/**
Plain JavaScript replacement of jQuery .extend based on jQuery sources.
@license Copyright (c) 2015 by James M. Devlin. All rights reserved.
*/

function _extend() {

  function isPlainObject( obj ) {
    if ((typeof obj !== "object") || obj.nodeType ||
      (obj !== null && obj === obj.window)) {
      return false;
    }
    if (obj.constructor &&
      !hasOwnProperty.call( obj.constructor.prototype, "isPrototypeOf" )) {
      return false;
    }
    return true;
  }

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

  // Handle a deep copy situation
  if (typeof target === "boolean") {
    deep = target;
    // Skip the boolean and the target
    target = arguments[i] || {};
    i++;
  }

  // Handle case when target is a string or something (possible in deep copy)
  //if (typeof target !== "object" && !jQuery.isFunction(target))
  if (typeof target !== "object" && typeof target !== "function")
    target = {};

  for (; i < length; i++) {
    // Only deal with non-null/undefined values
    if ((options = arguments[i]) !== null) {
      // Extend the base object
      for (name in options) {
        src = target[name];
        copy = options[name];

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

        // Recurse if we're merging plain objects or arrays
        if (deep && copy && (isPlainObject(copy) ||
          (copyIsArray = (copy.constructor === Array)))) {
          if (copyIsArray) {
            copyIsArray = false;
            clone = src && (src.constructor === Array) ? src : [];
          } else {
            clone = src && isPlainObject(src) ? src : {};
          }
          // Never move original objects, clone them
          target[name] = _extend(deep, clone, copy);
          // Don't bring in undefined values
        } else if (copy !== undefined) {
          target[name] = copy;
        }
      }
    }
  }

  // Return the modified object
  return target;
}

module.exports = _extend;