/*
    * 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.proxy.backend.context;
  
  import lombok.AccessLevel;
  import lombok.Getter;
  import lombok.NoArgsConstructor;
  import org.apache.shardingsphere.infra.metadata.database.ShardingSphereDatabase;
  import org.apache.shardingsphere.infra.state.instance.InstanceStateContext;
  import org.apache.shardingsphere.mode.manager.ContextManager;
  import org.apache.shardingsphere.proxy.backend.connector.jdbc.datasource.JDBCBackendDataSource;
  
  import java.util.Collection;
  import java.util.Optional;
  import java.util.stream.Collectors;
  
  /**
   * Proxy context.
   */
  @NoArgsConstructor(access = AccessLevel.PRIVATE)
  @Getter
  public final class ProxyContext {
      
      private static final ProxyContext INSTANCE = new ProxyContext();
      
      private final JDBCBackendDataSource backendDataSource = new JDBCBackendDataSource();
      
      private ContextManager contextManager;
      
      /**
       * Initialize proxy context.
       *
       * @param contextManager context manager
       */
      public static void init(final ContextManager contextManager) {
          INSTANCE.contextManager = contextManager;
      }
      
      /**
       * Get instance of proxy context.
       *
       * @return got instance
       */
      public static ProxyContext getInstance() {
          return INSTANCE;
      }
      
      /**
       * Check database exists.
       *
       * @param name database name
       * @return database exists or not
       */
      public boolean databaseExists(final String name) {
          return contextManager.getMetaDataContexts().getMetaData().containsDatabase(name);
      }
      
      /**
       * Get all database names.
       *
       * @return all database names
       */
      public Collection<String> getAllDatabaseNames() {
          return contextManager.getMetaDataContexts().getMetaData().getDatabases().values().stream().map(ShardingSphereDatabase::getName).collect(Collectors.toList());
      }
      
      /**
       * Get instance state context.
       * 
       * @return instance state context
       */
      public Optional<InstanceStateContext> getInstanceStateContext() {
          return null == contextManager.getInstanceContext() ? Optional.empty() : Optional.ofNullable(contextManager.getInstanceContext().getInstance().getState());
      }
  }