/*
 * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */

 (function(scope) {
    // super

    // `arrayOfArgs` is an optional array of args like one might pass
    // to `Function.apply`

    // TODO(sjmiles):
    //    $super must be installed on an instance or prototype chain
    //    as `super`, and invoked via `this`, e.g.
    //      `this.super();`

    //    will not work if function objects are not unique, for example,
    //    when using mixins.
    //    The memoization strategy assumes each function exists on only one 
    //    prototype chain i.e. we use the function object for memoizing)
    //    perhaps we can bookkeep on the prototype itself instead
    function $super(arrayOfArgs) {
      // since we are thunking a method call, performance is important here: 
      // memoize all lookups, once memoized the fast path calls no other 
      // functions
      //
      // find the caller (cannot be `strict` because of 'caller')
      var caller = $super.caller;
      // memoized 'name of method' 
      var nom = caller.nom;
      // memoized next implementation prototype
      var _super = caller._super;
      if (!_super) {
        if (!nom) {
          nom = caller.nom = nameInThis.call(this, caller);
        }
        if (!nom) {
          console.warn('called super() on a method not installed declaratively (has no .nom property)');
        }
        // super prototype is either cached or we have to find it
        // by searching __proto__ (at the 'top')
        // invariant: because we cache _super on fn below, we never reach 
        // here from inside a series of calls to super(), so it's ok to 
        // start searching from the prototype of 'this' (at the 'top')
        // we must never memoize a null super for this reason
        _super = memoizeSuper(caller, nom, getPrototypeOf(this));
      }
      // our super function
      var fn = _super[nom];
      if (fn) {
        // memoize information so 'fn' can call 'super'
        if (!fn._super) {
          // must not memoize null, or we lose our invariant above
          memoizeSuper(fn, nom, _super);
        }
        // invoke the inherited method
        // if 'fn' is not function valued, this will throw
        return fn.apply(this, arrayOfArgs || []);
      }
    }

    function nameInThis(value) {
      var p = this.__proto__;
      while (p && p !== HTMLElement.prototype) {
        // TODO(sjmiles): getOwnPropertyNames is absurdly expensive
        var n$ = Object.getOwnPropertyNames(p);
        for (var i=0, l=n$.length, n; i<l && (n=n$[i]); i++) {
          var d = Object.getOwnPropertyDescriptor(p, n);
          if (typeof d.value === 'function' && d.value === value) {
            return n;
          }
        }
        p = p.__proto__;
      }
    }

    function memoizeSuper(method, name, proto) {
      // find and cache next prototype containing `name`
      // we need the prototype so we can do another lookup
      // from here
      var s = nextSuper(proto, name, method);
      if (s[name]) {
        // `s` is a prototype, the actual method is `s[name]`
        // tag super method with it's name for quicker lookups
        s[name].nom = name;
      }
      return method._super = s;
    }

    function nextSuper(proto, name, caller) {
      // look for an inherited prototype that implements name
      while (proto) {
        if ((proto[name] !== caller) && proto[name]) {
          return proto;
        }
        proto = getPrototypeOf(proto);
      }
      // must not return null, or we lose our invariant above
      // in this case, a super() call was invoked where no superclass
      // method exists
      // TODO(sjmiles): thow an exception?
      return Object;
    }

    // NOTE: In some platforms (IE10) the prototype chain is faked via 
    // __proto__. Therefore, always get prototype via __proto__ instead of
    // the more standard Object.getPrototypeOf.
    function getPrototypeOf(prototype) {
      return prototype.__proto__;
    }

    // utility function to precompute name tags for functions
    // in a (unchained) prototype
    function hintSuper(prototype) {
      // tag functions with their prototype name to optimize
      // super call invocations
      for (var n in prototype) {
        var pd = Object.getOwnPropertyDescriptor(prototype, n);
        if (pd && typeof pd.value === 'function') {
          pd.value.nom = n;
        }
      }
    }

    // exports

    scope.super = $super;

})(Polymer);