// 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.server.change;

import com.google.common.base.Strings;
import com.google.common.collect.ImmutableMap;
import com.google.gerrit.extensions.restapi.BadRequestException;
import com.google.gerrit.extensions.restapi.BinaryResult;
import com.google.gerrit.extensions.restapi.RestReadView;
import com.google.gerrit.server.config.ConfigUtil;
import com.google.gerrit.server.config.GerritServerConfig;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.inject.Inject;
import com.google.inject.Singleton;

import org.eclipse.jgit.api.ArchiveCommand;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.kohsuke.args4j.Option;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

public class GetArchive implements RestReadView<RevisionResource> {
  @Singleton
  public static class AllowedFormats {
    final ImmutableMap<String, ArchiveFormat> extensions;
    final Set<ArchiveFormat> allowed;

    @Inject
    AllowedFormats(@GerritServerConfig Config cfg) {
      Collection<ArchiveFormat> enabled;
      String v = cfg.getString("download", null, "archive");
      if (v == null) {
        enabled = Arrays.asList(ArchiveFormat.values());
      } else if (v.isEmpty() || "off".equalsIgnoreCase(v)) {
        enabled = Collections.emptyList();
      } else {
        enabled = ConfigUtil.getEnumList(cfg,
            "download", null, "archive",
            ArchiveFormat.TGZ);
      }

      Map<String, ArchiveFormat> exts = new HashMap<>();
      for (ArchiveFormat format : enabled) {
        for (String ext : format.getSuffixes()) {
          exts.put(ext, format);
        }
        exts.put(format.name().toLowerCase(), format);
      }
      extensions = ImmutableMap.copyOf(exts);
      allowed = Collections.unmodifiableSet(new LinkedHashSet<>(enabled));
    }

    public Set<ArchiveFormat> getAllowed() {
      return allowed;
    }
  }

  private final GitRepositoryManager repoManager;
  private final AllowedFormats allowedFormats;

  @Option(name = "--format")
  private String format;

  @Inject
  GetArchive(GitRepositoryManager repoManager, AllowedFormats allowedFormats) {
    this.repoManager = repoManager;
    this.allowedFormats = allowedFormats;
  }

  @Override
  public BinaryResult apply(RevisionResource rsrc)
      throws BadRequestException, IOException {
    if (Strings.isNullOrEmpty(format)) {
      throw new BadRequestException("format is not specified");
    }
    final ArchiveFormat f = allowedFormats.extensions.get("." + format);
    if (f == null) {
      throw new BadRequestException("unknown archive format");
    }
    boolean close = true;
    final Repository repo = repoManager
        .openRepository(rsrc.getControl().getProject().getNameKey());
    try {
      final RevWalk rw = new RevWalk(repo);
      try {
        final RevCommit commit =
            rw.parseCommit(ObjectId.fromString(rsrc.getPatchSet()
                .getRevision().get()));
        BinaryResult bin = new BinaryResult() {
          @Override
          public void writeTo(OutputStream out) throws IOException {
            try {
              new ArchiveCommand(repo)
                  .setFormat(f.name())
                  .setTree(commit.getTree())
                  .setOutputStream(out).call();
            } catch (GitAPIException e) {
              throw new IOException(e);
            }
          }

          @Override
          public void close() throws IOException {
            rw.release();
            repo.close();
          }
        };

        bin.disableGzip()
            .setContentType(f.getMimeType())
            .setAttachmentName(name(f, rw, commit));

        close = false;
        return bin;
      } finally {
        if (close) {
          rw.release();
        }
      }
    } finally {
      if (close) {
        repo.close();
      }
    }
  }

  private static String name(ArchiveFormat format, RevWalk rw, RevCommit commit)
      throws IOException {
    return String.format("%s%s",
        rw.getObjectReader().abbreviate(commit,7).name(),
        format.getDefaultSuffix());
  }
}