js/pz2.js

   1 /*
   2 ** $Id: pz2.js,v 1.70 2008-03-12 11:36:57 jakub 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     //current raw record offset
  89     this.currRecOffset = null;
  90
  91     //timers
  92     this.statTime = paramArray.stattime || 1000;
  93     this.statTimer = null;
  94     this.termTime = paramArray.termtime || 1000;
  95     this.termTimer = null;
  96     this.showTime = paramArray.showtime || 1000;
  97     this.showTimer = null;
  98     this.showFastCount = 4;
  99     this.bytargetTime = paramArray.bytargettime || 1000;
 100     this.bytargetTimer = null;
 101
 102     // counters for each command and applied delay
 103     this.dumpFactor = 500;
 104     this.showCounter = 0;
 105     this.termCounter = 0;
 106     this.statCounter = 0;
 107     this.bytargetCounter = 0;
 108
 109     // active clients, updated by stat and show
 110     // might be an issue since bytarget will poll accordingly
 111     this.activeClients = 1;
 112
 113     // if in proxy mode no need to init
 114     if (paramArray.usesessions != undefined) {
 115          this.useSessions = paramArray.usesessions;
 116         this.initStatusOK = true;
 117     }
 118     // else, auto init session or wait for a user init?
 119     if (this.useSessions && paramArray.autoInit !== false) {
 120         this.init();
 121     }
 122 };
 123
 124 pz2.prototype =
 125 {
 126     //error handler for async error throws
 127    throwError: function (errMsg, errCode)
 128    {
 129         var err = new Error(errMsg);
 130         if (errCode) err.code = errCode;
 131
 132         if (this.errorHandler) {
 133             this.errorHandler(err);
 134         }
 135         else {
 136             throw err;
 137         }
 138    },
 139
 140     // stop activity by clearing tiemouts
 141    stop: function ()
 142    {
 143        clearTimeout(this.statTimer);
 144        clearTimeout(this.showTimer);
 145        clearTimeout(this.termTimer);
 146        clearTimeout(this.bytargetTimer);
 147     },
 148
 149     // reset status variables
 150     reset: function ()
 151     {
 152         if ( this.useSessions ) {
 153             this.sessionID = null;
 154             this.initStatusOK = false;
 155             this.pingStatusOK = false;
 156         }
 157         this.searchStatusOK = false;
 158         this.stop();
 159
 160         if ( this.resetCallback )
 161                 this.resetCallback();
 162     },
 163
 164     init: function ( sessionId )
 165     {
 166         this.reset();
 167
 168         // session id as a param
 169         if ( sessionId != undefined && this.useSessions ) {
 170             this.initStatusOK = true;
 171             this.sessionID = sessionId;
 172             this.ping();
 173         // old school direct pazpar2 init
 174         } else if (this.useSessions) {
 175             var context = this;
 176             var request = new pzHttpRequest(this.pz2String, this.errorHandler);
 177             request.safeGet(
 178                 { "command": "init" },
 179                 function(data) {
 180                     if ( data.getElementsByTagName("status")[0]
 181                             .childNodes[0].nodeValue == "OK" ) {
 182                         if ( data.getElementsByTagName("protocol")[0]
 183                                 .childNodes[0].nodeValue
 184                             != context.suppProtoVer )
 185                             throw new Error(
 186                                 "Server's protocol not supported by the client"
 187                             );
 188                         context.initStatusOK = true;
 189                         context.sessionID =
 190                             data.getElementsByTagName("session")[0]
 191                                 .childNodes[0].nodeValue;
 192                         setTimeout(
 193                             function () {
 194                                 context.ping();
 195                             },
 196                             context.keepAlive
 197                         );
 198                         if ( context.initCallback )
 199                             context.initCallback();
 200                     }
 201                     else
 202                         context.throwError('Init failed. Malformed WS resonse.',
 203                                             110);
 204                 }
 205             );
 206         // when through proxy no need to init
 207         } else {
 208             this.initStatusOK = true;
 209         }
 210     },
 211     // no need to ping explicitly
 212     ping: function ()
 213     {
 214         // pinging only makes sense when using pazpar2 directly
 215         if( !this.initStatusOK || !this.useSessions )
 216             throw new Error(
 217             'Pz2.js: Ping not allowed (proxy mode) or session not initialized.'
 218             );
 219         var context = this;
 220         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
 221         request.safeGet(
 222             { "command": "ping", "session": this.sessionID },
 223             function(data) {
 224                 if ( data.getElementsByTagName("status")[0]
 225                         .childNodes[0].nodeValue == "OK" ) {
 226                     context.pingStatusOK = true;
 227                     setTimeout(
 228                         function () {
 229                             context.ping();
 230                         },
 231                         context.keepAlive
 232                     );
 233                 }
 234                 else
 235                     context.throwError('Ping failed. Malformed WS resonse.',
 236                                         111);
 237             }
 238         );
 239     },
 240     search: function (query, num, sort, filter, showfrom, addParamsArr)
 241     {
 242         clearTimeout(this.statTimer);
 243         clearTimeout(this.showTimer);
 244         clearTimeout(this.termTimer);
 245         clearTimeout(this.bytargetTimer);
 246
 247         this.showCounter = 0;
 248         this.termCounter = 0;
 249         this.bytargetCounter = 0;
 250         this.statCounter = 0;
 251
 252         // no proxy mode
 253         if( !this.initStatusOK )
 254             throw new Error('Pz2.js: session not initialized.');
 255
 256         if( query !== undefined )
 257             this.currQuery = query;
 258         else
 259             throw new Error("Pz2.js: no query supplied to the search command.");
 260
 261         if ( showfrom !== undefined )
 262             var start = showfrom;
 263         else
 264             var start = 0;
 265
 266         var searchParams = {
 267             "command": "search",
 268             "query": this.currQuery,
 269             "session": this.sessionID
 270         };
 271
 272         if (filter !== undefined)
 273             searchParams["filter"] = filter;
 274
 275         // copy additional parmeters, do not overwrite
 276         if (addParamsArr != undefined) {
 277             for (var prop in addParamsArr) {
 278                 if (!searchParams.hasOwnProperty(prop))
 279                     searchParams[prop] = addParamsArr[prop];
 280             }
 281         }
 282
 283         var context = this;
 284         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
 285         request.safeGet(
 286             searchParams,
 287             function(data) {
 288                 if ( data.getElementsByTagName("status")[0]
 289                         .childNodes[0].nodeValue == "OK" ) {
 290                     context.searchStatusOK = true;
 291                     //piggyback search
 292                     context.show(start, num, sort);
 293                     if ( context.statCallback )
 294                         context.stat();
 295                     if ( context.termlistCallback )
 296                         context.termlist();
 297                     if ( context.bytargetCallback )
 298                         context.bytarget();
 299                 }
 300                 else
 301                     context.throwError('Search failed. Malformed WS resonse.',
 302                                         112);
 303             }
 304         );
 305     },
 306     stat: function()
 307     {
 308         if( !this.initStatusOK )
 309             throw new Error('Pz2.js: session not initialized.');
 310
 311         // if called explicitly takes precedence
 312         clearTimeout(this.statTimer);
 313
 314         var context = this;
 315         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
 316         request.safeGet(
 317             { "command": "stat", "session": this.sessionID },
 318             function(data) {
 319                 if ( data.getElementsByTagName("stat") ) {
 320                     var activeClients =
 321                         Number( data.getElementsByTagName("activeclients")[0]
 322                                     .childNodes[0].nodeValue );
 323                     context.activeClients = activeClients;
 324                     var stat = {
 325                         "activeclients": activeClients,
 326                         "hits":
 327                             Number( data.getElementsByTagName("hits")[0]
 328                                         .childNodes[0].nodeValue ),
 329                         "records":
 330                             Number( data.getElementsByTagName("records")[0]
 331                                         .childNodes[0].nodeValue ),
 332                         "clients":
 333                             Number( data.getElementsByTagName("clients")[0]
 334                                         .childNodes[0].nodeValue ),
 335                         "initializing":
 336                             Number( data.getElementsByTagName("initializing")[0]
 337                                         .childNodes[0].nodeValue ),
 338                         "searching":
 339                             Number( data.getElementsByTagName("searching")[0]
 340                                         .childNodes[0].nodeValue ),
 341                         "presenting":
 342                             Number( data.getElementsByTagName("presenting")[0]
 343                                         .childNodes[0].nodeValue ),
 344                         "idle":
 345                             Number( data.getElementsByTagName("idle")[0]
 346                                         .childNodes[0].nodeValue ),
 347                         "failed":
 348                             Number( data.getElementsByTagName("failed")[0]
 349                                         .childNodes[0].nodeValue ),
 350                         "error":
 351                             Number( data.getElementsByTagName("error")[0]
 352                                         .childNodes[0].nodeValue )
 353                     };
 354
 355                     context.statCounter++;
 356                     var delay = context.statTime
 357                         + context.statCounter * context.dumpFactor;
 358
 359                     if ( activeClients > 0 )
 360                         context.statTimer =
 361                             setTimeout(
 362                                 function () {
 363                                     context.stat();
 364                                 },
 365                                 delay
 366                             );
 367                     context.statCallback(stat);
 368                 }
 369                 else
 370                     context.throwError('Stat failed. Malformed WS resonse.',
 371                                         113);
 372             }
 373         );
 374     },
 375     show: function(start, num, sort)
 376     {
 377         if( !this.searchStatusOK && this.useSessions )
 378             throw new Error(
 379                 'Pz2.js: show command has to be preceded with a search command.'
 380             );
 381
 382         // if called explicitly takes precedence
 383         clearTimeout(this.showTimer);
 384
 385         if( sort !== undefined )
 386             this.currentSort = sort;
 387         if( start !== undefined )
 388             this.currentStart = Number( start );
 389         if( num !== undefined )
 390             this.currentNum = Number( num );
 391
 392         var context = this;
 393         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
 394         request.safeGet(
 395             {
 396                 "command": "show",
 397                 "session": this.sessionID,
 398                 "start": this.currentStart,
 399                 "num": this.currentNum,
 400                 "sort": this.currentSort,
 401                 "block": 1
 402             },
 403             function(data) {
 404                 if ( data.getElementsByTagName("status")[0]
 405                         .childNodes[0].nodeValue == "OK" ) {
 406                     // first parse the status data send along with records
 407                     // this is strictly bound to the format
 408                     var activeClients =
 409                         Number( data.getElementsByTagName("activeclients")[0]
 410                                     .childNodes[0].nodeValue );
 411                     context.activeClients = activeClients;
 412                     var show = {
 413                         "activeclients": activeClients,
 414                         "merged":
 415                             Number( data.getElementsByTagName("merged")[0]
 416                                         .childNodes[0].nodeValue ),
 417                         "total":
 418                             Number( data.getElementsByTagName("total")[0]
 419                                         .childNodes[0].nodeValue ),
 420                         "start":
 421                             Number( data.getElementsByTagName("start")[0]
 422                                         .childNodes[0].nodeValue ),
 423                         "num":
 424                             Number( data.getElementsByTagName("num")[0]
 425                                         .childNodes[0].nodeValue ),
 426                         "hits": []
 427                     };
 428                     // parse all the first-level nodes for all <hit> tags
 429                     var hits = data.getElementsByTagName("hit");
 430                     for (i = 0; i < hits.length; i++)
 431                         show.hits[i] = Element_parseChildNodes(hits[i]);
 432
 433                     context.showCounter++;
 434                     var delay = context.showTime;
 435                     if (context.showCounter > context.showFastCount)
 436                             delay += context.showCounter * context.dumpFactor;
 437                     if ( activeClients > 0 )
 438                         context.showTimer = setTimeout(
 439                             function () {
 440                                 context.show();
 441                             },
 442                             delay);
 443                     global_show = show;
 444                     context.showCallback(show);
 445                 }
 446                 else
 447                     context.throwError('Show failed. Malformed WS resonse.',
 448                                         114);
 449             }
 450         );
 451     },
 452     record: function(id, offset, syntax, handler)
 453     {
 454         // we may call record with no previous search if in proxy mode
 455         if(!this.searchStatusOK && this.useSessions)
 456            throw new Error(
 457             'Pz2.js: record command has to be preceded with a search command.'
 458             );
 459
 460         if( id !== undefined )
 461             this.currRecID = id;
 462
 463         var recordParams = {
 464             "command": "record",
 465             "session": this.sessionID,
 466             "id": this.currRecID
 467         };
 468
 469         this.currRecOffset = null;
 470         if (offset != undefined) {
 471             recordParams["offset"] = offset;
 472             this.currRecOffset = offset;
 473         }
 474
 475         if (syntax != undefined)
 476             recordParams['syntax'] = syntax;
 477
 478         //overwrite default callback id needed
 479         var callback = this.recordCallback;
 480         var args = undefined;
 481         if (handler != undefined) {
 482             callback = handler['callback'];
 483             args = handler['args'];
 484         }
 485
 486         var context = this;
 487         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
 488
 489         request.safeGet(
 490             recordParams,
 491             function(data) {
 492                 var recordNode;
 493                 var record;
 494                 //raw record
 495                 if (context.currRecOffset !== null) {
 496                     record = new Array();
 497                     record['xmlDoc'] = data;
 498                     record['offset'] = context.currRecOffset;
 499                     callback(record, args);
 500                 //pz2 record
 501                 } else if ( recordNode =
 502                     data.getElementsByTagName("record")[0] ) {
 503                     // if stylesheet was fetched do not parse the response
 504                     if ( context.xslDoc ) {
 505                         record = new Array();
 506                         record['xmlDoc'] = data;
 507                         record['xslDoc'] = context.xslDoc;
 508                         record['recid'] =
 509                             recordNode.getElementsByTagName("recid")[0]
 510                                 .firstChild.nodeValue;
 511                     //parse record
 512                     } else {
 513                         record = Element_parseChildNodes(recordNode);
 514                     }
 515                     callback(record, args);
 516                 }
 517                 else
 518                     context.throwError('Record failed. Malformed WS resonse.',
 519                                         115);
 520             }
 521         );
 522     },
 523
 524     termlist: function()
 525     {
 526         if( !this.searchStatusOK && this.useSessions )
 527             throw new Error(
 528             'Pz2.js: termlist command has to be preceded with a search command.'
 529             );
 530
 531         // if called explicitly takes precedence
 532         clearTimeout(this.termTimer);
 533
 534         var context = this;
 535         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
 536         request.safeGet(
 537             {
 538                 "command": "termlist",
 539                 "session": this.sessionID,
 540                 "name": this.termKeys
 541             },
 542             function(data) {
 543                 if ( data.getElementsByTagName("termlist") ) {
 544                     var activeClients =
 545                         Number( data.getElementsByTagName("activeclients")[0]
 546                                     .childNodes[0].nodeValue );
 547                     context.activeClients = activeClients;
 548                     var termList = { "activeclients":  activeClients };
 549                     var termLists = data.getElementsByTagName("list");
 550                     //for each termlist
 551                     for (i = 0; i < termLists.length; i++) {
 552                         var listName = termLists[i].getAttribute('name');
 553                         termList[listName] = new Array();
 554                         var terms = termLists[i].getElementsByTagName('term');
 555                         //for each term in the list
 556                         for (j = 0; j < terms.length; j++) {
 557                             var term = {
 558                                 "name":
 559                                     (terms[j].getElementsByTagName("name")[0]
 560                                         .childNodes.length
 561                                     ? terms[j].getElementsByTagName("name")[0]
 562                                         .childNodes[0].nodeValue
 563                                     : 'ERROR'),
 564                                 "freq":
 565                                     terms[j]
 566                                     .getElementsByTagName("frequency")[0]
 567                                     .childNodes[0].nodeValue || 'ERROR'
 568                             };
 569
 570                             var termIdNode =
 571                                 terms[j].getElementsByTagName("id");
 572                             if(terms[j].getElementsByTagName("id").length)
 573                                 term["id"] =
 574                                     termIdNode[0].childNodes[0].nodeValue;
 575                             termList[listName][j] = term;
 576                         }
 577                     }
 578
 579                     context.termCounter++;
 580                     var delay = context.termTime
 581                         + context.termCounter * context.dumpFactor;
 582                     if ( activeClients > 0 )
 583                         context.termTimer =
 584                             setTimeout(
 585                                 function () {
 586                                     context.termlist();
 587                                 },
 588                                 delay
 589                             );
 590
 591                    context.termlistCallback(termList);
 592                 }
 593                 else
 594                     context.throwError('Termlist failed. Malformed WS resonse.',
 595                                         116);
 596             }
 597         );
 598
 599     },
 600     bytarget: function()
 601     {
 602         if( !this.initStatusOK && this.useSessions )
 603             throw new Error(
 604             'Pz2.js: bytarget command has to be preceded with a search command.'
 605             );
 606
 607         // no need to continue
 608         if( !this.searchStatusOK )
 609             return;
 610
 611         // if called explicitly takes precedence
 612         clearTimeout(this.bytargetTimer);
 613
 614         var context = this;
 615         var request = new pzHttpRequest(this.pz2String, this.errorHandler);
 616         request.safeGet(
 617             { "command": "bytarget", "session": this.sessionID },
 618             function(data) {
 619                 if ( data.getElementsByTagName("status")[0]
 620                         .childNodes[0].nodeValue == "OK" ) {
 621                     var targetNodes = data.getElementsByTagName("target");
 622                     var bytarget = new Array();
 623                     for ( i = 0; i < targetNodes.length; i++) {
 624                         bytarget[i] = new Array();
 625                         for( j = 0; j < targetNodes[i].childNodes.length; j++ ) {
 626                             if ( targetNodes[i].childNodes[j].nodeType
 627                                 == Node.ELEMENT_NODE ) {
 628                                 var nodeName =
 629                                     targetNodes[i].childNodes[j].nodeName;
 630                                 var nodeText =
 631                                     targetNodes[i].childNodes[j]
 632                                         .firstChild.nodeValue;
 633                                 bytarget[i][nodeName] = nodeText;
 634                             }
 635                         }
 636                     }
 637
 638                     context.bytargetCounter++;
 639                     var delay = context.bytargetTime
 640                         + context.bytargetCounter * context.dumpFactor;
 641                     if ( context.activeClients > 0 )
 642                         context.bytargetTimer =
 643                             setTimeout(
 644                                 function () {
 645                                     context.bytarget();
 646                                 },
 647                                 delay
 648                             );
 649
 650                     context.bytargetCallback(bytarget);
 651                 }
 652                 else
 653                     context.throwError('Bytarget failed. Malformed WS resonse.',
 654                                         117);
 655             }
 656         );
 657     },
 658
 659     // just for testing, probably shouldn't be here
 660     showNext: function(page)
 661     {
 662         var step = page || 1;
 663         this.show( ( step * this.currentNum ) + this.currentStart );
 664     },
 665
 666     showPrev: function(page)
 667     {
 668         if (this.currentStart == 0 )
 669             return false;
 670         var step = page || 1;
 671         var newStart = this.currentStart - (step * this.currentNum );
 672         this.show( newStart > 0 ? newStart : 0 );
 673     },
 674
 675     showPage: function(pageNum)
 676     {
 677         //var page = pageNum || 1;
 678         this.show(pageNum * this.currentNum);
 679     }
 680 };
 681
 682 /*
 683 ********************************************************************************
 684 ** AJAX HELPER CLASS ***********************************************************
 685 ********************************************************************************
 686 */
 687 var pzHttpRequest = function ( url, errorHandler ) {
 688         this.maxUrlLength = 2048;
 689         this.request = null;
 690         this.url = url;
 691         this.errorHandler = errorHandler || null;
 692         this.async = true;
 693         this.requestHeaders = {};
 694
 695         if ( window.XMLHttpRequest ) {
 696             this.request = new XMLHttpRequest();
 697         } else if ( window.ActiveXObject ) {
 698             try {
 699                 this.request = new ActiveXObject( 'Msxml2.XMLHTTP' );
 700             } catch (err) {
 701                 this.request = new ActiveXObject( 'Microsoft.XMLHTTP' );
 702             }
 703         }
 704 };
 705
 706 pzHttpRequest.prototype =
 707 {
 708     safeGet: function ( params, callback )
 709     {
 710         var encodedParams =  this.encodeParams(params);
 711         var url = this._urlAppendParams(encodedParams);
 712         if (url.length >= this.maxUrlLength) {
 713             this.requestHeaders["Content-Type"]
 714                 = "application/x-www-form-urlencoded";
 715             this._send( 'POST', this.url, encodedParams, callback );
 716         } else {
 717             this._send( 'GET', url, '', callback );
 718         }
 719     },
 720
 721     get: function ( params, callback )
 722     {
 723         this._send( 'GET', this._urlAppendParams(this.encodeParams(params)),
 724             '', callback );
 725     },
 726
 727     post: function ( params, data, callback )
 728     {
 729         this._send( 'POST', this._urlAppendParams(this.encodeParams(params)),
 730             data, callback );
 731     },
 732
 733     load: function ()
 734     {
 735         this.async = false;
 736         this.request.open( 'GET', this.url, this.async );
 737         this.request.send('');
 738         if ( this.request.status == 200 )
 739             return this.request.responseXML;
 740     },
 741
 742     encodeParams: function (params)
 743     {
 744         var sep = "";
 745         var encoded = "";
 746         for (var key in params) {
 747             if (params[key] != null) {
 748                 encoded += sep + key + '=' + encodeURIComponent(params[key]);
 749                 sep = '&';
 750             }
 751         }
 752         return encoded;
 753     },
 754
 755     _send: function ( type, url, data, callback)
 756     {
 757         var context = this;
 758         this.callback = callback;
 759         this.async = true;
 760         this.request.open( type, url, this.async );
 761         for (var key in this.requestHeaders)
 762             this.request.setRequestHeader(key, this.requestHeaders[key]);
 763         this.request.onreadystatechange = function () {
 764             context._handleResponse();
 765         }
 766         this.request.send(data);
 767     },
 768
 769     _urlAppendParams: function (encodedParams)
 770     {
 771         if (encodedParams)
 772             return this.url + "?" + encodedParams;
 773         else
 774             return this.url;
 775     },
 776
 777     _handleResponse: function ()
 778     {
 779         if ( this.request.readyState == 4 ) {
 780             // pick up pazpr2 errors first
 781             if ( this.request.responseXML
 782                 && this.request.responseXML.documentElement.nodeName == 'error'
 783                 && this.request.responseXML.getElementsByTagName("error")
 784                     .length ) {
 785                 var errAddInfo = '';
 786                 if ( this.request.responseXML.getElementsByTagName("error")[0]
 787                         .childNodes.length )
 788                     errAddInfo = ': ' +
 789                         this.request.responseXML
 790                             .getElementsByTagName("error")[0]
 791                             .childNodes[0].nodeValue;
 792                 var errMsg =
 793                     this.request.responseXML.getElementsByTagName("error")[0]
 794                         .getAttribute("msg");
 795                 var errCode =
 796                     this.request.responseXML.getElementsByTagName("error")[0]
 797                         .getAttribute("code");
 798
 799                 var err = new Error(errMsg + errAddInfo);
 800                 err.code = errCode;
 801
 802                 if (this.errorHandler) {
 803                     this.errorHandler(err);
 804                 }
 805                 else {
 806                     throw err;
 807                 }
 808             } else if ( this.request.status == 200 ) {
 809                 this.callback( this.request.responseXML );
 810             } else {
 811                 var err = new Error("Pz2.js: HTTP request error (AJAX). Code: "
 812                             + this.request.status + " Info: "
 813                             + this.request.statusText );
 814                 err.code = 'HTTP';
 815
 816                 if (this.errorHandler) {
 817                     this.errorHandler(err);
 818                 }
 819                 else {
 820                     throw err;
 821                 }
 822             }
 823         }
 824     }
 825 };
 826
 827 /*
 828 ********************************************************************************
 829 ** XML HELPER FUNCTIONS ********************************************************
 830 ********************************************************************************
 831 */
 832
 833 // DOMDocument
 834
 835 if ( window.ActiveXObject) {
 836     var DOMDoc = document;
 837 } else {
 838     var DOMDoc = Document.prototype;
 839 }
 840
 841 DOMDoc.newXmlDoc = function ( root )
 842 {
 843     var doc;
 844
 845     if (document.implementation && document.implementation.createDocument) {
 846         doc = document.implementation.createDocument('', root, null);
 847     } else if ( window.ActiveXObject ) {
 848         doc = new ActiveXObject("MSXML2.DOMDocument");
 849         doc.loadXML('<' + root + '/>');
 850     } else {
 851         throw new Error ('No XML support in this browser');
 852     }
 853
 854     return doc;
 855 }
 856
 857
 858 DOMDoc.parseXmlFromString = function ( xmlString )
 859 {
 860     var doc;
 861
 862     if ( window.DOMParser ) {
 863         var parser = new DOMParser();
 864         doc = parser.parseFromString( xmlString, "text/xml");
 865     } else if ( window.ActiveXObject ) {
 866         doc = new ActiveXObject("MSXML2.DOMDocument");
 867         doc.loadXML( xmlString );
 868     } else {
 869         throw new Error ("No XML parsing support in this browser.");
 870     }
 871
 872     return doc;
 873 }
 874
 875 DOMDoc.transformToDoc = function (xmlDoc, xslDoc)
 876 {
 877     if ( window.XSLTProcessor ) {
 878         var proc = new XSLTProcessor();
 879         proc.importStylesheet( xslDoc );
 880         return proc.transformToDocument(xmlDoc);
 881     } else if ( window.ActiveXObject ) {
 882         return document.parseXmlFromString(xmlDoc.transformNode(xslDoc));
 883     } else {
 884         alert( 'Unable to perform XSLT transformation in this browser' );
 885     }
 886 }
 887
 888 // DOMElement
 889
 890 Element_removeFromDoc = function (DOM_Element)
 891 {
 892     DOM_Element.parentNode.removeChild(DOM_Element);
 893 }
 894
 895 Element_emptyChildren = function (DOM_Element)
 896 {
 897     while( DOM_Element.firstChild ) {
 898         DOM_Element.removeChild( DOM_Element.firstChild )
 899     }
 900 }
 901
 902 Element_appendTransformResult = function ( DOM_Element, xmlDoc, xslDoc )
 903 {
 904     if ( window.XSLTProcessor ) {
 905         var proc = new XSLTProcessor();
 906         proc.importStylesheet( xslDoc );
 907         var docFrag = false;
 908         docFrag = proc.transformToFragment( xmlDoc, DOM_Element.ownerDocument );
 909         DOM_Element.appendChild(docFrag);
 910     } else if ( window.ActiveXObject ) {
 911         DOM_Element.innerHTML = xmlDoc.transformNode( xslDoc );
 912     } else {
 913         alert( 'Unable to perform XSLT transformation in this browser' );
 914     }
 915 }
 916
 917 Element_appendTextNode = function (DOM_Element, tagName, textContent )
 918 {
 919     var node = DOM_Element.ownerDocument.createElement(tagName);
 920     var text = DOM_Element.ownerDocument.createTextNode(textContent);
 921
 922     DOM_Element.appendChild(node);
 923     node.appendChild(text);
 924
 925     return node;
 926 }
 927
 928 Element_setTextContent = function ( DOM_Element, textContent )
 929 {
 930     if (typeof DOM_Element.textContent !== "undefined") {
 931         DOM_Element.textContent = textContent;
 932     } else if (typeof DOM_Element.innerText !== "undefined" ) {
 933         DOM_Element.innerText = textContent;
 934     } else {
 935         throw new Error("Cannot set text content of the node, no such method.");
 936     }
 937 }
 938
 939 Element_getTextContent = function (DOM_Element)
 940 {
 941     if ( typeof DOM_Element.textContent != 'undefined' ) {
 942         return DOM_Element.textContent;
 943     } else if (typeof DOM_Element.text != 'undefined') {
 944         return DOM_Element.text;
 945     } else {
 946         throw new Error("Cannot get text content of the node, no such method.");
 947     }
 948 }
 949
 950 Element_parseChildNodes = function (node)
 951 {
 952     var parsed = {};
 953     var hasChildElems = false;
 954
 955     if (node.hasChildNodes()) {
 956         var children = node.childNodes;
 957         for (var i = 0; i < children.length; i++) {
 958             var child = children[i];
 959             if (child.nodeType == Node.ELEMENT_NODE) {
 960                 hasChildElems = true;
 961                 var nodeName = child.nodeName;
 962                 if (!(nodeName in parsed))
 963                     parsed[nodeName] = [];
 964                 parsed[nodeName].push(Element_parseChildNodes(child));
 965             }
 966         }
 967     }
 968
 969     var attrs = node.attributes;
 970     for (var i = 0; i < attrs.length; i++) {
 971         var attrName = '@' + attrs[i].nodeName;
 972         var attrValue = attrs[i].nodeValue;
 973         parsed[attrName] = attrValue;
 974     }
 975
 976     // if no nested elements, get text content
 977     if (node.hasChildNodes() && !hasChildElems) {
 978         if (node.attributes.length)
 979             parsed['textContent'] = node.firstChild.nodeValue;
 980         else
 981             parsed = node.firstChild.nodeValue;
 982     }
 983
 984     return parsed;
 985 }
 986
 987 /* do not remove trailing bracket */
 988 }