// Copyright 2014 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.sandbox;

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Maps;
import com.google.devtools.build.lib.actions.ActionExecutionContext;
import com.google.devtools.build.lib.actions.ExecException;
import com.google.devtools.build.lib.actions.ExecutionStrategy;
import com.google.devtools.build.lib.actions.Executor;
import com.google.devtools.build.lib.actions.Spawn;
import com.google.devtools.build.lib.actions.SpawnActionContext;
import com.google.devtools.build.lib.actions.UserExecException;
import com.google.devtools.build.lib.analysis.BlazeDirectories;
import com.google.devtools.build.lib.buildtool.BuildRequest;
import com.google.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.runtime.CommandEnvironment;
import com.google.devtools.build.lib.vfs.FileSystemUtils;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.io.IOException;
import java.util.Set;
import java.util.SortedMap;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;

/** Strategy that uses sandboxing to execute a process. */
@ExecutionStrategy(
  name = {"sandboxed"},
  contextType = SpawnActionContext.class
)
public class LinuxSandboxedStrategy extends SandboxStrategy {
  private static Boolean sandboxingSupported = null;

  public static boolean isSupported(CommandEnvironment env) {
    if (sandboxingSupported == null) {
      sandboxingSupported =
          ProcessWrapperRunner.isSupported(env) || LinuxSandboxRunner.isSupported(env);
    }
    return sandboxingSupported.booleanValue();
  }

  private final SandboxOptions sandboxOptions;
  private final BlazeDirectories blazeDirs;
  private final Path execRoot;
  private final boolean verboseFailures;
  private final String productName;
  private final boolean fullySupported;

  private final UUID uuid = UUID.randomUUID();
  private final AtomicInteger execCounter = new AtomicInteger();

  LinuxSandboxedStrategy(
      BuildRequest buildRequest,
      BlazeDirectories blazeDirs,
      boolean verboseFailures,
      String productName,
      boolean fullySupported) {
    super(
        buildRequest,
        blazeDirs,
        verboseFailures,
        buildRequest.getOptions(SandboxOptions.class));
    this.sandboxOptions = buildRequest.getOptions(SandboxOptions.class);
    this.blazeDirs = blazeDirs;
    this.execRoot = blazeDirs.getExecRoot();
    this.verboseFailures = verboseFailures;
    this.productName = productName;
    this.fullySupported = fullySupported;
  }

  /** Executes the given {@code spawn}. */
  @Override
  public void exec(Spawn spawn, ActionExecutionContext actionExecutionContext)
      throws ExecException, InterruptedException {
    exec(spawn, actionExecutionContext, null);
  }

  @Override
  public void exec(
      Spawn spawn,
      ActionExecutionContext actionExecutionContext,
      AtomicReference<Class<? extends SpawnActionContext>> writeOutputFiles)
      throws ExecException, InterruptedException {
    Executor executor = actionExecutionContext.getExecutor();

    // Certain actions can't run remotely or in a sandbox - pass them on to the standalone strategy.
    if (!spawn.isRemotable() || spawn.hasNoSandbox()) {
      SandboxHelpers.fallbackToNonSandboxedExecution(spawn, actionExecutionContext, executor);
      return;
    }

    SandboxHelpers.reportSubcommand(executor, spawn);
    SandboxHelpers.postActionStatusMessage(executor, spawn);

    // Each invocation of "exec" gets its own sandbox.
    Path sandboxPath = SandboxHelpers.getSandboxRoot(blazeDirs, productName, uuid, execCounter);
    Path sandboxExecRoot = sandboxPath.getRelative("execroot").getRelative(execRoot.getBaseName());
    Path sandboxTempDir = sandboxPath.getRelative("tmp");

    Set<Path> writableDirs = getWritableDirs(sandboxExecRoot, spawn.getEnvironment());

    SymlinkedExecRoot symlinkedExecRoot = new SymlinkedExecRoot(sandboxExecRoot);
    ImmutableSet<PathFragment> outputs = SandboxHelpers.getOutputFiles(spawn);
    try {
      symlinkedExecRoot.createFileSystem(
          getMounts(spawn, actionExecutionContext), outputs, writableDirs);
      sandboxTempDir.createDirectory();
    } catch (IOException e) {
      throw new UserExecException("I/O error during sandboxed execution", e);
    }

    SandboxRunner runner = getSandboxRunner(spawn, sandboxPath, sandboxExecRoot, sandboxTempDir);
    try {
      runSpawn(
          spawn,
          actionExecutionContext,
          spawn.getEnvironment(),
          symlinkedExecRoot,
          outputs,
          runner,
          writeOutputFiles);
    } finally {
      if (!sandboxOptions.sandboxDebug) {
        try {
          FileSystemUtils.deleteTree(sandboxPath);
        } catch (IOException e) {
          executor
              .getEventHandler()
              .handle(
                  Event.warn(
                      String.format(
                          "Cannot delete sandbox directory after action execution: %s (%s)",
                          sandboxPath.getPathString(), e)));
        }
      }
    }
  }

  private SandboxRunner getSandboxRunner(
      Spawn spawn, Path sandboxPath, Path sandboxExecRoot, Path sandboxTempDir)
      throws UserExecException {
    if (fullySupported) {
      return new LinuxSandboxRunner(
          execRoot,
          sandboxPath,
          sandboxExecRoot,
          sandboxTempDir,
          getWritableDirs(sandboxExecRoot, spawn.getEnvironment()),
          getInaccessiblePaths(),
          getTmpfsPaths(),
          getReadOnlyBindMounts(blazeDirs, sandboxExecRoot),
          verboseFailures,
          sandboxOptions.sandboxDebug);
    } else {
      return new ProcessWrapperRunner(execRoot, sandboxExecRoot, verboseFailures);
    }
  }

  private ImmutableSet<Path> getTmpfsPaths() {
    ImmutableSet.Builder<Path> tmpfsPaths = ImmutableSet.builder();
    for (String tmpfsPath : sandboxOptions.sandboxTmpfsPath) {
      tmpfsPaths.add(blazeDirs.getFileSystem().getPath(tmpfsPath));
    }
    return tmpfsPaths.build();
  }

  private SortedMap<Path, Path> getReadOnlyBindMounts(
      BlazeDirectories blazeDirs, Path sandboxExecRoot) throws UserExecException {
    Path tmpPath = blazeDirs.getFileSystem().getPath("/tmp");
    final SortedMap<Path, Path> bindMounts = Maps.newTreeMap();
    if (blazeDirs.getWorkspace().startsWith(tmpPath)) {
      bindMounts.put(blazeDirs.getWorkspace(), blazeDirs.getWorkspace());
    }
    if (blazeDirs.getOutputBase().startsWith(tmpPath)) {
      bindMounts.put(blazeDirs.getOutputBase(), blazeDirs.getOutputBase());
    }
    for (ImmutableMap.Entry<String, String> additionalMountPath :
        sandboxOptions.sandboxAdditionalMounts) {
      try {
        final Path mountTarget = blazeDirs.getFileSystem().getPath(additionalMountPath.getValue());
        // If source path is relative, treat it as a relative path inside the execution root
        final Path mountSource = sandboxExecRoot.getRelative(additionalMountPath.getKey());
        // If a target has more than one source path, the latter one will take effect.
        bindMounts.put(mountTarget, mountSource);
      } catch (IllegalArgumentException e) {
        throw new UserExecException(
            String.format("Error occurred when analyzing bind mount pairs. %s", e.getMessage()));
      }
    }
    validateBindMounts(bindMounts);
    return bindMounts;
  }

  /**
   * This method does the following things: - If mount source does not exist on the host system,
   * throw an error message - If mount target exists, check whether the source and target are of the
   * same type - If mount target does not exist on the host system, throw an error message
   *
   * @param bindMounts the bind mounts map with target as key and source as value
   * @throws UserExecException
   */
  private void validateBindMounts(SortedMap<Path, Path> bindMounts) throws UserExecException {
    for (SortedMap.Entry<Path, Path> bindMount : bindMounts.entrySet()) {
      final Path source = bindMount.getValue();
      final Path target = bindMount.getKey();
      // Mount source should exist in the file system
      if (!source.exists()) {
        throw new UserExecException(String.format("Mount source '%s' does not exist.", source));
      }
      // If target exists, but is not of the same type as the source, then we cannot mount it.
      if (target.exists()) {
        boolean areBothDirectories = source.isDirectory() && target.isDirectory();
        boolean isSourceFile = source.isFile() || source.isSymbolicLink();
        boolean isTargetFile = target.isFile() || target.isSymbolicLink();
        boolean areBothFiles = isSourceFile && isTargetFile;
        if (!(areBothDirectories || areBothFiles)) {
          // Source and target are not of the same type; we cannot mount it.
          throw new UserExecException(
              String.format(
                  "Mount target '%s' is not of the same type as mount source '%s'.",
                  target, source));
        }
      } else {
        // Mount target should exist in the file system
        throw new UserExecException(
            String.format(
                "Mount target '%s' does not exist. Bazel only supports bind mounting on top of "
                    + "existing files/directories. Please create an empty file or directory at "
                    + "the mount target path according to the type of mount source.",
                target));
      }
    }
  }
}