/**
 * wp.media.controller.Region
 *
 * A region is a persistent application layout area.
 *
 * A region assumes one mode at any time, and can be switched to another.
 *
 * When mode changes, events are triggered on the region's parent view.
 * The parent view will listen to specific events and fill the region with an
 * appropriate view depending on mode. For example, a frame listens for the
 * 'browse' mode t be activated on the 'content' view and then fills the region
 * with an AttachmentsBrowser view.
 *
 * @memberOf wp.media.controller
 *
 * @class
 *
 * @param {object}        options          Options hash for the region.
 * @param {string}        options.id       Unique identifier for the region.
 * @param {Backbone.View} options.view     A parent view the region exists within.
 * @param {string}        options.selector jQuery selector for the region within the parent view.
 */
var Region = function( options ) {
	_.extend( this, _.pick( options || {}, 'id', 'view', 'selector' ) );
};

// Use Backbone's self-propagating `extend` inheritance method.
Region.extend = Backbone.Model.extend;

_.extend( Region.prototype,/** @lends wp.media.controller.Region.prototype */{
	/**
	 * Activate a mode.
	 *
	 * @since 3.5.0
	 *
	 * @param {string} mode
	 *
	 * @fires Region#activate
	 * @fires Region#deactivate
	 *
	 * @return {wp.media.controller.Region} Returns itself to allow chaining.
	 */
	mode: function( mode ) {
		if ( ! mode ) {
			return this._mode;
		}
		// Bail if we're trying to change to the current mode.
		if ( mode === this._mode ) {
			return this;
		}

		/**
		 * Region mode deactivation event.
		 *
		 * @event wp.media.controller.Region#deactivate
		 */
		this.trigger('deactivate');

		this._mode = mode;
		this.render( mode );

		/**
		 * Region mode activation event.
		 *
		 * @event wp.media.controller.Region#activate
		 */
		this.trigger('activate');
		return this;
	},
	/**
	 * Render a mode.
	 *
	 * @since 3.5.0
	 *
	 * @param {string} mode
	 *
	 * @fires Region#create
	 * @fires Region#render
	 *
	 * @return {wp.media.controller.Region} Returns itself to allow chaining.
	 */
	render: function( mode ) {
		// If the mode isn't active, activate it.
		if ( mode && mode !== this._mode ) {
			return this.mode( mode );
		}

		var set = { view: null },
			view;

		/**
		 * Create region view event.
		 *
		 * Region view creation takes place in an event callback on the frame.
		 *
		 * @event wp.media.controller.Region#create
		 * @type {object}
		 * @property {object} view
		 */
		this.trigger( 'create', set );
		view = set.view;

		/**
		 * Render region view event.
		 *
		 * Region view creation takes place in an event callback on the frame.
		 *
		 * @event wp.media.controller.Region#render
		 * @type {object}
		 */
		this.trigger( 'render', view );
		if ( view ) {
			this.set( view );
		}
		return this;
	},

	/**
	 * Get the region's view.
	 *
	 * @since 3.5.0
	 *
	 * @return {wp.media.View}
	 */
	get: function() {
		return this.view.views.first( this.selector );
	},

	/**
	 * Set the region's view as a subview of the frame.
	 *
	 * @since 3.5.0
	 *
	 * @param {Array|Object} views
	 * @param {Object} [options={}]
	 * @return {wp.Backbone.Subviews} Subviews is returned to allow chaining.
	 */
	set: function( views, options ) {
		if ( options ) {
			options.add = false;
		}
		return this.view.views.set( this.selector, views, options );
	},

	/**
	 * Trigger regional view events on the frame.
	 *
	 * @since 3.5.0
	 *
	 * @param {string} event
	 * @return {undefined|wp.media.controller.Region} Returns itself to allow chaining.
	 */
	trigger: function( event ) {
		var base, args;

		if ( ! this._mode ) {
			return;
		}

		args = _.toArray( arguments );
		base = this.id + ':' + event;

		// Trigger `{this.id}:{event}:{this._mode}` event on the frame.
		args[0] = base + ':' + this._mode;
		this.view.trigger.apply( this.view, args );

		// Trigger `{this.id}:{event}` event on the frame.
		args[0] = base;
		this.view.trigger.apply( this.view, args );
		return this;
	}
});

module.exports = Region;
