// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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 streamer;

/**
 * One time switch for handshake and initialization stages.
 * 
 * At beginning, element handles data internally, sending output to "otout" pad.
 * After switchOff() method is called, element drops its links, so packets from
 * "stdin" pad are forwarded directly to "stdout" pad, without processing.
 * 
 * Event STREAM_START is captured by this element and not propagated further.
 * When switchOff() method is called, event STREAM_START is generated and sent
 * to "stdout".
 */
public abstract class OneTimeSwitch extends BaseElement {

  /**
   * One-time out - name of output pad for one time logic. By default, output
   * directly to socket.
   */
  public static final String OTOUT = "otout";

  private boolean switched = false;

  public OneTimeSwitch(String id) {
    super(id);
    declarePads();
  }

  protected void declarePads() {
    inputPads.put(STDIN, null);
    outputPads.put(OTOUT, null);
    outputPads.put(STDOUT, null);
  }

  @Override
  public void handleData(ByteBuffer buf, Link link) {
    if (switched)
      throw new RuntimeException(this + " element is switched off and must not receive any data or events anymore.");

    if (buf == null)
      return;

    handleOneTimeData(buf, link);
  }

  public void pushDataToOTOut(ByteBuffer buf) {
    if (verbose)
      System.out.println("[" + this + "] INFO: Sending data:  " + buf + ".");

    outputPads.get(OTOUT).sendData(buf);
  }

  /**
   * Switch this element off. Pass data directly to main output(s).
   */
  public void switchOff() {
    if (verbose)
      System.out.println("[" + this + "] INFO: Switching OFF.");

    switched = true;
    verbose = false;

    // Rewire links: drop otout link, replace stdout link by stdin to send data
    // directly to stdout
    Link stdout = (Link) outputPads.get(STDOUT);
    Link stdin = (Link) inputPads.get(STDIN);
    Link otout = (Link) outputPads.get(OTOUT);

    otout.drop();

    // Wake up next peer(s)
    sendEventToAllPads(Event.STREAM_START, Direction.OUT);

    stdin.setSink(null);
    inputPads.remove(STDIN);

    Element nextPeer = stdout.getSink();
    nextPeer.replaceLink(stdout, stdin);
    stdout.drop();

    for (Object link : inputPads.values().toArray())
      ((Link) link).drop();
    for (Object link : outputPads.values().toArray())
      ((Link) link).drop();

  }

  public void switchOn() {
    if (verbose)
      System.out.println("[" + this + "] INFO: Switching ON.");

    switched = false;
  }

  /**
   * Override this method to handle one-time packet(s) at handshake or
   * initialization stages. Execute method @see switchRoute() when this method
   * is no longer necessary.
   */
  protected abstract void handleOneTimeData(ByteBuffer buf, Link link);

  @Override
  public void handleEvent(Event event, Direction direction) {
    if (event == Event.STREAM_START) {
      if (verbose)
        System.out.println("[" + this + "] INFO: Event " + event + " is received.");

      switchOn();

      // Execute this element onStart(), but do not propagate event further,
      // to not wake up next elements too early
      onStart();
    } else
      super.handleEvent(event, direction);
  }

}