// 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.exec.local;

import static java.nio.charset.StandardCharsets.UTF_8;
import static java.util.logging.Level.INFO;
import static java.util.logging.Level.SEVERE;
import static java.util.logging.Level.WARNING;

import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;
import com.google.common.io.ByteStreams;
import com.google.devtools.build.lib.actions.ActionExecutionMetadata;
import com.google.devtools.build.lib.actions.ResourceManager;
import com.google.devtools.build.lib.actions.ResourceManager.ResourceHandle;
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.concurrent.ThreadSafety.ThreadSafe;
import com.google.devtools.build.lib.exec.SpawnRunner;
import com.google.devtools.build.lib.shell.AbnormalTerminationException;
import com.google.devtools.build.lib.shell.Command;
import com.google.devtools.build.lib.shell.CommandException;
import com.google.devtools.build.lib.shell.CommandResult;
import com.google.devtools.build.lib.util.NetUtil;
import com.google.devtools.build.lib.util.OS;
import com.google.devtools.build.lib.util.OsUtils;
import com.google.devtools.build.lib.util.io.FileOutErr;
import com.google.devtools.build.lib.vfs.FileSystemUtils;
import com.google.devtools.build.lib.vfs.Path;
import java.io.IOException;
import java.io.OutputStream;
import java.time.Duration;
import java.util.ArrayList;
import java.util.EnumMap;
import java.util.List;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.Nullable;

/**
 * A class that runs local commands. Each request follows state transitions from "parsing" to
 * completion.
 */
@ThreadSafe
public final class LocalSpawnRunner implements SpawnRunner {
  private static final Joiner SPACE_JOINER = Joiner.on(' ');
  private static final String UNHANDLED_EXCEPTION_MSG = "Unhandled exception running a local spawn";
  private static final int LOCAL_EXEC_ERROR = -1;
  private static final int POSIX_TIMEOUT_EXIT_CODE = /*SIGNAL_BASE=*/128 + /*SIGALRM=*/14;

  private static final Logger logger = Logger.getLogger(LocalSpawnRunner.class.getName());

  private final Path execRoot;
  private final ResourceManager resourceManager;

  private final String hostName;

  private final LocalExecutionOptions localExecutionOptions;

  private final boolean useProcessWrapper;
  private final String processWrapper;

  private final String productName;
  private final LocalEnvProvider localEnvProvider;

  private static Path getProcessWrapper(Path execRoot, OS localOs) {
    return execRoot.getRelative("_bin/process-wrapper" + OsUtils.executableExtension(localOs));
  }

  public LocalSpawnRunner(
      Path execRoot,
      LocalExecutionOptions localExecutionOptions,
      ResourceManager resourceManager,
      boolean useProcessWrapper,
      OS localOs,
      String productName,
      LocalEnvProvider localEnvProvider) {
    this.execRoot = execRoot;
    this.processWrapper = getProcessWrapper(execRoot, localOs).getPathString();
    this.localExecutionOptions = Preconditions.checkNotNull(localExecutionOptions);
    this.hostName = NetUtil.getCachedShortHostName();
    this.resourceManager = resourceManager;
    this.useProcessWrapper = useProcessWrapper;
    this.productName = productName;
    this.localEnvProvider = localEnvProvider;
  }

  public LocalSpawnRunner(
      Path execRoot,
      LocalExecutionOptions localExecutionOptions,
      ResourceManager resourceManager,
      String productName,
      LocalEnvProvider localEnvProvider) {
    this(
        execRoot,
        localExecutionOptions,
        resourceManager,
        OS.getCurrent() != OS.WINDOWS && getProcessWrapper(execRoot, OS.getCurrent()).exists(),
        OS.getCurrent(),
        productName,
        localEnvProvider);
  }

  @Override
  public SpawnResult exec(
      Spawn spawn,
      SpawnExecutionPolicy policy) throws IOException, InterruptedException {
    ActionExecutionMetadata owner = spawn.getResourceOwner();
    policy.report(ProgressStatus.SCHEDULING, "local");
    try (ResourceHandle handle =
        resourceManager.acquireResources(owner, spawn.getLocalResources())) {
      policy.report(ProgressStatus.EXECUTING, "local");
      policy.lockOutputFiles();
      return new SubprocessHandler(spawn, policy).run();
    }
  }

  private static Path createActionTemp(Path execRoot) throws IOException {
    // Use this executor thread's ID as the directory name's suffix.
    // The ID is safe for the following reasons:
    // - being a thread ID, it's guaranteed to be unique among other action executor threads
    // - this thread will only execute one action at a time, so there's no risk of concurrently
    //   running actions using the same temp directory.
    // The next action that this thread executes can reuse the temp directory name. The only caveat
    // is, if {@link #start} fails to delete directory after the action is done, the next
    // action will see stale files in its temp directory.
    String idStr = Long.toHexString(Thread.currentThread().getId());
    Path result = execRoot.getRelative("tmp" + idStr);
    if (!result.exists() && !result.createDirectory()) {
      throw new IOException(String.format("Could not create temp directory '%s'", result));
    }
    return result;
  }

  private final class SubprocessHandler {
    private final Spawn spawn;
    private final SpawnExecutionPolicy policy;

    private final long creationTime = System.currentTimeMillis();
    private long stateStartTime = creationTime;
    private State currentState = State.INITIALIZING;
    private final Map<State, Long> stateTimes = new EnumMap<>(State.class);

    private final int id;

    public SubprocessHandler(
        Spawn spawn,
        SpawnExecutionPolicy policy) {
      Preconditions.checkArgument(!spawn.getArguments().isEmpty());
      this.spawn = spawn;
      this.policy = policy;
      this.id = policy.getId();
      setState(State.PARSING);
    }

    public SpawnResult run() throws InterruptedException, IOException {
      try {
        return start();
      } catch (Error e) {
        stepLog(SEVERE, UNHANDLED_EXCEPTION_MSG, e);
        throw e;
      } catch (IOException e) {
        stepLog(SEVERE, "Local I/O error", e);
        throw e;
      } catch (RuntimeException e) {
        stepLog(SEVERE, UNHANDLED_EXCEPTION_MSG, e);
        throw new RuntimeException(UNHANDLED_EXCEPTION_MSG, e);
      }
    }

    private void stepLog(Level level, String fmt, Object... args) {
      stepLog(level, fmt, /*cause=*/ null, args);
    }

    @SuppressWarnings("unused")
    private void stepLog(Level level, String fmt, @Nullable Throwable cause, Object... args) {
      String msg = String.format(fmt, args);
      String toLog = String.format("%s (#%d %s)", msg, id, desc());
      logger.log(level, toLog, cause);
    }

    private String desc() {
      String progressMessage = spawn.getResourceOwner().getProgressMessage();
      return progressMessage != null
          ? progressMessage
          : "ActionType=" + spawn.getResourceOwner().getMnemonic();
    }

    private void setState(State newState) {
      long now = System.currentTimeMillis();
      long totalDelta = now - creationTime;
      long stepDelta = now - stateStartTime;
      stateStartTime = now;

      Long stateTimeBoxed = stateTimes.get(currentState);
      long stateTime = (stateTimeBoxed == null) ? 0 : stateTimeBoxed;
      stateTimes.put(currentState, stateTime + stepDelta);

      logger.info(String.format(
          "Step #%d time: %.3f delta: %.3f state: %s --> %s",
          id, totalDelta / 1000f, stepDelta / 1000f, currentState, newState));
      currentState = newState;
    }

    private String debugCmdString() {
      String cmd = SPACE_JOINER.join(spawn.getArguments());
      if (cmd.length() > 500) {
        // Shrink argstr by replacing middle of string with "...".
        return cmd.substring(0, 250) + "..." + cmd.substring(cmd.length() - 250);
      }
      return cmd;
    }

    /** Parse the request and run it locally. */
    private SpawnResult start() throws InterruptedException, IOException {
      logger.info(String.format("starting local subprocess #%d, argv: %s", id, debugCmdString()));

      FileOutErr outErr = policy.getFileOutErr();
      String actionType = spawn.getResourceOwner().getMnemonic();
      if (localExecutionOptions.allowedLocalAction != null
          && !localExecutionOptions.allowedLocalAction.matcher(actionType).matches()) {
        setState(State.PERMANENT_ERROR);
        outErr.getErrorStream().write(
            ("Action type " + actionType + " is not allowed to run locally due to regex filter: "
                + localExecutionOptions.allowedLocalAction + "\n").getBytes(UTF_8));
        return new SpawnResult.Builder()
            .setStatus(Status.LOCAL_ACTION_NOT_ALLOWED)
            .setExitCode(LOCAL_EXEC_ERROR)
            .setExecutorHostname(hostName)
            .build();
      }

      if (Spawns.shouldPrefetchInputsForLocalExecution(spawn)) {
        stepLog(INFO, "prefetching inputs for local execution");
        setState(State.PREFETCHING_LOCAL_INPUTS);
        policy.prefetchInputs();
      }

      stepLog(INFO, "running locally");
      setState(State.LOCAL_ACTION_RUNNING);

      Path tmpDir = createActionTemp(execRoot);
      try {
        Command cmd;
        OutputStream stdOut = ByteStreams.nullOutputStream();
        OutputStream stdErr = ByteStreams.nullOutputStream();
        if (useProcessWrapper) {
          // If the process wrapper is enabled, we use its timeout feature, which first interrupts
          // the subprocess and only kills it after a grace period so that the subprocess can output
          // a stack trace, test log or similar, which is incredibly helpful for debugging. The
          // process wrapper also supports output file redirection, so we don't need to stream the
          // output through this process.
          List<String> cmdLine = new ArrayList<>();
          cmdLine.add(processWrapper);
          cmdLine.add("--timeout=" + policy.getTimeout().getSeconds());
          cmdLine.add("--kill_delay=" + localExecutionOptions.localSigkillGraceSeconds);
          cmdLine.add("--stdout=" + getPathOrDevNull(outErr.getOutputPath()));
          cmdLine.add("--stderr=" + getPathOrDevNull(outErr.getErrorPath()));
          cmdLine.addAll(spawn.getArguments());
          cmd =
              new Command(
                  cmdLine.toArray(new String[0]),
                  localEnvProvider.rewriteLocalEnv(
                      spawn.getEnvironment(), execRoot, tmpDir, productName),
                  execRoot.getPathFile());
        } else {
          stdOut = outErr.getOutputStream();
          stdErr = outErr.getErrorStream();
          cmd =
              new Command(
                  spawn.getArguments().toArray(new String[0]),
                  localEnvProvider.rewriteLocalEnv(
                      spawn.getEnvironment(), execRoot, tmpDir, productName),
                  execRoot.getPathFile(),
                  policy.getTimeout());
        }

        long startTime = System.currentTimeMillis();
        CommandResult result = null;
        try {
          result = cmd.execute(stdOut, stdErr);
          if (Thread.currentThread().isInterrupted()) {
            throw new InterruptedException();
          }
        } catch (AbnormalTerminationException e) {
          if (Thread.currentThread().isInterrupted()) {
            throw new InterruptedException();
          }
          result = e.getResult();
        } catch (CommandException e) {
          // At the time this comment was written, this must be a ExecFailedException encapsulating
          // an IOException from the underlying Subprocess.Factory.
          String msg = e.getMessage() == null ? e.getClass().getName() : e.getMessage();
          setState(State.PERMANENT_ERROR);
          outErr
              .getErrorStream()
              .write(("Action failed to execute: " + msg + "\n").getBytes(UTF_8));
          outErr.getErrorStream().flush();
          return new SpawnResult.Builder()
              .setStatus(Status.EXECUTION_FAILED)
              .setExitCode(LOCAL_EXEC_ERROR)
              .setExecutorHostname(hostName)
              .build();
        }
        setState(State.SUCCESS);
        Duration wallTime = Duration.ofMillis(System.currentTimeMillis() - startTime);
        boolean wasTimeout =
            result.getTerminationStatus().timedOut()
                || (useProcessWrapper && wasTimeout(policy.getTimeout(), wallTime));
        Status status = wasTimeout ? Status.TIMEOUT : Status.SUCCESS;
        int exitCode =
            status == Status.TIMEOUT
                ? POSIX_TIMEOUT_EXIT_CODE
                : result.getTerminationStatus().getRawExitCode();
        return new SpawnResult.Builder()
            .setStatus(status)
            .setExitCode(exitCode)
            .setExecutorHostname(hostName)
            .setWallTime(wallTime)
            .build();
      } finally {
        // Delete the temp directory tree, so the next action that this thread executes will get a
        // fresh, empty temp directory.
        // File deletion tends to be slow on Windows, so deleting this tree may take several
        // seconds. Delete it after having measured the wallTime.
        try {
          FileSystemUtils.deleteTree(tmpDir);
        } catch (IOException ignored) {
          // We can't handle this exception in any meaningful way, nor should we, but let's log it.
          stepLog(
              WARNING,
              String.format(
                  "failed to delete temp directory '%s'; this might indicate that the action "
                      + "created subprocesses that didn't terminate and hold files open in that "
                      + "directory",
                  tmpDir));
        }
      }
    }

    private String getPathOrDevNull(Path path) {
      return path == null ? "/dev/null" : path.getPathString();
    }

    private boolean wasTimeout(Duration timeout, Duration wallTime) {
      return !timeout.isZero() && wallTime.compareTo(timeout) > 0;
    }
  }

  private enum State {
    INITIALIZING,
    PARSING,
    PREFETCHING_LOCAL_INPUTS,
    LOCAL_ACTION_RUNNING,
    PERMANENT_ERROR,
    SUCCESS;
  }
}