/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF 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
    *
    *     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 org.apache.shardingsphere.sharding.cache.route;
  
  import org.apache.shardingsphere.infra.config.props.ConfigurationProperties;
  import org.apache.shardingsphere.infra.metadata.database.ShardingSphereDatabase;
  import org.apache.shardingsphere.infra.metadata.database.rule.RuleMetaData;
  import org.apache.shardingsphere.infra.route.context.RouteContext;
  import org.apache.shardingsphere.infra.session.connection.ConnectionContext;
  import org.apache.shardingsphere.infra.session.query.QueryContext;
  import org.apache.shardingsphere.sharding.cache.ShardingCache;
  import org.apache.shardingsphere.sharding.cache.checker.ShardingRouteCacheableCheckResult;
  import org.apache.shardingsphere.sharding.cache.route.cache.ShardingRouteCacheKey;
  import org.apache.shardingsphere.sharding.cache.route.cache.ShardingRouteCacheValue;
  import org.apache.shardingsphere.sharding.rule.ShardingRule;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Optional;
  
  /**
   * Cached sharding SQL router.
   */
  public final class CachedShardingSQLRouter {
      
      /**
       * Find {@link RouteContext} from cache or calculate and try caching.
       *
       * @param originSQLRouter origin SQL router
       * @param queryContext query context
       * @param globalRuleMetaData global rule meta data
       * @param database database
       * @param shardingCache sharding cache
       * @param props configuration properties
       * @param connectionContext connection context
       * @return route context
       */
      public Optional<RouteContext> loadRouteContext(final OriginSQLRouter originSQLRouter, final QueryContext queryContext, final RuleMetaData globalRuleMetaData,
                                                     final ShardingSphereDatabase database, final ShardingCache shardingCache, final ConfigurationProperties props,
                                                     final ConnectionContext connectionContext) {
          if (queryContext.getSql().length() > shardingCache.getConfiguration().getAllowedMaxSqlLength()) {
              return Optional.empty();
          }
          ShardingRouteCacheableCheckResult cacheableCheckResult = shardingCache.getRouteCacheableChecker().check(database, queryContext);
          if (!cacheableCheckResult.isProbablyCacheable()) {
              return Optional.empty();
          }
          List<Object> shardingConditionParams = new ArrayList<>(cacheableCheckResult.getShardingConditionParameterMarkerIndexes().size());
          for (int each : cacheableCheckResult.getShardingConditionParameterMarkerIndexes()) {
              if (each >= queryContext.getParameters().size()) {
                  return Optional.empty();
              }
              shardingConditionParams.add(queryContext.getParameters().get(each));
          }
          Optional<RouteContext> cachedResult = shardingCache.getRouteCache().get(new ShardingRouteCacheKey(queryContext.getSql(), shardingConditionParams))
                  .flatMap(ShardingRouteCacheValue::getCachedRouteContext);
          RouteContext result = cachedResult.orElseGet(
                  () -> originSQLRouter.createRouteContext(queryContext, globalRuleMetaData, database, shardingCache.getShardingRule(), props, connectionContext));
          if (!cachedResult.isPresent() && hitOneShardOnly(result)) {
              shardingCache.getRouteCache().put(new ShardingRouteCacheKey(queryContext.getSql(), shardingConditionParams), new ShardingRouteCacheValue(result));
          }
          return Optional.of(result);
      }
      
      private boolean hitOneShardOnly(final RouteContext routeContext) {
          return 1 == routeContext.getRouteUnits().size() && 1 == routeContext.getRouteUnits().iterator().next().getTableMappers().size()
                  && 1 == routeContext.getOriginalDataNodes().size() && 1 == routeContext.getOriginalDataNodes().iterator().next().size();
      }
      
      @FunctionalInterface
      public interface OriginSQLRouter {
          
          /**
           * Create route context.
           *
           * @param queryContext query context
           * @param globalRuleMetaData global rule meta data
           * @param database database
           * @param rule rule
           * @param props configuration properties
           * @param connectionContext connection context
           * @return route context
           */
          RouteContext createRouteContext(QueryContext queryContext, RuleMetaData globalRuleMetaData, ShardingSphereDatabase database, ShardingRule rule,
                                         ConfigurationProperties props, ConnectionContext connectionContext);
     }
 }