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/**
 * Copyright 2015 Red Hat, Inc.
 *
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  and Apache License v2.0 which accompanies this distribution.
 *
 *  The Eclipse Public License is available at
 *  http://www.eclipse.org/legal/epl-v10.html
 *
 *  The Apache License v2.0 is available at
 *  http://www.opensource.org/licenses/apache2.0.php
 *
 *  You may elect to redistribute this code under either of these licenses.
 */
package io.vertx.redis.impl;

import io.vertx.core.Handler;
import io.vertx.core.buffer.Buffer;

public class ReplyParser implements Handler {
  
  private static class IndexOutOfBoundsException extends Exception {
    public IndexOutOfBoundsException(String message) {
      super(message);
    }
    
    @Override
    public synchronized Throwable fillInStackTrace() {
      return this;
    }
  }

  private Buffer _buffer;
  private int _offset;
  private final String _encoding = "utf-8";

  private final Handler handler;

  public ReplyParser(Handler handler) {
    this.handler = handler;
  }

  public void reset() {
    _buffer = null;
    _offset = 0;
  }


  private Reply parseResult(byte type) throws IndexOutOfBoundsException {
    int start, end, offset;
    int packetSize;

    if (type == '+' || type == '-') {
      // up to the delimiter
      end = packetEndOffset() - 1;
      start = _offset;

      // include the delimiter
      _offset = end + 2;

      if (end > _buffer.length()) {
        _offset = start;
        throw new IndexOutOfBoundsException("Wait for more data.");
      }

      if (type == '+') {
        return new Reply(type, _buffer.getString(start, end, _encoding));
      } else {
        return new Reply(type, _buffer.getString(start, end, _encoding));
      }
    } else if (type == ':') {
      // up to the delimiter
      end = packetEndOffset() - 1;
      start = _offset;

      // include the delimiter
      _offset = end + 2;

      if (end > _buffer.length()) {
        _offset = start;
        throw new IndexOutOfBoundsException("Wait for more data.");
      }

      // return the coerced numeric value
      return new Reply(type, Long.parseLong(_buffer.getString(start, end)));
    } else if (type == '$') {
      // set a rewind point, as the packet could be larger than the
      // buffer in memory
      offset = _offset - 1;

      packetSize = parsePacketSize();

      // packets with a size of -1 are considered null
      if (packetSize == -1) {
        return new Reply(type, null);
      }

      end = _offset + packetSize;
      start = _offset;

      // set the offset to after the delimiter
      _offset = end + 2;

      if (end > _buffer.length()) {
        _offset = offset;
        throw new IndexOutOfBoundsException("Wait for more data.");
      }

      return new Reply(type, _buffer.getBuffer(start, end));
    } else if (type == '*') {
      offset = _offset;
      packetSize = parsePacketSize();

      // packets with a size of -1 are considered null
      if (packetSize == -1) {
        return new Reply(type, null);
      }

      if (packetSize > bytesRemaining()) {
        _offset = offset - 1;
        throw new IndexOutOfBoundsException("Wait for more data.");
      }

      Reply reply = new Reply(type, packetSize);

      byte ntype;
      Reply res;

      for (int i = 0; i < packetSize; i++) {
        if (_offset + 1 >= _buffer.length()) {
          throw new IndexOutOfBoundsException("Wait for more data.");
        }

        ntype = _buffer.getByte(_offset++);

        res = parseResult(ntype);
        reply.set(i, res);
      }

      return reply;
    }

    throw new RuntimeException("Unsupported message type");
  }

  public void handle(Buffer buffer) {

    append(buffer);

    byte type;
    int offset;

    loop:
    while (true) {
      offset = _offset;
      try {
        // at least 4 bytes: :1\r\n
        if (bytesRemaining() < 4) {
          break;
        }

        type = _buffer.getByte(_offset++);

        switch (type) {
          case '*':
            // set a rewind point. if a failure occurs,
            // wait for the next handle()/append() and try again
            offset = _offset - 1;
          case '+':
          case '-':
          case ':':
          case '$':
            final Reply ret = parseResult(type);

            if (ret == null) {
              break loop;
            }

            handler.handle(ret);
            break;
        }
      } catch (IndexOutOfBoundsException err) {
        // catch the error (not enough data), rewind, and wait
        // for the next packet to appear
        _offset = offset;
        break;
      }
    }
  }

  private void append(Buffer newBuffer) {
    if (newBuffer == null) {
      return;
    }

    // first run
    if (_buffer == null) {
      _buffer = newBuffer;

      return;
    }

    // out of data
    if (_offset >= _buffer.length()) {
      _buffer = newBuffer;
      _offset = 0;

      return;
    }

    // very large packet
    if (_offset > 0) {
      _buffer = _buffer.getBuffer(_offset, _buffer.length());
    }
    _buffer.appendBuffer(newBuffer);

    _offset = 0;
  }

  private int parsePacketSize() throws IndexOutOfBoundsException {
    int end = packetEndOffset();
    String value = _buffer.getString(_offset, end - 1, _encoding);

    _offset = end + 1;

    long size = Long.parseLong(value);

    if (size > Integer.MAX_VALUE) {
      throw new RuntimeException("Cannot allocate more than " + Integer.MAX_VALUE + " bytes");
    }

    if (size < Integer.MIN_VALUE) {
      throw new RuntimeException("Cannot allocate less than " + Integer.MIN_VALUE + " bytes");
    }
    return (int) size;
  }

  private int packetEndOffset() throws IndexOutOfBoundsException {
    int offset = _offset;

    if (offset + 1 >= _buffer.length()) {
      throw new IndexOutOfBoundsException("Not enough data.");
    }

    while (_buffer.getByte(offset) != '\r' && _buffer.getByte(offset + 1) != '\n') {
      offset++;

      if (offset + 1 == _buffer.length()) {
        throw new IndexOutOfBoundsException("didn't see LF after NL reading multi bulk count (" + offset + " => " + _buffer.length() + ", " + _offset + ")");
      }
    }

    offset++;
    return offset;
  }

  private int bytesRemaining() {
    return (_buffer.length() - _offset) < 0 ? 0 : (_buffer.length() - _offset);
  }
}