> if the length bytes was successfully
   *         read.
   * @throws IOException
   *           If an error occurs while reading from the stream.
   */
  private boolean needAdditionalLengthBytesState(boolean isBlocking,
      boolean throwEofException) throws IOException
  {
    if (!isBlocking && (in.available() < lengthBytesNeeded))
    {
      return false;
    }

    int readByte;
    while (lengthBytesNeeded > 0)
    {
      readByte = in.read();
      if (readByte == -1)
      {
        state = ELEMENT_READ_STATE_NEED_ADDITIONAL_LENGTH_BYTES;
        if (throwEofException)
        {
          LocalizableMessage message = ERR_ASN1_TRUNCATED_LENGTH_BYTES
              .get(lengthBytesNeeded);
          throw DecodeException.fatalError(message);
        }
        return false;
      }
      peekLength = (peekLength << 8) | (readByte & 0xFF);
      lengthBytesNeeded--;
    }

    // Make sure that the element is not larger than the maximum allowed
    // message size.
    if ((maxElementSize > 0) && (peekLength > maxElementSize))
    {
      LocalizableMessage message = ERR_LDAP_CLIENT_DECODE_MAX_REQUEST_SIZE_EXCEEDED
          .get(peekLength, maxElementSize);
      throw DecodeException.fatalError(message);
    }
    state = ELEMENT_READ_STATE_NEED_VALUE_BYTES;
    return true;
  }



  /**
   * Internal helper method reading the first length bytes and
   * transition to the next state if successful.
   *
   * @param isBlocking
   *          <code>true</code> to block if the type byte is not
   *          available or <code>false</code> to check for availability
   *          first.
   * @param throwEofException
   *          <code>true</code> to throw an exception when an EOF is
   *          encountered or <code>false</code> to return false.
   * @return <code>true</code> if the length bytes was successfully read
   * @throws IOException
   *           If an error occurs while reading from the stream.
   */
  private boolean needFirstLengthByteState(boolean isBlocking,
      boolean throwEofException) throws IOException
  {
    if (!isBlocking && (in.available() <= 0))
    {
      return false;
    }

    int readByte = in.read();
    if (readByte == -1)
    {
      if (throwEofException)
      {
        LocalizableMessage message = ERR_ASN1_TRUNCATED_LENGTH_BYTE.get();
        throw DecodeException.fatalError(message);
      }
      return false;
    }
    peekLength = (readByte & 0x7F);
    if (peekLength != readByte)
    {
      lengthBytesNeeded = peekLength;
      if (lengthBytesNeeded > 4)
      {
        LocalizableMessage message = ERR_ASN1_INVALID_NUM_LENGTH_BYTES
            .get(lengthBytesNeeded);
        throw DecodeException.fatalError(message);
      }
      peekLength = 0x00;

      if (!isBlocking && (in.available() < lengthBytesNeeded))
      {
        state = ELEMENT_READ_STATE_NEED_ADDITIONAL_LENGTH_BYTES;
        return false;
      }

      while (lengthBytesNeeded > 0)
      {
        readByte = in.read();
        if (readByte == -1)
        {
          state = ELEMENT_READ_STATE_NEED_ADDITIONAL_LENGTH_BYTES;
          if (throwEofException)
          {
            LocalizableMessage message = ERR_ASN1_TRUNCATED_LENGTH_BYTES
                .get(lengthBytesNeeded);
            throw DecodeException.fatalError(message);
          }
          return false;
        }
        peekLength = (peekLength << 8) | (readByte & 0xFF);
        lengthBytesNeeded--;
      }
    }

    // Make sure that the element is not larger than the maximum allowed
    // message size.
    if ((maxElementSize > 0) && (peekLength > maxElementSize))
    {
      LocalizableMessage message = ERR_LDAP_CLIENT_DECODE_MAX_REQUEST_SIZE_EXCEEDED
          .get(peekLength, maxElementSize);
      throw DecodeException.fatalError(message);
    }
    state = ELEMENT_READ_STATE_NEED_VALUE_BYTES;
    return true;
  }



  /**
   * Internal helper method reading the ASN.1 type byte and transition
   * to the next state if successful.
   *
   * @param isBlocking
   *          <code>true</code> to block if the type byte is not
   *          available or <code>false</code> to check for availability
   *          first.
   * @param throwEofException
   *          <code>true</code> to throw an exception when an EOF is
   *          encountered or <code>false</code> to return false.
   * @return <code>true</code> if the type byte was successfully read
   * @throws IOException
   *           If an error occurs while reading from the stream.
   */
  private boolean needTypeState(boolean isBlocking,
      boolean throwEofException) throws IOException
  {
    // Read just the type.
    if (!isBlocking && (in.available() <= 0))
    {
      return false;
    }

    int type = in.read();
    if (type == -1)
    {
      if (throwEofException)
      {
        LocalizableMessage message = ERR_ASN1_TRUCATED_TYPE_BYTE.get();
        throw DecodeException.fatalError(message);
      }
      return false;
    }

    peekType = (byte) type;
    state = ELEMENT_READ_STATE_NEED_FIRST_LENGTH_BYTE;
    return true;
  }
}