amzn/style-dictionary

/*
 * Copyright 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance with
 * the License. A copy of the License is located at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
 * and limitations under the License.
 */

var _ = require('lodash');

/**
 * Performs an deep extend on the objects, from right to left.
 * @private
 * @param {Object[]} objects - An array of JS objects
 * @param {Function} collision - A function to be called when a merge collision happens.
 * @param {string[]} path - (for internal use) An array of strings which is the current path down the object when this is called recursively.
 * @returns {Object}
 */
function deepExtend(objects, collision, path) {
  if (objects == null)
    return {};

  var src, copyIsArray, copy, name, options, clone,
    target = objects[0] || {},
    i = 1,
    length = objects.length;

  path = path || [];

  // Handle case when target is a string or something (possible in deep copy)
  if ( typeof target !== 'object' ) {
    target = {};
  }

  for ( ; i < length; i++) {
    // Only deal with non-null/undefined values
    if ( (options = objects[ i ]) != null ) {
      // Extend the base object
      for (name in options) {
        if (!options.hasOwnProperty(name))
          continue;

        src = target[name];
        copy = options[name];

        // Prevent never-ending loop
        if (target === copy) {
          continue;
        }

        // Recurse if we're merging plain objects or arrays
        if ( copy && ( _.isPlainObject(copy) || (copyIsArray = _.isArray(copy)) ) ) {
          if ( copyIsArray ) {
            copyIsArray = false;
            clone = src && _.isArray(src) ? src : [];
          } else {
            clone = src && _.isPlainObject(src) ? src : {};
          }

          var nextPath = path.slice(0);
          nextPath.push(name);

          // Never move original objects, clone them
          target[ name ] = deepExtend( [clone, copy], collision, nextPath );

          // Don't bring in undefined values
        } else if ( copy !== undefined ) {
          if (src != null && typeof collision == 'function') {
            collision({target: target, copy: options, path: path, key: name});
          }
          target[ name ] = copy;
        }
      }
    }
  }

  return target;
}

module.exports = deepExtend;