/*
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
package org.apache.http.pool;

import java.io.IOException;
import java.util.Date;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

import org.apache.http.annotation.ThreadSafe;
import org.apache.http.concurrent.FutureCallback;
import org.apache.http.util.Args;

@ThreadSafe
abstract class PoolEntryFuture<T> implements Future<T> {

    private final Lock lock;
    private final FutureCallback<T> callback;
    private final Condition condition;
    private volatile boolean cancelled;
    private volatile boolean completed;
    private T result;

    PoolEntryFuture(final Lock lock, final FutureCallback<T> callback) {
        super();
        this.lock = lock;
        this.condition = lock.newCondition();
        this.callback = callback;
    }

    @Override
    public boolean cancel(final boolean mayInterruptIfRunning) {
        this.lock.lock();
        try {
            if (this.completed) {
                return false;
            }
            this.completed = true;
            this.cancelled = true;
            if (this.callback != null) {
                this.callback.cancelled();
            }
            this.condition.signalAll();
            return true;
        } finally {
            this.lock.unlock();
        }
    }

    @Override
    public boolean isCancelled() {
        return this.cancelled;
    }

    @Override
    public boolean isDone() {
        return this.completed;
    }

    @Override
    public T get() throws InterruptedException, ExecutionException {
        try {
            return get(0, TimeUnit.MILLISECONDS);
        } catch (final TimeoutException ex) {
            throw new ExecutionException(ex);
        }
    }

    @Override
    public T get(
            final long timeout,
            final TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
        Args.notNull(unit, "Time unit");
        this.lock.lock();
        try {
            if (this.completed) {
                return this.result;
            }
            this.result = getPoolEntry(timeout, unit);
            this.completed = true;
            if (this.callback != null) {
                this.callback.completed(this.result);
            }
            return result;
        } catch (final IOException ex) {
            this.completed = true;
            this.result = null;
            if (this.callback != null) {
                this.callback.failed(ex);
            }
            throw new ExecutionException(ex);
        } finally {
            this.lock.unlock();
        }
    }

    protected abstract T getPoolEntry(
            long timeout, TimeUnit unit) throws IOException, InterruptedException, TimeoutException;

    public boolean await(final Date deadline) throws InterruptedException {
        this.lock.lock();
        try {
            if (this.cancelled) {
                throw new InterruptedException("Operation interrupted");
            }
            final boolean success;
            if (deadline != null) {
                success = this.condition.awaitUntil(deadline);
            } else {
                this.condition.await();
                success = true;
            }
            if (this.cancelled) {
                throw new InterruptedException("Operation interrupted");
            }
            return success;
        } finally {
            this.lock.unlock();
        }

    }

    public void wakeup() {
        this.lock.lock();
        try {
            this.condition.signalAll();
        } finally {
            this.lock.unlock();
        }
    }

}