'use strict'

const { AbstractKeyIterator, AbstractValueIterator } = require('../abstract-iterator')

const kIterator = Symbol('iterator')
const kCallback = Symbol('callback')
const kHandleOne = Symbol('handleOne')
const kHandleMany = Symbol('handleMany')

class DefaultKeyIterator extends AbstractKeyIterator {
  constructor (db, options) {
    super(db, options)

    this[kIterator] = db.iterator({ ...options, keys: true, values: false })
    this[kHandleOne] = this[kHandleOne].bind(this)
    this[kHandleMany] = this[kHandleMany].bind(this)
  }
}

class DefaultValueIterator extends AbstractValueIterator {
  constructor (db, options) {
    super(db, options)

    this[kIterator] = db.iterator({ ...options, keys: false, values: true })
    this[kHandleOne] = this[kHandleOne].bind(this)
    this[kHandleMany] = this[kHandleMany].bind(this)
  }
}

for (const Iterator of [DefaultKeyIterator, DefaultValueIterator]) {
  const keys = Iterator === DefaultKeyIterator
  const mapEntry = keys ? (entry) => entry[0] : (entry) => entry[1]

  Iterator.prototype._next = function (callback) {
    this[kCallback] = callback
    this[kIterator].next(this[kHandleOne])
  }

  Iterator.prototype[kHandleOne] = function (err, key, value) {
    const callback = this[kCallback]
    if (err) callback(err)
    else callback(null, keys ? key : value)
  }

  Iterator.prototype._nextv = function (size, options, callback) {
    this[kCallback] = callback
    this[kIterator].nextv(size, options, this[kHandleMany])
  }

  Iterator.prototype._all = function (options, callback) {
    this[kCallback] = callback
    this[kIterator].all(options, this[kHandleMany])
  }

  Iterator.prototype[kHandleMany] = function (err, entries) {
    const callback = this[kCallback]
    if (err) callback(err)
    else callback(null, entries.map(mapEntry))
  }

  Iterator.prototype._seek = function (target, options) {
    this[kIterator].seek(target, options)
  }

  Iterator.prototype._close = function (callback) {
    this[kIterator].close(callback)
  }
}

// Internal utilities, should be typed as AbstractKeyIterator and AbstractValueIterator
exports.DefaultKeyIterator = DefaultKeyIterator
exports.DefaultValueIterator = DefaultValueIterator