/**
 * JsHttpRequest: JavaScript "AJAX" data loader.
 * (C) 2006 Dmitry Koterov, http://forum.dklab.ru/users/DmitryKoterov/
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * See http://www.gnu.org/copyleft/lesser.html
 *
 * Do not remove this comment if you want to use script!
 * Не удаляйте данный комментарий, если вы хотите использовать скрипт!
 *
 * This library tries to use XMLHttpRequest (if available), and on
 * failure - use dynamically created <script> elements. Backend code
 * is the same for both cases. Library also supports file uploading;
 * in this case it uses FORM+IFRAME-based loading.
 *
 * @author Dmitry Koterov
 * @version 4.14
 */

function JsHttpRequest() { this._construct() }
(function() { // to create local-scope variables
	var COUNT       = 0;
	var PENDING     = {};
	var CACHE       = {};

	// Called by server script on data load. Static.
	JsHttpRequest.dataReady = function(id, text, js) {
		var undef;
		var th = PENDING[id];
		delete PENDING[id];
		if (th) {
			delete th._xmlReq;
			if (th.caching && th.hash) CACHE[th.hash] = [text, js];
			th._dataReady(text, js);
		} else if (th !== false) {
			throw "JsHttpRequest.dataReady(): unknown pending id: " + id;
		}
	}

	// Simple interface for most popular use-case.
	JsHttpRequest.query = function(url, content, onready, nocache) {
		var req = new JsHttpRequest();
		req.caching = !nocache;
		req.onreadystatechange = function() {
			if (req.readyState == 4) {
				onready(req.responseJS, req.responseText);
			}
		}
		req.open(null, url, true);
		req.send(content);
	},

	JsHttpRequest.prototype = {
		// Standard properties.
		onreadystatechange: null,
		readyState:         0,
		responseText:       null,
		responseXML:        null,
		status:             200,
		statusText:         "OK",
		// JavaScript response array/hash
		responseJS:         null,

		// Additional properties.
		session_name:       "PHPSESSID",  // set to SID cookie or GET parameter name
		caching:            false,        // need to use caching?
		loader:             null,         // loader to use ('form', 'script', 'xml'; null - autodetect)

		// Internals.
		_span:              null,
		_id:                null,
		_xmlReq:            null,
		_openArg:           null,
		_reqHeaders:        null,
		_maxUrlLen:         2000,

		dummy: function() {}, // empty constant function for ActiveX leak minimization

		abort: function() {
			if (this._xmlReq) {
				this._xmlReq.abort();
				this._xmlReq = null;
			}
			this._cleanupScript();
			this._changeReadyState(4, true); // 4 in IE & FF on abort() call; Opera does not change to 4.
		},

		open: function(method, url, asyncFlag, username, password) {
			// Append SID to original URL.
			var sid = this._getSid();
			if (sid) url += (url.indexOf('?')>=0? '&' : '?') + this.session_name + "=" + this.escape(sid);
			this._openArg = {
				method:     (method||'').toUpperCase(),
				url:        url,
				asyncFlag:  asyncFlag,
				username:   username != null? username : '',
				password:   password != null? password : ''
			};
			this._id = null;
			this._xmlReq = null;
			this._reqHeaders = [];
			this._changeReadyState(1, true); // compatibility with XMLHttpRequest
			return true;
		},

		send: function(content) {
			this._changeReadyState(1, true); // compatibility with XMLHttpRequest

			var id = (new Date().getTime()) + "" + COUNT++;
			var url = this._openArg.url;

			// Prepare to build QUERY_STRING from query hash.
			var queryText = [];
			var queryElem = [];
			if (!this._hash2query(content, null, queryText, queryElem)) return;

			var loader = (this.loader||'').toLowerCase();
			var method = this._openArg.method;
			var xmlReq = null;
			if (queryElem.length && !loader) {
				// Always use form loader if we have at least one form element.
				loader = 'form';
			} else {
				// Try to obtain XML request object.
				xmlReq = this._obtainXmlReq(id, url)
			}

			// Full URL if parameters are passed via GET.
			var fullGetUrl = url + (url.indexOf('?')>=0? '&' : '?') + queryText.join('&');

			// Solve hashcode BEFORE appending ID and check if cache is already present.
			this.hash = null;
			if (this.caching && !queryElem.length) {
				this.hash = fullGetUrl;
				if (CACHE[this.hash]) {
					var c = CACHE[this.hash];
					this._dataReady(c[0], c[1]);
					return false;
				}
			}

			// Detect loader and method. (Yes, lots of code and conditions!)
			var canSetHeaders = xmlReq && (window.ActiveXObject || xmlReq.setRequestHeader);
			if (!loader) {
				// Auto-detect loader.
				if (xmlReq) {
					// Can use XMLHttpRequest.
					loader = 'xml';
					switch (method) {
						case "POST":
							if (!canSetHeaders) {
								// Use POST method. Pass query in request body.
								// Opera 8.01 does not support setRequestHeader, so no POST method.
								loader = 'form';
							}
							break;
						case "GET":
							// Length of the query is checked later.
							break;
						default:
							// Method is not set: auto-detect method.
							if (canSetHeaders) {
								method = 'POST';
							} else {
								if (fullGetUrl.length > this._maxUrlLen) {
									method = 'POST';
									loader = 'form';
								} else {
									method = 'GET';
								}
							}
					}
				} else {
					// Cannot use XMLHttpRequest.
					loader = 'script';
					switch (method) {
						case "POST":
							loader = 'form';
							break;
						case "GET":
							// Length of the query is checked later.
							break;
						default:
							if (fullGetUrl.length > this._maxUrlLen) {
								method = 'POST';
								loader = 'form';
							} else {
								method = 'GET';
							}
					}
				}
			} else if (!method) {
				// Loader is pre-defined, but method is not set.
				switch (loader) {
					case 'form':
						method = 'POST';
						break;
					case 'script':
						method = 'GET';
						break;
					default:
						if (canSetHeaders) {
							method = 'POST';
						} else {
							method = 'GET';
						}
				}
			}

			// Correct GET URL.
			var requestBody = null;
			if (method == 'GET') {
				url = fullGetUrl;
				if (url.length > this._maxUrlLen) return this._error('Cannot use so long query (URL is ' + url.length + ' byte(s) length) with GET request.');
			} else if (method == 'POST') {
				requestBody = queryText.join('&');
			} else {
				return this._error('Unknown method: ' + method + '. Only GET and POST are supported.');
			}

			// Append loading ID to URL: a=aaa&b=bbb&<id>
			url = url + (url.indexOf('?')>=0? '&' : '?') + 'JsHttpRequest=' + id + '-' + loader;

			// Save loading script.
			PENDING[id] = this;

			// Send the request.
			switch (loader) {
				case 'xml':
					// Use XMLHttpRequest.
					if (!xmlReq) return this._error('Cannot use XMLHttpRequest or ActiveX loader: not supported');
					if (method == "POST" && !canSetHeaders) return this._error('Cannot use XMLHttpRequest loader or ActiveX loader, POST method: headers setting is not supported');
					if (queryElem.length) return this._error('Cannot use XMLHttpRequest loader: direct form elements using and uploading are not implemented');
					this._xmlReq = xmlReq;
					var a = this._openArg;
					this._xmlReq.open(method, url, a.asyncFlag, a.username, a.password);
					if (canSetHeaders) {
						// Pass pending headers.
						for (var i=0; i<this._reqHeaders.length; i++)
							this._xmlReq.setRequestHeader(this._reqHeaders[i][0], this._reqHeaders[i][1]);
						// Set non-default Content-type. We cannot use
						// "application/x-www-form-urlencoded" here, because
						// in PHP variable HTTP_RAW_POST_DATA is accessible only when
						// enctype is not default (e.g., "application/octet-stream"
						// is a good start). We parse POST data manually in backend
						// library code.
						this._xmlReq.setRequestHeader('Content-Type', 'application/octet-stream');
					}
					// Send the request.
					return this._xmlReq.send(requestBody);

				case 'script':
					// Create <script> element and run it.
					if (method != 'GET') return this._error('Cannot use SCRIPT loader: it supports only GET method');
					if (queryElem.length) return this._error('Cannot use SCRIPT loader: direct form elements using and uploading are not implemented');
					this._obtainScript(id, url);
					return true;

				case 'form':
					// Create & submit FORM.
					if (!this._obtainForm(id, url, method, queryText, queryElem)) return null;
					return true;

				default:
					return this._error('Unknown loader: ' + loader);
			}
		},

		getAllResponseHeaders: function() {
			if (this._xmlReq) return this._xmlReq.getAllResponseHeaders();
			return '';
		},

		getResponseHeader: function(label) {
			if (this._xmlReq) return this._xmlReq.getResponseHeader(label);
			return '';
		},

		setRequestHeader: function(label, value) {
			// Collect headers.
			this._reqHeaders[this._reqHeaders.length] = [label, value];
		},


		//
		// Internal functions.
		//

		// Constructor.
		_construct: function() {},

		// Do all work when data is ready.
		_dataReady: function(text, js) { with (this) {
			if (text !== null || js !== null) {
				status = 4;
				responseText = responseXML = text;
				responseJS = js;
			} else {
				status = 500;
				responseText = responseXML = responseJS = null;
			}
			_changeReadyState(2);
			_changeReadyState(3);
			_changeReadyState(4);
			_cleanupScript();
		}},

		// Called on error.
		_error: function(msg) {
			throw (window.Error? new Error(msg) : msg);
		},

		// Create new XMLHttpRequest object.
		_obtainXmlReq: function(id, url) {
			// If url.domain specified and differ from current, cannot use XMLHttpRequest!
			// XMLHttpRequest (and MS ActiveX'es) cannot work with different domains.
			var p = url.match(new RegExp('^[a-z]+://(.*)', 'i'));
			if (p) {
				var curHost = document.location.host.toLowerCase();
				if (p[1].substring(0, curHost.length).toLowerCase() == curHost) {
					url = p[1].substring(curHost.length, p[1].length);
				} else {
					return null;
				}
			}

			// Try to use built-in loaders.
			var req = null;
			if (window.XMLHttpRequest) {
				try { req = new XMLHttpRequest() } catch(e) {}
			} else if (window.ActiveXObject) {
				try { req = new ActiveXObject("Microsoft.XMLHTTP") } catch(e) {}
				if (!req) try { req = new ActiveXObject("Msxml2.XMLHTTP") } catch (e) {}
			}
			if (req) {
				var th = this;
				req.onreadystatechange = function() {
					if (req.readyState == 4) {
						// Avoid memory leak by removing closure.
						req.onreadystatechange = th.dummy;
						th.status = null;
						try {
							// In case of abort() call, req.status is unavailable and generates exception.
							// But req.readyState equals to 4 in this case. Stupid behaviour. :-(
							th.status = req.status;
							th.responseText = req.responseText;
						} catch (e) {}
						if (!th.status) return;
						var funcRequestBody = null;
						try {
							// Prepare generator function & catch syntax errors on this stage.
							eval('funcRequestBody = function() {\n' + th.responseText + '\n}');
						} catch (e) {
							return th._error("JavaScript code generated by backend is invalid!\n" + th.responseText)
						}
						// Call associated dataReady() outside try-catch block
						// to pass excaptions in onreadystatechange in usual manner.
						funcRequestBody();
					}
				};
				this._id = id;
			}
			return req;
		},

		// Create new script element and start loading.
		_obtainScript: function(id, href) { with (document) {
			// Oh shit! Damned stupid fucked Opera 7.23 does not allow to create SCRIPT
			// element over createElement (in HEAD or BODY section or in nested SPAN -
			// no matter): it is created deadly, and does not respons on href assignment.
			// So - always create SPAN.
			var span = createElement('SPAN');
			span.style.display = 'none';
			body.insertBefore(span, body.lastChild);
			span.innerHTML = 'Text for stupid IE.<s'+'cript></' + 'script>';
			setTimeout(function() {
				var s = span.getElementsByTagName('script')[0];
				s.language = 'JavaScript';
				if (s.setAttribute) s.setAttribute('src', href); else s.src = href;
			}, 10);
			this._id = id;
			this._span = span;
		}},

		// Create & submit form.
		_obtainForm: function(id, url, method, queryText, queryElem) {
			// In case of GET method - split real query string.
			if (method == 'GET') {
				queryText = url.split('?', 2)[1].split('&');
				url = url.split('?', 2)[0];
			}

			// Create invisible IFRAME with temporary form (form is used on empty queryElem).
			var div = document.createElement('DIV');
			div.id = 'jshr_d_' + id;
			div.style.position = 'absolute';
			div.style.visibility = 'hidden';
			div.innerHTML =
				'<form enctype="multipart/form-data"></form>' + // stupid IE, MUST use innerHTML assignment :-(
				'<iframe src="javascript:\'\'" name="jshr_i_' + id + '" style="width:0px; height:0px; overflow:hidden; border:none"></iframe>';
			var form = div.getElementsByTagName('FORM')[0];
			var iframe = div.getElementsByTagName('IFRAME')[0];

			// Check if all form elements belong to same form.
			if (queryElem.length) {
				// If we have at least one form element, we use its form as POST container.
				form = queryElem[0][1].form;
				var foundFile = false;
				for (var i = 0; i < queryElem.length; i++) {
					var e = queryElem[i][1];
					if (!e.form) {
						return this._error('Element "' + e.name + '" do not belongs to any form!');
					}
					if (e.form != form) {
						return this._error('Element "' + e.name + '" belongs to different form. All elements must belong to the same form!');
					}
					foundFile = foundFile || (e.tagName.toLowerCase() == 'input' && (e.type||'').toLowerCase() == 'file');
				}
				var et = "multipart/form-data";
				if (form.enctype != et && foundFile) {
					return this._error('Attribute "enctype" of elements\' form must be "' + et + '" (for IE), "' + form.enctype + '" given.');
				}
			}

			// Temporary disable ALL form elements in 'form' (including custom!).
			for (var i = 0; i < form.elements.length; i++) {
				var e = form.elements[i];
				if (e.name != null) {
					e.jshrSaveName = e.name;
					e.name = '';
				}
			}

			// Insert hidden fields to the form.
			var tmpE = [];
			for (var i=0; i<queryText.length; i++) {
				var pair = queryText[i].split('=', 2);
				var e = document.createElement('INPUT');
				e.type = 'hidden';
				e.name = unescape(pair[0]);
				e.value = pair[1] != null? unescape(pair[1]) : '';
				form.appendChild(e);
				tmpE[tmpE.length] = e;
			}

			// Enable custom form elements back & change their names.
			for (var i = 0; i < queryElem.length; i++) queryElem[i][1].name = queryElem[i][0];

			// Insert generated form inside the document.
			// Be careful: don't forget to close FORM container in document body!
			document.body.insertBefore(div, document.body.lastChild);
			this._span = div;

			// Temporary modify form attributes, submit form, restore attributes back.
			var sv = {};
			sv.enctype  = form.enctype;  form.enctype = "multipart/form-data";
			sv.action   = form.action;   form.action = url;
			sv.method   = form.method;   form.method = method;
			sv.target   = form.target;   form.target = iframe.name;
			sv.onsubmit = form.onsubmit; form.onsubmit = null;
			form.submit();
			for (var i in sv) form[i] = sv[i];

			// Remove generated temporary hidden elements from form.
			for (var i = 0; i < tmpE.length; i++) tmpE[i].parentNode.removeChild(tmpE[i]);

			// Enable all disabled elements back.
			for (var i = 0; i < form.elements.length; i++) {
				var e = form.elements[i];
				if (e.jshrSaveName != null) {
					e.name = e.jshrSaveName;
					e.jshrSaveName = null;
				}
			}
		},

		// Remove last used script element (clean memory).
		_cleanupScript: function() {
			var span = this._span;
			if (span) {
				this._span = null;
				setTimeout(function() {
					// without setTimeout - crash in IE 5.0!
					span.parentNode.removeChild(span);
				}, 50);
			}
			if (this._id) {
				// Mark this loading as aborted.
				PENDING[this._id] = false;
			}
			return false;
		},

		// Convert hash to QUERY_STRING.
		// If next value is scalar or hash, push it to queryText.
		// If next value is form element, push [name, element] to queryElem.
		_hash2query: function(content, prefix, queryText, queryElem) {
			if (prefix == null) prefix = "";
			if (content instanceof Object) {
				for (var k in content) {
					var v = content[k];
					if (v instanceof Function) continue;
					var curPrefix = prefix? prefix+'['+this.escape(k)+']' : this.escape(k);
					if (this._isFormElement(v)) {
						var tn = v.tagName.toLowerCase();
						if (tn == 'form') {
							// This is FORM itself. Add all its elements.
							for (var i=0; i<v.elements.length; i++) {
								var e = v.elements[i];
								if (e.name) queryElem[queryElem.length] = [e.name, e];
							}
						} else if (tn == 'input' || tn == 'textarea' || tn == 'select') {
							// This is a single form elemenent.
							queryElem[queryElem.length] = [curPrefix, v];
						} else {
							return this._error('Invalid FORM element detected: name=' + (e.name||'') + ', tag=' + e.tagName);
						}
					} else if (v instanceof Object) {
						this._hash2query(v, curPrefix, queryText, queryElem);
					} else {
						// We MUST skip NULL values, because there is no method
						// to pass NULL's via GET or POST request in PHP.
						if (v === null) continue;
						queryText[queryText.length] = curPrefix + "=" + this.escape('' + v);
					}
				}
			} else {
				queryText = [content];
			}
			return true;
		},

		// Return true if e is any form element of FORM itself.
		_isFormElement: function(e) {
			// Fast & dirty method.
			return e && e.ownerDocument && e.parentNode && e.parentNode.appendChild && e.tagName;
		},

		// Return value of SID based on QUERY_STRING or cookie
		// (PHP compatible sessions).
		_getSid: function() {
			var m = document.location.search.match(new RegExp('[&?]'+this.session_name+'=([^&?]*)'));
			var sid = null;
			if (m) {
				sid = m[1];
			} else {
				var m = document.cookie.match(new RegExp('(;|^)\\s*'+this.session_name+'=([^;]*)'));
				if (m) sid = m[2];
			}
			return sid;
		},

		// Change current readyState and call trigger method.
		_changeReadyState: function(s, reset) { with (this) {
			if (reset) {
				status = statusText = responseJS = null;
				responseText = '';
			}
			readyState = s;
			if (onreadystatechange) onreadystatechange();
		}},

		// Stupid JS escape() does not quote '+'.
		escape: function(s) {
			return escape(s).replace(new RegExp('\\+','g'), '%2B');
		}
	}
})();