package com.lianxin.pubqq.chat.video;

import java.util.ArrayDeque;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.os.Handler;
import android.os.Message;
import android.os.Process;

public abstract class AsyncTask<Params, Progress, Result> {

	private static final String LOG_TAG = "AsyncTask";
	private static final int CORE_POOL_SIZE = 5;
	private static final int MAXIMUM_POOL_SIZE = 128;
	private static final int KEEP_ALIVE = 1;

	private static final ThreadFactory sThreadFactory = new ThreadFactory() {
		private final AtomicInteger mCount = new AtomicInteger(1);

		@Override
		public Thread newThread(Runnable r) {
			return new Thread(r, "AsyncTask #" + mCount.getAndIncrement());
		}
	};

	@SuppressLint("NewApi")
	private static final BlockingQueue<Runnable> sPoolWorkQueue = new LinkedBlockingDeque<Runnable>(
			10);

	/**
	 * An {@link java.util.concurrent.Executor} that can be used to execute
	 * tasks in parallel.
	 */
	public static final Executor THREAD_POOL_EXECUTOR = new ThreadPoolExecutor(
			CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE, TimeUnit.SECONDS,
			sPoolWorkQueue, sThreadFactory,
			new ThreadPoolExecutor.DiscardOldestPolicy());

	/**
	 * An {@link java.util.concurrent.Executor} that executes tasks one at a
	 * time in serial order. This serialization is global to a particular
	 * process.
	 */
	public static final Executor SERIAL_EXECUTOR = Utils.hasHoneycomb() ? new SerialExecutor()
			: Executors.newSingleThreadExecutor(sThreadFactory);

	public static final Executor DUAL_THREAD_EXECUTOR = Executors
			.newFixedThreadPool(2, sThreadFactory);
	private static final int MESSAGE_POST_RESULT = 0x1;
	private static final int MESSAGE_POST_PROGRESS = 0x2;

	private static final InternalHandler sHandler = new InternalHandler();

	private static volatile Executor sDefaultExecutor = SERIAL_EXECUTOR;
	private final WorkerRunnable<Params, Result> mWorker;
	private final FutureTask<Result> mFuture;

	private volatile Status mStatus = Status.PENDING;
	private final AtomicBoolean mCancelled = new AtomicBoolean();
	private final AtomicBoolean mTaskInvoked = new AtomicBoolean();

	@TargetApi(11)
	private static class SerialExecutor implements Executor {
		final ArrayDeque<Runnable> mTasks = new ArrayDeque<Runnable>();
		Runnable mActive;

		public synchronized void execute(final Runnable r) {
			mTasks.offer(new Runnable() {
				public void run() {
					try {
						r.run();
					} finally {
						scheduleNext();
					}
				}
			});
			if (mActive == null) {
				scheduleNext();
			}
		}

		protected synchronized void scheduleNext() {
			if ((mActive = mTasks.poll()) != null) {
				THREAD_POOL_EXECUTOR.execute(mActive);
			}
		}
	}

	/**
	 * Indicates the current status of the task. Each status will be set only
	 * once during the lifetime of a task.
	 */
	public enum Status {
		/**
		 * Indicates that the task has not been executed yet.
		 */
		PENDING,
		/**
		 * Indicates that the task is running.
		 */
		RUNNING,
		/**
		 * Indicates that {@link AsyncTask#onPostExecute} has finished.
		 */
		FINISHED,
	}

	/** @hide Used to force static handler to be created. */
	public static void init() {
		sHandler.getLooper();
	}

	/** @hide */
	public static void setDefaultExecutor(Executor exec) {
		sDefaultExecutor = exec;
	}

	/**
	 * Creates a new asynchronous task. This constructor must be invoked on the
	 * UI thread.
	 */
	public AsyncTask() {
		mWorker = new WorkerRunnable<Params, Result>() {
			public Result call() throws Exception {
				mTaskInvoked.set(true);

				Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
				// noinspection unchecked
				return postResult(doInBackground(mParams));
			}
		};

		mFuture = new FutureTask<Result>(mWorker) {
			@Override
			protected void done() {
				try {
					postResultIfNotInvoked(get());
				} catch (InterruptedException e) {
					android.util.Log.w(LOG_TAG, e);
				} catch (ExecutionException e) {
					throw new RuntimeException(
							"An error occured while executing doInBackground()",
							e.getCause());
				} catch (CancellationException e) {
					postResultIfNotInvoked(null);
				}
			}
		};

	}

	private void postResultIfNotInvoked(Result result) {
		final boolean wasTaskInvoked = mTaskInvoked.get();
		if (!wasTaskInvoked) {
			postResult(result);
		}
	}

	private Result postResult(Result result) {
		@SuppressWarnings("unchecked")
		Message message = sHandler.obtainMessage(MESSAGE_POST_RESULT,
				new AsyncTaskResult<Result>(this, result));
		message.sendToTarget();
		return result;
	}

	/**
	 * Returns the current status of this task.
	 * 
	 * @return The current status.
	 */
	public final Status getStatus() {
		return mStatus;
	}

	/**
	 * Override this method to perform a computation on a background thread. The
	 * specified parameters are the parameters passed to {@link #execute} by the
	 * caller of this task.
	 * 
	 * This method can call {@link #publishProgress} to publish updates on the
	 * UI thread.
	 * 
	 * @param params
	 *            The parameters of the task.
	 * 
	 * @return A result, defined by the subclass of this task.
	 * 
	 * @see #onPreExecute()
	 * @see #onPostExecute
	 * @see #publishProgress
	 */
	protected abstract Result doInBackground(Params... params);

	/**
	 * Runs on the UI thread before {@link #doInBackground}.
	 * 
	 * @see #onPostExecute
	 * @see #doInBackground
	 */
	protected void onPreExecute() {
	}

	/**
	 * <p>
	 * Runs on the UI thread after {@link #doInBackground}. The specified result
	 * is the value returned by {@link #doInBackground}.
	 * </p>
	 * 
	 * <p>
	 * This method won't be invoked if the task was cancelled.
	 * </p>
	 * 
	 * @param result
	 *            The result of the operation computed by
	 *            {@link #doInBackground}.
	 * 
	 * @see #onPreExecute
	 * @see #doInBackground
	 * @see #onCancelled(Object)
	 */
	@SuppressWarnings({ "UnusedDeclaration" })
	protected void onPostExecute(Result result) {
	}

	/**
	 * Runs on the UI thread after {@link #publishProgress} is invoked. The
	 * specified values are the values passed to {@link #publishProgress}.
	 * 
	 * @param values
	 *            The values indicating progress.
	 * 
	 * @see #publishProgress
	 * @see #doInBackground
	 */
	@SuppressWarnings({ "UnusedDeclaration" })
	protected void onProgressUpdate(Progress... values) {
	}

	/**
	 * <p>
	 * Runs on the UI thread after {@link #cancel(boolean)} is invoked and
	 * {@link #doInBackground(Object[])} has finished.
	 * </p>
	 * 
	 * <p>
	 * The default implementation simply invokes {@link #onCancelled()} and
	 * ignores the result. If you write your own implementation, do not call
	 * <code>super.onCancelled(result)</code>.
	 * </p>
	 * 
	 * @param result
	 *            The result, if any, computed in
	 *            {@link #doInBackground(Object[])}, can be null
	 * 
	 * @see #cancel(boolean)
	 * @see #isCancelled()
	 */
	@SuppressWarnings({ "UnusedParameters" })
	protected void onCancelled(Result result) {
		onCancelled();
	}

	/**
	 * <p>
	 * Applications should preferably override {@link #onCancelled(Object)}.
	 * This method is invoked by the default implementation of
	 * {@link #onCancelled(Object)}.
	 * </p>
	 * 
	 * <p>
	 * Runs on the UI thread after {@link #cancel(boolean)} is invoked and
	 * {@link #doInBackground(Object[])} has finished.
	 * </p>
	 * 
	 * @see #onCancelled(Object)
	 * @see #cancel(boolean)
	 * @see #isCancelled()
	 */
	protected void onCancelled() {
	}

	/**
	 * Returns <tt>true</tt> if this task was cancelled before it completed
	 * normally. If you are calling {@link #cancel(boolean)} on the task, the
	 * value returned by this method should be checked periodically from
	 * {@link #doInBackground(Object[])} to end the task as soon as possible.
	 * 
	 * @return <tt>true</tt> if task was cancelled before it completed
	 * 
	 * @see #cancel(boolean)
	 */
	public final boolean isCancelled() {
		return mCancelled.get();
	}

	/**
	 * <p>
	 * Attempts to cancel execution of this task. This attempt will fail if the
	 * task has already completed, already been cancelled, or could not be
	 * cancelled for some other reason. If successful, and this task has not
	 * started when <tt>cancel</tt> is called, this task should never run. If
	 * the task has already started, then the <tt>mayInterruptIfRunning</tt>
	 * parameter determines whether the thread executing this task should be
	 * interrupted in an attempt to stop the task.
	 * </p>
	 * 
	 * <p>
	 * Calling this method will result in {@link #onCancelled(Object)} being
	 * invoked on the UI thread after {@link #doInBackground(Object[])} returns.
	 * Calling this method guarantees that {@link #onPostExecute(Object)} is
	 * never invoked. After invoking this method, you should check the value
	 * returned by {@link #isCancelled()} periodically from
	 * {@link #doInBackground(Object[])} to finish the task as early as
	 * possible.
	 * </p>
	 * 
	 * @param mayInterruptIfRunning
	 *            <tt>true</tt> if the thread executing this task should be
	 *            interrupted; otherwise, in-progress tasks are allowed to
	 *            complete.
	 * 
	 * @return <tt>false</tt> if the task could not be cancelled, typically
	 *         because it has already completed normally; <tt>true</tt>
	 *         otherwise
	 * 
	 * @see #isCancelled()
	 * @see #onCancelled(Object)
	 */
	public final boolean cancel(boolean mayInterruptIfRunning) {
		mCancelled.set(true);
		return mFuture.cancel(mayInterruptIfRunning);
	}

	/**
	 * Waits if necessary for the computation to complete, and then retrieves
	 * its result.
	 * 
	 * @return The computed result.
	 * 
	 * @throws java.util.concurrent.CancellationException
	 *             If the computation was cancelled.
	 * @throws java.util.concurrent.ExecutionException
	 *             If the computation threw an exception.
	 * @throws InterruptedException
	 *             If the current thread was interrupted while waiting.
	 */
	public final Result get() throws InterruptedException, ExecutionException {
		return mFuture.get();
	}

	/**
	 * Waits if necessary for at most the given time for the computation to
	 * complete, and then retrieves its result.
	 * 
	 * @param timeout
	 *            Time to wait before cancelling the operation.
	 * @param unit
	 *            The time unit for the timeout.
	 * 
	 * @return The computed result.
	 * 
	 * @throws java.util.concurrent.CancellationException
	 *             If the computation was cancelled.
	 * @throws java.util.concurrent.ExecutionException
	 *             If the computation threw an exception.
	 * @throws InterruptedException
	 *             If the current thread was interrupted while waiting.
	 * @throws java.util.concurrent.TimeoutException
	 *             If the wait timed out.
	 */
	public final Result get(long timeout, TimeUnit unit)
			throws InterruptedException, ExecutionException, TimeoutException {
		return mFuture.get(timeout, unit);
	}

	/**
	 * Executes the task with the specified parameters. The task returns itself
	 * (this) so that the caller can keep a reference to it.
	 * 
	 * <p>
	 * Note: this function schedules the task on a queue for a single background
	 * thread or pool of threads depending on the platform version. When first
	 * introduced, AsyncTasks were executed serially on a single background
	 * thread. Starting with {@link android.os.Build.VERSION_CODES#DONUT}, this
	 * was changed to a pool of threads allowing multiple tasks to operate in
	 * parallel. Starting {@link android.os.Build.VERSION_CODES#HONEYCOMB},
	 * tasks are back to being executed on a single thread to avoid common
	 * application errors caused by parallel execution. If you truly want
	 * parallel execution, you can use the {@link #executeOnExecutor} version of
	 * this method with {@link #THREAD_POOL_EXECUTOR}; however, see commentary
	 * there for warnings on its use.
	 * 
	 * <p>
	 * This method must be invoked on the UI thread.
	 * 
	 * @param params
	 *            The parameters of the task.
	 * 
	 * @return This instance of AsyncTask.
	 * 
	 * @throws IllegalStateException
	 *             If {@link #getStatus()} returns either
	 *             {@link AsyncTask.Status#RUNNING} or
	 *             {@link AsyncTask.Status#FINISHED}.
	 * 
	 * @see #executeOnExecutor(java.util.concurrent.Executor, Object[])
	 * @see #execute(Runnable)
	 */
	public final AsyncTask<Params, Progress, Result> execute(Params... params) {
		return executeOnExecutor(sDefaultExecutor, params);
	}

	/**
	 * Executes the task with the specified parameters. The task returns itself
	 * (this) so that the caller can keep a reference to it.
	 * 
	 * <p>
	 * This method is typically used with {@link #THREAD_POOL_EXECUTOR} to allow
	 * multiple tasks to run in parallel on a pool of threads managed by
	 * AsyncTask, however you can also use your own
	 * {@link java.util.concurrent.Executor} for custom behavior.
	 * 
	 * <p>
	 * <em>Warning:</em> Allowing multiple tasks to run in parallel from a
	 * thread pool is generally <em>not</em> what one wants, because the order
	 * of their operation is not defined. For example, if these tasks are used
	 * to modify any state in common (such as writing a file due to a button
	 * click), there are no guarantees on the order of the modifications.
	 * Without careful work it is possible in rare cases for the newer version
	 * of the data to be over-written by an older one, leading to obscure data
	 * loss and stability issues. Such changes are best executed in serial; to
	 * guarantee such work is serialized regardless of platform version you can
	 * use this function with {@link #SERIAL_EXECUTOR}.
	 * 
	 * <p>
	 * This method must be invoked on the UI thread.
	 * 
	 * @param exec
	 *            The executor to use. {@link #THREAD_POOL_EXECUTOR} is
	 *            available as a convenient process-wide thread pool for tasks
	 *            that are loosely coupled.
	 * @param params
	 *            The parameters of the task.
	 * 
	 * @return This instance of AsyncTask.
	 * 
	 * @throws IllegalStateException
	 *             If {@link #getStatus()} returns either
	 *             {@link AsyncTask.Status#RUNNING} or
	 *             {@link AsyncTask.Status#FINISHED}.
	 * 
	 * @see #execute(Object[])
	 */
	public final AsyncTask<Params, Progress, Result> executeOnExecutor(
			Executor exec, Params... params) {
		if (mStatus != Status.PENDING) {
			switch (mStatus) {
			case RUNNING:
				throw new IllegalStateException("Cannot execute task:"
						+ " the task is already running.");
			case FINISHED:
				throw new IllegalStateException("Cannot execute task:"
						+ " the task has already been executed "
						+ "(a task can be executed only once)");
			}
		}

		mStatus = Status.RUNNING;

		onPreExecute();

		mWorker.mParams = params;
		exec.execute(mFuture);

		return this;
	}

	/**
	 * Convenience version of {@link #execute(Object...)} for use with a simple
	 * Runnable object. See {@link #execute(Object[])} for more information on
	 * the order of execution.
	 * 
	 * @see #execute(Object[])
	 * @see #executeOnExecutor(java.util.concurrent.Executor, Object[])
	 */
	public static void execute(Runnable runnable) {
		sDefaultExecutor.execute(runnable);
	}

	/**
	 * This method can be invoked from {@link #doInBackground} to publish
	 * updates on the UI thread while the background computation is still
	 * running. Each call to this method will trigger the execution of
	 * {@link #onProgressUpdate} on the UI thread.
	 * 
	 * {@link #onProgressUpdate} will note be called if the task has been
	 * canceled.
	 * 
	 * @param values
	 *            The progress values to update the UI with.
	 * 
	 * @see #onProgressUpdate
	 * @see #doInBackground
	 */
	protected final void publishProgress(Progress... values) {
		if (!isCancelled()) {
			sHandler.obtainMessage(MESSAGE_POST_PROGRESS,
					new AsyncTaskResult<Progress>(this, values)).sendToTarget();
		}
	}

	private void finish(Result result) {
		if (isCancelled()) {
			onCancelled(result);
		} else {
			onPostExecute(result);
		}
		mStatus = Status.FINISHED;
	}

	private static class InternalHandler extends Handler {
		@SuppressWarnings({ "unchecked", "RawUseOfParameterizedType" })
		@Override
		public void handleMessage(Message msg) {
			AsyncTaskResult result = (AsyncTaskResult) msg.obj;
			switch (msg.what) {
			case MESSAGE_POST_RESULT:
				// There is only one result
				result.mTask.finish(result.mData[0]);
				break;
			case MESSAGE_POST_PROGRESS:
				result.mTask.onProgressUpdate(result.mData);
				break;
			}
		}
	}

	private static abstract class WorkerRunnable<Params, Result> implements
			Callable<Result> {
		Params[] mParams;
	}

	@SuppressWarnings({ "RawUseOfParameterizedType" })
	private static class AsyncTaskResult<Data> {
		final AsyncTask mTask;
		final Data[] mData;

		AsyncTaskResult(AsyncTask task, Data... data) {
			mTask = task;
			mData = data;
		}
	}

}
