var Util           = require('util');
var EventEmitter   = require('events').EventEmitter;
var Packets        = require('../packets');
var ErrorConstants = require('../constants/errors');
var Timer          = require('../Timer');

// istanbul ignore next: Node.js < 0.10 not covered
var listenerCount = EventEmitter.listenerCount
  || function(emitter, type){ return emitter.listeners(type).length; };

var LONG_STACK_DELIMITER = '\n    --------------------\n';

module.exports = Sequence;
Util.inherits(Sequence, EventEmitter);
function Sequence(options, callback) {
  if (typeof options === 'function') {
    callback = options;
    options = {};
  }

  EventEmitter.call(this);

  options = options || {};

  this._callback = callback;
  this._callSite = null;
  this._ended    = false;
  this._timeout  = options.timeout;
  this._timer    = new Timer(this);
}

Sequence.determinePacket = function(byte) {
  switch (byte) {
    case 0x00: return Packets.OkPacket;
    case 0xfe: return Packets.EofPacket;
    case 0xff: return Packets.ErrorPacket;
    default:   return undefined;
  }
};

Sequence.prototype.hasErrorHandler = function() {
  return Boolean(this._callback) || listenerCount(this, 'error') > 1;
};

Sequence.prototype._packetToError = function(packet) {
  var code = ErrorConstants[packet.errno] || 'UNKNOWN_CODE_PLEASE_REPORT';
  var err  = new Error(code + ': ' + packet.message);
  err.code = code;
  err.errno = packet.errno;

  err.sqlMessage = packet.message;
  err.sqlState   = packet.sqlState;

  return err;
};

Sequence.prototype.end = function(err) {
  if (this._ended) {
    return;
  }

  this._ended = true;

  if (err) {
    this._addLongStackTrace(err);
  }

  // Without this we are leaking memory. This problem was introduced in
  // 8189925374e7ce3819bbe88b64c7b15abac96b16. I suspect that the error object
  // causes a cyclic reference that the GC does not detect properly, but I was
  // unable to produce a standalone version of this leak. This would be a great
  // challenge for somebody interested in difficult problems : )!
  this._callSite = null;

  // try...finally for exception safety
  try {
    if (err) {
      this.emit('error', err);
    }
  } finally {
    try {
      if (this._callback) {
        this._callback.apply(this, arguments);
      }
    } finally {
      this.emit('end');
    }
  }
};

Sequence.prototype['OkPacket'] = function(packet) {
  this.end(null, packet);
};

Sequence.prototype['ErrorPacket'] = function(packet) {
  this.end(this._packetToError(packet));
};

// Implemented by child classes
Sequence.prototype.start = function() {};

Sequence.prototype._addLongStackTrace = function _addLongStackTrace(err) {
  var callSiteStack = this._callSite && this._callSite.stack;

  if (!callSiteStack || typeof callSiteStack !== 'string') {
    // No recorded call site
    return;
  }

  if (err.stack.indexOf(LONG_STACK_DELIMITER) !== -1) {
    // Error stack already looks long
    return;
  }

  var index = callSiteStack.indexOf('\n');

  if (index !== -1) {
    // Append recorded call site
    err.stack += LONG_STACK_DELIMITER + callSiteStack.substr(index + 1);
  }
};

Sequence.prototype._onTimeout = function _onTimeout() {
  this.emit('timeout');
};