/**
 * 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.drill.exec.planner.sql.parser;

import org.apache.drill.exec.planner.sql.handlers.AbstractSqlHandler;
import org.apache.drill.exec.planner.sql.handlers.SqlHandlerConfig;
import org.apache.drill.exec.planner.sql.handlers.UseSchemaHandler;
import org.apache.calcite.sql.SqlCall;
import org.apache.calcite.sql.SqlIdentifier;
import org.apache.calcite.sql.SqlKind;
import org.apache.calcite.sql.SqlLiteral;
import org.apache.calcite.sql.SqlNode;
import org.apache.calcite.sql.SqlOperator;
import org.apache.calcite.sql.SqlSpecialOperator;
import org.apache.calcite.sql.SqlWriter;
import org.apache.calcite.sql.parser.SqlParserPos;

import java.util.Collections;
import java.util.List;

/**
 * Sql parser tree node to represent <code>USE SCHEMA</code> statement.
 */
public class SqlUseSchema extends DrillSqlCall {

  public static final SqlSpecialOperator OPERATOR =
      new SqlSpecialOperator("USE_SCHEMA", SqlKind.OTHER){
    @Override
    public SqlCall createCall(SqlLiteral functionQualifier, SqlParserPos pos, SqlNode... operands) {
      return new SqlUseSchema(pos, (SqlIdentifier) operands[0]);
    }
  };

  private SqlIdentifier schema;

  public SqlUseSchema(SqlParserPos pos, SqlIdentifier schema) {
    super(pos);
    this.schema = schema;
    assert schema != null;
  }

  @Override
  public List<SqlNode> getOperandList() {
    return Collections.singletonList((SqlNode)schema);
  }

  @Override
  public SqlOperator getOperator() {
    return OPERATOR;
  }

  @Override
  public void unparse(SqlWriter writer, int leftPrec, int rightPrec) {
    writer.keyword("USE");
    schema.unparse(writer, leftPrec, rightPrec);
  }

  @Override
  public AbstractSqlHandler getSqlHandler(SqlHandlerConfig config) {
    return new UseSchemaHandler(config.getContext());
  }

  /**
   * Get the schema name. A schema identifier can contain more than one level of schema.
   * Ex: "dfs.home" identifier contains two levels "dfs" and "home".
   * @return schemas combined with "."
   */
  public String getSchema() {
    return schema.toString();
  }
}