(function($) {

  Sammy = Sammy || {};

  // A simple cache strategy that stores key/values in memory. 
  Sammy.MemoryCacheProxy = function(initial) {
    this._cache = initial || {};
  };

  $.extend(Sammy.MemoryCacheProxy.prototype, {
    exists: function(name) {
      return (typeof this._cache[name] != "undefined");
    },
    set: function(name, value) {
      return this._cache[name] = value;
    },
    get: function(name) {
      return this._cache[name];
    },
    clear: function(name) {
      delete this._cache[name];
    }
  });
  
  // A simple cache strategy that stores key/values <tt>$element.data()</tt> with a <tt>cache.</tt> prefix 
  Sammy.DataCacheProxy = function(initial, $element) {
    initial = initial || {};
    this.$element = $element;
    $.each(initial, function(key, value) {
      $element.data('cache.' + key, value);
    });
  };
  
  $.extend(Sammy.DataCacheProxy.prototype, {
    exists: function(name) {
      return (typeof this.$element.data('cache.' + name) != "undefined");
    },
    set: function(name, value) {
      return this.$element.data('cache.' + name, value);
    },
    get: function(name) {
      return this.$element.data('cache.' + name);
    },
    clear: function(name) {
      this.$element.removeData('cache.' + name);
    }
  });

  // Sammy.Cache provides helpers for caching data within the lifecycle of a 
  // Sammy app. The plugin provides two main methods on <tt>Sammy.Application<tt>,
  // <tt>cache</tt> and <tt>clearCache</tt>. Each app has its own cache store so that
  // you dont have to worry about collisions. There are currently two different 'cache proxies'
  // that share the same API but store the data in different ways. 
  //
  // === Arguments
  //
  // +proxy+:: decides which caching proxy to use, either 'memory'(default) or 'data' 
  //
  Sammy.Cache = function(app, proxy) {

    if (proxy == 'data') {
      this.cache_proxy = new Sammy.DataCacheProxy({}, this.$element());
    } else {
      this.cache_proxy = new Sammy.MemoryCacheProxy({});
    } 
    
    app.cache_partials = true;

    $.extend(app, {
      // cache is the main method for interacting with the cache store. The same
      // method is used for both setting and getting the value. The API is similar
      // to jQuery.fn.attr()
      //
      // === Examples
      //
      //      // setting a value
      //      cache('key', 'value');
      //
      //      // getting a value
      //      cache('key'); //=> 'value'
      //
      //      // setting a value with a callback
      //      cache('key', function() {
      //        // this is the app
      //        return app.element_selector;
      //      });
      //            
      cache: function(name, value) {
        if (typeof value == 'undefined') {
          return this.cache_proxy.get(name);
        } else if ($.isFunction(value) && !this.cache_proxy.exists(name)) {
          return this.cache_proxy.set(name, value.apply(this));
        } else {
          return this.cache_proxy.set(name, value)
        }
      },

      // clears the cached value for <tt>name</tt>
      clearCache: function(name) {
        return this.cache_proxy.clear(name);
      }
    });
    
    app.helpers({
      // a helper shortcut for use in <tt>Sammy.EventContext</tt>
      cache: function(name, value) {
        return this.app.cache(name, value);
      }
    });
  };

})(jQuery);