/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.beam.runners.core.construction;

import static org.apache.beam.vendor.guava.v20_0.com.google.common.base.Preconditions.checkArgument;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import org.apache.beam.sdk.util.ZipFiles;
import org.apache.beam.vendor.guava.v20_0.com.google.common.base.Strings;
import org.apache.beam.vendor.guava.v20_0.com.google.common.hash.Funnels;
import org.apache.beam.vendor.guava.v20_0.com.google.common.hash.Hasher;
import org.apache.beam.vendor.guava.v20_0.com.google.common.hash.Hashing;

/** Utilities for working with classpath resources for pipelines. */
public class PipelineResources {

  /**
   * Attempts to detect all the resources the class loader has access to. This does not recurse to
   * class loader parents stopping it from pulling in resources from the system class loader.
   *
   * @param classLoader The URLClassLoader to use to detect resources to stage.
   * @throws IllegalArgumentException If either the class loader is not a URLClassLoader or one of
   *     the resources the class loader exposes is not a file resource.
   * @return A list of absolute paths to the resources the class loader uses.
   */
  public static List<String> detectClassPathResourcesToStage(ClassLoader classLoader) {
    if (!(classLoader instanceof URLClassLoader)) {
      String message =
          String.format(
              "Unable to use ClassLoader to detect classpath elements. "
                  + "Current ClassLoader is %s, only URLClassLoaders are supported.",
              classLoader);
      throw new IllegalArgumentException(message);
    }

    List<String> files = new ArrayList<>();
    for (URL url : ((URLClassLoader) classLoader).getURLs()) {
      try {
        files.add(new File(url.toURI()).getAbsolutePath());
      } catch (IllegalArgumentException | URISyntaxException e) {
        String message = String.format("Unable to convert url (%s) to file.", url);
        throw new IllegalArgumentException(message, e);
      }
    }
    return files;
  }

  /**
   * Goes through the list of files that need to be staged on runner. Removes nonexistent
   * directories and packages existing ones. This is necessary for runners that require filesToStage
   * to be jars only.
   *
   * @param resourcesToStage list of resources that need to be staged
   * @param tmpJarLocation temporary directory to store the jars
   * @return A list of absolute paths to resources (jar files)
   */
  public static List<String> prepareFilesForStaging(
      List<String> resourcesToStage, String tmpJarLocation) {
    return resourcesToStage.stream()
        .map(File::new)
        .filter(File::exists)
        .map(
            file ->
                file.isDirectory()
                    ? packageDirectoriesToStage(file, tmpJarLocation)
                    : file.getAbsolutePath())
        .collect(Collectors.toList());
  }

  private static String packageDirectoriesToStage(File directoryToStage, String tmpJarLocation) {
    String hash = calculateDirectoryContentHash(directoryToStage);
    String pathForJar = getUniqueJarPath(hash, tmpJarLocation);
    zipDirectory(directoryToStage, pathForJar);
    return pathForJar;
  }

  private static String calculateDirectoryContentHash(File directoryToStage) {
    Hasher hasher = Hashing.sha256().newHasher();
    try (OutputStream hashStream = Funnels.asOutputStream(hasher)) {
      ZipFiles.zipDirectory(directoryToStage, hashStream);
      return hasher.hash().toString();
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  private static String getUniqueJarPath(String contentHash, String tmpJarLocation) {
    checkArgument(
        !Strings.isNullOrEmpty(tmpJarLocation),
        "Please provide temporary location for storing the jar files.");

    return String.format("%s%s%s.jar", tmpJarLocation, File.separator, contentHash);
  }

  private static void zipDirectory(File directoryToStage, String uniqueDirectoryPath) {
    try {
      ZipFiles.zipDirectory(directoryToStage, new FileOutputStream(uniqueDirectoryPath));
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }
}