###
  Get functionality for Node Index module

  This software is licensed under the MIT License.

  Copyright Fedor Indutny, 2011.

  Permission is hereby granted, free of charge, to any person obtaining a
  copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to permit
  persons to whom the Software is furnished to do so, subject to the
  following conditions:

  The above copyright notice and this permission notice shall be included
  in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  USE OR OTHER DEALINGS IN THE SOFTWARE.
###

utils = require '../../index/utils'
step = require 'step'

###
  Get value by key
###
exports.get = (key, callback) ->
  sort = @sort
  storage = @storage

  iterate = (err, index) ->
    if err
      return callback err

    item_index = utils.search index, sort, key
    item = index[item_index]

    # Item not found
    unless item
      return callback 'Not found'

    value = item[1]

    if item[2]
      # Key Value - return value
      if sort(item[0], key) isnt 0
        return callback 'Not found'

      # Read actual value
      storage.read value, (err, value) ->
        if err
          return callback err

        # value = [value, link-to-previous-value]
        callback null, value[0]
    else
      # Key Pointer - go further
      storage.read value, iterate

  storage.readRoot iterate

###
  Traverse btree
  filter can call callback w/ following result:
    true - if `traverse` should go deeper
    undefined - if `traverse` should skip element
    false - if `traverse` should stop traversing and return to higher level

  filter can
  @return promise.
###

exports.traverse = (filter) ->
  that = @
  promise = new process.EventEmitter

  # If no filter were provided - match all
  filter = filter || (kp, callback) -> callback(null, true)

  process.nextTick =>
    sort = @sort
    storage = @storage

    iterate = (callback) ->
      (err, page) ->
        if err
          promise.emit 'error', err
          promise.emit 'end'
          return

        index = -1
        pagelen = page.length

        asyncFilter = ->
          if ++index >= pagelen
            if callback
              callback null
            else
              promise.emit 'end'

            return

          current = page[index]

          filter.call that, current, (err, filter_value) ->
            if filter_value is true
              if current[2]
                # emit value
                storage.read current[1], (err, value) ->
                  # value = [value, link-to-previous-value]
                  promise.emit 'data', value[0], current
                  asyncFilter()

              else
                # go deeper
                storage.read current[1], iterate asyncFilter

            else
              if filter_value is false
                index = pagelen

              asyncFilter()

        asyncFilter()

    storage.readRoot iterate()

  promise

###
  Get in range
###
exports.rangeGet = (start_key, end_key) ->
  sort = @sort
  promise = new process.EventEmitter

  traverse_promise = @traverse (kp, callback) ->
    start_cmp = sort kp[0], start_key
    end_cmp = sort kp[0], end_key

    if kp[2]
      if start_cmp >= 0 and end_cmp <= 0
        return callback null, true

      if end_cmp > 0
        return callback null, false
    else
      if end_cmp <= 0
        return callback null, true
      if end_cmp > 0
        return callback null, false

    callback null

  traverse_promise.on 'data', (value) ->
    promise.emit 'data', value

  traverse_promise.on 'end', ->
    promise.emit 'end'

  promise