/*
 * Copyright 2013-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.java;

import com.facebook.buck.event.ThrowableLogEvent;
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.step.AbstractExecutionStep;
import com.facebook.buck.step.ExecutionContext;
import com.facebook.buck.step.Step;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableSortedSet;

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

/**
 * {@link Step} that takes a directory or zip of {@code .class} files and traverses it to get the
 * total set of {@code .class} files included by the directory or zip.
 */
public class AccumulateClassNamesStep extends AbstractExecutionStep {

  /**
   * Entries in the {@link #pathToJarOrClassesDirectory} that end with this suffix will be written
   * to {@link #whereClassNamesShouldBeWritten}. Since they all share the same suffix, the suffix
   * will be stripped when written to {@link #whereClassNamesShouldBeWritten}.
   */
  private static final String CLASS_NAME_SUFFIX = ".class";

  private final Path pathToJarOrClassesDirectory;
  private final Path whereClassNamesShouldBeWritten;

  public AccumulateClassNamesStep(Path pathToJarOrClassesDirectory,
      Path whereClassNamesShouldBeWritten) {
    super("get_class_names " + pathToJarOrClassesDirectory + " > " + whereClassNamesShouldBeWritten);
    this.pathToJarOrClassesDirectory = Preconditions.checkNotNull(pathToJarOrClassesDirectory);
    this.whereClassNamesShouldBeWritten = Preconditions.checkNotNull(whereClassNamesShouldBeWritten);
  }

  @Override
  public int execute(ExecutionContext context) {
    final ImmutableSortedSet.Builder<String> classNamesBuilder = ImmutableSortedSet.naturalOrder();
    Path path = context.getProjectFilesystem().resolve(pathToJarOrClassesDirectory);
    ClasspathTraversal traversal = new ClasspathTraversal(Collections.singleton(path)) {
      @Override
      public void visit(FileLike fileLike) throws IOException {
        String name = fileLike.getRelativePath();

        // When traversing a JAR file, it may have resources or directory entries that do not end
        // in .class, which should be ignored.
        if (name.endsWith(CLASS_NAME_SUFFIX)) {
          classNamesBuilder.add(name.substring(0, name.length() - CLASS_NAME_SUFFIX.length()));
        }
      }
    };

    try {
      new DefaultClasspathTraverser().traverse(traversal);
    } catch (IOException e) {
      e.printStackTrace(context.getStdErr());
      return 1;
    }

    ImmutableSortedSet<String> classNames = classNamesBuilder.build();
    try {
      context.getProjectFilesystem().writeLinesToPath(classNames, whereClassNamesShouldBeWritten);
    } catch (IOException e) {
      context.getBuckEventBus().post(ThrowableLogEvent.create(e,
          "There was an error writing the list of .class files to %s.",
          whereClassNamesShouldBeWritten));
      return 1;
    }

    return 0;
  }

}