/*
    *    Copyright 2016-2026 the original author or 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
    *
    *       https://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.mybatis.dynamic.sql.select;
  
  import java.util.Objects;
  import java.util.function.Function;
  
  import org.jspecify.annotations.Nullable;
  import org.mybatis.dynamic.sql.BasicColumn;
  import org.mybatis.dynamic.sql.SqlBuilder;
  import org.mybatis.dynamic.sql.SqlTable;
  import org.mybatis.dynamic.sql.dsl.AbstractCountDSL;
  
  /**
   * DSL for building count queries. Count queries are specializations of select queries. They have joins and where
   * clauses, but not the other parts of a select (group by, order by, etc.) Count queries always return
   * a long value. If these restrictions are not acceptable, then use the Select DSL for an unrestricted select statement.
   *
   * @param <R> the type of model built by this Builder. Typically, SelectModel.
   *
   * @author Jeff Butler
   */
  public class CountDSL<R> extends AbstractCountDSL<R, CountDSL<R>> {
      private final Function<SelectModel, R> adapterFunction;
  
      private CountDSL(Builder<R> builder) {
          super(Objects.requireNonNull(builder.column));
          adapterFunction = Objects.requireNonNull(builder.adapterFunction);
      }
  
      @Override
      public R build() {
          return buildSelectModel().map(adapterFunction);
      }
  
      @Override
      protected CountDSL<R> getThis() {
          return this;
      }
  
      public static CountDSL<SelectModel> countFrom(SqlTable table) {
          return countFrom(Function.identity(), table);
      }
  
      public static CountDSL<SelectModel> countFrom(SqlTable table, String tableAlias) {
          return new Builder<SelectModel>()
                  .withAdapterFunction(Function.identity())
                  .withColumn(SqlBuilder.count())
                  .build()
                  .from(table, tableAlias);
      }
  
      public static <R> CountDSL<R> countFrom(Function<SelectModel, R> adapterFunction, SqlTable table) {
          return new Builder<R>()
                  .withAdapterFunction(adapterFunction)
                  .withColumn(SqlBuilder.count())
                  .build()
                  .from(table);
      }
  
      public static CountDSL<SelectModel> count(BasicColumn column) {
          return count(Function.identity(), column);
      }
  
      public static <R> CountDSL<R> count(Function<SelectModel, R> adapterFunction, BasicColumn column) {
          return new Builder<R>()
                  .withAdapterFunction(adapterFunction)
                  .withColumn(SqlBuilder.count(column))
                  .build();
      }
  
      public static CountDSL<SelectModel> countDistinct(BasicColumn column) {
          return countDistinct(Function.identity(), column);
      }
  
      public static <R> CountDSL<R> countDistinct(Function<SelectModel, R> adapterFunction, BasicColumn column) {
          return new Builder<R>()
                  .withAdapterFunction(adapterFunction)
                  .withColumn(SqlBuilder.countDistinct(column))
                  .build();
      }
  
      public static class Builder<R> {
          private @Nullable BasicColumn column;
          private @Nullable Function<SelectModel, R> adapterFunction;
  
         public Builder<R> withColumn(BasicColumn column) {
             this.column = column;
             return this;
         }
 
         public Builder<R> withAdapterFunction(Function<SelectModel, R> adapterFunction) {
             this.adapterFunction = adapterFunction;
             return this;
         }
 
         public CountDSL<R> build() {
             return new CountDSL<>(this);
         }
     }
 }