/*
    *    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.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.List;
  import java.util.Optional;
  import java.util.function.Consumer;
  
  import org.jspecify.annotations.Nullable;
  import org.mybatis.dynamic.sql.SortSpecification;
  import org.mybatis.dynamic.sql.common.OrderByModel;
  import org.mybatis.dynamic.sql.configuration.StatementConfiguration;
  import org.mybatis.dynamic.sql.util.Buildable;
  import org.mybatis.dynamic.sql.util.ConfigurableStatement;
  
  public class MultiSelectDSL implements Buildable<MultiSelectModel>, ConfigurableStatement<MultiSelectDSL> {
      private final List<UnionQuery> unionQueries = new ArrayList<>();
      private final SelectModel initialSelect;
      private @Nullable OrderByModel orderByModel;
      private @Nullable Long limit;
      private @Nullable Long offset;
      private @Nullable Long fetchFirstRows;
      private final StatementConfiguration statementConfiguration = new StatementConfiguration();
  
      public MultiSelectDSL(Buildable<SelectModel> builder) {
          initialSelect = builder.build();
      }
  
      public MultiSelectDSL union(Buildable<SelectModel> builder) {
          unionQueries.add(new UnionQuery("union", builder.build())); //$NON-NLS-1$
          return this;
      }
  
      public MultiSelectDSL unionAll(Buildable<SelectModel> builder) {
          unionQueries.add(new UnionQuery("union all", builder.build())); //$NON-NLS-1$
          return this;
      }
  
      public MultiSelectDSL orderBy(SortSpecification... columns) {
          return orderBy(Arrays.asList(columns));
      }
  
      public MultiSelectDSL orderBy(Collection<? extends SortSpecification> columns) {
          orderByModel = OrderByModel.of(columns);
          return this;
      }
  
      public MultiSelectDSL.LimitFinisher limit(long limit) {
          return limitWhenPresent(limit);
      }
  
      public MultiSelectDSL.LimitFinisher limitWhenPresent(@Nullable Long limit) {
          this.limit = limit;
          return new LimitFinisher();
      }
  
      public MultiSelectDSL.OffsetFirstFinisher offset(long offset) {
          return offsetWhenPresent(offset);
      }
  
      public MultiSelectDSL.OffsetFirstFinisher offsetWhenPresent(@Nullable Long offset) {
          this.offset = offset;
          return new OffsetFirstFinisher();
      }
  
      public MultiSelectDSL.FetchFirstFinisher fetchFirst(long fetchFirstRows) {
          return fetchFirstWhenPresent(fetchFirstRows);
      }
  
      public MultiSelectDSL.FetchFirstFinisher fetchFirstWhenPresent(@Nullable Long fetchFirstRows) {
          this.fetchFirstRows = fetchFirstRows;
          return new FetchFirstFinisher();
      }
  
      @Override
      public MultiSelectModel build() {
          return new MultiSelectModel.Builder()
                  .withInitialSelect(initialSelect)
                  .withUnionQueries(unionQueries)
                  .withOrderByModel(orderByModel)
                  .withPagingModel(buildPagingModel().orElse(null))
                  .withStatementConfiguration(statementConfiguration)
                  .build();
     }
 
     private Optional<PagingModel> buildPagingModel() {
         return new PagingModel.Builder()
                 .withLimit(limit)
                 .withOffset(offset)
                 .withFetchFirstRows(fetchFirstRows)
                 .build();
     }
 
     @Override
     public MultiSelectDSL configureStatement(Consumer<StatementConfiguration> consumer) {
         consumer.accept(statementConfiguration);
         return this;
     }
 
     public class OffsetFirstFinisher implements Buildable<MultiSelectModel> {
         public FetchFirstFinisher fetchFirst(long fetchFirstRows) {
             return fetchFirstWhenPresent(fetchFirstRows);
         }
 
         public FetchFirstFinisher fetchFirstWhenPresent(@Nullable Long fetchFirstRows) {
             MultiSelectDSL.this.fetchFirstRows = fetchFirstRows;
             return new FetchFirstFinisher();
         }
 
         @Override
         public MultiSelectModel build() {
             return MultiSelectDSL.this.build();
         }
     }
 
     public class LimitFinisher implements Buildable<MultiSelectModel> {
         public MultiSelectDSL offset(long offset) {
             return offsetWhenPresent(offset);
         }
 
         public MultiSelectDSL offsetWhenPresent(@Nullable Long offset) {
             MultiSelectDSL.this.offset = offset;
             return MultiSelectDSL.this;
         }
 
         @Override
         public MultiSelectModel build() {
             return MultiSelectDSL.this.build();
         }
     }
 
     public class FetchFirstFinisher {
         public MultiSelectDSL rowsOnly() {
             return MultiSelectDSL.this;
         }
     }
 }