/*
 * XHRRequest
 * Visit http://createjs.com/ for documentation, updates and examples.
 *
 *
 * Copyright (c) 2012 gskinner.com, inc.
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/**
 * @module PreloadJS
 */

// namespace:
this.createjs = this.createjs || {};

(function () {
	"use strict";

// constructor
	/**
	 * A preloader that loads items using XHR requests, usually XMLHttpRequest. However XDomainRequests will be used
	 * for cross-domain requests if possible, and older versions of IE fall back on to ActiveX objects when necessary.
	 * XHR requests load the content as text or binary data, provide progress and consistent completion events, and
	 * can be canceled during load. Note that XHR is not supported in IE 6 or earlier, and is not recommended for
	 * cross-domain loading.
	 * @class XHRRequest
	 * @constructor
	 * @param {Object} item The object that defines the file to load. Please see the {{#crossLink "LoadQueue/loadFile"}}{{/crossLink}}
	 * for an overview of supported file properties.
	 * @extends AbstractLoader
	 */
	function XHRRequest(item) {
		this.AbstractRequest_constructor(item);

		// protected properties
		/**
		 * A reference to the XHR request used to load the content.
		 * @property _request
		 * @type {XMLHttpRequest | XDomainRequest | ActiveX.XMLHTTP}
		 * @private
		 */
		this._request = null;

		/**
		 * A manual load timeout that is used for browsers that do not support the onTimeout event on XHR (XHR level 1,
		 * typically IE9).
		 * @property _loadTimeout
		 * @type {Number}
		 * @private
		 */
		this._loadTimeout = null;

		/**
		 * The browser's XHR (XMLHTTPRequest) version. Supported versions are 1 and 2. There is no official way to detect
		 * the version, so we use capabilities to make a best guess.
		 * @property _xhrLevel
		 * @type {Number}
		 * @default 1
		 * @private
		 */
		this._xhrLevel = 1;

		/**
		 * The response of a loaded file. This is set because it is expensive to look up constantly. This property will be
		 * null until the file is loaded.
		 * @property _response
		 * @type {mixed}
		 * @private
		 */
		this._response = null;

		/**
		 * The response of the loaded file before it is modified. In most cases, content is converted from raw text to
		 * an HTML tag or a formatted object which is set to the <code>result</code> property, but the developer may still
		 * want to access the raw content as it was loaded.
		 * @property _rawResponse
		 * @type {String|Object}
		 * @private
		 */
		this._rawResponse = null;

		this._canceled = false;

		// Setup our event handlers now.
		this._handleLoadStartProxy = createjs.proxy(this._handleLoadStart, this);
		this._handleProgressProxy = createjs.proxy(this._handleProgress, this);
		this._handleAbortProxy = createjs.proxy(this._handleAbort, this);
		this._handleErrorProxy = createjs.proxy(this._handleError, this);
		this._handleTimeoutProxy = createjs.proxy(this._handleTimeout, this);
		this._handleLoadProxy = createjs.proxy(this._handleLoad, this);
		this._handleReadyStateChangeProxy = createjs.proxy(this._handleReadyStateChange, this);

		if (!this._createXHR(item)) {
			//TODO: Throw error?
		}
	};

	var p = createjs.extend(XHRRequest, createjs.AbstractRequest);

// static properties
	/**
	 * A list of XMLHTTP object IDs to try when building an ActiveX object for XHR requests in earlier versions of IE.
	 * @property ACTIVEX_VERSIONS
	 * @type {Array}
	 * @since 0.4.2
	 * @private
	 */
	XHRRequest.ACTIVEX_VERSIONS = [
		"Msxml2.XMLHTTP.6.0",
		"Msxml2.XMLHTTP.5.0",
		"Msxml2.XMLHTTP.4.0",
		"MSXML2.XMLHTTP.3.0",
		"MSXML2.XMLHTTP",
		"Microsoft.XMLHTTP"
	];

// Public methods
	/**
	 * Look up the loaded result.
	 * @method getResult
	 * @param {Boolean} [raw=false] Return a raw result instead of a formatted result. This applies to content
	 * loaded via XHR such as scripts, XML, CSS, and Images. If there is no raw result, the formatted result will be
	 * returned instead.
	 * @return {Object} A result object containing the content that was loaded, such as:
	 * <ul>
	 *      <li>An image tag (&lt;image /&gt;) for images</li>
	 *      <li>A script tag for JavaScript (&lt;script /&gt;). Note that scripts loaded with tags may be added to the
	 *      HTML head.</li>
	 *      <li>A style tag for CSS (&lt;style /&gt;)</li>
	 *      <li>Raw text for TEXT</li>
	 *      <li>A formatted JavaScript object defined by JSON</li>
	 *      <li>An XML document</li>
	 *      <li>An binary arraybuffer loaded by XHR</li>
	 * </ul>
	 * Note that if a raw result is requested, but not found, the result will be returned instead.
	 */
	p.getResult = function (raw) {
		if (raw && this._rawResponse) {
			return this._rawResponse;
		}
		return this._response;
	};

	// Overrides abstract method in AbstractRequest
	p.cancel = function () {
		this.canceled = true;
		this._clean();
		this._request.abort();
	};

	// Overrides abstract method in AbstractLoader
	p.load = function () {
		if (this._request == null) {
			this._handleError();
			return;
		}

		//Events
		this._request.addEventListener("loadstart", this._handleLoadStartProxy, false);
		this._request.addEventListener("progress", this._handleProgressProxy, false);
		this._request.addEventListener("abort", this._handleAbortProxy, false);
		this._request.addEventListener("error",this._handleErrorProxy, false);
		this._request.addEventListener("timeout", this._handleTimeoutProxy, false);

		// Note: We don't get onload in all browsers (earlier FF and IE). onReadyStateChange handles these.
		this._request.addEventListener("load", this._handleLoadProxy, false);
		this._request.addEventListener("readystatechange", this._handleReadyStateChangeProxy, false);

		// Set up a timeout if we don't have XHR2
		if (this._xhrLevel == 1) {
			this._loadTimeout = setTimeout(createjs.proxy(this._handleTimeout, this), this._item.loadTimeout);
		}

		// Sometimes we get back 404s immediately, particularly when there is a cross origin request.  // note this does not catch in Chrome
		try {
			if (!this._item.values || this._item.method == createjs.AbstractLoader.GET) {
				this._request.send();
			} else if (this._item.method == createjs.AbstractLoader.POST) {
				this._request.send(createjs.RequestUtils.formatQueryString(this._item.values));
			}
		} catch (error) {
			this.dispatchEvent(new createjs.ErrorEvent("XHR_SEND", null, error));
		}
	};

	p.setResponseType = function (type) {
		this._request.responseType = type;
	};

	/**
	 * Get all the response headers from the XmlHttpRequest.
	 *
	 * <strong>From the docs:</strong> Return all the HTTP headers, excluding headers that are a case-insensitive match
	 * for Set-Cookie or Set-Cookie2, as a single string, with each header line separated by a U+000D CR U+000A LF pair,
	 * excluding the status line, and with each header name and header value separated by a U+003A COLON U+0020 SPACE
	 * pair.
	 * @method getAllResponseHeaders
	 * @return {String}
	 * @since 0.4.1
	 */
	p.getAllResponseHeaders = function () {
		if (this._request.getAllResponseHeaders instanceof Function) {
			return this._request.getAllResponseHeaders();
		} else {
			return null;
		}
	};

	/**
	 * Get a specific response header from the XmlHttpRequest.
	 *
	 * <strong>From the docs:</strong> Returns the header field value from the response of which the field name matches
	 * header, unless the field name is Set-Cookie or Set-Cookie2.
	 * @method getResponseHeader
	 * @param {String} header The header name to retrieve.
	 * @return {String}
	 * @since 0.4.1
	 */
	p.getResponseHeader = function (header) {
		if (this._request.getResponseHeader instanceof Function) {
			return this._request.getResponseHeader(header);
		} else {
			return null;
		}
	};

// protected methods
	/**
	 * The XHR request has reported progress.
	 * @method _handleProgress
	 * @param {Object} event The XHR progress event.
	 * @private
	 */
	p._handleProgress = function (event) {
		if (!event || event.loaded > 0 && event.total == 0) {
			return; // Sometimes we get no "total", so just ignore the progress event.
		}

		var newEvent = new createjs.ProgressEvent(event.loaded, event.total);
		this.dispatchEvent(newEvent);
	};

	/**
	 * The XHR request has reported a load start.
	 * @method _handleLoadStart
	 * @param {Object} event The XHR loadStart event.
	 * @private
	 */
	p._handleLoadStart = function (event) {
		clearTimeout(this._loadTimeout);
		this.dispatchEvent("loadstart");
	};

	/**
	 * The XHR request has reported an abort event.
	 * @method handleAbort
	 * @param {Object} event The XHR abort event.
	 * @private
	 */
	p._handleAbort = function (event) {
		this._clean();
		this.dispatchEvent(new createjs.ErrorEvent("XHR_ABORTED", null, event));
	};

	/**
	 * The XHR request has reported an error event.
	 * @method _handleError
	 * @param {Object} event The XHR error event.
	 * @private
	 */
	p._handleError = function (event) {
		this._clean();
		this.dispatchEvent(new createjs.ErrorEvent(event.message));
	};

	/**
	 * The XHR request has reported a readyState change. Note that older browsers (IE 7 & 8) do not provide an onload
	 * event, so we must monitor the readyStateChange to determine if the file is loaded.
	 * @method _handleReadyStateChange
	 * @param {Object} event The XHR readyStateChange event.
	 * @private
	 */
	p._handleReadyStateChange = function (event) {
		if (this._request.readyState == 4) {
			this._handleLoad();
		}
	};

	/**
	 * The XHR request has completed. This is called by the XHR request directly, or by a readyStateChange that has
	 * <code>request.readyState == 4</code>. Only the first call to this method will be processed.
	 * @method _handleLoad
	 * @param {Object} event The XHR load event.
	 * @private
	 */
	p._handleLoad = function (event) {
		if (this.loaded) {
			return;
		}
		this.loaded = true;

		var error = this._checkError();
		if (error) {
			this._handleError(error);
			return;
		}

		this._response = this._getResponse();
		this._clean();

		this.dispatchEvent(new createjs.Event("complete"));
	};

	/**
	 * The XHR request has timed out. This is called by the XHR request directly, or via a <code>setTimeout</code>
	 * callback.
	 * @method _handleTimeout
	 * @param {Object} [event] The XHR timeout event. This is occasionally null when called by the backup setTimeout.
	 * @private
	 */
	p._handleTimeout = function (event) {
		this._clean();

		this.dispatchEvent(new createjs.ErrorEvent("PRELOAD_TIMEOUT", null, event));
	};

// Protected
	/**
	 * Determine if there is an error in the current load. This checks the status of the request for problem codes. Note
	 * that this does not check for an actual response. Currently, it only checks for 404 or 0 error code.
	 * @method _checkError
	 * @return {int} If the request status returns an error code.
	 * @private
	 */
	p._checkError = function () {
		//LM: Probably need additional handlers here, maybe 501
		var status = parseInt(this._request.status);

		switch (status) {
			case 404:   // Not Found
			case 0:     // Not Loaded
				return new Error(status);
		}
		return null;
	};

	/**
	 * Validate the response. Different browsers have different approaches, some of which throw errors when accessed
	 * in other browsers. If there is no response, the <code>_response</code> property will remain null.
	 * @method _getResponse
	 * @private
	 */
	p._getResponse = function () {
		if (this._response != null) {
			return this._response;
		}

		if (this._request.response != null) {
			return this._request.response;
		}

		// Android 2.2 uses .responseText
		try {
			if (this._request.responseText != null) {
				return this._request.responseText;
			}
		} catch (e) {
		}

		// When loading XML, IE9 does not return .response, instead it returns responseXML.xml
		try {
			if (this._request.responseXML != null) {
				return this._request.responseXML;
			}
		} catch (e) {
		}

		return null;
	};

	/**
	 * Create an XHR request. Depending on a number of factors, we get totally different results.
	 * <ol><li>Some browsers get an <code>XDomainRequest</code> when loading cross-domain.</li>
	 *      <li>XMLHttpRequest are created when available.</li>
	 *      <li>ActiveX.XMLHTTP objects are used in older IE browsers.</li>
	 *      <li>Text requests override the mime type if possible</li>
	 *      <li>Origin headers are sent for crossdomain requests in some browsers.</li>
	 *      <li>Binary loads set the response type to "arraybuffer"</li></ol>
	 * @method _createXHR
	 * @param {Object} item The requested item that is being loaded.
	 * @return {Boolean} If an XHR request or equivalent was successfully created.
	 * @private
	 */
	p._createXHR = function (item) {
		// Check for cross-domain loads. We can't fully support them, but we can try.
		var crossdomain = createjs.RequestUtils.isCrossDomain(item);
		var headers = {};

		// Create the request. Fallback to whatever support we have.
		var req = null;
		if (window.XMLHttpRequest) {
			req = new XMLHttpRequest();
			// This is 8 or 9, so use XDomainRequest instead.
			if (crossdomain && req.withCredentials === undefined && window.XDomainRequest) {
				req = new XDomainRequest();
			}
		} else { // Old IE versions use a different approach
			for (var i = 0, l = s.ACTIVEX_VERSIONS.length; i < l; i++) {
				var axVersion = s.ACTIVEX_VERSIONS[i];
				try {
					req = new ActiveXObject(axVersions);
					break;
				} catch (e) {}
			}
			if (req == null) { return false; }
		}

		// Default to utf-8 for Text requests.
		if (item.mimeType == null && createjs.RequestUtils.isText(item.type)) {
			item.mimeType = "text/plain; charset=utf-8";
		}

		// IE9 doesn't support overrideMimeType(), so we need to check for it.
		if (item.mimeType && req.overrideMimeType) {
			req.overrideMimeType(item.mimeType);
		}

		// Determine the XHR level
		this._xhrLevel = (typeof req.responseType === "string") ? 2 : 1;

		var src = null;
		if (item.method == createjs.AbstractLoader.GET) {
			src = createjs.RequestUtils.buildPath(item.src, item.values);
		} else {
			src = item.src;
		}

		// Open the request.  Set cross-domain flags if it is supported (XHR level 1 only)
		req.open(item.method || createjs.AbstractLoader.GET, src, true);

		if (crossdomain && req instanceof XMLHttpRequest && this._xhrLevel == 1) {
			headers["Origin"] = location.origin;
		}

		// To send data we need to set the Content-type header)
		if (item.values && item.method == createjs.AbstractLoader.POST) {
			headers["Content-Type"] = "application/x-www-form-urlencoded";
		}

		if (!crossdomain && !headers["X-Requested-With"]) {
			headers["X-Requested-With"] = "XMLHttpRequest";
		}

		if (item.headers) {
			for (var n in item.headers) {
				headers[n] = item.headers[n];
			}
		}

		for (n in headers) {
			req.setRequestHeader(n, headers[n])
		}

		if (req instanceof XMLHttpRequest && item.withCredentials !== undefined) {
			req.withCredentials = item.withCredentials;
		}

		this._request = req;

		return true;
	};

	/**
	 * A request has completed (or failed or canceled), and needs to be disposed.
	 * @method _clean
	 * @private
	 */
	p._clean = function () {
		clearTimeout(this._loadTimeout);

		this._request.removeEventListener("loadstart", this._handleLoadStartProxy);
		this._request.removeEventListener("progress", this._handleProgressProxy);
		this._request.removeEventListener("abort", this._handleAbortProxy);
		this._request.removeEventListener("error",this._handleErrorProxy);
		this._request.removeEventListener("timeout", this._handleTimeoutProxy);
		this._request.removeEventListener("load", this._handleLoadProxy);
		this._request.removeEventListener("readystatechange", this._handleReadyStateChangeProxy);
	};

	p.toString = function () {
		return "[PreloadJS XHRRequest]";
	};

	createjs.XHRRequest = createjs.promote(XHRRequest, "AbstractRequest");

}());