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/*
 * 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.calcite.sql.babel.postgresql;

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 org.apache.calcite.sql.type.ReturnTypes;

import com.google.common.collect.ImmutableList;

import org.checkerframework.checker.nullness.qual.Nullable;

import java.util.List;

/**
 * Parse tree node representing a {@code DISCARD} clause.
 *
 * @see DISCARD specification
 */
public class SqlDiscard extends SqlCall {
  public static final SqlSpecialOperator OPERATOR =
      new SqlSpecialOperator("DISCARD", SqlKind.OTHER_FUNCTION, 32, false, ReturnTypes.BOOLEAN,
          null, null) {
        @Override public SqlCall createCall(@Nullable final SqlLiteral functionQualifier,
            final SqlParserPos pos,
            final @Nullable SqlNode... operands) {
          return new SqlDiscard(pos, (SqlIdentifier) operands[0]);
        }
      };

  private final SqlIdentifier subcommand;

  public SqlDiscard(final SqlParserPos pos, final SqlIdentifier subcommand) {
    super(pos);
    this.subcommand = subcommand;
  }

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

  @Override public List getOperandList() {
    return ImmutableList.of(subcommand);
  }

  @Override public void unparse(final SqlWriter writer, final int leftPrec, final int rightPrec) {
    writer.keyword("DISCARD");
    writer.literal(subcommand.toString());
  }
}