
package org.zarroboogs.weibo.asynctask;

import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import android.os.Process;

import java.util.ArrayDeque;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.FutureTask;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.LinkedBlockingQueue;
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;

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

    private static final String LOG_TAG = "AsyncTask";

    private static final int CPU_COUNT = Runtime.getRuntime().availableProcessors();

    private static final int KEEP_ALIVE = 1;

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

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

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

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

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

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

    private static final Executor CANCEL_OPERATION__THREAD_POOL_EXECUTOR = new ThreadPoolExecutor(4, 4, KEEP_ALIVE,
            TimeUnit.SECONDS,
            new LinkedBlockingQueue<Runnable>(Integer.MAX_VALUE), new ThreadFactory() {
        private final AtomicInteger mCount = new AtomicInteger(1);

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

    /**
     * An {@link java.util.concurrent.Executor} that can be used to execute tasks in parallel.
     */
    private static final Executor IO_THREAD_POOL_EXECUTOR = new ThreadPoolExecutor(4, 10, KEEP_ALIVE, TimeUnit.SECONDS,
            new LinkedBlockingQueue<Runnable>(20),
            sIoThreadFactory, new ThreadPoolExecutor.DiscardOldestPolicy());

    public static final Executor THREAD_POOL_EXECUTOR = new ThreadPoolExecutor(8, 10, KEEP_ALIVE, TimeUnit.SECONDS,
            new LinkedBlockingDeque<Runnable>(128) {
                private static final long serialVersionUID = -8146732798569598158L;

                @Override
                public boolean offer(Runnable runnable) {
                    return super.offerFirst(runnable);
                }
            }, sThreadFactory, new ThreadPoolExecutor.DiscardOldestPolicy() {
        @Override
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
            if (!e.isShutdown()) {
                LinkedBlockingDeque<Runnable> deque = (LinkedBlockingDeque) e.getQueue();
                Runnable runnable = deque.pollLast();
                if (runnable instanceof FutureTask) {
                    FutureTask futureTask = (FutureTask) runnable;
                    futureTask.cancel(true);
                    CANCEL_OPERATION__THREAD_POOL_EXECUTOR.execute(futureTask);
                }
                e.execute(r);
            }
        }

    });

    private static final Executor WAIT_DOWNLOAD_THREAD_POOL_EXECUTOR = new ThreadPoolExecutor(4, 4, KEEP_ALIVE,
            TimeUnit.SECONDS,
            new LinkedBlockingDeque<Runnable>(50) {
                @Override
                public boolean offer(Runnable runnable) {
                    return super.offerFirst(runnable);
                }

            }, sDownloadThreadFactory, new ThreadPoolExecutor.DiscardOldestPolicy() {
        @Override
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
            if (!e.isShutdown()) {
                LinkedBlockingDeque<Runnable> deque = (LinkedBlockingDeque<Runnable>) e.getQueue();
                Runnable runnable = deque.pollLast();
                if (runnable instanceof FutureTask) {
                    FutureTask<?> futureTask = (FutureTask<?>) runnable;
                    futureTask.cancel(true);
                    CANCEL_OPERATION__THREAD_POOL_EXECUTOR.execute(futureTask);
                }
                e.execute(r);
            }
        }
    });

    /**
     * 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 = new SerialExecutor();

    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 mTaskInvoked = new AtomicBoolean();

    private static class SerialExecutor implements Executor {

        final ArrayDeque<Runnable> mTasks = new ArrayDeque<Runnable>();

        Runnable mActive;

        public synchronized void execute(final Runnable r) {
            mTasks.addFirst(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 android.os.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 MyAsyncTask() {
        mWorker = new WorkerRunnable<Params, Result>() {
            public Result call() throws Exception {
                mTaskInvoked.set(true);

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

        mFuture = new FutureTask<Result>(mWorker) {
            @Override
            protected void done() {
                try {
                    final Result result = get();

                    postResultIfNotInvoked(result);
                } 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);
                } catch (Throwable t) {
                    throw new RuntimeException("An error occured while executing " + "doInBackground()", t);
                }
            }
        };
    }

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

    private Result postResult(Result result) {
        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.
     * <p/>
     * 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/>
     * <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)
     */
    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
     */
    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/>
     * <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()
     */
    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/>
     * <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 mFuture.isCancelled();
    }

    /**
     * <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/>
     * <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) {
        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/>
     * <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. After {@link android.os.Build.VERSION_CODES#HONEYCOMB}
     * , it is planned to change this back to 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/>
     * <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 android.os.AsyncTask.Status#RUNNING} or {@link android.os.AsyncTask.Status#FINISHED}.
     */
    public final MyAsyncTask<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/>
     * <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/>
     * <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/>
     * <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 android.os.AsyncTask.Status#RUNNING} or {@link android.os.AsyncTask.Status#FINISHED}.
     */
    public final MyAsyncTask<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)");
                default:
                    break;
            }
        }

        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.
     */
    public static void execute(Runnable runnable) {
        sDefaultExecutor.execute(runnable);
    }

    public void executeOnIO(Params... params) {
        executeOnExecutor(IO_THREAD_POOL_EXECUTOR, params);
    }

    public void executeOnNormal(Params... params) {
        executeOnExecutor(THREAD_POOL_EXECUTOR, params);
    }

    public void executeOnWaitNetwork(Params... params) {
        executeOnExecutor(WAIT_DOWNLOAD_THREAD_POOL_EXECUTOR, params);
    }

    /**
     * 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.
     * <p/>
     * {@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 {

        @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;
    }

    private static class AsyncTaskResult<Data> {

        final MyAsyncTask mTask;

        final Data[] mData;

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