/*
    * 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.infra.session.query;
  
  import com.google.common.base.Joiner;
  import lombok.Getter;
  import org.apache.shardingsphere.database.exception.core.exception.syntax.database.NoDatabaseSelectedException;
  import org.apache.shardingsphere.database.exception.core.exception.syntax.database.UnknownDatabaseException;
  import org.apache.shardingsphere.infra.annotation.HighFrequencyInvocation;
  import org.apache.shardingsphere.infra.binder.context.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.exception.ShardingSpherePreconditions;
  import org.apache.shardingsphere.infra.exception.generic.UnsupportedSQLOperationException;
  import org.apache.shardingsphere.infra.hint.HintValueContext;
  import org.apache.shardingsphere.infra.metadata.ShardingSphereMetaData;
  import org.apache.shardingsphere.infra.metadata.database.ShardingSphereDatabase;
  import org.apache.shardingsphere.infra.session.connection.ConnectionContext;
  import org.apache.shardingsphere.sql.parser.statement.core.statement.SQLStatement;
  import org.apache.shardingsphere.sql.parser.statement.core.statement.attribute.type.AllowNotUseDatabaseSQLStatementAttribute;
  
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.Optional;
  
  /**
   * Query context.
   */
  @HighFrequencyInvocation
  @Getter
  public final class QueryContext {
      
      private final SQLStatementContext sqlStatementContext;
      
      private final String sql;
      
      private final List<Object> parameters;
      
      private final HintValueContext hintValueContext;
      
      private final ConnectionContext connectionContext;
      
      private final ShardingSphereMetaData metaData;
      
      private final Collection<String> usedDatabaseNames;
      
      private final boolean useCache;
      
      public QueryContext(final SQLStatementContext sqlStatementContext, final String sql, final List<Object> params, final HintValueContext hintValueContext, final ConnectionContext connectionContext,
                          final ShardingSphereMetaData metaData) {
          this(sqlStatementContext, sql, params, hintValueContext, connectionContext, metaData, false);
      }
      
      public QueryContext(final SQLStatementContext sqlStatementContext, final String sql, final List<Object> params, final HintValueContext hintValueContext, final ConnectionContext connectionContext,
                          final ShardingSphereMetaData metaData, final boolean useCache) {
          this.sqlStatementContext = sqlStatementContext;
          this.sql = sql;
          parameters = params;
          this.hintValueContext = hintValueContext;
          this.connectionContext = connectionContext;
          this.metaData = metaData;
          usedDatabaseNames = getUsedDatabaseNames(sqlStatementContext, connectionContext, metaData);
          this.useCache = useCache;
      }
      
      private Collection<String> getUsedDatabaseNames(final SQLStatementContext sqlStatementContext, final ConnectionContext connectionContext, final ShardingSphereMetaData metaData) {
          Collection<String> databaseNamesFromSQL = sqlStatementContext.getTablesContext().getDatabaseNames();
          return databaseNamesFromSQL.isEmpty()
                  ? connectionContext.getCurrentDatabaseName().map(Collections::singletonList)
                          .orElseGet(() -> getUsedDatabaseNamesFromSQLStatementAttribute(sqlStatementContext.getSqlStatement(), metaData))
                  : databaseNamesFromSQL;
      }
      
      private List<String> getUsedDatabaseNamesFromSQLStatementAttribute(final SQLStatement sqlStatement, final ShardingSphereMetaData metaData) {
          Optional<AllowNotUseDatabaseSQLStatementAttribute> attribute = sqlStatement.getAttributes().findAttribute(AllowNotUseDatabaseSQLStatementAttribute.class);
          if (attribute.isPresent() && attribute.get().isAllowNotUseDatabase()) {
              return attribute.get().findDatabaseName().map(Collections::singletonList).orElseGet(() -> findAnyDatabaseName(metaData).map(Collections::singletonList).orElse(Collections.emptyList()));
          }
          return Collections.emptyList();
      }
      
      private Optional<String> findAnyDatabaseName(final ShardingSphereMetaData metaData) {
          for (ShardingSphereDatabase each : metaData.getAllDatabases()) {
              if (each.isComplete()) {
                  return Optional.of(each.getName());
             }
         }
         return Optional.empty();
     }
     
     /**
      * Get used database.
      *
      * @return used database
      */
     public ShardingSphereDatabase getUsedDatabase() {
         ShardingSpherePreconditions.checkState(usedDatabaseNames.size() <= 1,
                 () -> new UnsupportedSQLOperationException(String.format("Can not support multiple logic databases [%s]", Joiner.on(", ").join(usedDatabaseNames))));
         ShardingSpherePreconditions.checkState(usedDatabaseNames.size() == 1, NoDatabaseSelectedException::new);
         String databaseName = usedDatabaseNames.iterator().next();
         ShardingSpherePreconditions.checkState(metaData.containsDatabase(databaseName), () -> new UnknownDatabaseException(databaseName));
         return metaData.getDatabase(databaseName);
     }
 }