import paginationToSql from './paginationToSql';
import { Pagination, PaginationOrder } from './types';

export interface ModelFeedPage {
	items: any[];
	has_more: boolean;
	total?: number;
}

export interface WhereQuery {
	sql: string;
	params?: any[];
}

// Note: this method might return more fields than was requested as it will
// also return fields that are necessary for pagination.
export default async function(db: any, tableName: string, pagination: Pagination, whereQuery: WhereQuery = null, fields: string[] = null): Promise<ModelFeedPage> {
	fields = fields ? fields.slice() : ['id'];

	const where = whereQuery ? [whereQuery.sql] : [];
	const sqlParams = whereQuery && whereQuery.params ? whereQuery.params.slice() : [];

	if (!pagination.order.length) throw new Error('Pagination order must be provided');
	if (pagination.order.length > 1) throw new Error('Only one pagination order field can be provided');

	const paginationOrder = pagination.order[0].dir;

	if (!pagination.order.find((o: PaginationOrder) => o.by === 'id')) {
		pagination = {
			...pagination,
			order: pagination.order.concat([{
				by: 'id',
				dir: paginationOrder,
				caseInsensitive: false,
			}]),
		};
	}

	const orderBySql = paginationToSql(pagination);
	const fieldsSql = fields.length ? db.escapeFields(fields) : '*';
	const offset = (pagination.page - 1) * pagination.limit;

	const sql = `
		SELECT ${fieldsSql} FROM \`${tableName}\`
		${where.length ? `WHERE ${where.join(' AND ')}` : ''}
		ORDER BY ${orderBySql}
		LIMIT ${pagination.limit}
		OFFSET ${offset}
	`;

	const rows = await db.selectAll(sql, sqlParams);

	return {
		items: rows,
		has_more: rows.length >= pagination.limit,
	};
}