/**
 * 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 4.15
 */

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) {
        if (p[2].toLowerCase() == document.location.hostname.toLowerCase()) {
          url = p[3];
        } 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');
    }
  }
})();