// Copyright (C) 2014 The Android Open Source Project
//
// 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.gerrit.common;

import static com.google.gerrit.common.FileUtil.lastModified;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.ComparisonChain;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Ordering;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.util.List;

@GwtIncompatible("Unemulated classes in java.nio and Guava")
public final class SiteLibraryLoaderUtil {
  private static final Logger log =
      LoggerFactory.getLogger(SiteLibraryLoaderUtil.class);

  public static void loadSiteLib(Path libdir) {
    try {
      IoUtil.loadJARs(listJars(libdir));
    } catch (IOException e) {
      log.error("Error scanning lib directory " + libdir, e);
    }
  }

  public static List<Path> listJars(Path dir) throws IOException {
    DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
      @Override
      public boolean accept(Path entry) throws IOException {
          String name = entry.getFileName().toString();
          return (name.endsWith(".jar") || name.endsWith(".zip"))
              && Files.isRegularFile(entry);
      }
    };
    try (DirectoryStream<Path> jars = Files.newDirectoryStream(dir, filter)) {
      return new Ordering<Path>() {
        @Override
        public int compare(Path a, Path b) {
          // Sort by reverse last-modified time so newer JARs are first.
          return ComparisonChain.start()
              .compare(lastModified(b), lastModified(a))
              .compare(a, b)
              .result();
        }
      }.sortedCopy(jars);
    } catch (NoSuchFileException nsfe) {
      return ImmutableList.of();
    }
  }

  private SiteLibraryLoaderUtil() {
  }
}