content: /*
   * 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.dialect;
  
  import org.apache.calcite.avatica.util.TimeUnitRange;
  import org.apache.calcite.config.NullCollation;
  import org.apache.calcite.rel.type.RelDataTypeSystem;
  import org.apache.calcite.rel.type.RelDataTypeSystemImpl;
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlDialect;
  import org.apache.calcite.sql.SqlLiteral;
  import org.apache.calcite.sql.SqlWriter;
  import org.apache.calcite.sql.fun.SqlLibraryOperators;
  import org.apache.calcite.sql.parser.SqlParserPos;
  import org.apache.calcite.sql.type.SqlTypeName;
  
  /**
   * A <code>SqlDialect</code> implementation for the DuckDB database.
   */
  public class DuckDBSqlDialect extends SqlDialect {
    public static final RelDataTypeSystem TYPE_SYSTEM =
        new RelDataTypeSystemImpl() {
  
          // We can refer to document of DuckDB 1.2.x:
          // https://duckdb.org/docs/stable/sql/data_types/numeric#fixed-point-decimals
          @Override public int getMaxPrecision(SqlTypeName typeName) {
            switch (typeName) {
            case DECIMAL:
              return 38;
            default:
              return super.getMaxPrecision(typeName);
            }
          }
  
          @Override public int getMaxScale(SqlTypeName typeName) {
            switch (typeName) {
            case DECIMAL:
              return 38;
            default:
              return super.getMaxScale(typeName);
            }
          }
  
          @Override public int getMaxNumericScale() {
            return getMaxScale(SqlTypeName.DECIMAL);
          }
        };
  
    public static final SqlDialect.Context DEFAULT_CONTEXT = SqlDialect.EMPTY_CONTEXT
        .withDatabaseProduct(SqlDialect.DatabaseProduct.DUCKDB)
        .withIdentifierQuoteString("\"")
        // Refer to document: https://duckdb.org/docs/stable/sql/query_syntax/orderby.html
        .withNullCollation(NullCollation.LAST)
        .withDataTypeSystem(TYPE_SYSTEM);
  
    public static final SqlDialect DEFAULT = new DuckDBSqlDialect(DEFAULT_CONTEXT);
  
    /** Creates a DuckDBSqlDialect. */
    public DuckDBSqlDialect(SqlDialect.Context context) {
      super(context);
    }
  
    @Override public boolean supportsApproxCountDistinct() {
      return true;
    }
  
    @Override public boolean supportsAliasedValues() {
      return false;
    }
  
    @Override public void unparseCall(SqlWriter writer, SqlCall call,
        int leftPrec, int rightPrec) {
      switch (call.getKind()) {
      case MAP_VALUE_CONSTRUCTOR:
        writer.keyword(call.getOperator().getName());
        final SqlWriter.Frame mapFrame = writer.startList("{", "}");
        for (int i = 0; i < call.operandCount(); i++) {
          String sep = i % 2 == 0 ? "," : ":";
          writer.sep(sep);
          call.operand(i).unparse(writer, leftPrec, rightPrec);
        }
        writer.endList(mapFrame);
        break;
      case FLOOR:
        if (call.operandCount() != 2) {
          super.unparseCall(writer, call, leftPrec, rightPrec);
          return;
        }
        unparseFloor(writer, call);
        break;
      case CHAR_LENGTH:
        SqlCall lengthCall = SqlLibraryOperators.LENGTH
            .createCall(SqlParserPos.ZERO, call.getOperandList());
        super.unparseCall(writer, lengthCall, leftPrec, rightPrec);
        break;
      default:
        super.unparseCall(writer, call, leftPrec, rightPrec);
      }
    }
  
    private static void unparseFloor(SqlWriter writer, SqlCall call) {
      SqlLiteral node = call.operand(1);
      TimeUnitRange unit = node.getValueAs(TimeUnitRange.class);
  
      String format;
      switch (unit) {
      case YEAR:
        format = "year";
        break;
      case MONTH:
        format = "month";
        break;
      case WEEK:
        format = "week";
        break;
      case DAY:
        format = "day";
        break;
      case HOUR:
        format = "hour";
        break;
      case MINUTE:
        format = "minute";
        break;
      case SECOND:
        format = "second";
        break;
      case MILLISECOND:
        format = "milliseconds";
        break;
      case MICROSECOND:
        format = "microseconds";
        break;
      default:
        throw new AssertionError("DUCKDB does not support FLOOR for time unit: "
            + unit);
      }
  
      // Refer to document: https://duckdb.org/docs/stable/sql/functions/date#date_truncpart-date
      writer.print("DATETRUNC");
      SqlWriter.Frame frame = writer.startList("(", ")");
      writer.print("'" + format + "'");
      writer.sep(",", true);
      call.operand(0).unparse(writer, 0, 0);
      writer.endList(frame);
    }
  
  }
  