// 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.rules.test;

import static java.nio.charset.StandardCharsets.ISO_8859_1;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.actions.ActionExecutionContext;
import com.google.devtools.build.lib.actions.ActionOwner;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.analysis.RuleContext;
import com.google.devtools.build.lib.analysis.actions.AbstractFileWriteAction;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.util.Fingerprint;
import com.google.devtools.build.lib.util.Preconditions;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Arrays;

/**
 * Writes a manifest of instrumented source and metadata files.
 */
@Immutable
final class InstrumentedFileManifestAction extends AbstractFileWriteAction {
  private static final Function<Artifact, String> TO_EXEC_PATH = new Function<Artifact, String>() {
    @Override
    public String apply(Artifact artifact) {
      return artifact.getExecPathString();
    }
  };

  private static final String GUID = "3833f0a3-7ea1-4d9f-b96f-66eff4c922b0";

  private final NestedSet<Artifact> files;

  @VisibleForTesting
  InstrumentedFileManifestAction(ActionOwner owner, NestedSet<Artifact> files, Artifact output) {
    super(owner, /*inputs=*/Artifact.NO_ARTIFACTS, output, /*makeExecutable=*/false);
    this.files = files;
  }

  @Override
  public DeterministicWriter newDeterministicWriter(ActionExecutionContext ctx) {
    return new DeterministicWriter() {
      @Override
      public void writeOutputFile(OutputStream out) throws IOException {
        // Sort the exec paths before writing them out.
        String[] fileNames =
            Iterables.toArray(Iterables.transform(files, TO_EXEC_PATH), String.class);
        Arrays.sort(fileNames);
        try (Writer writer = new OutputStreamWriter(out, ISO_8859_1)) {
          for (String name : fileNames) {
            writer.write(name);
            writer.write('\n');
          }
        }
      }
    };
  }

  @Override
  protected String computeKey() {
    Fingerprint f = new Fingerprint();
    f.addString(GUID);
    // Not sorting here is probably cheaper, though it might lead to unnecessary re-execution.
    f.addStrings(Iterables.transform(files, TO_EXEC_PATH));
    return f.hexDigestAndReset();
  }

  /**
   * Instantiates instrumented file manifest for the given target.
   *
   * @param ruleContext context of the executable configured target
   * @param additionalSourceFiles additional instrumented source files, as
   *                              collected by the {@link InstrumentedFilesCollector}
   * @param metadataFiles *.gcno/*.em files collected by the {@link InstrumentedFilesCollector}
   * @return instrumented file manifest artifact
   */
  public static Artifact getInstrumentedFileManifest(RuleContext ruleContext,
      NestedSet<Artifact> additionalSourceFiles, NestedSet<Artifact> metadataFiles) {
    // Instrumented manifest makes sense only for rules with binary output.
    Preconditions.checkState(ruleContext.getRule().hasBinaryOutput());
    Artifact instrumentedFileManifest = ruleContext.getBinArtifact(
        ruleContext.getTarget().getName()  + ".instrumented_files");

    NestedSet<Artifact> inputs = NestedSetBuilder.<Artifact>stableOrder()
        .addTransitive(additionalSourceFiles)
        .addTransitive(metadataFiles)
        .build();
    ruleContext.registerAction(new InstrumentedFileManifestAction(
        ruleContext.getActionOwner(), inputs, instrumentedFileManifest));

    return instrumentedFileManifest;
  }
}