/*!
 * Amplify Core @VERSION
 * 
 * Copyright 2011 appendTo LLC. (http://appendto.com/team)
 * Dual licensed under the MIT or GPL licenses.
 * http://appendto.com/open-source-licenses
 * 
 * http://amplifyjs.com
 */
(function ( global, undefined ) {

	var slice = [].slice,
		subscriptions = {};

	var amplify = global.amplify = {
		publish : function ( topic ) {
			var args = slice.call( arguments, 1 ),
				subscription,
				length,
				i = 0,
				ret;

			if ( !subscriptions[ topic ] ) {
				return true;
			}

			for ( length = subscriptions[ topic ].length; i < length; i++ ) {
				subscription = subscriptions[ topic ][ i ];
				ret = subscription.callback.apply( subscription.context, args );
				if ( ret === false ) {
					break;
				}
			}
			return ret !== false;
		},

		subscribe : function ( topic, context, callback, priority ) {
			if ( arguments.length === 3 && typeof callback === "number" ) {
				priority = callback;
				callback = context;
				context = null;
			}
			if ( arguments.length === 2 ) {
				callback = context;
				context = null;
			}
			priority = priority || 10;

			var topicIndex = 0,
				topics = topic.split( /\s/ ),
				topicLength = topics.length,
				added;
			for ( ; topicIndex < topicLength; topicIndex++ ) {
				topic = topics[ topicIndex ];
				added = false;
				if ( !subscriptions[ topic ] ) {
					subscriptions[ topic ] = [];
				}

				var i = subscriptions[ topic ].length - 1,
					subscriptionInfo = {
						callback : callback,
						context : context,
						priority : priority
					};

				for ( ; i >= 0; i-- ) {
					if ( subscriptions[ topic ][ i ].priority <= priority ) {
						subscriptions[ topic ].splice( i + 1, 0, subscriptionInfo );
						added = true;
						break;
					}
				}

				if ( !added ) {
					subscriptions[ topic ].unshift( subscriptionInfo );
				}
			}

			return callback;
		},

		unsubscribe : function ( topic, callback ) {
			if ( !subscriptions[ topic ] ) {
				return;
			}

			var length = subscriptions[ topic ].length,
				i = 0;

			for ( ; i < length; i++ ) {
				if ( subscriptions[ topic ][ i ].callback === callback ) {
					subscriptions[ topic ].splice( i, 1 );
					break;
				}
			}
		}
	};

}( this ) );