// Copyright (C) 2022 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.googlesource.gerrit.modules.gitrefsfilter;

import com.google.auto.value.AutoValue;
import com.google.common.cache.CacheLoader;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.entities.Change;
import com.google.gerrit.entities.Project;
import com.google.gerrit.server.cache.CacheModule;
import com.google.gerrit.server.notedb.ChangeNotes;
import com.google.gerrit.server.project.NoSuchChangeException;
import com.google.inject.Inject;
import com.google.inject.Module;
import com.google.inject.Singleton;
import com.google.inject.TypeLiteral;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Repository;

public class ChangeOpenCache {
  public static final String OPEN_CHANGES_CACHE = "open_changes";

  public static Module module() {
    return new CacheModule() {
      @Override
      protected void configure() {
        cache(OPEN_CHANGES_CACHE, Key.class, new TypeLiteral<Boolean>() {}).loader(Loader.class);
      }
    };
  }

  @AutoValue
  public abstract static class Key {
    /* Note: `repo` and `changeId` need to be part of the cache key because the
    Loader requires them in order to compute the relevant changeNote to extract
    the change openness status from. */
    public abstract Repository repo();

    public abstract Change.Id changeId();

    @Nullable
    public abstract ObjectId changeRevision();

    public abstract Project.NameKey project();

    static Key create(
        Repository repo,
        Change.Id changeId,
        @Nullable ObjectId changeRevision,
        Project.NameKey project) {
      return new AutoValue_ChangeOpenCache_Key(repo, changeId, changeRevision, project);
    }
  }

  @Singleton
  static class Loader extends CacheLoader<Key, Boolean> {
    private static final FluentLogger logger = FluentLogger.forEnclosingClass();
    private final ChangeNotes.Factory changeNotesFactory;

    @Inject
    Loader(ChangeNotes.Factory changeNotesFactory) {
      this.changeNotesFactory = changeNotesFactory;
    }

    @Override
    public Boolean load(Key key) throws Exception {
      try {
        ChangeNotes changeNotes =
            changeNotesFactory.createChecked(
                key.repo(), key.project(), key.changeId(), key.changeRevision());
        return changeNotes.getChange().getStatus().isOpen();
      } catch (NoSuchChangeException e) {
        logger.atFine().withCause(e).log(
            "Change %d does not exist: hiding from the advertised refs", key.changeId());
        return false;
      }
    }
  }
}