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.sql2rel;
  
  import org.apache.calcite.rex.RexBuilder;
  import org.apache.calcite.rex.RexCall;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.sql.SqlFunction;
  import org.apache.calcite.sql.fun.SqlStdOperatorTable;
  
  /** Converts an expression for a group window function (e.g. TUMBLE)
   * into an expression for an auxiliary group function (e.g. TUMBLE_START).
   *
   * @see SqlStdOperatorTable#TUMBLE_OLD
   */
  public interface AuxiliaryConverter {
    /** Converts an expression.
     *
     * @param rexBuilder Rex  builder
     * @param groupCall Call to the group function, e.g. "TUMBLE($2, 36000)"
     * @param e Expression holding result of the group function, e.g. "$0"
     *
     * @return Expression for auxiliary function, e.g. "$0 + 36000" converts
     * the result of TUMBLE to the result of TUMBLE_END
     */
    RexNode convert(RexBuilder rexBuilder, RexNode groupCall, RexNode e);
  
    /** Simple implementation of {@link AuxiliaryConverter}. */
    class Impl implements AuxiliaryConverter {
      private final SqlFunction f;
  
      public Impl(SqlFunction f) {
        this.f = f;
      }
  
      @Override public RexNode convert(RexBuilder rexBuilder, RexNode groupCall,
          RexNode e) {
        switch (f.getKind()) {
        case TUMBLE_START:
        case HOP_START:
        case SESSION_START:
        case SESSION_END:
          return e;
        case TUMBLE_END:
          return rexBuilder.makeCall(
              SqlStdOperatorTable.PLUS, e,
              ((RexCall) groupCall).operands.get(1));
        case HOP_END:
          return rexBuilder.makeCall(
              SqlStdOperatorTable.PLUS, e,
              ((RexCall) groupCall).operands.get(2));
        default:
          throw new AssertionError("unknown: " + f);
        }
      }
    }
  }
  