platform/diff-impl/src/com/intellij/diff/chains/AsyncDiffRequestChain.java

   1 // Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
   2 package com.intellij.diff.chains;
   3
   4 import com.intellij.diff.chains.SimpleDiffRequestChain.DiffRequestProducerWrapper;
   5 import com.intellij.diff.requests.ErrorDiffRequest;
   6 import com.intellij.diff.requests.LoadingDiffRequest;
   7 import com.intellij.openapi.Disposable;
   8 import com.intellij.openapi.ListSelection;
   9 import com.intellij.openapi.progress.ProgressIndicator;
  10 import com.intellij.openapi.progress.util.BackgroundTaskUtil;
  11 import com.intellij.openapi.util.UserDataHolderBase;
  12 import com.intellij.util.EventDispatcher;
  13 import com.intellij.util.concurrency.annotations.RequiresBackgroundThread;
  14 import com.intellij.util.concurrency.annotations.RequiresEdt;
  15 import org.jetbrains.annotations.NotNull;
  16 import org.jetbrains.annotations.Nullable;
  17
  18 import java.util.EventListener;
  19
  20 public abstract class AsyncDiffRequestChain extends UserDataHolderBase implements DiffRequestSelectionChain {
  21   private final EventDispatcher<Listener> myDispatcher = EventDispatcher.create(Listener.class);
  22
  23   private volatile ListSelection<? extends DiffRequestProducer> myRequests = null;
  24
  25   @Nullable private ProgressIndicator myIndicator;
  26   private int myAssignments = 0;
  27
  28   public void addListener(@NotNull Listener listener, @NotNull Disposable disposable) {
  29     myDispatcher.addListener(listener, disposable);
  30   }
  31
  32   public void removeListener(@NotNull Listener listener) {
  33     myDispatcher.removeListener(listener);
  34   }
  35
  36   @Override
  37   public @NotNull ListSelection<? extends DiffRequestProducer> getListSelection() {
  38     ListSelection<? extends DiffRequestProducer> requests = myRequests;
  39     if (requests == null) {
  40       return ListSelection.createSingleton(new DiffRequestProducerWrapper(new LoadingDiffRequest()));
  41     }
  42     return requests;
  43   }
  44
  45   @NotNull
  46   @RequiresBackgroundThread
  47   public ListSelection<? extends DiffRequestProducer> loadRequestsInBackground() {
  48     try {
  49       return loadRequestProducers();
  50     }
  51     catch (DiffRequestProducerException e) {
  52       return ListSelection.createSingleton(new DiffRequestProducerWrapper(new ErrorDiffRequest(e)));
  53     }
  54   }
  55
  56   @RequiresEdt
  57   public void onAssigned(boolean isAssigned) {
  58     if (isAssigned) {
  59       if (myAssignments == 0 && myIndicator == null) {
  60         myIndicator = startLoading();
  61       }
  62       myAssignments++;
  63     }
  64     else {
  65       myAssignments--;
  66       if (myAssignments == 0 && myIndicator != null) {
  67         myIndicator.cancel();
  68         myIndicator = null;
  69       }
  70     }
  71     assert myAssignments >= 0;
  72   }
  73
  74   @Nullable
  75   @RequiresEdt
  76   private ProgressIndicator startLoading() {
  77     if (myRequests != null) return null;
  78
  79     return BackgroundTaskUtil.executeAndTryWait(indicator -> {
  80       ListSelection<? extends DiffRequestProducer> producers = loadRequestsInBackground();
  81       return () -> {
  82         indicator.checkCanceled();
  83         applyLoadedChanges(producers);
  84       };
  85     }, null);
  86   }
  87
  88   @RequiresEdt
  89   private void applyLoadedChanges(@NotNull ListSelection<? extends DiffRequestProducer> producers) {
  90     if (myRequests != null) return;
  91
  92     myRequests = producers;
  93     myIndicator = null;
  94
  95     myDispatcher.getMulticaster().onRequestsLoaded();
  96   }
  97
  98   @NotNull
  99   @RequiresBackgroundThread
 100   protected abstract ListSelection<? extends DiffRequestProducer> loadRequestProducers() throws DiffRequestProducerException;
 101
 102   public interface Listener extends EventListener {
 103     @RequiresEdt
 104     void onRequestsLoaded();
 105   }
 106 }