/*
 * Dependency Tree Cache
 * 
 * Allows a build to pre-populate a dependency trace tree on the loader of 
 * the expected dependency tree, to be loaded upfront when requesting the
 * module, avoinding the n round trips latency of module loading, where 
 * n is the dependency tree depth.
 *
 * eg:
 * SystemJS.depCache = {
 *  'app': ['normalized', 'deps'],
 *  'normalized': ['another'],
 *  'deps': ['tree']
 * };
 * 
 * SystemJS.import('app') 
 * // simultaneously starts loading all of:
 * // 'normalized', 'deps', 'another', 'tree'
 * // before "app" source is even loaded
 *
 */

(function() {
  hookConstructor(function(constructor) {
    return function() {
      constructor.call(this);
      this.depCache = {};
    }
  });

  hook('locate', function(locate) {
    return function(load) {
      var loader = this;
      // load direct deps, in turn will pick up their trace trees
      var deps = loader.depCache[load.name];
      if (deps)
        for (var i = 0; i < deps.length; i++)
          loader['import'](deps[i], load.name);

      return locate.call(loader, load);
    };
  });
})();