/*
    * 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.route.engine.type.unicast;
  
  import com.google.common.collect.Sets;
  import lombok.RequiredArgsConstructor;
  import org.apache.shardingsphere.infra.binder.context.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.binder.context.statement.ddl.AlterViewStatementContext;
  import org.apache.shardingsphere.infra.binder.context.statement.ddl.CreateViewStatementContext;
  import org.apache.shardingsphere.infra.binder.context.statement.ddl.DropViewStatementContext;
  import org.apache.shardingsphere.infra.binder.context.type.CursorAvailable;
  import org.apache.shardingsphere.infra.session.connection.ConnectionContext;
  import org.apache.shardingsphere.infra.datanode.DataNode;
  import org.apache.shardingsphere.infra.route.context.RouteContext;
  import org.apache.shardingsphere.infra.route.context.RouteMapper;
  import org.apache.shardingsphere.infra.route.context.RouteUnit;
  import org.apache.shardingsphere.sharding.exception.syntax.DataSourceIntersectionNotFoundException;
  import org.apache.shardingsphere.sharding.route.engine.type.ShardingRouteEngine;
  import org.apache.shardingsphere.sharding.rule.ShardingRule;
  import org.apache.shardingsphere.sharding.rule.ShardingTable;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Set;
  import java.util.concurrent.ThreadLocalRandom;
  import java.util.stream.Collectors;
  
  /**
   * Sharding unicast routing engine.
   */
  @RequiredArgsConstructor
  public final class ShardingUnicastRoutingEngine implements ShardingRouteEngine {
      
      private final SQLStatementContext sqlStatementContext;
      
      private final Collection<String> logicTables;
      
      private final ConnectionContext connectionContext;
      
      @Override
      public RouteContext route(final ShardingRule shardingRule) {
          RouteContext result = new RouteContext();
          String dataSourceName = getDataSourceName(shardingRule.getDataSourceNames());
          RouteMapper dataSourceMapper = new RouteMapper(dataSourceName, dataSourceName);
          if (logicTables.isEmpty()) {
              result.getRouteUnits().add(new RouteUnit(dataSourceMapper, Collections.emptyList()));
          } else if (1 == logicTables.size()) {
              String logicTableName = logicTables.iterator().next();
              if (!shardingRule.findShardingTable(logicTableName).isPresent()) {
                  result.getRouteUnits().add(new RouteUnit(dataSourceMapper, Collections.emptyList()));
                  return result;
              }
              DataNode dataNode = shardingRule.getDataNode(logicTableName);
              result.getRouteUnits().add(new RouteUnit(new RouteMapper(dataNode.getDataSourceName(), dataNode.getDataSourceName()),
                      Collections.singletonList(new RouteMapper(logicTableName, dataNode.getTableName()))));
          } else {
              routeWithMultipleTables(result, shardingRule);
          }
          return result;
      }
      
      private String getDataSourceName(final Collection<String> dataSourceNames) {
          return sqlStatementContext instanceof CursorAvailable || isViewStatementContext(sqlStatementContext) ? dataSourceNames.iterator().next() : getRandomDataSourceName(dataSourceNames);
      }
      
      private boolean isViewStatementContext(final SQLStatementContext sqlStatementContext) {
          return sqlStatementContext instanceof CreateViewStatementContext || sqlStatementContext instanceof AlterViewStatementContext || sqlStatementContext instanceof DropViewStatementContext;
      }
      
      private void routeWithMultipleTables(final RouteContext routeContext, final ShardingRule shardingRule) {
          List<RouteMapper> tableMappers = new ArrayList<>(logicTables.size());
          Set<String> availableDataSourceNames = Collections.emptySet();
          boolean first = true;
          for (String each : logicTables) {
              ShardingTable shardingTable = shardingRule.getShardingTable(each);
              DataNode dataNode = shardingTable.getActualDataNodes().get(0);
              tableMappers.add(new RouteMapper(each, dataNode.getTableName()));
              Set<String> currentDataSourceNames = shardingTable.getActualDataNodes().stream().map(DataNode::getDataSourceName).collect(
                      Collectors.toCollection(() -> new LinkedHashSet<>(shardingTable.getActualDataSourceNames().size(), 1F)));
              if (first) {
                  availableDataSourceNames = currentDataSourceNames;
                 first = false;
             } else {
                 availableDataSourceNames = Sets.intersection(availableDataSourceNames, currentDataSourceNames);
             }
         }
         if (availableDataSourceNames.isEmpty()) {
             throw new DataSourceIntersectionNotFoundException(logicTables);
         }
         String dataSourceName = getDataSourceName(availableDataSourceNames);
         routeContext.getRouteUnits().add(new RouteUnit(new RouteMapper(dataSourceName, dataSourceName), tableMappers));
     }
     
     private String getRandomDataSourceName(final Collection<String> dataSourceNames) {
         Collection<String> usedDataSourceNames = connectionContext.getUsedDataSourceNames();
         List<String> availableDataSourceNames = new ArrayList<>(usedDataSourceNames.isEmpty() ? dataSourceNames : usedDataSourceNames);
         return availableDataSourceNames.get(ThreadLocalRandom.current().nextInt(availableDataSourceNames.size()));
     }
 }