/**
 * Copyright 2013-2015, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule update
 */

/* global hasOwnProperty:true */

'use strict';

var assign = require('./Object.assign');
var keyOf = require('fbjs/lib/keyOf');
var invariant = require('fbjs/lib/invariant');
var hasOwnProperty = ({}).hasOwnProperty;

function shallowCopy(x) {
  if (Array.isArray(x)) {
    return x.concat();
  } else if (x && typeof x === 'object') {
    return assign(new x.constructor(), x);
  } else {
    return x;
  }
}

var COMMAND_PUSH = keyOf({ $push: null });
var COMMAND_UNSHIFT = keyOf({ $unshift: null });
var COMMAND_SPLICE = keyOf({ $splice: null });
var COMMAND_SET = keyOf({ $set: null });
var COMMAND_MERGE = keyOf({ $merge: null });
var COMMAND_APPLY = keyOf({ $apply: null });

var ALL_COMMANDS_LIST = [COMMAND_PUSH, COMMAND_UNSHIFT, COMMAND_SPLICE, COMMAND_SET, COMMAND_MERGE, COMMAND_APPLY];

var ALL_COMMANDS_SET = {};

ALL_COMMANDS_LIST.forEach(function (command) {
  ALL_COMMANDS_SET[command] = true;
});

function invariantArrayCase(value, spec, command) {
  !Array.isArray(value) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'update(): expected target of %s to be an array; got %s.', command, value) : invariant(false) : undefined;
  var specValue = spec[command];
  !Array.isArray(specValue) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'update(): expected spec of %s to be an array; got %s. ' + 'Did you forget to wrap your parameter in an array?', command, specValue) : invariant(false) : undefined;
}

function update(value, spec) {
  !(typeof spec === 'object') ? process.env.NODE_ENV !== 'production' ? invariant(false, 'update(): You provided a key path to update() that did not contain one ' + 'of %s. Did you forget to include {%s: ...}?', ALL_COMMANDS_LIST.join(', '), COMMAND_SET) : invariant(false) : undefined;

  if (hasOwnProperty.call(spec, COMMAND_SET)) {
    !(Object.keys(spec).length === 1) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'Cannot have more than one key in an object with %s', COMMAND_SET) : invariant(false) : undefined;

    return spec[COMMAND_SET];
  }

  var nextValue = shallowCopy(value);

  if (hasOwnProperty.call(spec, COMMAND_MERGE)) {
    var mergeObj = spec[COMMAND_MERGE];
    !(mergeObj && typeof mergeObj === 'object') ? process.env.NODE_ENV !== 'production' ? invariant(false, 'update(): %s expects a spec of type \'object\'; got %s', COMMAND_MERGE, mergeObj) : invariant(false) : undefined;
    !(nextValue && typeof nextValue === 'object') ? process.env.NODE_ENV !== 'production' ? invariant(false, 'update(): %s expects a target of type \'object\'; got %s', COMMAND_MERGE, nextValue) : invariant(false) : undefined;
    assign(nextValue, spec[COMMAND_MERGE]);
  }

  if (hasOwnProperty.call(spec, COMMAND_PUSH)) {
    invariantArrayCase(value, spec, COMMAND_PUSH);
    spec[COMMAND_PUSH].forEach(function (item) {
      nextValue.push(item);
    });
  }

  if (hasOwnProperty.call(spec, COMMAND_UNSHIFT)) {
    invariantArrayCase(value, spec, COMMAND_UNSHIFT);
    spec[COMMAND_UNSHIFT].forEach(function (item) {
      nextValue.unshift(item);
    });
  }

  if (hasOwnProperty.call(spec, COMMAND_SPLICE)) {
    !Array.isArray(value) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'Expected %s target to be an array; got %s', COMMAND_SPLICE, value) : invariant(false) : undefined;
    !Array.isArray(spec[COMMAND_SPLICE]) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'update(): expected spec of %s to be an array of arrays; got %s. ' + 'Did you forget to wrap your parameters in an array?', COMMAND_SPLICE, spec[COMMAND_SPLICE]) : invariant(false) : undefined;
    spec[COMMAND_SPLICE].forEach(function (args) {
      !Array.isArray(args) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'update(): expected spec of %s to be an array of arrays; got %s. ' + 'Did you forget to wrap your parameters in an array?', COMMAND_SPLICE, spec[COMMAND_SPLICE]) : invariant(false) : undefined;
      nextValue.splice.apply(nextValue, args);
    });
  }

  if (hasOwnProperty.call(spec, COMMAND_APPLY)) {
    !(typeof spec[COMMAND_APPLY] === 'function') ? process.env.NODE_ENV !== 'production' ? invariant(false, 'update(): expected spec of %s to be a function; got %s.', COMMAND_APPLY, spec[COMMAND_APPLY]) : invariant(false) : undefined;
    nextValue = spec[COMMAND_APPLY](nextValue);
  }

  for (var k in spec) {
    if (!(ALL_COMMANDS_SET.hasOwnProperty(k) && ALL_COMMANDS_SET[k])) {
      nextValue[k] = update(value[k], spec[k]);
    }
  }

  return nextValue;
}

module.exports = update;