// Copyright 2016 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 static com.google.common.base.Strings.isNullOrEmpty;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.collect.compacthashmap.CompactHashMap;
import com.google.devtools.build.lib.exec.TreeDeleter;
import com.google.devtools.build.lib.sandbox.SandboxHelpers.SandboxInputs;
import com.google.devtools.build.lib.sandbox.SandboxHelpers.SandboxOutputs;
import com.google.devtools.build.lib.sandbox.SandboxHelpers.StashContents;
import com.google.devtools.build.lib.util.CommandDescriptionForm;
import com.google.devtools.build.lib.util.CommandFailureUtils;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.io.IOException;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Stream;
import javax.annotation.Nullable;

/**
 * Creates an execRoot for a Spawn that contains input files as symlinks to their original
 * destination.
 */
public class SymlinkedSandboxedSpawn extends AbstractContainerizingSandboxedSpawn {

  /** Mnemonic of the action running in this spawn. */
  private final String mnemonic;

  private final Label targetLabel;

  @Nullable private final ImmutableList<String> interactiveDebugArguments;

  public SymlinkedSandboxedSpawn(
      Path sandboxPath,
      Path sandboxExecRoot,
      ImmutableList<String> arguments,
      ImmutableMap<String, String> environment,
      SandboxInputs inputs,
      SandboxOutputs outputs,
      Set<Path> writableDirs,
      TreeDeleter treeDeleter,
      @Nullable Path sandboxDebugPath,
      @Nullable Path statisticsPath,
      @Nullable ImmutableList<String> interactiveDebugArguments,
      String mnemonic,
      Label targetLabel) {
    super(
        sandboxPath,
        sandboxExecRoot,
        arguments,
        environment,
        inputs,
        outputs,
        writableDirs,
        treeDeleter,
        sandboxDebugPath,
        statisticsPath,
        mnemonic);
    this.mnemonic = isNullOrEmpty(mnemonic) ? "_NoMnemonic_" : mnemonic;
    this.interactiveDebugArguments = interactiveDebugArguments;
    this.targetLabel = targetLabel;
  }

  @Override
  public void filterInputsAndDirsToCreate(
      Set<PathFragment> inputsToCreate, Set<PathFragment> dirsToCreate)
      throws IOException, InterruptedException {
    if (!SandboxStash.gotInstance()) {
      return;
    }
    Optional<StashContents> stashContents =
        SandboxStash.takeStashedSandbox(
            sandboxPath, mnemonic, getEnvironment(), outputs, targetLabel);
    sandboxExecRoot.createDirectoryAndParents();

    if (stashContents != null) {
      // Delete anything unnecessary, and update `inputsToCreate`/`dirsToCreate` if something can
      // be left without changes (e.g., a, symlink that already points to the right destination).
      // We're traversing from sandboxExecRoot's parent directory because external repositories can
      // now be symlinked as siblings of sandboxExecRoot when
      // --experimental_sibling_repository_layout is set.
      if (stashContents.isPresent()) {
        SandboxHelpers.cleanExisting(
            sandboxExecRoot.getParentDirectory(),
            inputs,
            inputsToCreate,
            dirsToCreate,
            sandboxExecRoot,
            treeDeleter,
            stashContents.get());
      } else {
        // No in-memory stashes enabled but there is a stash.
        // When reusing an old sandbox, we do a full traversal of the parent directory of
        // `sandboxExecRoot`.
        SandboxHelpers.cleanExisting(
            sandboxExecRoot.getParentDirectory(),
            inputs,
            inputsToCreate,
            dirsToCreate,
            sandboxExecRoot,
            treeDeleter);
        return;
      }
    }

    if (SandboxStash.useInMemoryStashes()) {
      Map<PathFragment, StashContents> stashContentsMap = CompactHashMap.create();
      for (Map.Entry<PathFragment, Path> entry : inputs.getFiles().entrySet()) {
        if (entry.getValue() == null) {
          continue;
        }
        PathFragment parent = entry.getKey().getParentDirectory();
        boolean parentWasPresent = !addParent(stashContentsMap, parent);
        stashContentsMap
            .get(parent)
            .filesToPath()
            .put(entry.getKey().getBaseName(), entry.getValue());
        addAllParents(stashContentsMap, parentWasPresent, parent);
      }
      for (Map.Entry<PathFragment, PathFragment> entry : inputs.getSymlinks().entrySet()) {
        if (entry.getValue() == null) {
          continue;
        }
        PathFragment parent = entry.getKey().getParentDirectory();
        boolean parentWasPresent = !addParent(stashContentsMap, parent);
        stashContentsMap
            .get(parent)
            .symlinksToPathFragment()
            .put(entry.getKey().getBaseName(), entry.getValue());
        addAllParents(stashContentsMap, parentWasPresent, parent);
      }

      for (var outputDir :
          Stream.concat(
                  outputs.files().values().stream().map(PathFragment::getParentDirectory),
                  outputs.dirs().values().stream())
              .distinct()
              .collect(ImmutableList.toImmutableList())) {
        PathFragment parent = outputDir;
        boolean parentWasPresent = !addParent(stashContentsMap, parent);
        addAllParents(stashContentsMap, parentWasPresent, parent);
      }
      StashContents main = new StashContents();
      main.dirEntries()
          .put(SandboxStash.getWorkspaceName(), stashContentsMap.get(PathFragment.EMPTY_FRAGMENT));
      SandboxStash.setPathContents(sandboxPath, main);
    }
  }

  private static boolean addParent(
      Map<PathFragment, StashContents> stashContentsMap, PathFragment parent) {
    boolean parentWasPresent = true;
    if (!stashContentsMap.containsKey(parent)) {
      stashContentsMap.put(parent, new StashContents());
      parentWasPresent = false;
    }
    return !parentWasPresent;
  }

  private static void addAllParents(
      Map<PathFragment, StashContents> stashContentsMap,
      boolean parentWasPresent,
      PathFragment parent) {
    PathFragment parentParent;
    while (!parentWasPresent && (parentParent = parent.getParentDirectory()) != null) {
      StashContents parentParentStashContents = stashContentsMap.get(parentParent);
      if (parentParentStashContents != null) {
        parentWasPresent = true;
      } else {
        parentParentStashContents = new StashContents();
        stashContentsMap.put(parentParent, parentParentStashContents);
      }
      if (!parentParentStashContents.dirEntries().containsKey(parent.getBaseName())) {
        parentParentStashContents
            .dirEntries()
            .put(parent.getBaseName(), stashContentsMap.get(parent));
      }
      parent = parentParent;
    }
  }

  @Override
  protected void copyFile(Path source, Path target) throws IOException {
    target.createSymbolicLink(source);
  }

  @Override
  public void delete() {
    SandboxStash.stashSandbox(
        sandboxPath, mnemonic, getEnvironment(), outputs, treeDeleter, targetLabel);
    super.delete();
  }

  @Nullable
  @Override
  public Optional<String> getInteractiveDebugInstructions() {
    if (interactiveDebugArguments == null) {
      return Optional.empty();
    }
    return Optional.of(
        "Run this command to start an interactive shell in an identical sandboxed environment:\n"
            + CommandFailureUtils.describeCommand(
                CommandDescriptionForm.COMPLETE,
                /* prettyPrintArgs= */ false,
                interactiveDebugArguments,
                getEnvironment(),
                /* environmentVariablesToClear= */ null,
                /* cwd= */ null,
                /* configurationChecksum= */ null,
                /* executionPlatformLabel= */ null));
  }
}