/*
    * Copyright 2018 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.admin.auth;
  
  import static java.util.Objects.requireNonNull;
  
  import java.util.concurrent.CompletableFuture;
  
  import com.github.benmanes.caffeine.cache.Cache;
  
  import com.linecorp.centraldogma.server.auth.Session;
  import com.linecorp.centraldogma.server.auth.SessionManager;
  
  /**
   * Memory cache based {@link SessionManager} implementation.
   */
  public final class CachedSessionManager extends ForwardingSessionManager {
  
      private final Cache<String, Session> cache;
  
      /**
       * Creates a new {@link SessionManager} instance which relies on the memory cache.
       *
       * @param delegate the {@link SessionManager} which manages the sessions using any kind of permanent
       *                 storage
       * @param cache the {@link Cache} instance which is configured by the caller
       */
      public CachedSessionManager(SessionManager delegate, Cache<String, Session> cache) {
          super(delegate);
          this.cache = requireNonNull(cache, "cache");
      }
  
      @Override
      public CompletableFuture<Boolean> exists(String sessionId) {
          requireNonNull(sessionId, "sessionId");
          if (cache.getIfPresent(sessionId) != null) {
              return CompletableFuture.completedFuture(true);
          }
          return super.exists(sessionId);
      }
  
      @Override
      public CompletableFuture<Session> get(String sessionId) {
          requireNonNull(sessionId, "sessionId");
          final Session session = cache.getIfPresent(sessionId);
          if (session != null) {
              return CompletableFuture.completedFuture(session);
          }
          return super.get(sessionId).thenApply(found -> {
              if (found != null) {
                  cache.put(sessionId, found);
              }
              return found;
          });
      }
  
      @Override
      public CompletableFuture<Void> create(Session session) {
          return super.create(session).thenApply(unused -> {
              cache.put(session.id(), session);
              return null;
          });
      }
  
      @Override
      public CompletableFuture<Void> update(Session session) {
          return super.update(session).thenApply(unused -> {
              cache.put(session.id(), session);
              return null;
          });
      }
  
      @Override
      public CompletableFuture<Void> delete(String sessionId) {
          return super.delete(sessionId).thenApply(unused -> {
              cache.invalidate(sessionId);
              return null;
          });
      }
  }