/*
    * Copyright (c) 2023. Roland T. Lichti, Kaiserpfalz EDV-Service.
    *
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
    * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program.  If not, see <https://www.gnu.org/licenses/>.
   */
  
  package de.kaiserpfalzedv.commons.core.resources;
  
  import org.eclipse.microprofile.openapi.annotations.media.Schema;
  
  import com.fasterxml.jackson.annotation.JsonIgnore;
  import com.fasterxml.jackson.annotation.JsonInclude;
  
  import de.kaiserpfalzedv.commons.api.resources.Paging;
  import lombok.AllArgsConstructor;
  import lombok.Builder;
  import lombok.EqualsAndHashCode;
  import lombok.Getter;
  import lombok.ToString;
  import lombok.extern.jackson.Jacksonized;
  
  /**
   * DispatchmentFile contains all data to a single dispatchment
   *
   * @author klenkes {@literal <rlichti@kaiserpfalz-edv.de>}
   * @since 2.0.0  2023-01-06
   */
  @Schema(
          description = "Paging data including calculating next/previous and first/last pages available.",
          example = "{\n" +
                  "  \"start\": 0, \n" +
                  "  \"size\": 100, \n" +
                  "  \"count\": 83, \n" +
                  "  \"total\": 83,\n" +
                  "}",
          title = "Pagination data for transfer lists"
  )
  @Jacksonized
  @JsonInclude(JsonInclude.Include.NON_ABSENT)
  @Builder(toBuilder = true)
  @AllArgsConstructor
  @Getter
  @ToString
  @EqualsAndHashCode
  public class PagingImpl implements Paging {
      private static final long serialVersionUID = 0L;
  
      @Builder.Default
      private final long start = 0;
  
      @Builder.Default
      private final long size = 20;
  
      private final long count;
  
      private final long total;
  
      @Override
      @JsonIgnore
      @Schema(hidden = true)
      public Paging firstPage() {
          return this.toBuilder()
                  .start(0)
                  .count(this.calculatePageSize(0))
                  .build();
      }
  
      @Override
      @JsonIgnore
      @Schema(hidden = true)
      public Paging previousPage() {
          if (this.start - this.size <= 0) {
              return this.firstPage();
          }
  
          return this.toBuilder()
                  .start(this.start - this.size)
                  .count(this.calculatePageSize(this.start - this.size))
                  .build();
      }
  
      @Override
      @JsonIgnore
      @Schema(hidden = true)
      public Paging nextPage() {
          return this.calculateNextPage(this.start + this.size);
      }
  
     @Override
     @JsonIgnore
     @Schema(hidden = true)
     public Paging lastPage() {
         return this.calculateNextPage(this.total / this.size * this.size);
     }
 
     private long calculatePageSize(final long start) {
         if (start >= this.total) {
             return 0;
         }
 
         if (start + this.size >= this.total) {
             return this.total - start;
         }
 
         return  this.size;
     }
 
     private Paging calculateNextPage(final long start) {
         return this.toBuilder()
                 .start(start)
                 .count(this.calculatePageSize(start))
                 .build();
     }
 }