/**
 * @class Ext.data.HttpProxy
 * @extends Ext.data.DataProxy
 * 
An implementation of {@link Ext.data.DataProxy} that processes data requests within the same
 * domain of the originating page.
 * 
Note: this class cannot be used to retrieve data from a domain other
 * than the domain from which the running page was served. For cross-domain requests, use a
 * {@link Ext.data.ScriptTagProxy ScriptTagProxy}.
 * 
Be aware that to enable the browser to parse an XML document, the server must set
 * the Content-Type header in the HTTP response to "text/xml".
 * @constructor
 * @param {Object} conn
 * An {@link Ext.data.Connection} object, or options parameter to {@link Ext.Ajax#request}.
 * 
Note that if this HttpProxy is being used by a {@link Ext.data.Store Store}, then the
 * Store's call to {@link #load} will override any specified callback and params
 * options. In this case, use the Store's {@link Ext.data.Store#events events} to modify parameters,
 * or react to loading events. The Store's {@link Ext.data.Store#baseParams baseParams} may also be
 * used to pass parameters known at instantiation time.
 * 
If an options parameter is passed, the singleton {@link Ext.Ajax} object will be used to make
 * the request.
 */
Ext.data.HttpProxy = function(conn){
    Ext.data.HttpProxy.superclass.constructor.call(this, conn);

    
/**
     * The Connection object (Or options parameter to {@link Ext.Ajax#request}) which this HttpProxy
     * uses to make requests to the server. Properties of this object may be changed dynamically to
     * change the way data is requested.
     * @property
     */
    this.conn = conn;

    // nullify the connection url.  The url param has been copied to 'this' above.  The connection
    // url will be set during each execution of doRequest when buildUrl is called.  This makes it easier for users to override the
    // connection url during beforeaction events (ie: beforeload, beforewrite, etc).
    // Url is always re-defined during doRequest.
    this.conn.url = null;

    this.useAjax = !conn || !conn.events;

    // A hash containing active requests, keyed on action [Ext.data.Api.actions.create|read|update|destroy]
    var actions = Ext.data.Api.actions;
    this.activeRequest = {};
    for (var verb in actions) {
        this.activeRequest[actions[verb]] = undefined;
    }
};

Ext.extend(Ext.data.HttpProxy, Ext.data.DataProxy, {
    
/**
     * Return the {@link Ext.data.Connection} object being used by this Proxy.
     * @return {Connection} The Connection object. This object may be used to subscribe to events on
     * a finer-grained basis than the DataProxy events.
     */
    getConnection : function() {
        return this.useAjax ? Ext.Ajax : this.conn;
    },

    
/**
     * Used for overriding the url used for a single request.  Designed to be called during a beforeaction event.  Calling setUrl
     * will override any urls set via the api configuration parameter.  Set the optional parameter makePermanent to set the url for
     * all subsequent requests.  If not set to makePermanent, the next request will use the same url or api configuration defined
     * in the initial proxy configuration.
     * @param {String} url
     * @param {Boolean} makePermanent (Optional) [false]
     *
     * (e.g.: beforeload, beforesave, etc).
     */
    setUrl : function(url, makePermanent) {
        this.conn.url = url;
        if (makePermanent === true) {
            this.url = url;
            this.api = null;
            Ext.data.Api.prepare(this);
        }
    },

    
/**
     * HttpProxy implementation of DataProxy#doRequest
     * @param {String} action The crud action type (create, read, update, destroy)
     * @param {Ext.data.Record/Ext.data.Record[]} rs If action is load, rs will be null
     * @param {Object} params An object containing properties which are to be used as HTTP parameters
     * for the request to the remote server.
     * @param {Ext.data.DataReader} reader The Reader object which converts the data
     * object into a block of Ext.data.Records.
     * @param {Function} callback
     * 
A function to be called after the request.
     * The callback is passed the following arguments:

     * 
r : Ext.data.Record[] The block of Ext.data.Records.
     * 
options: Options object from the action request
     * 
success: Boolean success indicator

     * @param {Object} scope The scope (this reference) in which the callback function is executed. Defaults to the browser window.
     * @param {Object} arg An optional argument which is passed to the callback as its second parameter.
     * @protected
     */
    doRequest : function(action, rs, params, reader, cb, scope, arg) {
        var  o = {
            method: (this.api[action]) ? this.api[action]['method'] : undefined,
            request: {
                callback : cb,
                scope : scope,
                arg : arg
            },
            reader: reader,
            callback : this.createCallback(action, rs),
            scope: this
        };

        // If possible, transmit data using jsonData || xmlData on Ext.Ajax.request (An installed DataWriter would have written it there.).
        // Use std HTTP params otherwise.
        if (params.jsonData) {
            o.jsonData = params.jsonData;
        } else if (params.xmlData) {
            o.xmlData = params.xmlData;
        } else {
            o.params = params || {};
        }
        // Set the connection url.  If this.conn.url is not null here,
        // the user must have overridden the url during a beforewrite/beforeload event-handler.
        // this.conn.url is nullified after each request.
        this.conn.url = this.buildUrl(action, rs);

        if(this.useAjax){

            Ext.applyIf(o, this.conn);

            // If a currently running request is found for this action, abort it.
            if (this.activeRequest[action]) {
                ////
                // Disabled aborting activeRequest while implementing REST.  activeRequest[action] will have to become an array
                // TODO ideas anyone?
                //
                //Ext.Ajax.abort(this.activeRequest[action]);
            }
            this.activeRequest[action] = Ext.Ajax.request(o);
        }else{
            this.conn.request(o);
        }
        // request is sent, nullify the connection url in preparation for the next request
        this.conn.url = null;
    },

    /**
     * Returns a callback function for a request.  Note a special case is made for the
     * read action vs all the others.
     * @param {String} action [create|update|delete|load]
     * @param {Ext.data.Record[]} rs The Store-recordset being acted upon
     * @private
     */
    createCallback : function(action, rs) {
        return function(o, success, response) {
            this.activeRequest[action] = undefined;
            if (!success) {
                if (action === Ext.data.Api.actions.read) {
                    // @deprecated: fire loadexception for backwards compat.
                    // TODO remove in 3.1
                    this.fireEvent('loadexception', this, o, response);
                }
                this.fireEvent('exception', this, 'response', action, o, response);
                o.request.callback.call(o.request.scope, null, o.request.arg, false);
                return;
            }
            if (action === Ext.data.Api.actions.read) {
                this.onRead(action, o, response);
            } else {
                this.onWrite(action, o, response, rs);
            }
        };
    },

    
/**
     * Callback for read action
     * @param {String} action Action name as per {@link Ext.data.Api.actions#read}.
     * @param {Object} o The request transaction object
     * @param {Object} res The server response
     * @fires loadexception (deprecated)
     * @fires exception
     * @fires load
     * @protected
     */
    onRead : function(action, o, response) {
        var result;
        try {
            result = o.reader.read(response);
        }catch(e){
            // @deprecated: fire old loadexception for backwards-compat.
            // TODO remove in 3.1
            this.fireEvent('loadexception', this, o, response, e);

            this.fireEvent('exception', this, 'response', action, o, response, e);
            o.request.callback.call(o.request.scope, null, o.request.arg, false);
            return;
        }
        if (result.success === false) {
            // @deprecated: fire old loadexception for backwards-compat.
            // TODO remove in 3.1
            this.fireEvent('loadexception', this, o, response);

            // Get DataReader read-back a response-object to pass along to exception event
            var res = o.reader.readResponse(action, response);
            this.fireEvent('exception', this, 'remote', action, o, res, null);
        }
        else {
            this.fireEvent('load', this, o, o.request.arg);
        }
        // TODO refactor onRead, onWrite to be more generalized now that we're dealing with Ext.data.Response instance
        // the calls to request.callback(...) in each will have to be made identical.
        // NOTE reader.readResponse does not currently return Ext.data.Response
        o.request.callback.call(o.request.scope, result, o.request.arg, result.success);
    },
    
/**
     * Callback for write actions
     * @param {String} action [Ext.data.Api.actions.create|read|update|destroy]
     * @param {Object} trans The request transaction object
     * @param {Object} res The server response
     * @fires exception
     * @fires write
     * @protected
     */
    onWrite : function(action, o, response, rs) {
        var reader = o.reader;
        var res;
        try {
            res = reader.readResponse(action, response);
        } catch (e) {
            this.fireEvent('exception', this, 'response', action, o, response, e);
            o.request.callback.call(o.request.scope, null, o.request.arg, false);
            return;
        }
        if (res.success === true) {
            this.fireEvent('write', this, action, res.data, res, rs, o.request.arg);
        } else {
            this.fireEvent('exception', this, 'remote', action, o, res, rs);
        }
        // TODO refactor onRead, onWrite to be more generalized now that we're dealing with Ext.data.Response instance
        // the calls to request.callback(...) in each will have to be made similar.
        // NOTE reader.readResponse does not currently return Ext.data.Response
        o.request.callback.call(o.request.scope, res.data, res, res.success);
    },

    // inherit docs
    destroy: function(){
        if(!this.useAjax){
            this.conn.abort();
        }else if(this.activeRequest){
            var actions = Ext.data.Api.actions;
            for (var verb in actions) {
                if(this.activeRequest[actions[verb]]){
                    Ext.Ajax.abort(this.activeRequest[actions[verb]]);
                }
            }
        }
        Ext.data.HttpProxy.superclass.destroy.call(this);
    }
});