/*******************************************************************************
 * @license
 * Copyright (c) 2012 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials are made 
 * available under the terms of the Eclipse Public License v1.0 
 * (http://www.eclipse.org/legal/epl-v10.html), and the Eclipse Distribution 
 * License v1.0 (http://www.eclipse.org/org/documents/edl-v10.html). 
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
/*global console define setTimeout clearTimeout XMLHttpRequest*/

/**
 * @name orion.xhr
 * @namespace Provides a promise-based API to {@link XMLHttpRequest}.
 */
define(['orion/Deferred'], function(Deferred) {

	/**
	 * @name orion.xhr.Result
	 * @class Wraps an XHR response or failure.
	 * @property {Object} args Arguments passed to the {@link orion.xhr.xhr} call.
	 * @property {Object|ArrayBuffer|Blob|Document|String} response The <code>response</code> object returned by the XMLHttpRequest.
	 * It is typed according to the <code>responseType</code> passed to the XHR call (by default it is a {@link String}).
	 * @property {String} [responseText] The <code>response</code> returned by the XMLHttpRequest, if it is a {@link String}.
	 * If the <code>response</code> is not a String, this property is <code>null</code>.
	 * @property {Number} status The HTTP status code returned by the XMLHttpRequest.
	 * @property {String} url The URL that the XHR request was made to.
	 * @property {XMLHttpRequest} xhr The underlying XMLHttpRequest object.
	 * @property {String|Error} error <i>Optional</i>. If a timeout occurred or an error was thrown while performing the
	 * XMLHttpRequest, this field contains information about the error.
	 */

	/**
	 * @param {String} url
	 * @param {Object} options
	 * @param {XMLHttpRequest} xhr
	 * @param {String|Error} [error]
	 */
	function makeResult(url, options, xhr, error) {
		var response = typeof xhr.response !== 'undefined' ? xhr.response : xhr.responseText; //$NON-NLS-0$
		var responseText = typeof response === 'string' ? response : null; //$NON-NLS-0$
		var status;
		try {
			status = xhr.status;
		} catch (e) {
			status = 0;
		}
		var result = {
			args: options,
			response: response,
			responseText: responseText,
			status: status,
			url: url,
			xhr: xhr
		};
		if (typeof error !== 'undefined') { //$NON-NLS-0$
			result.error = error;
		}
		return result;
	}

	/**
	 * Wrapper for {@link XMLHttpRequest} that returns a promise.
	 * @name xhr
	 * @methodOf orion.xhr
	 * @param {String} method One of 'GET', 'POST', 'PUT', 'DELETE'.
	 * @param {String} url The URL to request.
	 * @param {Object} [options]
	 * @param {Object|ArrayBuffer|Blob|Document} [options.data] The raw data to send as the request body. (Only allowed for POST and PUT).
	 * @param {Object} [options.headers] A map of header names and values to set on the request.
	 * @param {Boolean} [options.log=false] If <code>true</code>, failed requests will be logged to the JavaScript console.
	 * @param {String} [options.responseType=''] Determines the type of the response object returned. Value must be one of the following:
	 * <ul><li><code>'arraybuffer'</code>
	 * <li><code>'blob'</code>
	 * <li><code>'document'</code>
	 * <li><code>'json'</code>
	 * <li><code>'text'</code>
	 * <li><code>''</code> (same as <code>'text'</code>)</ul>
	 * @param {Number} [options.timeout=0] Timeout in milliseconds. Defaults to 0 (no timeout).
	 * @returns {Deferred} A deferred for the result. The deferred will resolve on 2xx, 3xx status codes or reject on 4xx, 5xx status codes.
	 * In both cases a {@link orion.xhr.Result} is provided to the listener.
	 */
	// TODO: upload progress, user/password
	function _xhr(method, url, options/*, XMLHttpRequestImpl */) {
		options = options || {};
		var xhr = (arguments.length > 3 && arguments[3]) ? arguments[3] : new XMLHttpRequest(); //$NON-NLS-0$
		var d = new Deferred();
		var headers = options.headers || {};
		var log = options.log || false;
		var data;
		if (typeof headers['X-Requested-With'] === 'undefined') { //$NON-NLS-1$ //$NON-NLS-0$
			headers['X-Requested-With'] = 'XMLHttpRequest'; //$NON-NLS-1$ //$NON-NLS-0$
		}
		if (typeof options.data !== 'undefined' && (method === 'POST' || method === 'PUT')) { //$NON-NLS-2$ //$NON-NLS-1$ //$NON-NLS-0$
			data = options.data;
		}
		if (typeof options.responseType === 'string') { //$NON-NLS-0$
			xhr.responseType = options.responseType;
		}
		xhr.onprogress = function(progressEvent) {
			progressEvent.xhr = xhr;
			d.progress(progressEvent);
		};
		xhr.onreadystatechange = function() {
			if (xhr.readyState === 4) {
				var result = makeResult(url, options, xhr);
				var statusCode = xhr.status;
				if (200 <= statusCode && statusCode < 400) {
					d.resolve(result);
				} else {
					if (log && typeof console !== 'undefined') { //$NON-NLS-0$
						console.log(new Error(xhr.statusText));
					}
					d.reject(result);
				}
			}
		};
		try {
			xhr.open(method, url, true /* async */);
			if (typeof options.timeout === 'number') { //$NON-NLS-0$
				if (typeof xhr.timeout === 'number') { //$NON-NLS-0$
					// Browser supports XHR timeout
					xhr.timeout = options.timeout;
					xhr.addEventListener('timeout', function(e) { //$NON-NLS-0$
						d.reject(makeResult(url, options, xhr, 'Timeout exceeded')); //$NON-NLS-0$
					});
				} else {
					// Use our own timer
					var timeoutId = setTimeout(function() {
						d.reject(makeResult(url, options, xhr, 'Timeout exceeded')); //$NON-NLS-0$
					}, options.timeout);
					d.then(clearTimeout.bind(null, timeoutId), clearTimeout.bind(null, timeoutId));
				}
			}
			Object.keys(headers).forEach(function(key) {
				xhr.setRequestHeader(key, headers[key]);
			});
			xhr.send(data);
		} catch (e) {
			d.reject(makeResult(url, options, xhr, e));
		}
		return d.promise;
	}
	return _xhr;
});