/**
 * 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 shouldUpdateReactComponent
 * @typechecks static-only
 */

'use strict';

var warning = require('warning');

/**
 * Given a `prevElement` and `nextElement`, determines if the existing
 * instance should be updated as opposed to being destroyed or replaced by a new
 * instance. Both arguments are elements. This ensures that this logic can
 * operate on stateless trees without any backing instance.
 *
 * @param {?object} prevElement
 * @param {?object} nextElement
 * @return {boolean} True if the existing instance should be updated.
 * @protected
 */
function shouldUpdateReactComponent(prevElement, nextElement) {
  if (prevElement != null && nextElement != null) {
    var prevType = typeof prevElement;
    var nextType = typeof nextElement;
    if (prevType === 'string' || prevType === 'number') {
      return (nextType === 'string' || nextType === 'number');
    } else {
      if (nextType === 'object' &&
          prevElement.type === nextElement.type &&
          prevElement.key === nextElement.key) {
        var ownersMatch = prevElement._owner === nextElement._owner;
        var prevName = null;
        var nextName = null;
        var nextDisplayName = null;
        if (__DEV__) {
          if (!ownersMatch) {
            if (prevElement._owner != null &&
                prevElement._owner.getPublicInstance() != null &&
                prevElement._owner.getPublicInstance().constructor != null) {
              prevName =
                prevElement._owner.getPublicInstance().constructor.displayName;
            }
            if (nextElement._owner != null &&
                nextElement._owner.getPublicInstance() != null &&
                nextElement._owner.getPublicInstance().constructor != null) {
              nextName =
                nextElement._owner.getPublicInstance().constructor.displayName;
            }
            if (nextElement.type != null &&
                nextElement.type.displayName != null) {
              nextDisplayName = nextElement.type.displayName;
            }
            if (nextElement.type != null && typeof nextElement.type === 'string') {
              nextDisplayName = nextElement.type;
            }
            if (typeof nextElement.type !== 'string' ||
                nextElement.type === 'input' ||
                nextElement.type === 'textarea') {
              if ((prevElement._owner != null &&
                  prevElement._owner._isOwnerNecessary === false) ||
                  (nextElement._owner != null &&
                  nextElement._owner._isOwnerNecessary === false)) {
                if (prevElement._owner != null) {
                  prevElement._owner._isOwnerNecessary = true;
                }
                if (nextElement._owner != null) {
                  nextElement._owner._isOwnerNecessary = true;
                }
                warning(
                  false,
                  '<%s /> is being rendered by both %s and %s using the same ' +
                  'key (%s) in the same place. Currently, this means that ' +
                  'they don\'t preserve state. This behavior should be very ' +
                  'rare so we\'re considering deprecating it. Please contact ' +
                  'the React team and explain your use case so that we can ' +
                  'take that into consideration.',
                  nextDisplayName || 'Unknown Component',
                  prevName || '[Unknown]',
                  nextName || '[Unknown]',
                  prevElement.key
                );
              }
            }
          }
        }
        return ownersMatch;
      }
    }
  }
  return false;
}

module.exports = shouldUpdateReactComponent;
