var Ajax = function(url, params, onSuccess, method, async, xhrtype) {
    this.newHttpRequest = function(xhrtype) {
        if(typeof(xhrtype) == 'string')
            return new ActiveXObject(xhrtype);
        else
            return typeof(XMLHttpRequest) != 'undefined' ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
    }

    this.xhr = this.newHttpRequest(xhrtype);
    this.method = typeof(method) == 'string' && method.length > 0 ? method :'POST';
    this.async = typeof(async) == 'boolean' ? async : true;
    this.type = 'TEXT';
    this.url = url;
    this.params = params;
    this.username = null;
    this.password = null;
    this.data = null;
    this.timeout = -1;
    this.timeoutID = null;
    this.completed = false;
    this.canceled = false;


    this.onSuccess = typeof(onSuccess) == 'function' ? onSuccess : null;
    this.onTimeout = function(){ alert('서버 응답 대기 시간을 초과했습니다.'); }
    this.onError = function(xhr, data) { alert('오류가 발생했습니다. {0} - 상태 값: {1}'.format(this.xhr.status, this.xhr.statusText)); }

    this.getParams = function() {
        if(this.params == null) return '';
        var sb = new StringBuffer(), cnt = 0;
        for (var param in this.params) {
            if(typeof(eval('this.' + param)) == 'function') continue;
            if (cnt++ > 0)
                sb.append("&");
            sb.append(param).append("=").append(encodeURIComponent(eval('this.params.' + param)));
        }
        return sb.toString();
    }

    this.send = function(async, type) {

        if(typeof(async) != 'undefined') this.async = async;
        if(typeof(type) != 'undefined') this.type = type;

        var req = this;
        var httpParams  = this.getParams();
        if(this.method == 'GET') this.url = this.url + "?" + httpParams;

        if(this.username != null && this.password != null)
            this.xhr.open(this.method, this.url, this.async, this.username, this.password);
        else
            this.xhr.open(this.method, this.url, this.async);

        if(this.async)
            this.xhr.onreadystatechange = function() { req.onStateChange.call(req); }

        if(this.timeout > 0) {
            if(typeof(this.xhr.timeout) != 'undefined') {
                this.xhr.timeout = this.timeout; //비동기. 동기 상관없이 타임아웃이 잘 동작함
                if(this.onTimeout)
                    this.xhr.ontimeout = this.onTimeout;
            } else { //비동기모드일때만 동작함.
                this.timeoutID = window.setTimeout( function() { req.onStateChange.call(req, 'timeout'); }, 5000);
            }
        }

        this.xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=utf-8");
        var result = null;
        try {
            this.xhr.send(this.method == 'POST' ? httpParams : null);
            result = !this.async ? (this.type == 'XML' ? this.xhr.responseXML : this.xhr.responseText) : null;
        } catch (e) {
            alert('서버와 연결할 수 없습니다.');
        }
//        if(!this.async) {
//            this.completed = true;
//            if(this.async && this.timeoutID)
//                clearTimeout(this.timeoutID);
//        }
        return result;
    }

    this.setTimeout = function(timeout, onTimeout) {
        this.timeout = timeout;
        this.onTimeout = typeof(onTimeout) == 'function' ? onTimeout : this.onTimeout;
    }

    this.onStateChange = function(timeout) {
        var rs = this.xhr.readyState;
        if(timeout == 'timeout' && this.timeout > 0) {
            if(rs < 4) {
                this.xhr.abort();
                this.canceled = true;
                if(this.completed)
                    clearTimeout(this.timeoutID);
                else
                    this.onTimeout();
            }
            return;
        }
        if (this.async && rs == 4) {
            var status = this.xhr.status;
            if (status == 200) {
                if(this.type == 'XML') {
                    if(this.data == null) this.onSuccess(this.xhr.responseXML);
                    else this.onSuccess(this.xhr.responseXML, this.data);
                } else {
                    if(this.data == null) this.onSuccess(this.xhr.responseText);
                    else this.onSuccess(this.xhr.responseText, this.data);
                }
            } else if (status > 0){
                this.onError(this.xhr, this.data);
            }
        }
    }

    this.setType = function(type) {
        if(type == 'XML' || type == 'TEXT') this.type = type;
        else alert("{0} 는 사용할 수 없습니다.".format(type));
    }

    this.setAsync = function(flag) { this.async = flag; };
    this.setTemp = function(tmp) { this.data = tmp; }
}