/*
---

script: Request.JSONP.js

name: Request.JSONP

description: Defines Request.JSONP, a class for cross domain javascript via script injection.

license: MIT-style license

authors:
  - Aaron Newton
  - Guillermo Rauch

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

provides: [Request.JSONP]

...
*/

Request.JSONP = new Class({

	Implements: [Chain, Events, Options, Log],

	options: {/*
		onRetry: $empty(intRetries),
		onRequest: $empty(scriptElement),
		onComplete: $empty(data),
		onSuccess: $empty(data),
		onCancel: $empty(),
		log: false,
		*/
		url: '',
		data: {},
		retries: 0,
		timeout: 0,
		link: 'ignore',
		callbackKey: 'callback',
		injectScript: document.head
	},

	initialize: function(options){
		this.setOptions(options);
		if (this.options.log) this.enableLog();
		this.running = false;
		this.requests = 0;
		this.triesRemaining = [];
	},

	check: function(){
		if (!this.running) return true;
		switch (this.options.link){
			case 'cancel': this.cancel(); return true;
			case 'chain': this.chain(this.caller.bind(this, arguments)); return false;
		}
		return false;
	},

	send: function(options){
		if (!$chk(arguments[1]) && !this.check(options)) return this;

		var type = $type(options), 
				old = this.options, 
				index = $chk(arguments[1]) ? arguments[1] : this.requests++;
		if (type == 'string' || type == 'element') options = {data: options};

		options = $extend({data: old.data, url: old.url}, options);

		if (!$chk(this.triesRemaining[index])) this.triesRemaining[index] = this.options.retries;
		var remaining = this.triesRemaining[index];

		(function(){
			var script = this.getScript(options);
			this.log('JSONP retrieving script with url: ' + script.get('src'));
			this.fireEvent('request', script);
			this.running = true;

			(function(){
				if (remaining){
					this.triesRemaining[index] = remaining - 1;
					if (script){
						script.destroy();
						this.send(options, index).fireEvent('retry', this.triesRemaining[index]);
					}
				} else if(this.running && script && this.options.timeout){
					script.destroy();
					this.cancel().fireEvent('failure');
				}
			}).delay(this.options.timeout, this);
		}).delay(Browser.Engine.trident ? 50 : 0, this);
		return this;
	},

	cancel: function(){
		if (!this.running) return this;
		this.running = false;
		this.fireEvent('cancel');
		return this;
	},

	getScript: function(options){
		var index = Request.JSONP.counter,
				data;
		Request.JSONP.counter++;

		switch ($type(options.data)){
			case 'element': data = document.id(options.data).toQueryString(); break;
			case 'object': case 'hash': data = Hash.toQueryString(options.data);
		}

		var src = options.url + 
			 (options.url.test('\\?') ? '&' :'?') + 
			 (options.callbackKey || this.options.callbackKey) + 
			 '=Request.JSONP.request_map.request_'+ index + 
			 (data ? '&' + data : '');
		if (src.length > 2083) this.log('JSONP '+ src +' will fail in Internet Explorer, which enforces a 2083 bytes length limit on URIs');

		var script = new Element('script', {type: 'text/javascript', src: src});
		Request.JSONP.request_map['request_' + index] = function(){ this.success(arguments, script); }.bind(this);
		return script.inject(this.options.injectScript);
	},

	success: function(args, script){
		if (!this.running) return false;
		if (script) script.destroy();
		this.running = false;
		this.log('JSONP successfully retrieved: ', args);
		this.fireEvent('complete', args).fireEvent('success', args).callChain();
	}

});

Request.JSONP.counter = 0;
Request.JSONP.request_map = {};
