/* Copyright (c) 2009 Google Inc.
 *
 * 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 com.google.appengine.demos.shardedcounter.v2;

import java.io.IOException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Renders an HTML page showing current count of the sharded counter.
 *
 * Through the form, the user can increment the counter or add new shards.
 *
 * @author j.s@google.com (Jeff Scudder)
 */
public class CounterPage extends HttpServlet {

  public void doGet(HttpServletRequest req, HttpServletResponse resp)
      throws IOException {
    displayPageStart(resp);
    ShardedCounter counter = getOrCreateCounter(resp);
    displayCounts(counter, resp);
    displayInputFormAndClose(resp);
  }

  public void doPost(HttpServletRequest req, HttpServletResponse resp)
      throws IOException {
    displayPageStart(resp);
    ShardedCounter counter = getOrCreateCounter(resp);
    String query = req.getQueryString();
    if (query != null && query.equals("addShard=true")) {
      displayCount(counter, resp);
      displayNumberOfShards(counter.addShard(), resp);
    } else {
      counter.increment();
      displayCount(counter, resp);
      displayNumberOfShards(counter.getNumShards(), resp);
    }
    displayInputFormAndClose(resp);
  }

  private void displayPageStart(HttpServletResponse resp) throws IOException {
    resp.getWriter().println("<html>");
    resp.getWriter().println("  <body>");
  }

  /**
   * Creates the sharded counter if it does not yet exist.
   */
  private ShardedCounter getOrCreateCounter(HttpServletResponse resp)
      throws IOException {
    CounterFactory factory = new CounterFactory();
    ShardedCounter counter = factory.getCounter("test'\"counter");
    if (counter == null) {
      // Create a counter with 0 shards.
      counter = factory.createCounter("test'\"counter");
      // Add a first shard to the counter.
      counter.addShard();
      resp.getWriter().println(
          "<p>No counter named 'test'\"counter', so we created one.</p>");
    }
    return counter;
  }

  private void displayCount(ShardedCounter counter, HttpServletResponse resp)
      throws IOException {
    resp.getWriter().println("  <p>Current count: " + counter.getCount() 
        + "</p>");
  }

  private void displayCounts(ShardedCounter counter, HttpServletResponse resp)
      throws IOException {
    // Displays the overall count for the counter and the number of shards.
    displayCount(counter, resp);
    displayNumberOfShards(counter.getNumShards(), resp);
  }

  private void displayNumberOfShards(int shards, HttpServletResponse resp)
      throws IOException {
    resp.getWriter().print("<p>Counter has " + shards);
    if (shards == 1) {
      resp.getWriter().println(" shard</p>");
    } else {
      resp.getWriter().println(" shards</p>");
    }
  }

  private void displayInputFormAndClose(HttpServletResponse resp)
      throws IOException {
    resp.getWriter().println("<form action=\"/v2\" method=\"post\">");
    resp.getWriter().println(
        "  <div><input type=\"submit\" value=\"+1\" /></div>");
    resp.getWriter().println("</form>");

    resp.getWriter().println(
        "<form action=\"/v2?addShard=true\" method=\"post\">");
    resp.getWriter().println(
        "  <div><input type=\"submit\" value=\"Add Shard\" /></div>");
    resp.getWriter().println("</form>");

    resp.getWriter().println("  </body>");
    resp.getWriter().println("</html>");
  }
}