/*
    *    Copyright 2016-2025 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.Consumer;
  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.configuration.StatementConfiguration;
  import org.mybatis.dynamic.sql.util.Buildable;
  import org.mybatis.dynamic.sql.where.AbstractWhereFinisher;
  import org.mybatis.dynamic.sql.where.EmbeddedWhereModel;
  
  /**
   * 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. 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 AbstractQueryExpressionDSL<CountDSL<R>.CountWhereBuilder, CountDSL<R>>
          implements Buildable<R> {
  
      private final Function<SelectModel, R> adapterFunction;
      private @Nullable CountWhereBuilder whereBuilder;
      private final BasicColumn countColumn;
      private final StatementConfiguration statementConfiguration = new StatementConfiguration();
  
      private CountDSL(BasicColumn countColumn, SqlTable table, Function<SelectModel, R> adapterFunction) {
          super(table);
          this.countColumn = Objects.requireNonNull(countColumn);
          this.adapterFunction = Objects.requireNonNull(adapterFunction);
      }
  
      @Override
      public CountWhereBuilder where() {
          whereBuilder = Objects.requireNonNullElseGet(whereBuilder, CountWhereBuilder::new);
          return whereBuilder;
      }
  
      @Override
      public R build() {
          return adapterFunction.apply(buildModel());
      }
  
      @Override
      public CountDSL<R> configureStatement(Consumer<StatementConfiguration> consumer) {
          consumer.accept(statementConfiguration);
          return this;
      }
  
      private SelectModel buildModel() {
          QueryExpressionModel queryExpressionModel = new QueryExpressionModel.Builder()
                  .withSelectColumn(countColumn)
                  .withTable(table())
                  .withTableAliases(tableAliases())
                  .withJoinModel(buildJoinModel().orElse(null))
                  .withWhereModel(whereBuilder == null ? null : whereBuilder.buildWhereModel())
                  .build();
  
          return new SelectModel.Builder()
                  .withQueryExpression(queryExpressionModel)
                  .withStatementConfiguration(statementConfiguration)
                  .build();
      }
  
      public static CountDSL<SelectModel> countFrom(SqlTable table) {
          return countFrom(Function.identity(), table);
      }
  
      public static <R> CountDSL<R> countFrom(Function<SelectModel, R> adapterFunction, SqlTable table) {
          return new CountDSL<>(SqlBuilder.count(), table, adapterFunction);
      }
  
      public static FromGatherer<SelectModel> count(BasicColumn column) {
          return count(Function.identity(), column);
      }
  
      public static <R> FromGatherer<R> count(Function<SelectModel, R> adapterFunction, BasicColumn column) {
          return new FromGatherer<>(adapterFunction, SqlBuilder.count(column));
     }
 
     public static FromGatherer<SelectModel> countDistinct(BasicColumn column) {
         return countDistinct(Function.identity(), column);
     }
 
     public static <R> FromGatherer<R> countDistinct(Function<SelectModel, R> adapterFunction, BasicColumn column) {
         return new FromGatherer<>(adapterFunction, SqlBuilder.countDistinct(column));
     }
 
     @Override
     protected CountDSL<R> getThis() {
         return this;
     }
 
     public static class FromGatherer<R> {
         private final BasicColumn column;
         private final Function<SelectModel, R> adapterFunction;
 
         public FromGatherer(Function<SelectModel, R> adapterFunction, BasicColumn column) {
             this.adapterFunction = adapterFunction;
             this.column = column;
         }
 
         public CountDSL<R> from(SqlTable table) {
             return new CountDSL<>(column, table, adapterFunction);
         }
     }
 
     public class CountWhereBuilder extends AbstractWhereFinisher<CountWhereBuilder>
             implements Buildable<R> {
         private CountWhereBuilder() {
             super(CountDSL.this);
         }
 
         @Override
         public R build() {
             return CountDSL.this.build();
         }
 
         @Override
         protected CountWhereBuilder getThis() {
             return this;
         }
 
         protected EmbeddedWhereModel buildWhereModel() {
             return super.buildModel();
         }
     }
 }