todomvc/examples/cujo/bower_components/cola/network/strategy/syncDataDirectly.js

> Helping you select an MV\* framework

(function (define) {
define(function () {
"use strict";

	/**
	 * Creates a strategy to push all data from a source into the consumers
	 * in the network directly (rather than as a sequence of 'add' events
	 * in the network) when a sync event happens.
	 *
	 * @description This strategy helps eliminate loops and complexities
	 * when data providers and consumers are added at unpredictable times.
	 * During a sync, all 'add' events are squelched while providers push
	 * all items to all consumers.
	 *
	 * @param [options.providersAreConsumers] {Boolean} if truthy, providers
	 *   are also treated as consumers and receive items from other providers.
	 * @return {Function} a network strategy function
	 */
	return function (options) {
		var synced, providers, consumers, undef;

		if (!options) options = {};

		// TODO: consider putting these on the api object so they can be shared across strategies
		// a list of all known providers and consumers
		// these lists tend to be very small
		providers = [];
		consumers = [];
		// the adapter currently being synced
		synced = undef;

		return function syncDataDirectly (source, dest, provide, type, api) {
			// this strategy stops sync events before going on the network
			if ('sync' == type && api.isBefore()) {
				synced = source;
				try {
					if (provide) {
						// provide data onto consumers in network
						if (typeof source.forEach != 'function') {
							throw new Error('syncDataDirectly: provider doesn\'t have `forEach()`.');
						}
						// keep track of providers
						add(providers, synced);
						// also add to consumers list, if specified
						if (options.providersAreConsumers) {
							add(consumers, synced);
						}
						// push data to all consumers
						forEach(consumers, function (consumer) {
							source.forEach(function (item) {
								consumer.add(item);
							});
						});
					}
					else {
						// keep track of consumers
						add(consumers, synced);
						// provide data onto consumers in network
						if (typeof source.add == 'function') {
							// consume data from all providers
							forEach(providers, function (provider) {
								provider.forEach(function (item) {
									synced.add(item);
								});
							});
						}
					}
					// the sync event never gets onto the network:
					api.cancel();
				}
				finally {
					synced = undef;
				}
			}
			// stop 'add' events between adapters while sync'ing, but allow
			// strategies interested in the event to see it before
			else if ('add' == type && synced && !api.isBefore()) {
				api.cancel();
			}
			// keep track of adapters that leave
			else if ('leave' == type && api.isAfter()) {
				// these just end up being noops if the source isn't in the list
				remove(providers, source);
				remove(consumers, source);
			}
		};

		function add (list, adapter) {
			list.push(adapter);
		}

		function remove (list, adapter) {
			forEach(list, function (provider, i , providers) {
				if (provider == adapter) {
					providers.splice(i, 1);
				}
			});
		}

		function forEach (list, lambda) {
			var i, obj;
			i = list.length;
			while ((obj = list[--i])) {
				lambda(obj, i, list);
			}
		}

	};

});
}(
	typeof define == 'function' && define.amd
		? define
		: function (factory) { module.exports = factory(); }
));