//var BigNumber = require("bignumber.js");
var ErrorCodeToName = require('../constants/errors').codeToName;

var bn = require('bn.js');

function Packet(id, buffer, start, end)
{
  this.sequenceId = id;
  this.buffer = buffer;
  this.offset = start || 0;
  this.start = start || 0;
  this.end = end || this.buffer.length;
}

// ==============================
// readers
// ==============================

Packet.prototype.reset = function() {
  this.offset = this.start;
};

Packet.prototype.length = function() {
  return this.end - this.start;
};

Packet.prototype.slice = function() {
  return this.buffer.slice(this.start, this.end);
};

Packet.prototype.dump = function() {
  console.log([this.buffer.asciiSlice(this.start, this.end)], this.buffer.slice(this.start, this.end), this.length(), this.sequenceId);
};

Packet.prototype.haveMoreData = function() {
  return this.end > this.offset;
};

Packet.prototype.skip = function(num) {
   if (!num)
     throw "Bad param in skip!"; // for some reason I keep doing skip(0) to indicate "skip one byte which should be 0"
   this.offset += num;
};

Packet.prototype.readInt8 = function()
{
  return this.buffer[this.offset++];
};

Packet.prototype.readInt16 = function()
{
  this.offset += 2;
  return this.buffer.readUInt16LE(this.offset - 2, true);
};

Packet.prototype.readInt24 = function() {
  return this.readInt16() + (this.readInt8() << 16);
};

Packet.prototype.readInt32 = function()
{
  this.offset += 4;
  return this.buffer.readUInt32LE(this.offset - 4, true);
};

Packet.prototype.readSInt8 = function()
{
  return this.buffer.readInt8(this.offset++, true);
};

Packet.prototype.readSInt16 = function()
{
  this.offset += 2;
  return this.buffer.readInt16LE(this.offset - 2, true);
};

Packet.prototype.readSInt32 = function()
{
  this.offset += 4;
  return this.buffer.readInt32LE(this.offset - 4, true);
};

Packet.prototype.readInt64 = function() {
  return this.readInt32() + 0x100000000*this.readInt32();
};

Packet.prototype.readSInt64 = function() {
  var word0 = this.readInt32();
  var word1 = this.readInt32();
  if (!(word1 & 0x80000000))
    return word0 + 0x100000000*word1;
  return -((((~word1)>>>0) * 0x100000000) + ((~word0)>>>0) + 1);
};

Packet.prototype.isEOF = function() {
  return this.buffer[this.offset] == 0xfe && this.length() < 9;
};

Packet.prototype.eofStatusFlags = function() {
  return this.buffer.readInt16LE(this.offset + 3);
};

Packet.prototype.eofWarningCount = function() {
  return this.buffer.readInt16LE(this.offset + 1);
};

Packet.prototype.readLengthCodedNumber = function(bigNumberStrings) {
   var word0, word1;
   var res;
   var byte1 = this.readInt8();
   if (byte1 < 0xfb)
     return byte1;
   if (byte1 == 0xfc) {
     return this.readInt8() + (this.readInt8() << 8);
   }
   if (byte1 == 0xfd) {
     return this.readInt8() + (this.readInt8() << 8) + (this.readInt8() << 16);
   }
   if (byte1 == 0xfe) {
     // TODO: check version
     // Up to MySQL 3.22, 0xfe was followed by a 4-byte integer.
     word0 = this.readInt32();
     word1 = this.readInt32();
     if (word1 === 0)
       return word0; // don't convert to float if possible
     if (word1 < 2097152) // max exact float point int, 2^52 / 2^32
       return  word1*0x100000000 + word0;

     res = (new bn(word1)).ishln(32).iaddn(word0);
     return bigNumberStrings ? res.toString() : res;
   }
   if (byte1 == 0xfb)
     return null;

   console.trace();
   throw "Should not reach here: " + byte1;
};

Packet.prototype.readFloat = function() {
  var res = this.buffer.readFloatLE(this.offset);
  this.offset += 4;
  return res;
};

Packet.prototype.readDouble = function() {
  var res = this.buffer.readDoubleLE(this.offset);
  this.offset += 8;
  return res;
};

Packet.prototype.readBuffer = function(len) {
  if (typeof len == 'undefined')
    len = this.end - this.offset;
  this.offset += len;
  return this.buffer.slice(this.offset - len, this.offset);
};

var INVALID_DATE = new Date(NaN);
// DATE, DATETIME and TIMESTAMP
Packet.prototype.readDateTime = function() {
  var length = this.readInt8();
  var y = 0;
  var m = 0;
  var d = 0;
  var H = 0;
  var M = 0;
  var S = 0;
  var ms = 0;
  if (length > 3) {
    y = this.readInt16();
    m = this.readInt8();
    d = this.readInt8();

  }
  if (length > 6) {
    H = this.readInt8();
    M = this.readInt8();
    S = this.readInt8();
  }
  if (length > 11)
    ms = this.readInt32();
  if ((y + m + d + H + M + S + ms) === 0) {
    return INVALID_DATE;
  }
  return new Date(y, m-1, d, H, M, S, ms);
};

// this is nearly duplicate of previous function so generated code is not slower
// due to "if (dateStrings)" branching
var pad = "000000000000";
function leftPad(num, value) {
  var s = value.toString();
  // if we don't need to pad
  if (s.length >= num)
    return s;
  return (pad + s).slice(-num);
}

Packet.prototype.readDateTimeString = function() {
  var length = this.readInt8();
  var y = 0;
  var m = 0;
  var d = 0;
  var H = 0;
  var M = 0;
  var S = 0;
  var ms = 0;
  var str;
  if (length > 3) {
    y = this.readInt16();
    m = this.readInt8();
    d = this.readInt8();
    str =  [leftPad(4, y), leftPad(2, m), leftPad(2, d)].join('-');
  }
  if (length > 6) {
    H = this.readInt8();
    M = this.readInt8();
    S = this.readInt8();
    str += ' ' + [leftPad(2, H), leftPad(2, M), leftPad(2, S)].join(':');
  }
  /* in text protocol you don't see microseconds as DATETIME/TIMESTAMP result.
     instead you need to use MICROSECOND() function
  if (length > 11) {
    ms = this.readInt32();
  }
  */
  return str;
};

// TIME - value as a string, Can be negative
Packet.prototype.readTimeString = function(convertTtoMs) {
  var length = this.readInt8();
  if (length === 0)
    return 0;

  var result = 0;
  var sign = this.readInt8() ? -1 : 1; // 'isNegative' flag byte
  var d = 0;
  var H = 0;
  var M = 0;
  var S = 0;
  var ms = 0;
  if (length > 7) {
    d = this.readInt32();
    H = this.readInt8();
    M = this.readInt8();
    S = this.readInt8();
  }
  if (length > 11)
    ms = this.readInt32();

  if (convertTtoMs) {
    H += d * 24;
    M += H * 60;
    S += M * 60;
    ms += S * 1000;
    ms *= sign;
    return ms;
  }
  return ( sign === -1 ? '-' : '' ) + [( d ? (d*24) + H : H ), leftPad(2, M), leftPad(2, S)].join(':') + ( ms ? '.'+ ms : '' );
};

Packet.prototype.readLengthCodedString = function() {
  var len = this.readLengthCodedNumber();
  // TODO: check manually first byte here to avoid polymorphic return type?
  if (len === null)
    return null;
  this.offset += len;
  return this.buffer.utf8Slice(this.offset - len, this.offset);
};

Packet.prototype.readLengthCodedBuffer = function() {
  var len = this.readLengthCodedNumber();
  return this.readBuffer(len);
};

Packet.prototype.readNullTerminatedString = function() {
  var start = this.offset;
  var end = this.offset;
  while (this.buffer[end])
    end = end + 1; // TODO: handle OOB check
  this.offset = end + 1;
  return this.buffer.utf8Slice(start, end);
};

// TODO reuse?
Packet.prototype.readString = function(len) {
  if (typeof len == 'undefined')
    len = this.end - this.offset;
  this.offset += len;
  return this.buffer.utf8Slice(this.offset - len, this.offset);
};

var minus = '-'.charCodeAt(0);
var plus = '+'.charCodeAt(0);
// TODO: faster versions of parseInt for smaller types?
// discard overflow checks if we know from type definition it's safe so
Packet.prototype.parseInt = function(len) {

  if (len === null)
    return null;

  var result = 0;
  var end = this.offset + len;
  var sign = 1;
  if (len === 0)
    return 0; // TODO: assert? exception?
  if (this.buffer[this.offset] == minus) {
    this.offset++;
    sign = -1;
  }

  // max precise int is 9007199254740992
  // note that we are here after handling optional +/-
  // treat everything above 9000000000000000 as potential overflow
  var str;
  var numDigits = end - this.offset;
  if (numDigits == 16 && (this.buffer[this.offset] - 48) > 8) {
    str = this.readString(end - this.offset);
    result = parseInt(str, 10);
    if (result.toString() == str)
      return sign*result;
    else
      return sign == -1 ? "-" + str : str;
  } else if (numDigits > 16) {
    str = this.readString(end - this.offset);
    return sign == -1 ? "-" + str : str;
  }

  if (this.buffer[this.offset] == plus) {
    this.offset++; // just ignore
  }
  while(this.offset < end) {
    result *= 10;
    result += this.buffer[this.offset] - 48;
    this.offset++;
  }
  return result*sign;
};

// copy-paste from https://github.com/felixge/node-mysql/blob/master/lib/protocol/Parser.js
Packet.prototype.parseGeometryValue = function() {
  var buffer = this.readLengthCodedBuffer();
  var offset = 4;

  if (buffer === null || !buffer.length) {
    return null;
  }

  function parseGeometry() {
    var x, y, i, j, numPoints, line;
    var result = null;
    var byteOrder = buffer.readUInt8(offset); offset += 1;
    var wkbType = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
    switch(wkbType) {
      case 1: // WKBPoint
        x = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
        y = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
        result = {x: x, y: y};
        break;
      case 2: // WKBLineString
        numPoints = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
        result = [];
        for(i=numPoints;i>0;i--) {
          x = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
          y = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
          result.push({x: x, y: y});
        }
        break;
      case 3: // WKBPolygon
        var numRings = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
        result = [];
        for(i=numRings;i>0;i--) {
          numPoints = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
          line = [];
          for(j=numPoints;j>0;j--) {
            x = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
            y = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
            line.push({x: x, y: y});
          }
          result.push(line);
        }
        break;
      case 4: // WKBMultiPoint
      case 5: // WKBMultiLineString
      case 6: // WKBMultiPolygon
      case 7: // WKBGeometryCollection
        var num = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
        result = [];
        for(i=num;i>0;i--) {
          result.push(parseGeometry());
        }
        break;
    }
    return result;
  }
  return parseGeometry();
};

Packet.prototype.parseDate = function() {
  var strLen = this.readLengthCodedNumber();
  if (strLen === null)
    return null;
  if (strLen != 10) {
    // we expect only YYYY-MM-DD here.
    // if for some reason it's not the case return invalid date
    return new Date(NaN);
  }
  var y = this.parseInt(4);
  this.offset++; // -
  var m = this.parseInt(2);
  this.offset++; // -
  var d = this.parseInt(2);
  return new Date(y, m-1, d);
};

Packet.prototype.parseDateTime = function() {
  var str = this.readLengthCodedString();
  if (str === null)
    return null;
  return new Date(str);
};


// TODO: handle E notation
var dot = '.'.charCodeAt(0);
var exponent = 'e'.charCodeAt(0);
var exponentCapital = 'E'.charCodeAt(0);
Packet.prototype.parseFloat = function(len) {

  if (len === null)
    return null;

  var result = 0;
  var end = this.offset + len;
  var factor = 1;
  var pastDot = false;
  var charCode = 0;
  if (len === 0)
    return 0; // TODO: assert? exception?

  if (this.buffer[this.offset] == minus) {
    this.offset++;
    factor = -1;
  }
  if (this.buffer[this.offset] == plus) {
    this.offset++; // just ignore
  }
  while(this.offset < end) {
    charCode = this.buffer[this.offset];
    if (charCode == dot)
    {
      pastDot = true;
      this.offset++;
    } else if (charCode == exponent || charCode == exponentCapital) {
      this.offset++;
      var exponentValue = this.parseInt(end - this.offset);
      return (result/factor)*Math.pow(10, exponentValue);
    } else {
      result *= 10;
      result += this.buffer[this.offset] - 48;
      this.offset++;
      if (pastDot)
        factor = factor*10;
    }
  }
  return result/factor;
};

Packet.prototype.parseLengthCodedInt = function() {
  return this.parseInt(this.readLengthCodedNumber());
};

Packet.prototype.parseLengthCodedFloat = function() {
  return this.parseFloat(this.readLengthCodedNumber());
};

Packet.prototype.isError = function() {
  return this.buffer[this.offset] == 0xff;
};

Packet.prototype.asError = function() {
  this.reset();

  var fieldCount = this.readInt8();
  var errorCode = this.readInt16();
  var sqlState  = '';
  if (this.buffer[this.offset] == 0x23)
    sqlState = this.readBuffer(6).toString();
  var message = this.readString();
  var err = new Error(message);
  err.code = ErrorCodeToName[errorCode];
  err.sqlState = sqlState;
  return err;
};


Packet.lengthCodedNumberLength = function(n) {
   if (n < 0xfb)
     return 1;
   if (n < 0xffff)
     return 3;
   if (n < 0xffffff)
     return 5;
   else
     return 9;
};

Packet.prototype.writeInt32 = function(n) {
  this.buffer.writeUInt32LE(n, this.offset);
  this.offset += 4;
};

Packet.prototype.writeInt24 = function(n) {
  this.writeInt8(n & 0xff);
  this.writeInt16(n >> 8);
};

Packet.prototype.writeInt16 = function(n) {
  this.buffer.writeUInt16LE(n, this.offset);
  this.offset += 2;
};

Packet.prototype.writeInt8 = function(n) {
  this.buffer.writeUInt8(n, this.offset);
  this.offset++;
};

Packet.prototype.writeBuffer = function(b) {
  b.copy(this.buffer, this.offset);
  this.offset += b.length;
};

Packet.prototype.writeNull = function() {
  this.buffer[this.offset] = 0xfb;
  this.offset++;
};

// TODO: refactor following three?
Packet.prototype.writeNullTerminatedString = function(s) {
  this.buffer.write(s, this.offset);
  this.offset += s.length;
  this.writeInt8(0);
};

Packet.prototype.writeString = function(s) {
  var bytes = Buffer.byteLength(s, 'utf8');
  this.buffer.write(s, this.offset, bytes, 'utf8');
  this.offset += bytes;
};

Packet.prototype.writeLengthCodedString = function(s) {
  var bytes = Buffer.byteLength(s, 'utf8');
  this.writeLengthCodedNumber(bytes);
  this.buffer.write(s, this.offset, bytes, 'utf8');
  this.offset += bytes;
};

Packet.prototype.writeLengthCodedBuffer = function(b) {
  this.writeLengthCodedNumber(b.length);
  b.copy(this.buffer, this.offset);
  this.offset += b.length;
};

Packet.prototype.writeLengthCodedNumber = function(n) {
  // TODO: null - http://dev.mysql.com/doc/internals/en/overview.html#length-encoded-integer
  if (n < 0xfb)
    return this.writeInt8(n);
  if (n < 0xffff) {
    this.writeInt8(0xfc);
    return this.writeInt16(n);
  }
  if (n < 0xffffff) {
    this.writeInt8(0xfd);
    return this.writeInt24(n);
  }
  console.log(n);
  console.trace();
  throw "No bignumbers yet";
};

Packet.prototype.writeHeader = function(sequenceId)
{
  var offset = this.offset;
  this.offset = 0;
  this.writeInt24(this.buffer.length - 4);
  this.writeInt8(sequenceId);
  this.offset = offset;
};

Packet.prototype.clone = function() {
  var buffer = this.buffer.slice(this.start, this.end);
  var other = new Packet(this.sequenceId, this.buffer);
  return other;
};

Packet.prototype.type = function() {
  if (this.isEOF())
    return 'EOF';
  if (this.isError())
    return 'Error';
  if (this.buffer[this.offset] == 0)
    return 'maybeOK'; // could be other packet types as well
  return '';
};
module.exports = Packet;