'use strict';

var Type = require('../type');

var _toString = Object.prototype.toString;

function resolveYamlPairs(data) {
  if (data === null) return true;

  var index, length, pair, keys, result,
      object = data;

  result = new Array(object.length);

  for (index = 0, length = object.length; index < length; index += 1) {
    pair = object[index];

    if (_toString.call(pair) !== '[object Object]') return false;

    keys = Object.keys(pair);

    if (keys.length !== 1) return false;

    result[index] = [ keys[0], pair[keys[0]] ];
  }

  return true;
}

function constructYamlPairs(data) {
  if (data === null) return [];

  var index, length, pair, keys, result,
      object = data;

  result = new Array(object.length);

  for (index = 0, length = object.length; index < length; index += 1) {
    pair = object[index];

    keys = Object.keys(pair);

    result[index] = [ keys[0], pair[keys[0]] ];
  }

  return result;
}

module.exports = new Type('tag:yaml.org,2002:pairs', {
  kind: 'sequence',
  resolve: resolveYamlPairs,
  construct: constructYamlPairs
});