// Copyright 2017 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.remote;

import static com.google.common.base.Strings.isNullOrEmpty;
import static com.google.devtools.build.lib.remote.util.Utils.createSpawnResult;
import static com.google.devtools.build.lib.remote.util.Utils.getInMemoryOutputPath;
import static com.google.devtools.build.lib.remote.util.Utils.hasFilesToDownload;
import static com.google.devtools.build.lib.remote.util.Utils.shouldDownloadAllSpawnOutputs;

import build.bazel.remote.execution.v2.Action;
import build.bazel.remote.execution.v2.ActionResult;
import build.bazel.remote.execution.v2.Command;
import build.bazel.remote.execution.v2.Digest;
import build.bazel.remote.execution.v2.Platform;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.actions.ActionInput;
import com.google.devtools.build.lib.actions.ExecException;
import com.google.devtools.build.lib.actions.ExecutionStrategy;
import com.google.devtools.build.lib.actions.FileArtifactValue;
import com.google.devtools.build.lib.actions.Spawn;
import com.google.devtools.build.lib.actions.SpawnResult;
import com.google.devtools.build.lib.actions.SpawnResult.Status;
import com.google.devtools.build.lib.actions.Spawns;
import com.google.devtools.build.lib.actions.cache.VirtualActionInput;
import com.google.devtools.build.lib.analysis.platform.PlatformUtils;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
import com.google.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.events.Reporter;
import com.google.devtools.build.lib.exec.SpawnCache;
import com.google.devtools.build.lib.exec.SpawnRunner.ProgressStatus;
import com.google.devtools.build.lib.exec.SpawnRunner.SpawnExecutionContext;
import com.google.devtools.build.lib.profiler.Profiler;
import com.google.devtools.build.lib.profiler.ProfilerTask;
import com.google.devtools.build.lib.profiler.SilentCloseable;
import com.google.devtools.build.lib.remote.common.CacheNotFoundException;
import com.google.devtools.build.lib.remote.common.RemoteCacheClient.ActionKey;
import com.google.devtools.build.lib.remote.merkletree.MerkleTree;
import com.google.devtools.build.lib.remote.options.RemoteOptions;
import com.google.devtools.build.lib.remote.options.RemoteOutputsMode;
import com.google.devtools.build.lib.remote.util.DigestUtil;
import com.google.devtools.build.lib.remote.util.TracingMetadataUtils;
import com.google.devtools.build.lib.remote.util.Utils;
import com.google.devtools.build.lib.remote.util.Utils.InMemoryOutput;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import io.grpc.Context;
import java.io.IOException;
import java.util.Collection;
import java.util.HashSet;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedMap;
import javax.annotation.Nullable;

/** A remote {@link SpawnCache} implementation. */
@ThreadSafe // If the RemoteActionCache implementation is thread-safe.
@ExecutionStrategy(
    name = {"remote-cache"},
    contextType = SpawnCache.class)
final class RemoteSpawnCache implements SpawnCache {

  private final Path execRoot;
  private final RemoteOptions options;

  private final RemoteCache remoteCache;
  private final String buildRequestId;
  private final String commandId;

  @Nullable private final Reporter cmdlineReporter;

  private final Set<String> reportedErrors = new HashSet<>();

  private final DigestUtil digestUtil;

  /**
   * If {@link RemoteOutputsMode#TOPLEVEL} is specified it contains the artifacts that should be
   * downloaded.
   */
  private final ImmutableSet<ActionInput> filesToDownload;

  RemoteSpawnCache(
      Path execRoot,
      RemoteOptions options,
      RemoteCache remoteCache,
      String buildRequestId,
      String commandId,
      @Nullable Reporter cmdlineReporter,
      DigestUtil digestUtil,
      ImmutableSet<ActionInput> filesToDownload) {
    this.execRoot = execRoot;
    this.options = options;
    this.remoteCache = remoteCache;
    this.cmdlineReporter = cmdlineReporter;
    this.buildRequestId = buildRequestId;
    this.commandId = commandId;
    this.digestUtil = digestUtil;
    this.filesToDownload = Preconditions.checkNotNull(filesToDownload, "filesToDownload");
  }

  @Override
  public CacheHandle lookup(Spawn spawn, SpawnExecutionContext context)
      throws InterruptedException, IOException, ExecException {
    if (!Spawns.mayBeCached(spawn)
        || (!Spawns.mayBeCachedRemotely(spawn) && isRemoteCache(options))) {
      // returning SpawnCache.NO_RESULT_NO_STORE in case the caching is disabled or in case
      // the remote caching is disabled and the only configured cache is remote.
      return SpawnCache.NO_RESULT_NO_STORE;
    }
    boolean checkCache = options.remoteAcceptCached;

    if (checkCache) {
      context.report(ProgressStatus.CHECKING_CACHE, "remote-cache");
    }

    SortedMap<PathFragment, ActionInput> inputMap = context.getInputMapping(true);
    MerkleTree merkleTree =
        MerkleTree.build(inputMap, context.getMetadataProvider(), execRoot, digestUtil);
    Digest merkleTreeRoot = merkleTree.getRootDigest();

    // Get the remote platform properties.
    Platform platform = PlatformUtils.getPlatformProto(spawn, options);

    Command command =
        RemoteSpawnRunner.buildCommand(
            spawn.getOutputFiles(), spawn.getArguments(), spawn.getEnvironment(), platform);
    RemoteOutputsMode remoteOutputsMode = options.remoteOutputsMode;
    Action action =
        RemoteSpawnRunner.buildAction(
            digestUtil.compute(command), merkleTreeRoot, context.getTimeout(), true);
    // Look up action cache, and reuse the action output if it is found.
    ActionKey actionKey = digestUtil.computeActionKey(action);
    Context withMetadata =
        TracingMetadataUtils.contextWithMetadata(buildRequestId, commandId, actionKey);

    Profiler prof = Profiler.instance();
    if (checkCache) {
      // Metadata will be available in context.current() until we detach.
      // This is done via a thread-local variable.
      Context previous = withMetadata.attach();
      try {
        ActionResult result;
        try (SilentCloseable c = prof.profile(ProfilerTask.REMOTE_CACHE_CHECK, "check cache hit")) {
          result = remoteCache.downloadActionResult(actionKey);
        }
        // In case the remote cache returned a failed action (exit code != 0) we treat it as a
        // cache miss
        if (result != null && result.getExitCode() == 0) {
          InMemoryOutput inMemoryOutput = null;
          boolean downloadOutputs =
              shouldDownloadAllSpawnOutputs(
                  remoteOutputsMode,
                  /* exitCode = */ 0,
                  hasFilesToDownload(spawn.getOutputFiles(), filesToDownload));
          if (downloadOutputs) {
            try (SilentCloseable c =
                prof.profile(ProfilerTask.REMOTE_DOWNLOAD, "download outputs")) {
              remoteCache.download(
                  result, execRoot, context.getFileOutErr(), context::lockOutputFiles);
            }
          } else {
            PathFragment inMemoryOutputPath = getInMemoryOutputPath(spawn);
            // inject output metadata
            try (SilentCloseable c =
                prof.profile(ProfilerTask.REMOTE_DOWNLOAD, "download outputs minimal")) {
              inMemoryOutput =
                  remoteCache.downloadMinimal(
                      result,
                      spawn.getOutputFiles(),
                      inMemoryOutputPath,
                      context.getFileOutErr(),
                      execRoot,
                      context.getMetadataInjector(),
                      context::lockOutputFiles);
            }
          }
          SpawnResult spawnResult =
              createSpawnResult(
                  result.getExitCode(), /* cacheHit= */ true, "remote", inMemoryOutput);
          return SpawnCache.success(spawnResult);
        }
      } catch (CacheNotFoundException e) {
        // Intentionally left blank
      } catch (IOException e) {
        String errorMsg = Utils.grpcAwareErrorMessage(e);
        if (isNullOrEmpty(errorMsg)) {
          errorMsg = e.getClass().getSimpleName();
        }
        errorMsg = "Reading from Remote Cache:\n" + errorMsg;
        report(Event.warn(errorMsg));
      } finally {
        withMetadata.detach(previous);
      }
    }

    context.prefetchInputs();

    if (options.remoteUploadLocalResults) {
      return new CacheHandle() {
        @Override
        public boolean hasResult() {
          return false;
        }

        @Override
        public SpawnResult getResult() {
          throw new NoSuchElementException();
        }

        @Override
        public boolean willStore() {
          return true;
        }

        @Override
        public void store(SpawnResult result) throws ExecException, InterruptedException {
          boolean uploadResults = Status.SUCCESS.equals(result.status()) && result.exitCode() == 0;
          if (!uploadResults) {
            return;
          }

          if (options.experimentalGuardAgainstConcurrentChanges) {
            try (SilentCloseable c = prof.profile("RemoteCache.checkForConcurrentModifications")) {
              checkForConcurrentModifications();
            } catch (IOException e) {
              report(Event.warn(e.getMessage()));
              return;
            }
          }

          Context previous = withMetadata.attach();
          Collection<Path> files =
              RemoteSpawnRunner.resolveActionInputs(execRoot, spawn.getOutputFiles());
          try (SilentCloseable c = prof.profile(ProfilerTask.UPLOAD_TIME, "upload outputs")) {
            remoteCache.upload(
                actionKey, action, command, execRoot, files, context.getFileOutErr());
          } catch (IOException e) {
            String errorMsg = Utils.grpcAwareErrorMessage(e);
            if (isNullOrEmpty(errorMsg)) {
              errorMsg = e.getClass().getSimpleName();
            }
            errorMsg = "Writing to Remote Cache:\n" + errorMsg;
            report(Event.warn(errorMsg));
          } finally {
            withMetadata.detach(previous);
          }
        }

        @Override
        public void close() {}

        private void checkForConcurrentModifications() throws IOException {
          for (ActionInput input : inputMap.values()) {
            if (input instanceof VirtualActionInput) {
              continue;
            }
            FileArtifactValue metadata = context.getMetadataProvider().getMetadata(input);
            Path path = execRoot.getRelative(input.getExecPath());
            if (metadata.wasModifiedSinceDigest(path)) {
              throw new IOException(path + " was modified during execution");
            }
          }
        }
      };
    } else {
      return SpawnCache.NO_RESULT_NO_STORE;
    }
  }

  private void report(Event evt) {
    if (cmdlineReporter == null) {
      return;
    }

    synchronized (this) {
      if (reportedErrors.contains(evt.getMessage())) {
        return;
      }
      reportedErrors.add(evt.getMessage());
      cmdlineReporter.handle(evt);
    }
  }

  private static boolean isRemoteCache(RemoteOptions options) {
    return !isNullOrEmpty(options.remoteCache);
  }
}