/*
    * Copyright 2017 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.storage.repository;
  
  import static java.util.Objects.requireNonNull;
  
  import java.util.concurrent.CompletableFuture;
  
  import javax.annotation.Nullable;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.github.benmanes.caffeine.cache.AsyncLoadingCache;
  import com.github.benmanes.caffeine.cache.Caffeine;
  import com.github.benmanes.caffeine.cache.CaffeineSpec;
  import com.github.benmanes.caffeine.cache.Weigher;
  import com.github.benmanes.caffeine.cache.stats.CacheStats;
  import com.google.common.base.MoreObjects;
  
  import io.micrometer.core.instrument.MeterRegistry;
  import io.micrometer.core.instrument.binder.cache.CaffeineCacheMetrics;
  
  public class RepositoryCache {
  
      private static final Logger logger = LoggerFactory.getLogger(RepositoryCache.class);
  
      @Nullable
      public static String validateCacheSpec(@Nullable String cacheSpec) {
          if (cacheSpec == null) {
              return null;
          }
  
          try {
              CaffeineSpec.parse(cacheSpec);
              return cacheSpec;
          } catch (IllegalArgumentException e) {
              throw new IllegalArgumentException("cacheSpec: " + cacheSpec + " (" + e.getMessage() + ')');
          }
      }
  
      @SuppressWarnings("rawtypes")
      private final AsyncLoadingCache<CacheableCall, Object> cache;
      private final String cacheSpec;
  
      @SuppressWarnings({ "rawtypes", "unchecked" })
      public RepositoryCache(String cacheSpec, MeterRegistry meterRegistry) {
          this.cacheSpec = requireNonNull(validateCacheSpec(cacheSpec), "cacheSpec");
          requireNonNull(meterRegistry, "meterRegistry");
  
          final Caffeine<Object, Object> builder = Caffeine.from(cacheSpec);
          if (cacheSpec.contains("maximumWeight=")) {
              builder.weigher((Weigher<CacheableCall, Object>) CacheableCall::weigh);
          }
          cache = builder.recordStats()
                         .buildAsync((key, executor) -> {
                             logger.debug("Cache miss: {}", key);
                             return key.execute();
                         });
  
          CaffeineCacheMetrics.monitor(meterRegistry, cache, "repository");
      }
  
      public <T> CompletableFuture<T> get(CacheableCall<T> call) {
          requireNonNull(call, "call");
          @SuppressWarnings("unchecked")
          final CompletableFuture<T> f = (CompletableFuture<T>) cache.get(call);
          return f;
      }
  
      @Nullable
      public <T> CompletableFuture<T> getIfPresent(CacheableCall<T> call) {
          requireNonNull(call, "call");
          @SuppressWarnings("unchecked")
          final CompletableFuture<T> f = (CompletableFuture<T>) cache.getIfPresent(call);
          return f;
      }
  
      public <T> void put(CacheableCall<T> call, T value) {
          requireNonNull(call, "call");
          requireNonNull(value, "value");
          cache.put(call, CompletableFuture.completedFuture(value));
      }
  
      public CacheStats stats() {
         return cache.synchronous().stats();
     }
 
     public void clear() {
         cache.synchronous().invalidateAll();
     }
 
     @Override
     public String toString() {
         return MoreObjects.toStringHelper(this)
                           .add("spec", cacheSpec)
                           .add("stats", stats())
                           .toString();
     }
 }