import com.google.common.collect.Lists;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

/**
 * 对list进行分页
 */
@Getter
@Setter
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class PageResult<T> {
    private List<T> resultList;

    private String next;

    private long total;

    /**
     * 内存list分页
     * 从开始遍历的话，start请输入"0"
     * 当返回的next为"0"时，表示到列表的末尾
     *
     * @param start start
     * @param limit limit
     * @param list list
     * @param <T> T
     * @return PageResult
     */
    public static <T> PageResult<T> pageList(int start, int limit, List<T> list) {
        List<T> safeList = Optional.ofNullable(list).orElseGet(Lists::newArrayList);
        int maxIndex = safeList.size();
        int nextIndex = start + limit;
        int fromIndex = Math.min(start, maxIndex);
        int toIndex = Math.min(nextIndex, maxIndex);
        String next = toIndex == maxIndex ? "0" : String.valueOf(nextIndex);
        return PageResult.<T> builder()
            .resultList(safeList.subList(fromIndex, toIndex))
            .next(next)
            .total(safeList.size())
            .build();
    }

    public static void main(String[] args) {
        PageResult<Integer> pageResult = PageResult.pageList(0, 2, Arrays.asList(1, 2, 3, 4, 5));
    }
}