/*
 * Copyright 2014-present Facebook, Inc.
 *
 * 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.facebook.buck.android;

import com.facebook.buck.java.classes.ClasspathTraversal;
import com.facebook.buck.java.classes.DefaultClasspathTraverser;
import com.facebook.buck.java.classes.FileLike;
import com.facebook.buck.rules.ImmutableSha1HashCode;
import com.facebook.buck.rules.Sha1HashCode;
import com.facebook.buck.step.AbstractExecutionStep;
import com.facebook.buck.step.ExecutionContext;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.base.Supplier;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Multimap;
import com.google.common.hash.HashCode;
import com.google.common.hash.Hasher;
import com.google.common.hash.Hashing;

import java.io.IOException;
import java.nio.file.Path;
import java.util.Collections;
import java.util.Map;
import java.util.Set;

/**
 * Step responsible for hashing dex inputs to be passed to {@link SmartDexingStep}. It goes through
 * each dex input, looks at the classes that went into that jar, and uses the class hashes collected
 * in {@link AndroidPackageableCollection} to calculate the final hash of the input.
 */
public class HashInputJarsToDexStep extends AbstractExecutionStep
    implements SmartDexingStep.DexInputHashesProvider {

  private final Supplier<Set<Path>> primaryInputsToDex;
  private final Optional<Supplier<Multimap<Path, Path>>> secondaryOutputToInputs;
  private final Supplier<Map<String, HashCode>> classNamesToHashesSupplier;

  private final ImmutableMap.Builder<Path, Sha1HashCode> dexInputsToHashes;
  private boolean stepFinished;

  public HashInputJarsToDexStep(
      Supplier<Set<Path>> primaryInputsToDex,
      Optional<Supplier<Multimap<Path, Path>>> secondaryOutputToInputs,
      Supplier<Map<String, HashCode>> classNamesToHashesSupplier) {
    super("collect_smart_dex_inputs_hash");
    this.primaryInputsToDex = primaryInputsToDex;
    this.secondaryOutputToInputs = secondaryOutputToInputs;
    this.classNamesToHashesSupplier = classNamesToHashesSupplier;

    this.dexInputsToHashes = ImmutableMap.builder();
    this.stepFinished = false;
  }

  @Override
  public int execute(final ExecutionContext context) {
    ImmutableList.Builder<Path> allInputs = ImmutableList.builder();
    allInputs.addAll(primaryInputsToDex.get());
    if (secondaryOutputToInputs.isPresent()) {
      allInputs.addAll(secondaryOutputToInputs.get().get().values());
    }

    final Map<String, HashCode> classNamesToHashes = classNamesToHashesSupplier.get();

    for (Path path : allInputs.build()) {
      try {
        final Hasher hasher = Hashing.sha1().newHasher();
        new DefaultClasspathTraverser().traverse(
            new ClasspathTraversal(Collections.singleton(path), context.getProjectFilesystem()) {
              @Override
              public void visit(FileLike fileLike) throws IOException {
                String className = fileLike.getRelativePath().replaceAll("\\.class$", "");
                if (classNamesToHashes.containsKey(className)) {
                  HashCode classHash =
                      Preconditions.checkNotNull(classNamesToHashes.get(className));
                  hasher.putBytes(classHash.asBytes());
                }
              }
            });
        dexInputsToHashes.put(path, ImmutableSha1HashCode.of(hasher.hash().toString()));
      } catch (IOException e) {
        context.logError(e, "Error hashing smart dex input: %s", path);
        return 1;
      }
    }
    stepFinished = true;
    return 0;
  }

  @Override
  public ImmutableMap<Path, Sha1HashCode> getDexInputHashes() {
    Preconditions.checkState(stepFinished,
        "Either the step did not complete successfully or getDexInputHashes() was called before " +
            "it could finish its execution.");
    return dexInputsToHashes.build();
  }
}