/*!
 * encoding.js - encoding utils for bcoin
 * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
 * Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
 * https://github.com/bcoin-org/bcoin
 */

'use strict';

/**
 * @module utils/encoding
 */

const assert = require('assert');
const {U64, I64} = require('n64');
const UINT128_MAX = U64.UINT64_MAX.shrn(7);
const MAX_SAFE_INTEGER = Number.MAX_SAFE_INTEGER;
const encoding = exports;

/**
 * An empty buffer.
 * @const {Buffer}
 * @default
 */

encoding.DUMMY = Buffer.from([0]);

/**
 * A hash of all zeroes with a `1` at the
 * end (used for the SIGHASH_SINGLE bug).
 * @const {Buffer}
 * @default
 */

encoding.ONE_HASH = Buffer.from(
  '0100000000000000000000000000000000000000000000000000000000000000',
  'hex'
);

/**
 * A hash of all zeroes.
 * @const {Buffer}
 * @default
 */

encoding.ZERO_HASH = Buffer.from(
  '0000000000000000000000000000000000000000000000000000000000000000',
  'hex'
);

/**
 * A hash of all 0xff.
 * @const {Buffer}
 * @default
 */

encoding.MAX_HASH = Buffer.from(
  'ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
  'hex'
);

/**
 * A hash of all zeroes.
 * @const {String}
 * @default
 */

encoding.NULL_HASH =
  '0000000000000000000000000000000000000000000000000000000000000000';

/**
 * A hash of all 0xff.
 * @const {String}
 * @default
 */

encoding.HIGH_HASH =
  'ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff';

/**
 * A hash of all zeroes.
 * @const {Buffer}
 * @default
 */

encoding.ZERO_HASH160 = Buffer.from(
  '0000000000000000000000000000000000000000',
  'hex'
);

/**
 * A hash of all 0xff.
 * @const {String}
 * @default
 */

encoding.MAX_HASH160 = Buffer.from(
  'ffffffffffffffffffffffffffffffffffffffff',
  'hex'
);

/**
 * A hash of all zeroes.
 * @const {String}
 * @default
 */

encoding.NULL_HASH160 = '0000000000000000000000000000000000000000';

/**
 * A hash of all 0xff.
 * @const {String}
 * @default
 */

encoding.HIGH_HASH160 = 'ffffffffffffffffffffffffffffffffffffffff';

/**
 * A compressed pubkey of all zeroes.
 * @const {Buffer}
 * @default
 */

encoding.ZERO_KEY = Buffer.from(
  '000000000000000000000000000000000000000000000000000000000000000000',
  'hex'
);

/**
 * A 73 byte signature of all zeroes.
 * @const {Buffer}
 * @default
 */

encoding.ZERO_SIG = Buffer.from(''
  + '0000000000000000000000000000000000000000000000000000000000000000'
  + '0000000000000000000000000000000000000000000000000000000000000000'
  + '000000000000000000',
  'hex'
);

/**
 * A 64 byte signature of all zeroes.
 * @const {Buffer}
 * @default
 */

encoding.ZERO_SIG64 = Buffer.from(''
  + '0000000000000000000000000000000000000000000000000000000000000000'
  + '0000000000000000000000000000000000000000000000000000000000000000',
  'hex'
);

/**
 * 4 zero bytes.
 * @const {Buffer}
 * @default
 */

encoding.ZERO_U32 = Buffer.from('00000000', 'hex');

/**
 * 8 zero bytes.
 * @const {Buffer}
 * @default
 */

encoding.ZERO_U64 = Buffer.from('0000000000000000', 'hex');

/**
 * Read uint64le as a js number.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {Number}
 * @throws on num > MAX_SAFE_INTEGER
 */

encoding.readU64 = function readU64(data, off) {
  const hi = data.readUInt32LE(off + 4, true);
  const lo = data.readUInt32LE(off, true);
  enforce((hi & 0xffe00000) === 0, off, 'Number exceeds 2^53-1');
  return hi * 0x100000000 + lo;
};

/**
 * Read uint64be as a js number.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {Number}
 * @throws on num > MAX_SAFE_INTEGER
 */

encoding.readU64BE = function readU64BE(data, off) {
  const hi = data.readUInt32BE(off, true);
  const lo = data.readUInt32BE(off + 4, true);
  enforce((hi & 0xffe00000) === 0, off, 'Number exceeds 2^53-1');
  return hi * 0x100000000 + lo;
};

/**
 * Read int64be as a js number.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {Number}
 * @throws on num > MAX_SAFE_INTEGER
 */

encoding.readI64 = function readI64(data, off) {
  const hi = data.readInt32LE(off + 4, true);
  const lo = data.readUInt32LE(off, true);
  enforce(isSafe(hi, lo), 'Number exceeds 2^53-1');
  return hi * 0x100000000 + lo;
};

/**
 * Read int64be as a js number.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {Number}
 * @throws on num > MAX_SAFE_INTEGER
 */

encoding.readI64BE = function readI64BE(data, off) {
  const hi = data.readInt32BE(off, true);
  const lo = data.readUInt32BE(off + 4, true);
  enforce(isSafe(hi, lo), 'Number exceeds 2^53-1');
  return hi * 0x100000000 + lo;
};

/**
 * Write a javascript number as a uint64le.
 * @param {Buffer} dst
 * @param {Number} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 * @throws on num > MAX_SAFE_INTEGER
 */

encoding.writeU64 = function writeU64(dst, num, off) {
  return write64(dst, num, off, false);
};

/**
 * Write a javascript number as a uint64be.
 * @param {Buffer} dst
 * @param {Number} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 * @throws on num > MAX_SAFE_INTEGER
 */

encoding.writeU64BE = function writeU64BE(dst, num, off) {
  return write64(dst, num, off, true);
};

/**
 * Write a javascript number as an int64le.
 * @param {Buffer} dst
 * @param {Number} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 * @throws on num > MAX_SAFE_INTEGER
 */

encoding.writeI64 = function writeI64(dst, num, off) {
  return write64(dst, num, off, false);
};

/**
 * Write a javascript number as an int64be.
 * @param {Buffer} dst
 * @param {Number} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 * @throws on num > MAX_SAFE_INTEGER
 */

encoding.writeI64BE = function writeI64BE(dst, num, off) {
  return write64(dst, num, off, true);
};

/**
 * Read uint64le.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {U64}
 */

encoding.readU64N = function readU64N(data, off) {
  return U64.readLE(data, off);
};

/**
 * Read uint64be.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {U64}
 */

encoding.readU64BEN = function readU64BEN(data, off) {
  return U64.readBE(data, off);
};

/**
 * Read int64le.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {I64}
 */

encoding.readI64N = function readI64N(data, off) {
  return I64.readLE(data, off);
};
/**
 * Read int64be.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {I64}
 */

encoding.readI64BEN = function readI64BEN(data, off) {
  return I64.readBE(data, off);
};

/**
 * Write uint64le.
 * @param {Buffer} dst
 * @param {U64} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 */

encoding.writeU64N = function writeU64N(dst, num, off) {
  enforce(!num.sign, off, 'Signed');
  return num.writeLE(dst, off);
};

/**
 * Write uint64be.
 * @param {Buffer} dst
 * @param {U64} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 */

encoding.writeU64BEN = function writeU64BEN(dst, num, off) {
  enforce(!num.sign, off, 'Signed');
  return num.writeBE(dst, off);
};

/**
 * Write int64le.
 * @param {Buffer} dst
 * @param {U64} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 */

encoding.writeI64N = function writeI64N(dst, num, off) {
  enforce(num.sign, off, 'Not signed');
  return num.writeLE(dst, off);
};

/**
 * Write int64be.
 * @param {Buffer} dst
 * @param {I64} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 */

encoding.writeI64BEN = function writeI64BEN(dst, num, off) {
  enforce(num.sign, off, 'Not signed');
  return num.writeBE(dst, off);
};

/**
 * Read a varint.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {Object}
 */

encoding.readVarint = function readVarint(data, off) {
  let value, size;

  check(off < data.length, off);

  switch (data[off]) {
    case 0xff:
      size = 9;
      check(off + size <= data.length, off);
      value = encoding.readU64(data, off + 1);
      enforce(value > 0xffffffff, off, 'Non-canonical varint');
      break;
    case 0xfe:
      size = 5;
      check(off + size <= data.length, off);
      value = data.readUInt32LE(off + 1, true);
      enforce(value > 0xffff, off, 'Non-canonical varint');
      break;
    case 0xfd:
      size = 3;
      check(off + size <= data.length, off);
      value = data[off + 1] | (data[off + 2] << 8);
      enforce(value >= 0xfd, off, 'Non-canonical varint');
      break;
    default:
      size = 1;
      value = data[off];
      break;
  }

  return new Varint(size, value);
};

/**
 * Write a varint.
 * @param {Buffer} dst
 * @param {Number} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 */

encoding.writeVarint = function writeVarint(dst, num, off) {
  if (num < 0xfd) {
    dst[off++] = num & 0xff;
    return off;
  }

  if (num <= 0xffff) {
    dst[off++] = 0xfd;
    dst[off++] = num & 0xff;
    dst[off++] = (num >> 8) & 0xff;
    return off;
  }

  if (num <= 0xffffffff) {
    dst[off++] = 0xfe;
    dst[off++] = num & 0xff;
    dst[off++] = (num >> 8) & 0xff;
    dst[off++] = (num >> 16) & 0xff;
    dst[off++] = num >>> 24;
    return off;
  }

  dst[off++] = 0xff;
  off = encoding.writeU64(dst, num, off);
  return off;
};

/**
 * Calculate size of varint.
 * @param {Number} num
 * @returns {Number} size
 */

encoding.sizeVarint = function sizeVarint(num) {
  if (num < 0xfd)
    return 1;

  if (num <= 0xffff)
    return 3;

  if (num <= 0xffffffff)
    return 5;

  return 9;
};

/**
 * Read a varint.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {Object}
 */

encoding.readVarintN = function readVarintN(data, off) {
  check(off < data.length, off);

  if (data[off] === 0xff) {
    const size = 9;
    check(off + size <= data.length, off);
    const value = encoding.readU64N(data, off + 1);
    enforce(value.hi !== 0, off, 'Non-canonical varint');
    return new Varint(size, value);
  }

  const {size, value} = encoding.readVarint(data, off);

  return new Varint(size, U64.fromInt(value));
};

/**
 * Write a varint.
 * @param {Buffer} dst
 * @param {U64} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 */

encoding.writeVarintN = function writeVarintN(dst, num, off) {
  enforce(!num.sign, off, 'Signed');

  if (num.hi !== 0) {
    dst[off++] = 0xff;
    return encoding.writeU64N(dst, num, off);
  }

  return encoding.writeVarint(dst, num.toInt(), off);
};

/**
 * Calculate size of varint.
 * @param {U64} num
 * @returns {Number} size
 */

encoding.sizeVarintN = function sizeVarintN(num) {
  enforce(!num.sign, 0, 'Signed');

  if (num.hi !== 0)
    return 9;

  return encoding.sizeVarint(num.toInt());
};

/**
 * Read a varint (type 2).
 * @param {Buffer} data
 * @param {Number} off
 * @returns {Object}
 */

encoding.readVarint2 = function readVarint2(data, off) {
  let num = 0;
  let size = 0;

  for (;;) {
    check(off < data.length, off);

    const ch = data[off++];
    size++;

    // Number.MAX_SAFE_INTEGER >>> 7
    enforce(num <= 0x3fffffffffff - (ch & 0x7f), off, 'Number exceeds 2^53-1');

    // num = (num << 7) | (ch & 0x7f);
    num = (num * 0x80) + (ch & 0x7f);

    if ((ch & 0x80) === 0)
      break;

    enforce(num !== MAX_SAFE_INTEGER, off, 'Number exceeds 2^53-1');
    num++;
  }

  return new Varint(size, num);
};

/**
 * Write a varint (type 2).
 * @param {Buffer} dst
 * @param {Number} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 */

encoding.writeVarint2 = function writeVarint2(dst, num, off) {
  const tmp = [];

  let len = 0;

  for (;;) {
    tmp[len] = (num & 0x7f) | (len ? 0x80 : 0x00);
    if (num <= 0x7f)
      break;
    // num = (num >>> 7) - 1;
    num = ((num - (num % 0x80)) / 0x80) - 1;
    len++;
  }

  check(off + len + 1 <= dst.length, off);

  do {
    dst[off++] = tmp[len];
  } while (len--);

  return off;
};

/**
 * Calculate size of varint (type 2).
 * @param {Number} num
 * @returns {Number} size
 */

encoding.sizeVarint2 = function sizeVarint2(num) {
  let size = 0;

  for (;;) {
    size++;
    if (num <= 0x7f)
      break;
    // num = (num >>> 7) - 1;
    num = ((num - (num % 0x80)) / 0x80) - 1;
  }

  return size;
};

/**
 * Read a varint (type 2).
 * @param {Buffer} data
 * @param {Number} off
 * @returns {Object}
 */

encoding.readVarint2N = function readVarint2N(data, off) {
  const num = new U64();

  let size = 0;

  for (;;) {
    check(off < data.length, off);

    const ch = data[off++];
    size++;

    enforce(num.lte(UINT128_MAX), off, 'Number exceeds 2^64-1');

    num.ishln(7).iorn(ch & 0x7f);

    if ((ch & 0x80) === 0)
      break;

    enforce(!num.eq(U64.UINT64_MAX), off, 'Number exceeds 2^64-1');
    num.iaddn(1);
  }

  return new Varint(size, num);
};

/**
 * Write a varint (type 2).
 * @param {Buffer} dst
 * @param {U64} num
 * @param {Number} off
 * @returns {Number} Buffer offset.
 */

encoding.writeVarint2N = function writeVarint2N(dst, num, off) {
  enforce(!num.sign, off, 'Signed');

  if (num.hi === 0)
    return encoding.writeVarint2(dst, num.toInt(), off);

  num = num.clone();

  const tmp = [];

  let len = 0;

  for (;;) {
    tmp[len] = num.andln(0x7f) | (len ? 0x80 : 0x00);
    if (num.lten(0x7f))
      break;
    num.ishrn(7).isubn(1);
    len++;
  }

  enforce(off + len + 1 <= dst.length, off, 'Out of bounds write');

  do {
    dst[off++] = tmp[len];
  } while (len--);

  return off;
};

/**
 * Calculate size of varint (type 2).
 * @param {U64} num
 * @returns {Number} size
 */

encoding.sizeVarint2N = function sizeVarint2N(num) {
  enforce(!num.sign, 0, 'Signed');

  if (num.hi === 0)
    return encoding.sizeVarint2(num.toInt());

  num = num.clone();

  let size = 0;

  for (;;) {
    size++;
    if (num.lten(0x7f))
      break;
    num.ishrn(7).isubn(1);
  }

  return size;
};

/**
 * Serialize number as a u8.
 * @param {Number} num
 * @returns {Buffer}
 */

encoding.u8 = function u8(num) {
  const data = Buffer.allocUnsafe(1);
  data[0] = num >>> 0;
  return data;
};

/**
 * Serialize number as a u32le.
 * @param {Number} num
 * @returns {Buffer}
 */

encoding.u32 = function u32(num) {
  const data = Buffer.allocUnsafe(4);
  data.writeUInt32LE(num, 0, true);
  return data;
};

/**
 * Get size of varint-prefixed bytes.
 * @param {Buffer} data
 * @returns {Number}
 */

encoding.sizeVarBytes = function sizeVarBytes(data) {
  return encoding.sizeVarint(data.length) + data.length;
};

/**
 * Get size of varint-prefixed length.
 * @param {Number} len
 * @returns {Number}
 */

encoding.sizeVarlen = function sizeVarlen(len) {
  return encoding.sizeVarint(len) + len;
};

/**
 * Get size of varint-prefixed string.
 * @param {String} str
 * @returns {Number}
 */

encoding.sizeVarString = function sizeVarString(str, enc) {
  if (typeof str !== 'string')
    return encoding.sizeVarBytes(str);

  const len = Buffer.byteLength(str, enc);

  return encoding.sizeVarint(len) + len;
};

/**
 * Reverse a hex-string (used because of
 * bitcoind's affinity for uint256le).
 * @param {String} str - Hex string.
 * @returns {String} Reversed hex string.
 */

encoding.revHex = function revHex(str) {
  assert(typeof str === 'string');
  assert(str.length > 0);
  assert(str.length % 2 === 0);

  let out = '';

  for (let i = str.length - 2; i >= 0; i -= 2)
    out += str[i] + str[i + 1];

  return out;
};

/**
 * EncodingError
 * @constructor
 * @param {Number} offset
 * @param {String} reason
 */

encoding.EncodingError = function EncodingError(offset, reason, start) {
  if (!(this instanceof EncodingError))
    return new EncodingError(offset, reason, start);

  Error.call(this);

  this.type = 'EncodingError';
  this.message = `${reason} (offset=${offset}).`;

  if (Error.captureStackTrace)
    Error.captureStackTrace(this, start || EncodingError);
};

Object.setPrototypeOf(encoding.EncodingError.prototype, Error.prototype);

/*
 * Helpers
 */

function isSafe(hi, lo) {
  if (hi < 0) {
    hi = ~hi;
    if (lo === 0)
      hi += 1;
  }

  return (hi & 0xffe00000) === 0;
}

function write64(dst, num, off, be) {
  let neg = false;

  if (num < 0) {
    num = -num;
    neg = true;
  }

  let hi = (num * (1 / 0x100000000)) | 0;
  let lo = num | 0;

  if (neg) {
    if (lo === 0) {
      hi = (~hi + 1) | 0;
    } else {
      hi = ~hi;
      lo = ~lo + 1;
    }
  }

  if (be) {
    off = dst.writeInt32BE(hi, off, true);
    off = dst.writeInt32BE(lo, off, true);
  } else {
    off = dst.writeInt32LE(lo, off, true);
    off = dst.writeInt32LE(hi, off, true);
  }

  return off;
}

function Varint(size, value) {
  this.size = size;
  this.value = value;
}

function check(value, offset) {
  if (!value)
    throw new encoding.EncodingError(offset, 'Out of bounds read', check);
}

function enforce(value, offset, reason) {
  if (!value)
    throw new encoding.EncodingError(offset, reason, enforce);
}