/*
 * Copyright 2000-2009 JetBrains s.r.o.
 *
 * 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.intellij.debugger.impl;

import com.intellij.openapi.application.ApplicationManager;
import com.intellij.openapi.diagnostic.Logger;
import com.sun.jdi.VMDisconnectedException;
import org.jetbrains.annotations.NotNull;

import java.util.concurrent.*;

/**
 * @author lex
 */
public abstract class InvokeThread<E extends PrioritizedTask> {
  private static final Logger LOG = Logger.getInstance("#com.intellij.debugger.impl.InvokeThread");

  private static final ThreadLocal<WorkerThreadRequest> ourWorkerRequest = new ThreadLocal<WorkerThreadRequest>();

  public static final class WorkerThreadRequest<E extends PrioritizedTask> implements Runnable {
    private final InvokeThread<E> myOwner;
    private volatile Future<?> myRequestFuture;
    private volatile boolean myStopRequested = false;

    WorkerThreadRequest(InvokeThread<E> owner) {
      myOwner = owner;
    }

    @Override
    public void run() {
      synchronized (this) {
        while (myRequestFuture == null) {
          try {
            wait();
          }
          catch (InterruptedException ignore) {
          }
        }
      }
      ourWorkerRequest.set(this);
      try {
        myOwner.run(this);
      } 
      finally {
        ourWorkerRequest.set(null);
        boolean b = Thread.interrupted(); // reset interrupted status to return into pool
      }
    }

    public void requestStop() {
      final Future<?> future = myRequestFuture;
      assert future != null;
      myStopRequested = true;
      future.cancel(true);
    }

    public boolean isStopRequested() {
      final Future<?> future = myRequestFuture;
      assert future != null;
      return myStopRequested || future.isCancelled() || future.isDone();
    }

    public void join() throws InterruptedException, ExecutionException {
      assert myRequestFuture != null;
      try {
        myRequestFuture.get();
      }
      catch(CancellationException ignored) {
      }
    }

    public void join(long timeout) throws InterruptedException, ExecutionException {
      assert myRequestFuture != null;
      try {
        myRequestFuture.get(timeout, TimeUnit.MILLISECONDS);
      }
      catch (TimeoutException ignored) {
      } 
      catch (CancellationException ignored) {
      }
    }

    final void setRequestFuture(Future<?> requestFuture) {
      synchronized (this) {
        myRequestFuture = requestFuture;
        notifyAll();
      }
    }

    public InvokeThread<E> getOwner() {
      return myOwner;
    }

    public boolean isDone() {
      assert myRequestFuture != null;
      return myRequestFuture.isDone() && ourWorkerRequest.get() == null;
    }
  }

  protected final EventQueue<E> myEvents;

  private volatile WorkerThreadRequest myCurrentRequest = null;

  public InvokeThread() {
    myEvents = new EventQueue<E>(PrioritizedTask.Priority.values().length);
    startNewWorkerThread();
  }

  protected abstract void processEvent(E e);

  protected void startNewWorkerThread() {
    final WorkerThreadRequest workerRequest = new WorkerThreadRequest<E>(this);
    myCurrentRequest = workerRequest;
    workerRequest.setRequestFuture( ApplicationManager.getApplication().executeOnPooledThread(workerRequest) );
  }

  private void run(final @NotNull WorkerThreadRequest threadRequest) {
    try {
      while(true) {
        try {
          if(threadRequest.isStopRequested()) {
            break;
          }

          final WorkerThreadRequest currentRequest = getCurrentRequest();
          if(currentRequest != threadRequest) {
            LOG.error("Expected " + threadRequest + " instead of " + currentRequest);
            if (currentRequest != null && !currentRequest.isDone()) {
              continue; // ensure events are processed by one thread at a time
            }
          }

          processEvent(myEvents.get());
        }
        catch (VMDisconnectedException ignored) {
          break;
        }
        catch (EventQueueClosedException ignored) {
          break;
        }
        catch (RuntimeException e) {
          if(e.getCause() instanceof InterruptedException) {
            break;
          }
          LOG.error(e);
        }
        catch (Throwable e) {
          LOG.error(e);
        }
      }
    }
    finally {
      // ensure that all scheduled events are processed
      if (threadRequest == getCurrentRequest()) {
        for (E event : myEvents.clearQueue()) {
          try {
            processEvent(event);
          }
          catch (Throwable ignored) {
          }
        }
      }

      if (LOG.isDebugEnabled()) {
        LOG.debug("Request " + toString() + " exited");
      }
    }

  }

  protected static InvokeThread currentThread() {
    final WorkerThreadRequest request = getCurrentThreadRequest();
    return request != null? request.getOwner() : null;
  }

  public boolean schedule(E r) {
    if(LOG.isDebugEnabled()) {
      LOG.debug("schedule " + r + " in " + this);
    }
    return myEvents.put(r, r.getPriority().ordinal());
  }

  public boolean pushBack(E r) {
    if(LOG.isDebugEnabled()) {
      LOG.debug("pushBack " + r + " in " + this);
    }
    return myEvents.pushBack(r, r.getPriority().ordinal());
  }

  protected void switchToRequest(WorkerThreadRequest newRequest) {
    final WorkerThreadRequest currentThreadRequest = getCurrentThreadRequest();
    LOG.assertTrue(currentThreadRequest != null);
    myCurrentRequest = newRequest;
    if (LOG.isDebugEnabled()) {
      LOG.debug("Closing " + currentThreadRequest + " new request = " + newRequest);
    }

    currentThreadRequest.requestStop();
  }

  public WorkerThreadRequest getCurrentRequest() {
    return myCurrentRequest;
  }

  public static WorkerThreadRequest getCurrentThreadRequest() {
    return ourWorkerRequest.get();
  }

  public void close() {
    myEvents.close();
    if (LOG.isDebugEnabled()) {
      LOG.debug("Closing evaluation");
    }
  }
}