import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;

public class OffsetBasedPageRequest implements Pageable {
    private int offset;
    private int limit;
    private Sort sort;

    public OffsetBasedPageRequest(int offset, int limit, Sort sort) {
        this.offset = offset;
        this.limit = limit;
        this.sort = sort;
    }

    public OffsetBasedPageRequest(int offset, int limit) {
        this.offset = offset;
        this.limit = limit;
    }

    @Override
    public int getPageNumber() {
        return offset / limit;
    }

    @Override
    public int getPageSize() {
        return limit;
    }

    @Override
    public Pageable next() {
        return new OffsetBasedPageRequest(offset + limit, limit, sort);
    }

    @Override
    public Pageable previousOrFirst() {
        if(offset == 0) {
            return this;
        } 
        if(offset < limit) {
            return new OffsetBasedPageRequest(0, offset, sort);
        }
        return new OffsetBasedPageRequest(offset - limit, limit, sort);
    }

    @Override
    public Pageable first() {
        return new OffsetBasedPageRequest(0, limit, sort);
    }

    @Override
    public boolean hasPrevious() {
        return offset > 0;
    }

    @Override
    public long getOffset() {
        return offset;
    }

    @Override
    public Sort getSort() {
        return sort;
    }
}