// Copyright (C) 2021 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.plugins.cachedrefdb;

import com.google.common.cache.Cache;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.server.cache.CacheModule;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import com.google.inject.TypeLiteral;
import com.google.inject.name.Named;
import java.util.Optional;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import org.eclipse.jgit.lib.Ref;

@Singleton
class RefByNameCacheImpl implements RefByNameCache {
  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
  private static final String REF_BY_NAME = "ref_by_name";

  static com.google.inject.Module module() {
    return new CacheModule() {
      @Override
      protected void configure() {
        cache(REF_BY_NAME, String.class, new TypeLiteral<Optional<Ref>>() {});
      }
    };
  }

  private final Cache<String, Optional<Ref>> refByName;

  @Inject
  RefByNameCacheImpl(@Named(REF_BY_NAME) Cache<String, Optional<Ref>> refByName) {
    this.refByName = refByName;
  }

  @Override
  public Ref computeIfAbsent(
      String identifier, String ref, Callable<? extends Optional<Ref>> loader) {
    String uniqueRefName = getUniqueName(identifier, ref);
    try {
      return refByName.get(uniqueRefName, loader).orElse(null);
    } catch (ExecutionException e) {
      logger.atWarning().withCause(e).log("Getting ref for [%s] failed.", uniqueRefName);
      return null;
    }
  }

  @Override
  public void evict(String identifier, String ref) {
    refByName.invalidate(getUniqueName(identifier, ref));
  }

  private static String getUniqueName(String identifier, String ref) {
    return String.format("%s$%s", identifier, ref);
  }
}