/**
 * @description    
 * @author
**/

var Ajax = {
  filename : "ajax.js",

  /* *
  * 存储是否进入调试模式的开关，打印调试消息的方式，换行符，调试用的容器的ID。
  *
  * @private
  */
  debugging :{
    isDebugging : 0,
    debuggingMode : 0,
    linefeed : "",
    containerId : 0
  },

  /* *
  * 设置调试模式以及打印调试消息方式的方法。
  *
  * @public
  * @param   {int}   是否打开调试模式      0：关闭，1：打开
  * @param   {int}   打印调试消息的方式    0：alert，1：innerHTML
  *
  */
  debug : function (isDebugging, debuggingMode){
    this.debugging = {
      "isDebugging" : isDebugging,
      "debuggingMode" : debuggingMode,
      "linefeed" : debuggingMode ? "<br />" : "\n",
      "containerId" : "dubugging-container" + new Date().getTime()
    };
  },
  /**
  * 在发送前的调用
  */
  onBeforeRequest : function(){
      
  },
  /* *
  * 传输完毕后自动调用的方法
  *
  * @public
  */
  onComplete : function (){
  },

  /* *
  * 传输过程中自动调用的方法
  *
  * @public
  */
  onRunning : function (){
  },

  /* *
  * 调用此方法发送HTTP请求。
  *
  * @public
  * @param   {string}    url             请求的URL地址
  * @param   {mix}       params          发送参数
  * @param   {Function}  callback        回调函数
  * @param   {string}    ransferMode     请求的方式，有"GET"和"POST"两种
  * @param   {string}    responseType    响应类型，有"JSON"、"XML"和"TEXT"三种
  * @param   {boolean}   asyn            是否异步请求的方式
  * @param   {boolean}   quiet           是否安静模式请求
  */
  run : function (url, params, callback, transferMode, responseType, asyn, quiet){
    /* 处理用户在调用该方法时输入的参数 */
    var self = this;
    if (typeof(self.onBeforeRequest) === "function"){
        self.onBeforeRequest();
    }
    
    params = this.parseParams(params);
    transferMode = typeof(transferMode) === "string"
    && transferMode.toUpperCase() === "GET"
    ? "GET"
    : "POST";

    if (transferMode === "GET"){
      var d = new Date();

      url += params ? (url.indexOf("?") === - 1 ? "?" : "&") + params : "";
      url = encodeURI(url) + (url.indexOf("?") === - 1 ? "?" : "&") + d.getTime() + d.getMilliseconds();
      params = null;
    }

    responseType = typeof(responseType) === "string" && ((responseType = responseType.toUpperCase()) === "JSON" || responseType === "XML") ? responseType : "TEXT";
    asyn = asyn === false ? false : true;

    /* 处理HTTP请求和响应 */
    var xhr = this.createXMLHttpRequest();

    try{

      if (typeof(self.onRunning) === "function" && !quiet){
        self.onRunning();
      }

      xhr.open(transferMode, url, asyn);

      if (transferMode === "POST"){
        xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
      }

      if (asyn){
        xhr.onreadystatechange = function (){
          if (xhr.readyState == 4){
            switch ( xhr.status ){
              case 0:
              case 200: // OK!
                /*
                 * If the request was to create a new resource
                 * (such as post an item to the database)
                 * You could instead return a status code of '201 Created'
                 */

                if (typeof(self.onComplete) === "function"){
                  self.onComplete();
                }

                if (typeof(callback) === "function"){
                  callback.call(self, self.parseResult(responseType, xhr), xhr.responseText);
                }
              break;

              case 304: // Not Modified
                /*
                 * This would be used when your Ajax widget is
                 * checking for updated content,
                 * such as the Twitter interface.
                 */
              break;

              case 400: // Bad Request
                /*
                 * A bit like a safety net for requests by your JS interface
                 * that aren't supported on the server.
                 * "Your browser made a request that the server cannot understand"
                 */
                 alert("XmlHttpRequest status: [400] Bad Request");
              break;

              case 404: // Not Found
                alert("XmlHttpRequest status: [404] \nThe requested URL "+url+" was not found on this server.");
              break;

              case 409: // Conflict
                /*
                 * Perhaps your JavaScript request attempted to
                 * update a Database record
                 * but failed due to a conflict
                 * (eg: a field that must be unique)
                 */
              break;

              case 503: // Service Unavailable
                /*
                 * A resource that this request relies upon
                 * is currently unavailable
                 * (eg: a file is locked by another process)
                 */
                 alert("XmlHttpRequest status: [503] Service Unavailable");
              break;

              default:
                alert("XmlHttpRequest status: [" + xhr.status + "] Unknow status.");
            }
            xhr = null;
          }
        }
        if (xhr != null) xhr.send(params);
      }else{
        if (typeof(self.onRunning) === "function"){
          self.onRunning();
        }

        xhr.send(params);

        var result = self.parseResult(responseType, xhr);
        //xhr = null;

        if (typeof(self.onComplete) === "function"){
          self.onComplete();
        }
        if (typeof(callback) === "function"){
          callback.call(self, result, xhr.responseText);
        }

        return result;
      }
    }
    catch (ex){
      if (typeof(self.onComplete) === "function"){
        self.onComplete();
      }

      alert(this.filename + "/run() error:" + ex.description);
    }
  },
  /**
  * 获取JSON数据
  */
  getJSON : function(url,params,callback){
      this.run(url, params, callback, 'GET', 'JSON');
  },

  /* *
  * 如果开启了调试模式，该方法会打印出相应的信息。
  *
  * @private
  * @param   {string}    info    调试信息
  * @param   {string}    type    信息类型
  */
  displayDebuggingInfo : function (info, type){
    if ( ! this.debugging.debuggingMode){
      alert(info);
    }else{

      var id = this.debugging.containerId;
      if ( ! document.getElementById(id)){
        div = document.createElement("DIV");
        div.id = id;
        div.style.position = "absolute";
        div.style.width = "98%";
        div.style.border = "1px solid #f00";
        div.style.backgroundColor = "#eef";
        var pageYOffset = document.body.scrollTop
        || window.pageYOffset
        || 0;
        div.style.top = document.body.clientHeight * 0.6
        + pageYOffset
        + "px";
        document.body.appendChild(div);
        div.innerHTML = "<div></div>"
        + "<hr style='height:1px;border:1px dashed red;'>"
        + "<div></div>";
      }

      var subDivs = div.getElementsByTagName("DIV");
      if (type === "param"){
        subDivs[0].innerHTML = info;
      }else{
        subDivs[1].innerHTML = info;
      }
    }
  },

  /* *
  * 创建XMLHttpRequest对象的方法。
  *
  * @private
  * @return      返回一个XMLHttpRequest对象
  * @type    Object
  */
  createXMLHttpRequest : function (){
    var xhr = null;

    if (window.ActiveXObject){
      var versions = ['Microsoft.XMLHTTP', 'MSXML6.XMLHTTP', 'MSXML5.XMLHTTP', 'MSXML4.XMLHTTP', 'MSXML3.XMLHTTP', 'MSXML2.XMLHTTP', 'MSXML.XMLHTTP'];

      for (var i = 0; i < versions.length; i ++ ){
        try{
          xhr = new ActiveXObject(versions[i]);
          break;
        }catch (ex){
          continue;
        }
      }
    }else{
      xhr = new XMLHttpRequest();
    }

    return xhr;
  },

  /* *
  * 当传输过程发生错误时将调用此方法。
  *
  * @private
  * @param   {Object}    xhr     XMLHttpRequest对象
  * @param   {String}    url     HTTP请求的地址
  */
  onXMLHttpRequestError : function (xhr, url){
    throw "URL: " + url + "\n"
    +  "readyState: " + xhr.readyState + "\n"
    + "state: " + xhr.status + "\n"
    + "headers: " + xhr.getAllResponseHeaders();
  },

  /* *
  * 对将要发送的参数进行格式化。
  *
  * @private
  * @params {mix}    params      将要发送的参数
  * @return 返回合法的参数
  * @type string
  */
  parseParams : function (params){
    var legalParams = "";
    params = params ? params : "";

    if (typeof(params) === "string"){
      legalParams = params;
    }else if (typeof(params) === "object"){
      try{
//        legalParams = "JSON=" + params.toJSONString();
        legalParams = params;
      }catch (ex){
        alert("Can't stringify JSON!");
        return false;
      }
    }else{
      alert("Invalid parameters!");
      return false;
    }

    if (this.debugging.isDebugging){
      var lf = this.debugging.linefeed,
      info = "[Original Parameters]" + lf + params + lf + lf
      + "[Parsed Parameters]" + lf + legalParams;

      this.displayDebuggingInfo(info, "param");
    }

    return legalParams;
  },

  /* *
  * 对返回的HTTP响应结果进行过滤。
  *
  * @public
  * @params   {mix}   result   HTTP响应结果
  * @return  返回过滤后的结果
  * @type string
  */
  preFilter : function (result){
    return result.replace(/\xEF\xBB\xBF/g, "");
  },

  /* *
  * 对返回的结果进行格式化。
  *
  * @private
  * @return 返回特定格式的数据结果
  * @type mix
  */
  parseResult : function (responseType, xhr){
    var result = null;

    switch (responseType){
      case "JSON" :
        result = this.preFilter(xhr.responseText);
        try{
//          result = result.parseJSON();
            
        }catch (ex){
          throw this.filename + "/parseResult() error: can't parse to JSON.\n\n" + xhr.responseText;
        }
        break;
      case "XML" :
        result = xhr.responseXML;
        break;
      case "TEXT" :
        result = this.preFilter(xhr.responseText);
        break;
      default :
        throw this.filename + "/parseResult() error: unknown response type:" + responseType;
    }

    if (this.debugging.isDebugging){
      var lf = this.debugging.linefeed,
      info = "[Response Result of " + responseType + " Format]" + lf
      + result;

      if (responseType === "JSON"){
        info = "[Response Result of TEXT Format]" + lf
        + xhr.responseText + lf + lf
        + info;
      }
      this.displayDebuggingInfo(info, "result");
    }

    return result;
  }
};

/*
    Public Domain

    This file adds these methods to JavaScript:

        array.toJSONString()
        boolean.toJSONString()
        date.toJSONString()
        number.toJSONString()
        object.toJSONString()
        string.toJSONString()
            These methods produce a JSON text from a JavaScript value.
            It must not contain any cyclical references. Illegal values
            will be excluded.

            The default conversion for dates is to an ISO string. You can
            add a toJSONString method to any date object to get a different
            representation.

        string.parseJSON(filter)
            This method parses a JSON text to produce an object or
            array. It can throw a SyntaxError exception.

            The optional filter parameter is a function which can filter and
            transform the results. It receives each of the keys and values, and
            its return value is used instead of the original value. If it
            returns what it received, then structure is not modified. If it
            returns undefined then the member is deleted.

            Example:

            // Parse the text. If a key contains the string 'date' then
            // convert the value to a date.

            myData = text.parseJSON(function (key, value) {
                return key.indexOf('date') >= 0 ? new Date(value) : value;
            });

    It is expected that these methods will formally become part of the
    JavaScript Programming Language in the Fourth Edition of the
    ECMAScript standard in 2008.
*/

// Augment the basic prototypes if they have not already been augmented.