// Copyright 2024 The Bazel Authors. All rights reserved.
//
// 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.google.devtools.build.lib.skyframe.rewinding;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.truth.Truth.assertThat;

import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Sets;
import com.google.devtools.build.lib.actions.ActionInput;
import com.google.devtools.build.lib.actions.FileArtifactValue;
import com.google.devtools.build.lib.actions.ImportantOutputHandler;
import com.google.devtools.build.lib.actions.InputMetadataProvider;
import com.google.devtools.build.lib.buildtool.BuildRequest;
import com.google.devtools.build.lib.exec.ModuleActionContextRegistry;
import com.google.devtools.build.lib.runtime.BlazeModule;
import com.google.devtools.build.lib.runtime.CommandEnvironment;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.io.IOException;
import java.util.Set;
import java.util.function.Function;

/**
 * Installs an {@link ImportantOutputHandler} that allows customizing lost outputs for rewinding
 * tests.
 */
final class LostImportantOutputHandlerModule extends BlazeModule {

  private final Set<String> pathsToConsiderLost = Sets.newConcurrentHashSet();
  private final Function<byte[], String> digestFn;
  private PathFragment execRoot;

  LostImportantOutputHandlerModule(Function<byte[], String> digestFn) {
    this.digestFn = checkNotNull(digestFn);
  }

  void addLostOutput(String execPath) {
    pathsToConsiderLost.add(execPath);
  }

  void verifyAllLostOutputsConsumed() {
    assertThat(pathsToConsiderLost).isEmpty();
  }

  @Override
  public void beforeCommand(CommandEnvironment env) {
    env.getEventBus().register(this);
  }

  @Override
  public void registerActionContexts(
      ModuleActionContextRegistry.Builder registryBuilder,
      CommandEnvironment env,
      BuildRequest buildRequest) {
    execRoot = env.getExecRoot().asFragment();
    registryBuilder.register(ImportantOutputHandler.class, this::getLostOutputs);
  }

  private ImmutableMap<String, ActionInput> getLostOutputs(
      ImmutableCollection<ActionInput> outputs, InputMetadataProvider metadataProvider) {
    ImmutableMap.Builder<String, ActionInput> lost = ImmutableMap.builder();
    for (ActionInput output : outputs) {
      PathFragment execPath = output.getExecPath();
      if (execPath.isAbsolute()) {
        execPath = execPath.relativeTo(execRoot);
      }
      if (!pathsToConsiderLost.remove(execPath.getPathString())) {
        continue;
      }
      FileArtifactValue metadata;
      try {
        metadata = metadataProvider.getInputMetadata(output);
      } catch (IOException e) {
        throw new IllegalStateException(e);
      }
      lost.put(digestFn.apply(metadata.getDigest()), output);
    }
    return lost.buildKeepingLast();
  }
}