/*
 * Copyright 2000-2016 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.openapi.progress.util;

import com.intellij.openapi.Disposable;
import com.intellij.openapi.application.ApplicationManager;
import com.intellij.openapi.application.ModalityState;
import com.intellij.openapi.diagnostic.Logger;
import com.intellij.openapi.progress.EmptyProgressIndicator;
import com.intellij.openapi.progress.ProcessCanceledException;
import com.intellij.openapi.progress.ProgressIndicator;
import com.intellij.openapi.progress.ProgressManager;
import com.intellij.openapi.util.Disposer;
import com.intellij.openapi.util.EmptyRunnable;
import com.intellij.openapi.util.Ref;
import com.intellij.util.Consumer;
import com.intellij.util.Function;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import consulo.annotations.RequiredDispatchThread;

import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

public class BackgroundTaskUtil {
  private static final Logger LOG = Logger.getInstance(BackgroundTaskUtil.class);
  private static final Runnable TOO_SLOW_OPERATION = new EmptyRunnable();

  /*
   * Executor to perform <possibly> long operations on pooled thread
   * It can be used to reduce blinking if background task completed fast. In this case callback will be called without invokeLater().
   *
   * Simple approach:
   *
   * onSlowAction.run() // show "Loading..."
   * executeOnPooledThread({
   *     Runnable callback = backgroundTask(); // some background computations
   *     invokeLater(callback); // apply changes
   *   });
   *
   * will lead to "Loading..." visible between current moment and execution of invokeLater() event.
   * This period can be very short and looks like 'jumping' if background operation is fast.
   */
  @RequiredDispatchThread
  @NotNull
  public static ProgressIndicator executeAndTryWait(@NotNull final Function<ProgressIndicator, Runnable> backgroundTask,
                                                    @Nullable final Runnable onSlowAction,
                                                    final int waitMillis) {
    return executeAndTryWait(backgroundTask, onSlowAction, waitMillis, false);
  }

  @RequiredDispatchThread
  @NotNull
  public static ProgressIndicator executeAndTryWait(@NotNull final Function<ProgressIndicator, Runnable> backgroundTask,
                                                    @Nullable final Runnable onSlowAction,
                                                    final int waitMillis,
                                                    final boolean forceEDT) {
    final ModalityState modality = ModalityState.current();
    final ProgressIndicator indicator = new EmptyProgressIndicator() {
      @NotNull
      @Override
      public ModalityState getModalityState() {
        return modality;
      }
    };

    final Semaphore semaphore = new Semaphore(0);
    final AtomicReference<Runnable> resultRef = new AtomicReference<Runnable>();

    if (forceEDT) {
      try {
        Runnable callback = backgroundTask.fun(indicator);
        finish(callback, indicator);
      }
      catch (ProcessCanceledException ignore) {
      }
      catch (Throwable t) {
        LOG.error(t);
      }
    }
    else {
      ApplicationManager.getApplication().executeOnPooledThread(new Runnable() {
        @Override
        public void run() {
          ProgressManager.getInstance().executeProcessUnderProgress(new Runnable() {
            @Override
            public void run() {
              final Runnable callback = backgroundTask.fun(indicator);

              if (indicator.isCanceled()) {
                semaphore.release();
                return;
              }

              if (!resultRef.compareAndSet(null, callback)) {
                ApplicationManager.getApplication().invokeLater(new Runnable() {
                  @Override
                  public void run() {
                    finish(callback, indicator);
                  }
                }, modality);
              }
              semaphore.release();
            }
          }, indicator);
        }
      });

      try {
        semaphore.tryAcquire(waitMillis, TimeUnit.MILLISECONDS);
      }
      catch (InterruptedException ignore) {
      }
      if (!resultRef.compareAndSet(null, TOO_SLOW_OPERATION)) {
        // update presentation in the same thread to reduce blinking, caused by 'invokeLater' and fast background operation
        finish(resultRef.get(), indicator);
      }
      else {
        if (onSlowAction != null) onSlowAction.run();
      }
    }

    return indicator;
  }

  @RequiredDispatchThread
  private static void finish(@NotNull Runnable result, @NotNull ProgressIndicator indicator) {
    if (indicator.isCanceled()) return;
    result.run();
    indicator.stop();
  }

  @RequiredDispatchThread
  @Nullable
  public static <T> T tryComputeFast(@NotNull final Function<ProgressIndicator, T> backgroundTask,
                                     final int waitMillis) {
    final Ref<T> resultRef = new Ref<T>();
    ProgressIndicator indicator = executeAndTryWait(new Function<ProgressIndicator, Runnable>() {
      @Override
      public Runnable fun(ProgressIndicator indicator1) {
        final T result = backgroundTask.fun(indicator1);
        return new Runnable() {
          @Override
          public void run() {
            resultRef.set(result);
          }
        };
      }
    }, null, waitMillis, false);
    indicator.cancel();

    return resultRef.get();
  }

  @RequiredDispatchThread
  @NotNull
  public static ProgressIndicator executeOnPooledThread(@NotNull Consumer<ProgressIndicator> task, @NotNull Disposable parent) {
    final ModalityState modalityState = ModalityState.current();
    return executeOnPooledThread(task, parent, modalityState);
  }

  @NotNull
  public static ProgressIndicator executeOnPooledThread(@NotNull final Runnable runnable, @NotNull Disposable parent) {
    return executeOnPooledThread(new Consumer<ProgressIndicator>() {
      @Override
      public void consume(ProgressIndicator indicator) {
        runnable.run();
      }
    }, parent, ModalityState.NON_MODAL);
  }

  @NotNull
  public static ProgressIndicator executeOnPooledThread(@NotNull final Consumer<ProgressIndicator> task,
                                                        @NotNull Disposable parent,
                                                        final ModalityState modalityState) {
    final ProgressIndicator indicator = new EmptyProgressIndicator() {
      @NotNull
      @Override
      public ModalityState getModalityState() {
        return modalityState;
      }
    };

    final Disposable disposable = new Disposable() {
      @Override
      public void dispose() {
        if (indicator.isRunning()) indicator.cancel();
      }
    };
    Disposer.register(parent, disposable);
    indicator.start();

    ApplicationManager.getApplication().executeOnPooledThread(new Runnable() {
      @Override
      public void run() {
        ProgressManager.getInstance().executeProcessUnderProgress(new Runnable() {
          @Override
          public void run() {
            try {
              task.consume(indicator);
            }
            finally {
              indicator.stop();
              Disposer.dispose(disposable);
            }
          }
        }, indicator);
      }
    });

    return indicator;
  }
}