/*
---

script: Request.Queue.js

name: Request.Queue

description: Controls several instances of Request and its variants to run only one request at a time.

license: MIT-style license

authors:
  - Aaron Newton

requires:
  - Core/Element
  - Core/Request
  - /Log

provides: [Request.Queue]

...
*/

Request.Queue = new Class({

	Implements: [Options, Events],

	Binds: ['attach', 'request', 'complete', 'cancel', 'success', 'failure', 'exception'],

	options: {/*
		onRequest: $empty(argsPassedToOnRequest),
		onSuccess: $empty(argsPassedToOnSuccess),
		onComplete: $empty(argsPassedToOnComplete),
		onCancel: $empty(argsPassedToOnCancel),
		onException: $empty(argsPassedToOnException),
		onFailure: $empty(argsPassedToOnFailure),
		onEnd: $empty,
		*/
		stopOnFailure: true,
		autoAdvance: true,
		concurrent: 1,
		requests: {}
	},

	initialize: function(options){
		if(options){
			var requests = options.requests;
			delete options.requests;	
		}
		this.setOptions(options);
		this.requests = new Hash;
		this.queue = [];
		this.reqBinders = {};
		
		if(requests) this.addRequests(requests);
	},

	addRequest: function(name, request){
		this.requests.set(name, request);
		this.attach(name, request);
		return this;
	},

	addRequests: function(obj){
		$each(obj, function(req, name){
			this.addRequest(name, req);
		}, this);
		return this;
	},

	getName: function(req){
		return this.requests.keyOf(req);
	},

	attach: function(name, req){
		if (req._groupSend) return this;
		['request', 'complete', 'cancel', 'success', 'failure', 'exception'].each(function(evt){
			if(!this.reqBinders[name]) this.reqBinders[name] = {};
			this.reqBinders[name][evt] = function(){
				this['on' + evt.capitalize()].apply(this, [name, req].extend(arguments));
			}.bind(this);
			req.addEvent(evt, this.reqBinders[name][evt]);
		}, this);
		req._groupSend = req.send;
		req.send = function(options){
			this.send(name, options);
			return req;
		}.bind(this);
		return this;
	},

	removeRequest: function(req){
		var name = $type(req) == 'object' ? this.getName(req) : req;
		if (!name && $type(name) != 'string') return this;
		req = this.requests.get(name);
		if (!req) return this;
		['request', 'complete', 'cancel', 'success', 'failure', 'exception'].each(function(evt){
			req.removeEvent(evt, this.reqBinders[name][evt]);
		}, this);
		req.send = req._groupSend;
		delete req._groupSend;
		return this;
	},

	getRunning: function(){
		return this.requests.filter(function(r){
			return r.running;
		});
	},

	isRunning: function(){
		return !!(this.getRunning().getKeys().length);
	},

	send: function(name, options){
		var q = function(){
			this.requests.get(name)._groupSend(options);
			this.queue.erase(q);
		}.bind(this);
		q.name = name;
		if (this.getRunning().getKeys().length >= this.options.concurrent || (this.error && this.options.stopOnFailure)) this.queue.push(q);
		else q();
		return this;
	},

	hasNext: function(name){
		return (!name) ? !!this.queue.length : !!this.queue.filter(function(q){ return q.name == name; }).length;
	},

	resume: function(){
		this.error = false;
		(this.options.concurrent - this.getRunning().getKeys().length).times(this.runNext, this);
		return this;
	},

	runNext: function(name){
		if (!this.queue.length) return this;
		if (!name){
			this.queue[0]();
		} else {
			var found;
			this.queue.each(function(q){
				if (!found && q.name == name){
					found = true;
					q();
				}
			});
		}
		return this;
	},

	runAll: function() {
		this.queue.each(function(q) {
			q();
		});
		return this;
	},

	clear: function(name){
		if (!name){
			this.queue.empty();
		} else {
			this.queue = this.queue.map(function(q){
				if (q.name != name) return q;
				else return false;
			}).filter(function(q){ return q; });
		}
		return this;
	},

	cancel: function(name){
		this.requests.get(name).cancel();
		return this;
	},

	onRequest: function(){
		this.fireEvent('request', arguments);
	},

	onComplete: function(){
		this.fireEvent('complete', arguments);
		if (!this.queue.length) this.fireEvent('end');
	},

	onCancel: function(){
		if (this.options.autoAdvance && !this.error) this.runNext();
		this.fireEvent('cancel', arguments);
	},

	onSuccess: function(){
		if (this.options.autoAdvance && !this.error) this.runNext();
		this.fireEvent('success', arguments);
	},

	onFailure: function(){
		this.error = true;
		if (!this.options.stopOnFailure && this.options.autoAdvance) this.runNext();
		this.fireEvent('failure', arguments);
	},

	onException: function(){
		this.error = true;
		if (!this.options.stopOnFailure && this.options.autoAdvance) this.runNext();
		this.fireEvent('exception', arguments);
	}

});
