/* Copyright (c) 2013 Rod Vagg, MIT License */

var xtend                = require('xtend')
  , AbstractIterator     = require('./abstract-iterator')
  , AbstractChainedBatch = require('./abstract-chained-batch')

function AbstractLevelDOWN (location) {
  if (!arguments.length || location === undefined)
    throw new Error('constructor requires at least a location argument')

  if (typeof location != 'string')
    throw new Error('constructor requires a location string argument')

  this.location = location
}

AbstractLevelDOWN.prototype.open = function (options, callback) {
  if (typeof options == 'function')
    callback = options

  if (typeof callback != 'function')
    throw new Error('open() requires a callback argument')

  if (typeof options != 'object')
    options = {}

  if (typeof this._open == 'function')
    return this._open(options, callback)

  process.nextTick(callback)
}

AbstractLevelDOWN.prototype.close = function (callback) {
  if (typeof callback != 'function')
    throw new Error('close() requires a callback argument')

  if (typeof this._close == 'function')
    return this._close(callback)

  process.nextTick(callback)
}

AbstractLevelDOWN.prototype.get = function (key, options, callback) {
  var err

  if (typeof options == 'function')
    callback = options

  if (typeof callback != 'function')
    throw new Error('get() requires a callback argument')

  if (err = this._checkKeyValue(key, 'key', this._isBuffer))
    return callback(err)

  if (!this._isBuffer(key))
    key = String(key)

  if (typeof options != 'object')
    options = {}

  if (typeof this._get == 'function')
    return this._get(key, options, callback)

  process.nextTick(function () { callback(new Error('NotFound')) })
}

AbstractLevelDOWN.prototype.put = function (key, value, options, callback) {
  var err

  if (typeof options == 'function')
    callback = options

  if (typeof callback != 'function')
    throw new Error('put() requires a callback argument')

  if (err = this._checkKeyValue(key, 'key', this._isBuffer))
    return callback(err)

  if (err = this._checkKeyValue(value, 'value', this._isBuffer))
    return callback(err)

  if (!this._isBuffer(key))
    key = String(key)

  // coerce value to string in node, don't touch it in browser
  // (indexeddb can store any JS type)
  if (!this._isBuffer(value) && !process.browser)
    value = String(value)

  if (typeof options != 'object')
    options = {}

  if (typeof this._put == 'function')
    return this._put(key, value, options, callback)

  process.nextTick(callback)
}

AbstractLevelDOWN.prototype.del = function (key, options, callback) {
  var err

  if (typeof options == 'function')
    callback = options

  if (typeof callback != 'function')
    throw new Error('del() requires a callback argument')

  if (err = this._checkKeyValue(key, 'key', this._isBuffer))
    return callback(err)

  if (!this._isBuffer(key))
    key = String(key)

  if (typeof options != 'object')
    options = {}

  if (typeof this._del == 'function')
    return this._del(key, options, callback)

  process.nextTick(callback)
}

AbstractLevelDOWN.prototype.batch = function (array, options, callback) {
  if (!arguments.length)
    return this._chainedBatch()

  if (typeof options == 'function')
    callback = options

  if (typeof callback != 'function')
    throw new Error('batch(array) requires a callback argument')

  if (!Array.isArray(array))
    return callback(new Error('batch(array) requires an array argument'))

  if (typeof options != 'object')
    options = {}

  var i = 0
    , l = array.length
    , e
    , err

  for (; i < l; i++) {
    e = array[i]
    if (typeof e != 'object')
      continue

    if (err = this._checkKeyValue(e.type, 'type', this._isBuffer))
      return callback(err)

    if (err = this._checkKeyValue(e.key, 'key', this._isBuffer))
      return callback(err)

    if (e.type == 'put') {
      if (err = this._checkKeyValue(e.value, 'value', this._isBuffer))
        return callback(err)
    }
  }

  if (typeof this._batch == 'function')
    return this._batch(array, options, callback)

  process.nextTick(callback)
}

//TODO: remove from here, not a necessary primitive
AbstractLevelDOWN.prototype.approximateSize = function (start, end, callback) {
  if (   start == null
      || end == null
      || typeof start == 'function'
      || typeof end == 'function') {
    throw new Error('approximateSize() requires valid `start`, `end` and `callback` arguments')
  }

  if (typeof callback != 'function')
    throw new Error('approximateSize() requires a callback argument')

  if (!this._isBuffer(start))
    start = String(start)

  if (!this._isBuffer(end))
    end = String(end)

  if (typeof this._approximateSize == 'function')
    return this._approximateSize(start, end, callback)

  process.nextTick(function () {
    callback(null, 0)
  })
}

AbstractLevelDOWN.prototype._setupIteratorOptions = function (options) {
  var self = this

  options = xtend(options)

  ;[ 'start', 'end', 'gt', 'gte', 'lt', 'lte' ].forEach(function (o) {
    if (options[o] && self._isBuffer(options[o]) && options[o].length === 0)
      delete options[o]
  })

  options.reverse = !!options.reverse

  // fix `start` so it takes into account gt, gte, lt, lte as appropriate
  if (options.reverse && options.lt)
    options.start = options.lt
  if (options.reverse && options.lte)
    options.start = options.lte
  if (!options.reverse && options.gt)
    options.start = options.gt
  if (!options.reverse && options.gte)
    options.start = options.gte

  if ((options.reverse && options.lt && !options.lte)
    || (!options.reverse && options.gt && !options.gte))
    options.exclusiveStart = true // start should *not* include matching key

  return options
}

AbstractLevelDOWN.prototype.iterator = function (options) {
  if (typeof options != 'object')
    options = {}

  options = this._setupIteratorOptions(options)

  if (typeof this._iterator == 'function')
    return this._iterator(options)

  return new AbstractIterator(this)
}

AbstractLevelDOWN.prototype._chainedBatch = function () {
  return new AbstractChainedBatch(this)
}

AbstractLevelDOWN.prototype._isBuffer = function (obj) {
  return Buffer.isBuffer(obj)
}

AbstractLevelDOWN.prototype._checkKeyValue = function (obj, type) {

  if (obj === null || obj === undefined)
    return new Error(type + ' cannot be `null` or `undefined`')

  if (this._isBuffer(obj)) {
    if (obj.length === 0)
      return new Error(type + ' cannot be an empty Buffer')
  } else if (String(obj) === '')
    return new Error(type + ' cannot be an empty String')
}

module.exports.AbstractLevelDOWN    = AbstractLevelDOWN
module.exports.AbstractIterator     = AbstractIterator
module.exports.AbstractChainedBatch = AbstractChainedBatch