/**
 * Copyright 2012 Apache Wave
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
package org.waveprotocol.box.server.rpc;

import com.google.common.base.Function;
import com.google.common.collect.MapMaker;

import org.waveprotocol.box.server.persistence.file.FileAccountStore;
import org.waveprotocol.box.server.persistence.file.FileUtils;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.inject.Singleton;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * The servlet for fetching available gadgets from a json file on the server.
 */
@SuppressWarnings("serial")
@Singleton
public class GadgetProviderServlet extends HttpServlet {

  private static final Logger LOG = Logger.getLogger(FileAccountStore.class.getName());

  private final ConcurrentMap<String, String> jsonCache = new MapMaker().expireAfterWrite(5,
      TimeUnit.MINUTES).makeComputingMap(new Function<String, String>() {
    public String apply(String key) {
      String jsonString = "";
      try {
        jsonString = FileUtils.getStringFromFile("jsongadgets.json");
      } catch (IOException e) {
        LOG.log(Level.WARNING, "Error while loading gadgets json", e);
      }
      return jsonString;
    }
  });

  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
    String jsonString = jsonCache.get("");
    if (jsonString.equals("")) {
      response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
          "Error loading json data from file");
    } else {
      PrintWriter out = response.getWriter();
      out.print(jsonCache.get(""));
      out.flush();
    }
  }
}