'use strict';

var _ = require('lodash');
var $ = require('../util/preconditions');
var BufferUtil = require('../util/buffer');
var BN = require('../crypto/bn');

var BufferReader = function BufferReader(buf) {
  if (!(this instanceof BufferReader)) {
    return new BufferReader(buf);
  }
  if (_.isUndefined(buf)) {
    return;
  }
  if (Buffer.isBuffer(buf)) {
    this.set({
      buf: buf
    });
  } else if (_.isString(buf)) {
    this.set({
      buf: new Buffer(buf, 'hex'),
    });
  } else if (_.isObject(buf)) {
    var obj = buf;
    this.set(obj);
  } else {
    throw new TypeError('Unrecognized argument for BufferReader');
  }
};

BufferReader.prototype.set = function(obj) {
  this.buf = obj.buf || this.buf || undefined;
  this.pos = obj.pos || this.pos || 0;
  return this;
};

BufferReader.prototype.eof = function() {
  return this.pos >= this.buf.length;
};

BufferReader.prototype.finished = BufferReader.prototype.eof;

BufferReader.prototype.read = function(len) {
  $.checkArgument(!_.isUndefined(len), 'Must specify a length');
  var buf = this.buf.slice(this.pos, this.pos + len);
  this.pos = this.pos + len;
  return buf;
};

BufferReader.prototype.readAll = function() {
  var buf = this.buf.slice(this.pos, this.buf.length);
  this.pos = this.buf.length;
  return buf;
};

BufferReader.prototype.readUInt8 = function() {
  var val = this.buf.readUInt8(this.pos);
  this.pos = this.pos + 1;
  return val;
};

BufferReader.prototype.readUInt16BE = function() {
  var val = this.buf.readUInt16BE(this.pos);
  this.pos = this.pos + 2;
  return val;
};

BufferReader.prototype.readUInt16LE = function() {
  var val = this.buf.readUInt16LE(this.pos);
  this.pos = this.pos + 2;
  return val;
};

BufferReader.prototype.readUInt32BE = function() {
  var val = this.buf.readUInt32BE(this.pos);
  this.pos = this.pos + 4;
  return val;
};

BufferReader.prototype.readUInt32LE = function() {
  var val = this.buf.readUInt32LE(this.pos);
  this.pos = this.pos + 4;
  return val;
};

BufferReader.prototype.readInt32LE = function() {
  var val = this.buf.readInt32LE(this.pos);
  this.pos = this.pos + 4;
  return val;
};

BufferReader.prototype.readUInt64BEBN = function() {
  var buf = this.buf.slice(this.pos, this.pos + 8);
  var bn = BN.fromBuffer(buf);
  this.pos = this.pos + 8;
  return bn;
};

BufferReader.prototype.readUInt64LEBN = function() {
  var second = this.buf.readUInt32LE(this.pos);
  var first = this.buf.readUInt32LE(this.pos + 4);
  var combined = (first * 0x100000000) + second;
  // Instantiating an instance of BN with a number is faster than with an
  // array or string. However, the maximum safe number for a double precision
  // floating point is 2 ^ 52 - 1 (0x1fffffffffffff), thus we can safely use
  // non-floating point numbers less than this amount (52 bits). And in the case
  // that the number is larger, we can instatiate an instance of BN by passing
  // an array from the buffer (slower) and specifying the endianness.
  var bn;
  if (combined