/*
 * 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.vfs.newvfs;

import com.intellij.codeInsight.daemon.impl.FileStatusMap;
import com.intellij.openapi.application.ApplicationManager;
import com.intellij.openapi.application.ModalityState;
import com.intellij.openapi.application.TransactionId;
import com.intellij.openapi.application.WriteAction;
import com.intellij.openapi.diagnostic.Logger;
import com.intellij.openapi.vfs.LocalFileSystem;
import com.intellij.openapi.vfs.VirtualFile;
import com.intellij.openapi.vfs.VirtualFileManager;
import com.intellij.openapi.vfs.ex.VirtualFileManagerEx;
import com.intellij.openapi.vfs.impl.local.LocalFileSystemImpl;
import com.intellij.openapi.vfs.newvfs.events.VFileEvent;
import com.intellij.openapi.vfs.newvfs.persistent.PersistentFS;
import com.intellij.openapi.vfs.newvfs.persistent.RefreshWorker;
import com.intellij.util.concurrency.Semaphore;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.*;
import java.util.concurrent.atomic.AtomicLong;

/**
 * @author max
 */
public class RefreshSessionImpl extends RefreshSession {
  private static final Logger LOG = Logger.getInstance(RefreshSession.class);

  private static final AtomicLong ID_COUNTER = new AtomicLong(0);

  private final long myId = ID_COUNTER.incrementAndGet();
  private final boolean myIsAsync;
  private final boolean myIsRecursive;
  private final Runnable myFinishRunnable;
  private final Throwable myStartTrace;
  private final Semaphore mySemaphore = new Semaphore();

  private List<VirtualFile> myWorkQueue = new ArrayList<>();
  private List<VFileEvent> myEvents = new ArrayList<>();
  private volatile boolean myHaveEventsToFire;
  private volatile RefreshWorker myWorker;
  private volatile boolean myCancelled;
  private final TransactionId myTransaction;

  RefreshSessionImpl(boolean async, boolean recursive, @Nullable Runnable finishRunnable, @Nullable TransactionId context) {
    myIsAsync = async;
    myIsRecursive = recursive;
    myFinishRunnable = finishRunnable;
    myTransaction = context;
    LOG.assertTrue(context == ModalityState.NON_MODAL || context != ModalityState.any(), "Refresh session should have a specific modality");
    myStartTrace = rememberStartTrace();
  }

  private Throwable rememberStartTrace() {
    if (ApplicationManager.getApplication().isUnitTestMode() &&
        (myIsAsync || !ApplicationManager.getApplication().isDispatchThread())) {
      return new Throwable();
    }
    return null;
  }

  RefreshSessionImpl(@NotNull List<VFileEvent> events) {
    this(false, false, null, null);
    myEvents.addAll(events);
  }

  @Override
  public long getId() {
    return myId;
  }

  @Override
  public void addAllFiles(@NotNull Collection<? extends VirtualFile> files) {
    for (VirtualFile file : files) {
      if (file == null) {
        LOG.error("null passed among " + files);
      }
      else {
        myWorkQueue.add(file);
      }
    }
  }

  @Override
  public void addFile(@NotNull VirtualFile file) {
    myWorkQueue.add(file);
  }

  @Override
  public boolean isAsynchronous() {
    return myIsAsync;
  }

  @Override
  public void launch() {
    mySemaphore.down();
    ((RefreshQueueImpl)RefreshQueue.getInstance()).execute(this);
  }

  public void scan() {
    List<VirtualFile> workQueue = myWorkQueue;
    myWorkQueue = new ArrayList<>();
    boolean haveEventsToFire = myFinishRunnable != null || !myEvents.isEmpty();

    if (!workQueue.isEmpty()) {
      LocalFileSystem fs = LocalFileSystem.getInstance();
      if (fs instanceof LocalFileSystemImpl) {
        ((LocalFileSystemImpl)fs).markSuspiciousFilesDirty(workQueue);
      }

      long t = 0;
      if (LOG.isTraceEnabled()) {
        LOG.trace("scanning " + workQueue);
        t = System.currentTimeMillis();
      }

      int count = 0;
      refresh: do {
        if (LOG.isTraceEnabled()) LOG.trace("try=" + count);

        for (VirtualFile file : workQueue) {
          if (myCancelled) break refresh;

          NewVirtualFile nvf = (NewVirtualFile)file;
          if (!myIsRecursive && !myIsAsync) {
            nvf.markDirty();  // always scan when non-recursive AND synchronous - needed e.g. when refreshing project files on open
          }

          RefreshWorker worker = new RefreshWorker(nvf, myIsRecursive);
          myWorker = worker;
          worker.scan();
          haveEventsToFire |= myEvents.addAll(worker.getEvents());
        }

        count++;
        if (LOG.isTraceEnabled()) LOG.trace("events=" + myEvents.size());
      }
      while (!myCancelled && myIsRecursive && count < 3 && workQueue.stream().anyMatch(f -> ((NewVirtualFile)f).isDirty()));

      if (t != 0) {
        t = System.currentTimeMillis() - t;
        LOG.trace((myCancelled ? "cancelled, " : "done, ") + t + " ms, events " + myEvents);
      }
    }

    myWorker = null;
    myHaveEventsToFire = haveEventsToFire;
  }

  void cancel() {
    myCancelled = true;

    RefreshWorker worker = myWorker;
    if (worker != null) {
      worker.cancel();
    }
  }

  void fireEvents() {
    if (!myHaveEventsToFire || ApplicationManager.getApplication().isDisposed()) {
      mySemaphore.up();
      return;
    }

    try {
      if (LOG.isDebugEnabled()) LOG.debug("events are about to fire: " + myEvents);
      WriteAction.run(this::fireEventsInWriteAction);
    }
    finally {
      mySemaphore.up();
    }
  }

  private void fireEventsInWriteAction() {
    final VirtualFileManagerEx manager = (VirtualFileManagerEx)VirtualFileManager.getInstance();

    manager.fireBeforeRefreshStart(myIsAsync);
    try {
      while (!myWorkQueue.isEmpty() || !myEvents.isEmpty()) {
        PersistentFS.getInstance().processEvents(mergeEventsAndReset());
        scan();
      }
    }
    catch (AssertionError e) {
      if (FileStatusMap.CHANGES_NOT_ALLOWED_DURING_HIGHLIGHTING.equals(e.getMessage())) {
        throw new AssertionError("VFS changes are not allowed during highlighting", myStartTrace);
      }
      throw e;
    }
    finally {
      try {
        manager.fireAfterRefreshFinish(myIsAsync);
      }
      finally {
        if (myFinishRunnable != null) {
          myFinishRunnable.run();
        }
      }
    }
  }

  public void waitFor() {
    mySemaphore.waitFor();
  }

  private List<VFileEvent> mergeEventsAndReset() {
    Set<VFileEvent> mergedEvents = new LinkedHashSet<>(myEvents);
    List<VFileEvent> events = new ArrayList<>(mergedEvents);
    myEvents = new ArrayList<>();
    return events;
  }

  @Nullable
  TransactionId getTransaction() {
    return myTransaction;
  }

  @Override
  public String toString() {
    return myWorkQueue.size() <= 1 ? "" : myWorkQueue.size() + " roots in queue.";
  }
}