/*
    * Copyright 2023 LINE Corporation
    *
    * LINE Corporation 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:
    *
    *   https://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.linecorp.centraldogma.server.internal;
  
  import static java.util.Objects.requireNonNull;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_COMMIT_SECTION;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_CORE_SECTION;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_DIFF_SECTION;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_GC_SECTION;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_ALGORITHM;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_AUTO;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_AUTOGC;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_AUTOPACKLIMIT;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_FILEMODE;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_GPGSIGN;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_HIDEDOTFILES;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_LOGALLREFUPDATES;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_PRECOMPOSEUNICODE;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_RENAMES;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_REPO_FORMAT_VERSION;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_SYMLINKS;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_RECEIVE_SECTION;
  
  import java.io.IOException;
  import java.util.Objects;
  
  import org.eclipse.jgit.lib.Config;
  import org.eclipse.jgit.lib.StoredConfig;
  
  public final class JGitUtil {
  
      public static final int REPO_FORMAT_VERSION = 1;
  
      private static final String REPO_FORMAT_VERSION_STR = String.valueOf(REPO_FORMAT_VERSION);
  
      public static void applyDefaultsAndSave(StoredConfig config) throws IOException {
          if (applyDefaults(config)) {
              config.save();
          }
      }
  
      public static boolean applyDefaults(Config config) {
          boolean updated = false;
          // Update the repository settings to upgrade to format version 1 and reftree.
          updated |= set(config, CONFIG_CORE_SECTION, CONFIG_KEY_REPO_FORMAT_VERSION, REPO_FORMAT_VERSION_STR);
  
          // Disable hidden files, symlinks and file modes we do not use.
          updated |= set(config, CONFIG_CORE_SECTION, CONFIG_KEY_HIDEDOTFILES, "false");
          updated |= set(config, CONFIG_CORE_SECTION, CONFIG_KEY_SYMLINKS, "false");
          updated |= set(config, CONFIG_CORE_SECTION, CONFIG_KEY_FILEMODE, "false");
  
          // Don't log ref updates.
          updated |= set(config, CONFIG_CORE_SECTION, CONFIG_KEY_LOGALLREFUPDATES, "false");
  
          // Do not decompose file names in macOS.
          updated |= set(config, CONFIG_CORE_SECTION, CONFIG_KEY_PRECOMPOSEUNICODE, "true");
  
          // Disable GPG signing.
          updated |= set(config, CONFIG_COMMIT_SECTION, CONFIG_KEY_GPGSIGN, "false");
  
          // Set the diff algorithm.
          updated |= set(config, CONFIG_DIFF_SECTION, CONFIG_KEY_ALGORITHM, "histogram");
  
          // Disable rename detection which we do not use.
          updated |= set(config, CONFIG_DIFF_SECTION, CONFIG_KEY_RENAMES, "false");
  
          // Disable auto-GC by default because of the following reasons:
          // - GC can take long time affecting performance.
          // - jGit's GC task has memory leak which adds a JVM shutdown hook for each GC task.
          //   See https://github.com/eclipse-mirrors/org.eclipse.jgit/blob/2e3f12a0fc63deba80e725bfa985c0c5bd31de99/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java#L1769
          updated |= set(config, CONFIG_GC_SECTION, CONFIG_KEY_AUTO, "0");
          updated |= set(config, CONFIG_GC_SECTION, CONFIG_KEY_AUTOPACKLIMIT, "0");
          updated |= set(config, CONFIG_RECEIVE_SECTION, CONFIG_KEY_AUTOGC, "false");
  
          return updated;
      }
  
      private static boolean set(Config config, String section, String name, String value) {
          requireNonNull(section, "section");
          requireNonNull(name, "name");
          requireNonNull(value, "value");
  
          final String oldValue = config.getString(section, null, name);
          if (Objects.equals(oldValue, value)) {
              return false;
          }
 
         config.setString(section, null, name, value);
         return true;
     }
 
     private JGitUtil() {}
 }