ed3c69dd7ebc135ebc2448c4880f52b580d2c60a
[pazpar2-moved-to-github.git] / js / pz2.js
1 /*
2 ** $Id: pz2.js,v 1.65 2007-11-01 10:59:32 marc Exp $
3 ** pz2.js - pazpar2's javascript client library.
4 */
5
6 //since explorer is flawed
7 if (!window['Node']) {
8     window.Node = new Object();
9     Node.ELEMENT_NODE = 1;
10     Node.ATTRIBUTE_NODE = 2;
11     Node.TEXT_NODE = 3;
12     Node.CDATA_SECTION_NODE = 4;
13     Node.ENTITY_REFERENCE_NODE = 5;
14     Node.ENTITY_NODE = 6;
15     Node.PROCESSING_INSTRUCTION_NODE = 7;
16     Node.COMMENT_NODE = 8;
17     Node.DOCUMENT_NODE = 9;
18     Node.DOCUMENT_TYPE_NODE = 10;
19     Node.DOCUMENT_FRAGMENT_NODE = 11;
20     Node.NOTATION_NODE = 12;
21 }
22
23 // prevent execution of more than once
24 if(typeof window.pz2 == "undefined") {
25 window.undefined = window.undefined;
26
27 var pz2 = function ( paramArray )
28 {
29     
30     // at least one callback required
31     if ( !paramArray )
32         throw new Error("Pz2.js: Array with parameters has to be suplied."); 
33
34     //supported pazpar2's protocol version
35     this.suppProtoVer = '1';
36     if (typeof paramArray.pazpar2path != "undefined")
37         this.pz2String = paramArray.pazpar2path;
38     else
39         this.pz2String = "/pazpar2/search.pz2";
40     this.useSessions = true;
41     
42     this.stylesheet = paramArray.detailstylesheet || null;
43     //load stylesheet if required in async mode
44     if( this.stylesheet ) {
45         var context = this;
46         var request = new pzHttpRequest( this.stylesheet );
47         request.get( {}, function ( doc ) { context.xslDoc = doc; } );
48     }
49     
50     this.errorHandler = paramArray.errorhandler || null;
51     
52     // function callbacks
53     this.initCallback = paramArray.oninit || null;
54     this.statCallback = paramArray.onstat || null;
55     this.showCallback = paramArray.onshow || null;
56     this.termlistCallback = paramArray.onterm || null;
57     this.recordCallback = paramArray.onrecord || null;
58     this.bytargetCallback = paramArray.onbytarget || null;
59     this.resetCallback = paramArray.onreset || null;
60
61     // termlist keys
62     this.termKeys = paramArray.termlist || "subject";
63     
64     // some configurational stuff
65     this.keepAlive = 50000;
66     
67     if ( paramArray.keepAlive < this.keepAlive )
68         this.keepAlive = paramArray.keepAlive;
69
70     this.sessionID = null;
71     this.initStatusOK = false;
72     this.pingStatusOK = false;
73     this.searchStatusOK = false;
74     
75     // for sorting
76     this.currentSort = "relevance";
77
78     // where are we?
79     this.currentStart = 0;
80     this.currentNum = 20;
81
82     // last full record retrieved
83     this.currRecID = null;
84     
85     // current query
86     this.currQuery = null;
87
88     //timers
89     this.statTime = paramArray.stattime || 1000;
90     this.statTimer = null;
91     this.termTime = paramArray.termtime || 1000;
92     this.termTimer = null;
93     this.showTime = paramArray.showtime || 1000;
94     this.showTimer = null;
95     this.showFastCount = 4;
96     this.bytargetTime = paramArray.bytargettime || 1000;
97     this.bytargetTimer = null;
98
99     // counters for each command and applied delay
100     this.dumpFactor = 500;
101     this.showCounter = 0;
102     this.termCounter = 0;
103     this.statCounter = 0;
104     this.bytargetCounter = 0;
105
106     // active clients, updated by stat and show
107     // might be an issue since bytarget will poll accordingly
108     this.activeClients = 1;
109
110     // if in proxy mode no need to init
111     if (paramArray.usesessions != undefined) {
112          this.useSessions = paramArray.usesessions;
113         this.initStatusOK = true;
114     }
115     // else, auto init session or wait for a user init?
116     if (this.useSessions && paramArray.autoInit !== false) {
117         this.init();
118     }
119 };
120
121 pz2.prototype = 
122 {
123     //error handler for async error throws
124    throwError: function (errMsg, errCode)
125    {
126         var err = new Error(errMsg);
127         if (errCode) err.code = errCode;
128                 
129         if (this.errorHandler) {
130             this.errorHandler(err);
131         }
132         else {
133             throw err;
134         }
135    },
136
137     // stop activity by clearing tiemouts 
138    stop: function ()
139    {
140        clearTimeout(this.statTimer);
141        clearTimeout(this.showTimer);
142        clearTimeout(this.termTimer);
143        clearTimeout(this.bytargetTimer);
144     },
145     
146     // reset status variables
147     reset: function ()
148     {   
149         if ( this.useSessions ) {
150             this.sessionID = null;
151             this.initStatusOK = false;
152             this.pingStatusOK = false;
153         }
154         this.searchStatusOK = false;
155         this.stop();
156             
157         if ( this.resetCallback )
158                 this.resetCallback();
159     },
160
161     init: function ( sessionId ) 
162     {
163         this.reset();
164         
165         // session id as a param
166         if ( sessionId != undefined && this.useSessions ) {
167             this.initStatusOK = true;
168             this.sessionID = sessionId;
169             this.ping();
170         // old school direct pazpar2 init
171         } else if (this.useSessions) {
172             var context = this;
173             var request = new pzHttpRequest(this.pz2String, this.errorHandler);
174             request.get(
175                 { "command": "init" },
176                 function(data) {
177                     if ( data.getElementsByTagName("status")[0]
178                             .childNodes[0].nodeValue == "OK" ) {
179                         if ( data.getElementsByTagName("protocol")[0]
180                                 .childNodes[0].nodeValue 
181                             != context.suppProtoVer )
182                             throw new Error(
183                                 "Server's protocol not supported by the client"
184                             );
185                         context.initStatusOK = true;
186                         context.sessionID = 
187                             data.getElementsByTagName("session")[0]
188                                 .childNodes[0].nodeValue;
189                         setTimeout(
190                             function () {
191                                 context.ping();
192                             },
193                             context.keepAlive
194                         );
195                         if ( context.initCallback )
196                             context.initCallback();
197                     }
198                     else
199                         context.throwError('Init failed. Malformed WS resonse.',
200                                             110);
201                 }
202             );
203         // when through proxy no need to init
204         } else {
205             this.initStatusOK = true;
206         }
207     },
208     // no need to ping explicitly
209     ping: function () 
210     {
211         // pinging only makes sense when using pazpar2 directly
212         if( !this.initStatusOK || !this.useSessions )
213             throw new Error(
214             'Pz2.js: Ping not allowed (proxy mode) or session not initialized.'
215             );
216         var context = this;
217         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
218         request.get(
219             { "command": "ping", "session": this.sessionID },
220             function(data) {
221                 if ( data.getElementsByTagName("status")[0]
222                         .childNodes[0].nodeValue == "OK" ) {
223                     context.pingStatusOK = true;
224                     setTimeout(
225                         function () {
226                             context.ping();
227                         }, 
228                         context.keepAlive
229                     );
230                 }
231                 else
232                     context.throwError('Ping failed. Malformed WS resonse.',
233                                         111);
234             }
235         );
236     },
237     search: function (query, num, sort, filter, showfrom)
238     {
239         clearTimeout(this.statTimer);
240         clearTimeout(this.showTimer);
241         clearTimeout(this.termTimer);
242         clearTimeout(this.bytargetTimer);
243         
244         this.showCounter = 0;
245         this.termCounter = 0;
246         this.bytargetCounter = 0;
247         this.statCounter = 0;
248         
249         // no proxy mode
250         if( !this.initStatusOK )
251             throw new Error('Pz2.js: session not initialized.');
252         
253         if( query !== undefined )
254             this.currQuery = query;
255         else
256             throw new Error("Pz2.js: no query supplied to the search command.");
257         
258         if ( showfrom !== undefined )
259             var start = showfrom;
260         else
261             var start = 0;
262
263         var searchParams = { 
264             "command": "search",
265             "query": this.currQuery, 
266             "session": this.sessionID 
267         };
268         
269         if (filter !== undefined)
270             searchParams["filter"] = filter;
271         
272         var context = this;
273         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
274         request.get(
275             searchParams,
276             function(data) {
277                 if ( data.getElementsByTagName("status")[0]
278                         .childNodes[0].nodeValue == "OK" ) {
279                     context.searchStatusOK = true;
280                     //piggyback search
281                     context.show(start, num, sort);
282                     if ( context.statCallback )
283                         context.stat();
284                     if ( context.termlistCallback )
285                         context.termlist();
286                     if ( context.bytargetCallback )
287                         context.bytarget();
288                 }
289                 else
290                     context.throwError('Search failed. Malformed WS resonse.',
291                                         112);
292             }
293         );
294     },
295     stat: function()
296     {
297         if( !this.initStatusOK )
298             throw new Error('Pz2.js: session not initialized.');
299         
300         // if called explicitly takes precedence
301         clearTimeout(this.statTimer);
302         
303         var context = this;
304         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
305         request.get(
306             { "command": "stat", "session": this.sessionID },
307             function(data) {
308                 if ( data.getElementsByTagName("stat") ) {
309                     var activeClients = 
310                         Number( data.getElementsByTagName("activeclients")[0]
311                                     .childNodes[0].nodeValue );
312                     context.activeClients = activeClients;
313                     var stat = {
314                         "activeclients": activeClients,
315                         "hits": 
316                             Number( data.getElementsByTagName("hits")[0]
317                                         .childNodes[0].nodeValue ),
318                         "records": 
319                             Number( data.getElementsByTagName("records")[0]
320                                         .childNodes[0].nodeValue ),
321                         "clients": 
322                             Number( data.getElementsByTagName("clients")[0]
323                                         .childNodes[0].nodeValue ),
324                         "initializing": 
325                             Number( data.getElementsByTagName("initializing")[0]
326                                         .childNodes[0].nodeValue ),
327                         "searching": 
328                             Number( data.getElementsByTagName("searching")[0]
329                                         .childNodes[0].nodeValue ),
330                         "presenting": 
331                             Number( data.getElementsByTagName("presenting")[0]
332                                         .childNodes[0].nodeValue ),
333                         "idle": 
334                             Number( data.getElementsByTagName("idle")[0]
335                                         .childNodes[0].nodeValue ),
336                         "failed": 
337                             Number( data.getElementsByTagName("failed")[0]
338                                         .childNodes[0].nodeValue ),
339                         "error": 
340                             Number( data.getElementsByTagName("error")[0]
341                                         .childNodes[0].nodeValue )
342                     };
343                     
344                     context.statCounter++;
345                     var delay = context.statTime 
346                         + context.statCounter * context.dumpFactor;
347                     
348                     if ( activeClients > 0 )
349                         context.statTimer = 
350                             setTimeout( 
351                                 function () {
352                                     context.stat();
353                                 },
354                                 delay
355                             );
356                     context.statCallback(stat);
357                 }
358                 else
359                     context.throwError('Stat failed. Malformed WS resonse.',
360                                         113);
361             }
362         );
363     },
364     show: function(start, num, sort)
365     {
366         if( !this.searchStatusOK && this.useSessions )
367             throw new Error(
368                 'Pz2.js: show command has to be preceded with a search command.'
369             );
370         
371         // if called explicitly takes precedence
372         clearTimeout(this.showTimer);
373         
374         if( sort !== undefined )
375             this.currentSort = sort;
376         if( start !== undefined )
377             this.currentStart = Number( start );
378         if( num !== undefined )
379             this.currentNum = Number( num );
380
381         var context = this;
382         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
383         request.get(
384             { 
385                 "command": "show", 
386                 "session": this.sessionID, 
387                 "start": this.currentStart,
388                 "num": this.currentNum, 
389                 "sort": this.currentSort, 
390                 "block": 1 
391             },
392             function(data) {
393                 if ( data.getElementsByTagName("status")[0]
394                         .childNodes[0].nodeValue == "OK" ) {
395                     // first parse the status data send along with records
396                     // this is strictly bound to the format
397                     var activeClients = 
398                         Number( data.getElementsByTagName("activeclients")[0]
399                                     .childNodes[0].nodeValue );
400                     context.activeClients = activeClients; 
401                     var show = {
402                         "activeclients": activeClients,
403                         "merged": 
404                             Number( data.getElementsByTagName("merged")[0]
405                                         .childNodes[0].nodeValue ),
406                         "total": 
407                             Number( data.getElementsByTagName("total")[0]
408                                         .childNodes[0].nodeValue ),
409                         "start": 
410                             Number( data.getElementsByTagName("start")[0]
411                                         .childNodes[0].nodeValue ),
412                         "num": 
413                             Number( data.getElementsByTagName("num")[0]
414                                         .childNodes[0].nodeValue ),
415                         "hits": []
416                     };
417                     // parse all the first-level nodes for all <hit> tags
418                     var hits = data.getElementsByTagName("hit");
419                     var hit = new Array();
420                     for (i = 0; i < hits.length; i++) {
421                         show.hits[i] = new Array();
422                         show.hits[i]['location'] = new Array();
423                         var locCount = 0;
424                         for ( j = 0; j < hits[i].childNodes.length; j++) {
425                             if ( hits[i].childNodes[j].nodeType 
426                                 == Node.ELEMENT_NODE ) {
427                                 if (hits[i].childNodes[j].nodeName 
428                                     == 'location') {
429                                     var locNode = hits[i].childNodes[j];
430                                     var id = locNode.getAttribute('id');
431                                     show.hits[i]['location'][locCount] = {
432                                         "id": locNode.getAttribute("id"),
433                                         "name": locNode.getAttribute("name")
434                                     };
435                                     locCount++;
436                                 }
437                                 else {
438                                     var nodeName = 
439                                         hits[i].childNodes[j].nodeName;
440                                     var nodeText = 'ERROR'
441                                     if ( hits[i].childNodes[j].firstChild )
442                                         nodeText = 
443                                             hits[i].childNodes[j]
444                                                 .firstChild.nodeValue;
445                                     show.hits[i][nodeName] = nodeText;
446                                 }
447                             }
448                         }
449                     }
450                     context.showCounter++;
451                     var delay = context.showTime;
452                     if (context.showCounter > context.showFastCount)
453                             delay += context.showCounter * context.dumpFactor;
454                     if ( activeClients > 0 )
455                         context.showTimer = setTimeout(
456                             function () {
457                                 context.show();
458                             }, 
459                             delay);
460
461                     context.showCallback(show);
462                 }
463                 else
464                     context.throwError('Show failed. Malformed WS resonse.',
465                                         114);
466             }
467         );
468     },
469     record: function(id, offset, params)
470     {
471         // we may call record with no previous search if in proxy mode
472         if( !this.searchStatusOK && this.useSessions)
473            throw new Error(
474             'Pz2.js: record command has to be preceded with a search command.'
475             ); 
476         if ( params == undefined )
477             params = {};
478
479         if ( params.callback != undefined ) {
480             callback = params.callback;
481         } else {
482             callback = this.recordCallback;
483         }
484         
485         // what is that?
486         if ( params['handle'] == undefined )
487             handle = {};
488         else
489             handle = params['handle'];
490
491         if( id !== undefined )
492             this.currRecID = id;
493         
494         var context = this;
495         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
496
497         var recordParams = { "command": "record", 
498                             "session": this.sessionID,
499                             "id": this.currRecID };
500         
501         if (offset !== undefined) {
502             recordParams["offset"] = offset;
503         }
504
505         if (params.syntax != undefined) {
506             recordParams['syntax'] = params.syntax;
507         }
508
509         this.currRecOffset = offset;
510
511         request.get(
512             recordParams,
513             function(data) {
514                 var recordNode;
515                 var record = new Array();
516                 record['xmlDoc'] = data;
517                 if (context.currRecOffset !== undefined) {
518                     record['offset'] = context.currRecOffset;
519                     callback(record, handle);
520                 } else if ( recordNode = 
521                     data.getElementsByTagName("record")[0] ) {
522                     // if stylesheet was fetched do not parse the response
523                     if ( context.xslDoc ) {
524                         record['recid'] = 
525                             recordNode.getElementsByTagName("recid")[0]
526                                 .firstChild.nodeValue;
527                         record['xslDoc'] = 
528                             context.xslDoc;
529                     } else {
530                         for ( i = 0; i < recordNode.childNodes.length; i++) {
531                             if ( recordNode.childNodes[i].nodeType 
532                                 == Node.ELEMENT_NODE
533                                 && recordNode.childNodes[i].nodeName 
534                                 != 'location' ) {
535                                 var nodeName = 
536                                     recordNode.childNodes[i].nodeName;
537                                 var nodeText = '';
538                                 if (recordNode.childNodes[i].firstChild)
539                                     nodeText = recordNode.childNodes[i]
540                                         .firstChild.nodeValue;
541                                 record[nodeName] = nodeText;                            
542                             }
543                         }
544                         // the location might be empty!!
545                         var locationNodes = 
546                             recordNode.getElementsByTagName("location");
547                         record["location"] = new Array();
548                         for ( i = 0; i < locationNodes.length; i++ ) {
549                             record["location"][i] = {
550                                 "id": locationNodes[i].getAttribute("id"),
551                                 "name": locationNodes[i].getAttribute("name")
552                             };
553                             
554                             for (j = 0; 
555                                 j < locationNodes[i].childNodes.length; 
556                                 j++) {
557                                 if ( locationNodes[i].childNodes[j].nodeType 
558                                     == Node.ELEMENT_NODE ) {
559                                     var nodeName = 
560                                         locationNodes[i].childNodes[j].nodeName;
561                                     var nodeText = '';
562                                     if (locationNodes[i].childNodes[j]
563                                             .firstChild)
564                                         nodeText = 
565                                             locationNodes[i].childNodes[j]
566                                                 .firstChild.nodeValue;
567                                     record["location"][i][nodeName] = nodeText;                            
568                                 }
569                             }
570                         }
571                     }
572                     
573                     callback(record, handle);
574                 }
575                 else
576                     context.throwError('Record failed. Malformed WS resonse.',
577                                         115);
578             }
579         );
580     },
581
582     termlist: function()
583     {
584         if( !this.searchStatusOK && this.useSessions )
585             throw new Error(
586             'Pz2.js: termlist command has to be preceded with a search command.'
587             );
588
589         // if called explicitly takes precedence
590         clearTimeout(this.termTimer);
591         
592         var context = this;
593         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
594         request.get(
595             { 
596                 "command": "termlist", 
597                 "session": this.sessionID, 
598                 "name": this.termKeys 
599             },
600             function(data) {
601                 if ( data.getElementsByTagName("termlist") ) {
602                     var activeClients = 
603                         Number( data.getElementsByTagName("activeclients")[0]
604                                     .childNodes[0].nodeValue );
605                     context.activeClients = activeClients;
606                     var termList = { "activeclients":  activeClients };
607                     var termLists = data.getElementsByTagName("list");
608                     //for each termlist
609                     for (i = 0; i < termLists.length; i++) {
610                         var listName = termLists[i].getAttribute('name');
611                         termList[listName] = new Array();
612                         var terms = termLists[i].getElementsByTagName('term');
613                         //for each term in the list
614                         for (j = 0; j < terms.length; j++) { 
615                             var term = {
616                                 "name": 
617                                     (terms[j].getElementsByTagName("name")[0]
618                                         .childNodes.length 
619                                     ? terms[j].getElementsByTagName("name")[0]
620                                         .childNodes[0].nodeValue
621                                     : 'ERROR'),
622                                 "freq": 
623                                     terms[j]
624                                     .getElementsByTagName("frequency")[0]
625                                     .childNodes[0].nodeValue || 'ERROR'
626                             };
627
628                             var termIdNode = 
629                                 terms[j].getElementsByTagName("id");
630                             if(terms[j].getElementsByTagName("id").length)
631                                 term["id"] = 
632                                     termIdNode[0].childNodes[0].nodeValue;
633                             termList[listName][j] = term;
634                         }
635                     }
636
637                     context.termCounter++;
638                     var delay = context.termTime 
639                         + context.termCounter * context.dumpFactor;
640                     if ( activeClients > 0 )
641                         context.termTimer = 
642                             setTimeout(
643                                 function () {
644                                     context.termlist();
645                                 }, 
646                                 delay
647                             );
648                    
649                    context.termlistCallback(termList);
650                 }
651                 else
652                     context.throwError('Termlist failed. Malformed WS resonse.',
653                                         116);
654             }
655         );
656
657     },
658     bytarget: function()
659     {
660         if( !this.initStatusOK && this.useSessions )
661             throw new Error(
662             'Pz2.js: bytarget command has to be preceded with a search command.'
663             );
664         
665         // no need to continue
666         if( !this.searchStatusOK )
667             return;
668
669         // if called explicitly takes precedence
670         clearTimeout(this.bytargetTimer);
671         
672         var context = this;
673         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
674         request.get(
675             { "command": "bytarget", "session": this.sessionID },
676             function(data) {
677                 if ( data.getElementsByTagName("status")[0]
678                         .childNodes[0].nodeValue == "OK" ) {
679                     var targetNodes = data.getElementsByTagName("target");
680                     var bytarget = new Array();
681                     for ( i = 0; i < targetNodes.length; i++) {
682                         bytarget[i] = new Array();
683                         for( j = 0; j < targetNodes[i].childNodes.length; j++ ) {
684                             if ( targetNodes[i].childNodes[j].nodeType 
685                                 == Node.ELEMENT_NODE ) {
686                                 var nodeName = 
687                                     targetNodes[i].childNodes[j].nodeName;
688                                 var nodeText = 
689                                     targetNodes[i].childNodes[j]
690                                         .firstChild.nodeValue;
691                                 bytarget[i][nodeName] = nodeText;
692                             }
693                         }
694                     }
695                     
696                     context.bytargetCounter++;
697                     var delay = context.bytargetTime 
698                         + context.bytargetCounter * context.dumpFactor;
699                     if ( context.activeClients > 0 )
700                         context.bytargetTimer = 
701                             setTimeout(
702                                 function () {
703                                     context.bytarget();
704                                 }, 
705                                 delay
706                             );
707
708                     context.bytargetCallback(bytarget);
709                 }
710                 else
711                     context.throwError('Bytarget failed. Malformed WS resonse.',
712                                         117);
713             }
714         );
715     },
716     
717     // just for testing, probably shouldn't be here
718     showNext: function(page)
719     {
720         var step = page || 1;
721         this.show( ( step * this.currentNum ) + this.currentStart );     
722     },
723
724     showPrev: function(page)
725     {
726         if (this.currentStart == 0 )
727             return false;
728         var step = page || 1;
729         var newStart = this.currentStart - (step * this.currentNum );
730         this.show( newStart > 0 ? newStart : 0 );
731     },
732
733     showPage: function(pageNum)
734     {
735         //var page = pageNum || 1;
736         this.show(pageNum * this.currentNum);
737     }
738 };
739
740 /*
741 ********************************************************************************
742 ** AJAX HELPER CLASS ***********************************************************
743 ********************************************************************************
744 */
745 var pzHttpRequest = function ( url, errorHandler ) {
746         this.request = null;
747         this.url = url;
748         this.errorHandler = errorHandler || null;
749         this.async = true;
750         
751         if ( window.XMLHttpRequest ) {
752             this.request = new XMLHttpRequest();
753         } else if ( window.ActiveXObject ) {
754             try {
755                 this.request = new ActiveXObject( 'Msxml2.XMLHTTP' );
756             } catch (err) {
757                 this.request = new ActiveXObject( 'Microsoft.XMLHTTP' );
758             }
759         }
760 };
761
762 pzHttpRequest.prototype = 
763 {
764     get: function ( params, callback ) 
765     {
766         this._send( 'GET', params, '', callback );
767     },
768
769     post: function ( params, data, callback )
770     {
771         this._send( 'POST', params, data, callback );
772     },
773
774     load: function ()
775     {
776         this.async = false;
777         this.request.open( 'GET', this.url, this.async );
778         this.request.send('');
779         if ( this.request.status == 200 )
780             return this.request.responseXML;
781     },
782
783     _send: function ( type, params, data, callback )
784     {
785         this.callback = callback;
786         var context = this;
787         this.async = true;
788         this.request.open( type, this._urlAppendParams(params), this.async );
789         this.request.onreadystatechange = function () {
790             context._handleResponse();
791         }
792         this.request.send(data);
793     },
794
795     _urlAppendParams: function (params)
796     {
797         var getUrl = this.url;
798
799         var sep = '?';
800         var el = params;
801         for (var key in el) {
802             if (el[key] != null) {
803                 getUrl += sep + key + '=' + encodeURIComponent(el[key]);
804                 sep = '&';
805             }
806         }
807         return getUrl;
808     },
809
810     _handleResponse: function ()
811     {
812         if ( this.request.readyState == 4 ) { 
813             // pick up pazpr2 errors first
814             if ( this.request.responseXML 
815                 && this.request.responseXML.documentElement.nodeName == 'error'
816                 && this.request.responseXML.getElementsByTagName("error")
817                     .length ) {
818                 var errAddInfo = '';
819                 if ( this.request.responseXML.getElementsByTagName("error")[0]
820                         .childNodes.length )
821                     errAddInfo = ': ' + 
822                         this.request.responseXML
823                             .getElementsByTagName("error")[0]
824                             .childNodes[0].nodeValue;
825                 var errMsg = 
826                     this.request.responseXML.getElementsByTagName("error")[0]
827                         .getAttribute("msg");
828                 var errCode = 
829                     this.request.responseXML.getElementsByTagName("error")[0]
830                         .getAttribute("code");
831             
832                 var err = new Error(errMsg + errAddInfo);
833                 err.code = errCode;
834             
835                 if (this.errorHandler) {
836                     this.errorHandler(err);
837                 }
838                 else {
839                     throw err;
840                 }
841             } else if ( this.request.status == 200 ) {
842                 this.callback( this.request.responseXML );
843             } else {
844                 var err = new Error("Pz2.js: HTTP request error (AJAX). Code: " 
845                             + this.request.status + " Info: " 
846                             + this.request.statusText );
847                 err.code = 'HTTP';
848                 
849                 if (this.errorHandler) {
850                     this.errorHandler(err);
851                 }
852                 else {
853                     throw err;
854                 }
855             }
856         }
857     }
858 };
859
860 /*
861 ********************************************************************************
862 ** XML HELPER FUNCTIONS ********************************************************
863 ********************************************************************************
864 */
865
866 // DOMDocument
867
868 if ( window.ActiveXObject) {
869     var DOMDoc = document;
870 } else {
871     var DOMDoc = Document.prototype;
872 }
873
874 DOMDoc.newXmlDoc = function ( root )
875 {
876     var doc;
877
878     if (document.implementation && document.implementation.createDocument) {
879         doc = document.implementation.createDocument('', root, null);
880     } else if ( window.ActiveXObject ) {
881         doc = new ActiveXObject("MSXML2.DOMDocument");
882         doc.loadXML('<' + root + '/>');
883     } else {
884         throw new Error ('No XML support in this browser');
885     }
886
887     return doc;
888 }
889
890    
891 DOMDoc.parseXmlFromString = function ( xmlString ) 
892 {
893     var doc;
894
895     if ( window.DOMParser ) {
896         var parser = new DOMParser();
897         doc = parser.parseFromString( xmlString, "text/xml");
898     } else if ( window.ActiveXObject ) {
899         doc = new ActiveXObject("MSXML2.DOMDocument");
900         doc.loadXML( xmlString );
901     } else {
902         throw new Error ("No XML parsing support in this browser.");
903     }
904
905     return doc;
906 }
907
908 DOMDoc.transformToDoc = function (xmlDoc, xslDoc)
909 {
910     if ( window.XSLTProcessor ) {
911         var proc = new XSLTProcessor();
912         proc.importStylesheet( xslDoc );
913         return proc.transformToDocument(xmlDoc);
914     } else if ( window.ActiveXObject ) {
915         return document.parseXmlFromString(xmlDoc.transformNode(xslDoc));
916     } else {
917         alert( 'Unable to perform XSLT transformation in this browser' );
918     }
919 }
920  
921 // DOMElement
922
923 Element_removeFromDoc = function (DOM_Element)
924 {
925     DOM_Element.parentNode.removeChild(DOM_Element);
926 }
927
928 Element_emptyChildren = function (DOM_Element)
929 {
930     while( DOM_Element.firstChild ) {
931         DOM_Element.removeChild( DOM_Element.firstChild )
932     }
933 }
934
935 Element_appendTransformResult = function ( DOM_Element, xmlDoc, xslDoc )
936 {
937     if ( window.XSLTProcessor ) {
938         var proc = new XSLTProcessor();
939         proc.importStylesheet( xslDoc );
940         var docFrag = false;
941         docFrag = proc.transformToFragment( xmlDoc, DOM_Element.ownerDocument );
942         DOM_Element.appendChild(docFrag);
943     } else if ( window.ActiveXObject ) {
944         DOM_Element.innerHTML = xmlDoc.transformNode( xslDoc );
945     } else {
946         alert( 'Unable to perform XSLT transformation in this browser' );
947     }
948 }
949  
950 Element_appendTextNode = function (DOM_Element, tagName, textContent )
951 {
952     var node = DOM_Element.ownerDocument.createElement(tagName);
953     var text = DOM_Element.ownerDocument.createTextNode(textContent);
954
955     DOM_Element.appendChild(node);
956     node.appendChild(text);
957
958     return node;
959 }
960
961 Element_setTextContent = function ( DOM_Element, textContent )
962 {
963     if (typeof DOM_Element.textContent !== "undefined") {
964         DOM_Element.textContent = textContent;
965     } else if (typeof DOM_Element.innerText !== "undefined" ) {
966         DOM_Element.innerText = textContent;
967     } else {
968         throw new Error("Cannot set text content of the node, no such method.");
969     }
970 }
971
972 Element_getTextContent = function (DOM_Element)
973 {
974     if ( typeof DOM_Element.textContent != 'undefined' ) {
975         return DOM_Element.textContent;
976     } else if (typeof DOM_Element.text != 'undefined') {
977         return DOM_Element.text;
978     } else {
979         throw new Error("Cannot get text content of the node, no such method.");
980     }
981 }
982
983 /* do not remove trailing bracket */
984 }