var Writer = function(size) {
  this.size = size || 1024;
  this.buffer = new Buffer(this.size + 5);
  this.offset = 5;
};

var p = Writer.prototype;

//resizes internal buffer if not enough size left
p._ensure = function(size) {
  var remaining = this.buffer.length - this.offset;
  if(remaining < size) {
    var oldBuffer = this.buffer;
    this.buffer = Buffer(oldBuffer.length + size);
    oldBuffer.copy(this.buffer);
  }
}

p.addInt32 = function(num) {
  this._ensure(4)
  this.buffer[this.offset++] = (num >>> 24 & 0xFF)
  this.buffer[this.offset++] = (num >>> 16 & 0xFF)
  this.buffer[this.offset++] = (num >>>  8 & 0xFF)
  this.buffer[this.offset++] = (num >>>  0 & 0xFF)
  return this;
}

p.addInt16 = function(num) {
  this._ensure(2)
  this.buffer[this.offset++] = (num >>>  8 & 0xFF)
  this.buffer[this.offset++] = (num >>>  0 & 0xFF)
  return this;
}

p.addCString = function(string) {
  var string = string || "";
  var len = Buffer.byteLength(string) + 1;
  this._ensure(len);
  this.buffer.write(string, this.offset);
  this.offset += len;
  this.buffer[this.offset] = 0; //add null terminator
  return this;
}

p.addChar = function(char) {
  this._ensure(1);
  this.buffer.write(char, this.offset);
  this.offset++;
  return this;
}

p.addString = function(string) {
  var string = string || "";
  var len = Buffer.byteLength(string);
  this._ensure(len);
  this.buffer.write(string, this.offset);
  this.offset += len;
  return this;
}

p.getByteLength = function() {
  return this.offset - 5;
}

p.add = function(otherBuffer) {
  this._ensure(otherBuffer.length);
  otherBuffer.copy(this.buffer, this.offset);
  this.offset += otherBuffer.length;
  return this;
}

p.clear = function() {
  this.offset=5;
}

p.join = function(code) {
  if(code) {
    var end = this.offset;
    this.offset = 0;
    this.buffer[this.offset++] = code;
    //write the length which is length of entire packet not including
    //message type code byte
    this.addInt32(end - 1);
    this.offset = end;
  }
  return this.buffer.slice(code ? 0 : 5, this.offset);
}

p.flush = function(code) {
  var result = this.join(code);
  this.clear();
  return result;
}

module.exports = Writer;