// 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.skyframe;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Function;
import com.google.common.base.MoreObjects;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Maps;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
import com.google.devtools.build.lib.actions.cache.DigestUtils;
import com.google.devtools.build.lib.actions.cache.Metadata;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.build.skyframe.SkyValue;
import java.io.IOException;
import java.util.Arrays;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * Value for TreeArtifacts, which contains a digest and the {@link FileArtifactValue}s of its child
 * {@link TreeFileArtifact}s.
 */
public class TreeArtifactValue implements SkyValue {
  private static final Function<Artifact, PathFragment> PARENT_RELATIVE_PATHS =
      new Function<Artifact, PathFragment>() {
        @Override
        public PathFragment apply(Artifact artifact) {
            return artifact.getParentRelativePath();
        }
      };

  private final byte[] digest;
  private final Map<TreeFileArtifact, FileArtifactValue> childData;

  private TreeArtifactValue(byte[] digest, Map<TreeFileArtifact, FileArtifactValue> childData) {
    this.digest = digest;
    this.childData = ImmutableMap.copyOf(childData);
  }

  /**
   * Returns a TreeArtifactValue out of the given Artifact-relative path fragments
   * and their corresponding FileArtifactValues.
   */
  @VisibleForTesting
  public static TreeArtifactValue create(Map<TreeFileArtifact, FileArtifactValue> childFileValues) {
    Map<String, Metadata> digestBuilder =
        Maps.newHashMapWithExpectedSize(childFileValues.size());
    for (Map.Entry<TreeFileArtifact, FileArtifactValue> e : childFileValues.entrySet()) {
      digestBuilder.put(
          e.getKey().getParentRelativePath().getPathString(),
          new Metadata(e.getValue().getDigest()));
    }

    return new TreeArtifactValue(
        DigestUtils.fromMetadata(digestBuilder).getDigestBytesUnsafe(),
        ImmutableMap.copyOf(childFileValues));
  }

  public FileArtifactValue getSelfData() {
    return FileArtifactValue.createProxy(digest);
  }

  public Metadata getMetadata() {
    return new Metadata(digest.clone());
  }

  public Set<PathFragment> getChildPaths() {
    return ImmutableSet.copyOf(Iterables.transform(childData.keySet(), PARENT_RELATIVE_PATHS));
  }

  @Nullable
  public byte[] getDigest() {
    return digest.clone();
  }

  public Iterable<TreeFileArtifact> getChildren() {
    return childData.keySet();
  }

  public FileArtifactValue getChildValue(TreeFileArtifact artifact) {
    return childData.get(artifact);
  }

  @Override
  public int hashCode() {
    return Arrays.hashCode(digest);
  }

  @Override
  public boolean equals(Object other) {
    if (this == other) {
      return true;
    }

    if (!(other instanceof TreeArtifactValue)) {
      return false;
    }

    TreeArtifactValue that = (TreeArtifactValue) other;
    if (!Arrays.equals(digest, that.digest)) {
      return false;
    }

    return childData.equals(that.childData);
  }

  @Override
  public String toString() {
    return MoreObjects.toStringHelper(TreeArtifactValue.class)
        .add("digest", digest)
        .add("childData", childData)
        .toString();
  }

  /**
   * A TreeArtifactValue that represents a missing TreeArtifact.
   * This is occasionally useful because Java's concurrent collections disallow null members.
   */
  static final TreeArtifactValue MISSING_TREE_ARTIFACT = new TreeArtifactValue(null,
      ImmutableMap.<TreeFileArtifact, FileArtifactValue>of()) {
    @Override
    public FileArtifactValue getSelfData() {
      throw new UnsupportedOperationException();
    }

    @Override
    public Iterable<TreeFileArtifact> getChildren() {
      throw new UnsupportedOperationException();
    }

    @Override
    public FileArtifactValue getChildValue(TreeFileArtifact artifact) {
      throw new UnsupportedOperationException();
    }

    @Override
    public Metadata getMetadata() {
      throw new UnsupportedOperationException();
    }

    @Override
    public Set<PathFragment> getChildPaths() {
      throw new UnsupportedOperationException();
    }

    @Nullable
    @Override
    public byte[] getDigest() {
      throw new UnsupportedOperationException();
    }

    @Override
    public int hashCode() {
      return 24; // my favorite number
    }

    @Override
    public boolean equals(Object other) {
      return this == other;
    }

    @Override
    public String toString() {
      return "MISSING_TREE_ARTIFACT";
    }
  };

  /**
   * Exception used when the contents of a directory do not form a valid SetArtifact.
   * (We cannot use IOException because ActionMetadataHandler, in some code paths,
   * interprets IOExceptions as missing files.)
   */
  static class TreeArtifactException extends Exception {
    TreeArtifactException(String message) {
      super(message);
    }
  }

  private static void explodeDirectory(Artifact rootArtifact,
      PathFragment pathToExplode, ImmutableSet.Builder<PathFragment> valuesBuilder)
      throws IOException, TreeArtifactException {
    for (Path subpath : rootArtifact.getPath().getRelative(pathToExplode).getDirectoryEntries()) {
      PathFragment canonicalSubpathFragment =
          pathToExplode.getChild(subpath.getBaseName()).normalize();
      if (subpath.isDirectory()) {
        explodeDirectory(rootArtifact,
            pathToExplode.getChild(subpath.getBaseName()), valuesBuilder);
      } else if (subpath.isSymbolicLink()) {
        throw new TreeArtifactException(
            "A SetArtifact may not contain a symlink, found " + subpath);
      } else if (subpath.isFile()) {
        valuesBuilder.add(canonicalSubpathFragment);
      } else {
        // We shouldn't ever reach here.
        throw new IllegalStateException("Could not determine type of file " + subpath);
      }
    }
  }

  /**
   * Recursively get all child files in a directory
   * (excluding child directories themselves, but including all files in them).
   * @throws IOException if one was thrown reading directory contents from disk.
   * @throws TreeArtifactException if the on-disk directory is not a valid TreeArtifact.
   */
  static Set<PathFragment> explodeDirectory(Artifact rootArtifact)
      throws IOException, TreeArtifactException {
    ImmutableSet.Builder<PathFragment> explodedDirectory = ImmutableSet.builder();
    explodeDirectory(rootArtifact, PathFragment.EMPTY_FRAGMENT, explodedDirectory);
    return explodedDirectory.build();
  }
}