/*
 * Copyright © 2021 DataSQRL (contact@datasqrl.com)
 *
 * Licensed 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 com.datasqrl.function.translation.duckdb.builtin;

import com.datasqrl.function.CalciteFunctionUtil;
import com.datasqrl.function.translation.DuckDbSqlTranslation;
import com.datasqrl.function.translation.SqlTranslation;
import com.google.auto.service.AutoService;
import org.apache.calcite.sql.SqlCall;
import org.apache.calcite.sql.SqlLiteral;
import org.apache.calcite.sql.SqlWriter;
import org.apache.calcite.sql.fun.SqlStdOperatorTable;
import org.apache.calcite.sql.parser.SqlParserPos;

@AutoService(SqlTranslation.class)
public class ElementSqlTranslation extends DuckDbSqlTranslation {

  public ElementSqlTranslation() {
    super(CalciteFunctionUtil.lightweightOp("ELEMENT"));
  }

  @Override
  public void unparse(SqlCall call, SqlWriter writer, int leftPrec, int rightPrec) {
    var array = call.operand(0);
    var one = SqlLiteral.createExactNumeric("1", SqlParserPos.ZERO);
    var nullLit = SqlLiteral.createNull(SqlParserPos.ZERO);

    var cardinality =
        CalciteFunctionUtil.lightweightOp("array_length").createCall(SqlParserPos.ZERO, array);
    var eq = SqlStdOperatorTable.EQUALS.createCall(SqlParserPos.ZERO, cardinality, one);
    var wrappedArr = CalciteFunctionUtil.wrapNodeWithParenthesis(array);
    var item = SqlStdOperatorTable.ITEM.createCall(SqlParserPos.ZERO, wrappedArr, one);

    // IF(array_length(array) = 1, array[1], NULL)
    CalciteFunctionUtil.lightweightOp("IF")
        .createCall(SqlParserPos.ZERO, eq, item, nullLit)
        .unparse(writer, 0, 0);
  }
}
