const models = require('../models');
const { Op } = require("sequelize");
import * as api from '../../client/src/api';
import { EndpointError, EndpointHandler, catchUnhandledErrors } from './types';

const sequelizeOps: any = {
    [api.SongQueryFilterOp.Eq]: Op.eq,
    [api.SongQueryFilterOp.Ne]: Op.ne,
    [api.SongQueryFilterOp.In]: Op.in,
    [api.SongQueryFilterOp.NotIn]: Op.notIn,
    [api.SongQueryElemOp.And]: Op.and,
    [api.SongQueryElemOp.Or]: Op.or,
};

const sequelizeProps: any = {
    [api.SongQueryElemProperty.id]: "id",
    [api.SongQueryElemProperty.artistIds]: "$Artists.id$",
    [api.SongQueryElemProperty.albumIds]: "$Albums.id$",
};

// Returns the "where" clauses for Sequelize, per object type.
const getSequelizeWhere = (queryElem: api.SongQueryElem) => {
    var where: any = {
        [Op.and]: []
    };

    if (queryElem.prop && queryElem.propOperator && queryElem.propOperand) {
        // Visit a filter-like subquery leaf.
        where[Op.and].push({
            [sequelizeProps[queryElem.prop]]: {
                [sequelizeOps[queryElem.propOperator]]: queryElem.propOperand
            }
        });
    }
    if (queryElem.childrenOperator && queryElem.children) {
        // Recursively visit a nested subquery.

        const children = queryElem.children.map((child: api.SongQueryElem) => getSequelizeWhere(child));
        where[Op.and].push({
            [sequelizeOps[queryElem.childrenOperator]]: children
        });
    }

    return where;
}

export const QuerySongsEndpointHandler: EndpointHandler = async (req: any, res: any) => {
    if (!api.checkQuerySongsRequest(req)) {
        const e: EndpointError = {
            internalMessage: 'Invalid QuerySongs request: ' + JSON.stringify(req.body),
            httpStatus: 400
        };
        throw e;
    }
    const reqObject: api.QuerySongsRequest = req.body;

    await models.Song.findAll({
        where: getSequelizeWhere(reqObject.query),
        include: [models.Artist, models.Album]
    })
        .then((songs: any[]) => {
            const response: api.QuerySongsResponse = {
                ids: songs.map((song: any) => {
                    return song.id;
                })
            };
            res.send(response);
        })
        .catch(catchUnhandledErrors);
}