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/**
 * Ext GWT 3.0.0-rc2 - Ext for GWT
 * Copyright(c) 2007-2012, Sencha, Inc.
 * [email protected]
 *
 * http://sencha.com/license
 */
package com.sencha.gxt.data.client.loader;

import com.google.gwt.core.client.Callback;
import com.google.gwt.http.client.Request;
import com.google.gwt.http.client.RequestBuilder;
import com.google.gwt.http.client.RequestCallback;
import com.google.gwt.http.client.Response;
import com.sencha.gxt.data.shared.loader.DataProxy;
import com.sencha.gxt.data.shared.writer.DataWriter;

/**
 * A {@link DataProxy} that retrieves data using a {@link RequestBuilder}
 * instance.
 * 
 * 
 * When using a load config object that implements LoadConfig or
 * ModelData, all properties and property values will be sent as
 * request parameters in the load request.
 * 
 * @param  the type of data used to configure the load from the proxy
 * 
 * @see RequestBuilder
 * @see ScriptTagProxy
 */
public class HttpProxy implements DataProxy {

  /**
   * The request builder used by this data proxy.
   */
  protected RequestBuilder builder;

  /**
   * The URL of the HTTP service, initialized from
   * {@link RequestBuilder#getUrl()} and used by {@link #load} as the base part
   * of the URL when appending encoded parameters for an HTTP GET request.
   */
  protected String initUrl;
  private DataWriter writer;

  /**
   * Creates a new HttpProxy.
   * 
   * @param builder the request builder. The URL must be set to the URL of the
   *          service. For requests that use the HTTP GET method, the URL should
   *          be set to the base part of the URL. It will be updated
   *          automatically to include the encoded request.
   */
  public HttpProxy(RequestBuilder builder) {
    this.builder = builder;
    this.initUrl = builder.getUrl();
  }

  /**
   * Returns the data writer for this proxy. The data writer is responsible for
   * encoding the load config.
   * 
   * @return the data writer
   */
  public DataWriter getWriter() {
    return writer;
  }

  @Override
  public void load(final C loadConfig, final Callback callback) {
    try {
      String data = null;
      if (builder.getHTTPMethod().equals("POST")) {
        data = generateUrl(loadConfig);
      } else {
        StringBuilder url = new StringBuilder(initUrl);
        url.append(url.indexOf("?") == -1 ? "?" : "&");
        String params = generateUrl(loadConfig);
        url.append(params);
        setUrl(builder, url.toString());
      }

      builder.sendRequest(data, new RequestCallback() {

        @Override
        public void onError(Request request, Throwable exception) {
          callback.onFailure(exception);
        }

        @Override
        public void onResponseReceived(Request request, Response response) {
          if (response.getStatusCode() != Response.SC_OK) {
            callback.onFailure(new RuntimeException("HttpProxy: Invalid status code " + response.getStatusCode()));
            return;
          }
          callback.onSuccess(response.getText());

        }
      });
    } catch (Exception e) {
      callback.onFailure(e);
    }
  }

  /**
   * Sets the data writer for this proxy. The data writer is responsible for
   * encoding the load config.
   * 
   * @param writer the data writer
   */
  public void setWriter(DataWriter writer) {
    this.writer = writer;
  }

  /**
   * Encodes the load config into a format that can be used for a GET query
   * string or a POST url-encoded body. Use {@link #setWriter} to set the data
   * writer responsible for encoding the load config. If it is not set the load
   * config is assumed to require no further encoding and its value is retrieved
   * using its toString method.
   * 
   * @param loadConfig the load config to encode
   * @return the encoded load config
   */
  protected String generateUrl(C loadConfig) {
    if (writer != null) {
      return writer.write(loadConfig);
    } else {
      if (loadConfig == null) {
        return "";
      }
      return loadConfig.toString();
    }
  }

  private native void setUrl(RequestBuilder rb, String url) /*-{
		[email protected]::url = url;
  }-*/;

}