package eu.eudat.managers;

import eu.eudat.entities.DataEntity;
import eu.eudat.models.helpers.common.ColumnOrderings;
import eu.eudat.models.helpers.common.Ordering;
import eu.eudat.models.helpers.requests.TableRequest;
import eu.eudat.queryable.QueryableList;

public class PaginationManager {

    public static <T extends DataEntity<T>> QueryableList<T> applyPaging(QueryableList<T> items, TableRequest tableRequest) throws Exception {
        if(tableRequest.getOrderings()!=null) applyOrder(items,tableRequest);
        if(tableRequest.getLength()!=null)items.take(tableRequest.getLength());
        if(tableRequest.getOffset()!=null)items.skip(tableRequest.getOffset());
        return items;
    }

    public static  <T extends DataEntity<T>> void  applyOrder(QueryableList<T> items, TableRequest tableRequest) throws Exception {
        ColumnOrderings columnOrderings = tableRequest.getOrderings();
        for(Ordering ordering:columnOrderings.getFieldOrderings()){
            if(ordering.getType() == Ordering.OrderByType.ASC) items.orderByAsc(root -> root.get(ordering.getFieldName()));
            if(ordering.getType() == Ordering.OrderByType.DESC) items.orderByDesc(root -> root.get(ordering.getFieldName()));
        }
        return;
    }
}