/*
    * Copyright 2021 TiKV Project Authors.
    *
    * 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 org.tikv.common.expression;
  
  import static java.util.Objects.requireNonNull;
  
  import com.google.common.base.Joiner;
  import com.google.common.collect.ImmutableList;
  import java.util.List;
  import java.util.Objects;
  import org.tikv.common.types.DataType;
  
  public class AggregateFunction extends Expression {
    private final FunctionType type;
    private final Expression argument;
  
    private AggregateFunction(FunctionType type, Expression argument, DataType dataType) {
      super(dataType);
      this.type = requireNonNull(type, "function type is null");
      this.argument = requireNonNull(argument, "function argument is null");
    }
  
    public static AggregateFunction newCall(FunctionType type, Expression argument) {
      return newCall(type, argument, argument.dataType);
    }
  
    public static AggregateFunction newCall(
        FunctionType type, Expression argument, DataType dataType) {
      return new AggregateFunction(type, argument, dataType);
    }
  
    public FunctionType getType() {
      return type;
    }
  
    public Expression getArgument() {
      return argument;
    }
  
    @Override
    public List<Expression> getChildren() {
      return ImmutableList.of(argument);
    }
  
    @Override
    public <R, C> R accept(Visitor<R, C> visitor, C context) {
      return visitor.visit(this, context);
    }
  
    @Override
    public boolean equals(Object other) {
      if (this == other) {
        return true;
      }
      if (!(other instanceof AggregateFunction)) {
        return false;
      }
  
      AggregateFunction that = (AggregateFunction) other;
      return type == that.type && Objects.equals(argument, that.argument);
    }
  
    @Override
    public int hashCode() {
      return Objects.hash(type, argument);
    }
  
    @Override
    public String toString() {
      return String.format(
          "%s(%s)", getType(), Joiner.on(",").useForNull("NULL").join(getChildren()));
    }
  
    public enum FunctionType {
      Sum,
      Count,
      Min,
      Max,
      First
    }
  }