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SQL Parser and Optimizer
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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 com.hazelcast.org.apache.calcite.sql.fun;

import com.hazelcast.org.apache.calcite.sql.SqlCall;
import com.hazelcast.org.apache.calcite.sql.SqlFunction;
import com.hazelcast.org.apache.calcite.sql.SqlFunctionCategory;
import com.hazelcast.org.apache.calcite.sql.SqlJsonQueryEmptyOrErrorBehavior;
import com.hazelcast.org.apache.calcite.sql.SqlJsonQueryWrapperBehavior;
import com.hazelcast.org.apache.calcite.sql.SqlKind;
import com.hazelcast.org.apache.calcite.sql.SqlLiteral;
import com.hazelcast.org.apache.calcite.sql.SqlNode;
import com.hazelcast.org.apache.calcite.sql.SqlWriter;
import com.hazelcast.org.apache.calcite.sql.parser.SqlParserPos;
import com.hazelcast.org.apache.calcite.sql.type.OperandTypes;
import com.hazelcast.org.apache.calcite.sql.type.ReturnTypes;
import com.hazelcast.org.apache.calcite.sql.type.SqlTypeFamily;
import com.hazelcast.org.apache.calcite.sql.type.SqlTypeTransforms;

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

import static java.util.Objects.requireNonNull;

/**
 * The JSON_QUERY function.
 */
public class SqlJsonQueryFunction extends SqlFunction {
  public SqlJsonQueryFunction() {
    super("JSON_QUERY", SqlKind.OTHER_FUNCTION,
        ReturnTypes.VARCHAR_2000.andThen(SqlTypeTransforms.FORCE_NULLABLE),
        null,
        OperandTypes.family(SqlTypeFamily.ANY, SqlTypeFamily.CHARACTER,
            SqlTypeFamily.ANY, SqlTypeFamily.ANY, SqlTypeFamily.ANY),
        SqlFunctionCategory.SYSTEM);
  }

  @Override public @Nullable String getSignatureTemplate(int operandsCount) {
    return "{0}({1} {2} {3} WRAPPER {4} ON EMPTY {5} ON ERROR)";
  }

  @Override public void unparse(SqlWriter writer, SqlCall call, int leftPrec,
      int rightPrec) {
    final SqlWriter.Frame frame = writer.startFunCall(getName());
    call.operand(0).unparse(writer, 0, 0);
    writer.sep(",", true);
    call.operand(1).unparse(writer, 0, 0);
    final SqlJsonQueryWrapperBehavior wrapperBehavior =
        getEnumValue(call.operand(2));
    switch (wrapperBehavior) {
    case WITHOUT_ARRAY:
      writer.keyword("WITHOUT ARRAY");
      break;
    case WITH_CONDITIONAL_ARRAY:
      writer.keyword("WITH CONDITIONAL ARRAY");
      break;
    case WITH_UNCONDITIONAL_ARRAY:
      writer.keyword("WITH UNCONDITIONAL ARRAY");
      break;
    default:
      throw new IllegalStateException("unreachable code");
    }
    writer.keyword("WRAPPER");
    unparseEmptyOrErrorBehavior(writer, getEnumValue(call.operand(3)));
    writer.keyword("ON EMPTY");
    unparseEmptyOrErrorBehavior(writer, getEnumValue(call.operand(4)));
    writer.keyword("ON ERROR");
    writer.endFunCall(frame);
  }

  @Override public SqlCall createCall(@Nullable SqlLiteral functionQualifier,
      SqlParserPos pos, @Nullable SqlNode... operands) {
    if (operands[2] == null) {
      operands[2] = SqlLiteral.createSymbol(SqlJsonQueryWrapperBehavior.WITHOUT_ARRAY, pos);
    }
    if (operands[3] == null) {
      operands[3] = SqlLiteral.createSymbol(SqlJsonQueryEmptyOrErrorBehavior.NULL, pos);
    }
    if (operands[4] == null) {
      operands[4] = SqlLiteral.createSymbol(SqlJsonQueryEmptyOrErrorBehavior.NULL, pos);
    }
    return super.createCall(functionQualifier, pos, operands);
  }

  private static void unparseEmptyOrErrorBehavior(SqlWriter writer,
      SqlJsonQueryEmptyOrErrorBehavior emptyBehavior) {
    switch (emptyBehavior) {
    case NULL:
      writer.keyword("NULL");
      break;
    case ERROR:
      writer.keyword("ERROR");
      break;
    case EMPTY_ARRAY:
      writer.keyword("EMPTY ARRAY");
      break;
    case EMPTY_OBJECT:
      writer.keyword("EMPTY OBJECT");
      break;
    default:
      throw new IllegalStateException("unreachable code");
    }
  }

  @SuppressWarnings("unchecked")
  private static > E getEnumValue(SqlNode operand) {
    return (E) requireNonNull(((SqlLiteral) operand).getValue(), "operand.value");
  }
}