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

enum QueryType {
    Song = 0,
    Artist,
    Tag,
}

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

const sequelizeProps: any = {
    [QueryType.Song]: {
        [api.QueryElemProperty.songTitle]: "title",
        [api.QueryElemProperty.songId]: "id",
        [api.QueryElemProperty.artistName]: "$Artists.name$",
        [api.QueryElemProperty.albumName]: "$Albums.name$",
    },
    [QueryType.Artist]: {
        [api.QueryElemProperty.songTitle]: "$Songs.title$",
        [api.QueryElemProperty.songId]: "$Songs.id$",
        [api.QueryElemProperty.artistName]: "name",
        [api.QueryElemProperty.albumName]: "$Albums.name$",
    },
    [QueryType.Tag]: {
        [api.QueryElemProperty.songTitle]: "$Songs.title$",
        [api.QueryElemProperty.songId]: "$Songs.id$",
        [api.QueryElemProperty.artistName]: "$Artists.name$",
        [api.QueryElemProperty.albumName]: "$Albums.name$",
    }
};

const sequelizeOrderColumns: any = {
    [QueryType.Song]: {
        [api.OrderBy.Name]: 'title'
    },
    [QueryType.Artist]: {
        [api.OrderBy.Name]: 'name'
    },
    [QueryType.Tag]: {
        [api.OrderBy.Name]: 'name'
    },
}

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

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

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

    return where;
}

function getSequelizeOrder(order: api.Ordering, type: QueryType) {
    const ascstring = order.ascending ? 'ASC' : 'DESC';

    return [
        [ sequelizeOrderColumns[type][order.orderBy], ascstring ]
    ];
}

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

    try {
        const songs = (reqObject.songLimit > 0) && await models.Song.findAll({
            // NOTE: have to disable limit and offset because of bug: https://github.com/sequelize/sequelize/issues/11938.
            // Custom pagination is implemented before responding.
            where: getSequelizeWhere(reqObject.query, QueryType.Song),
            order: getSequelizeOrder(reqObject.ordering, QueryType.Song),
            include: [models.Artist, models.Album, models.Tag, models.Ranking],
            //limit: reqObject.limit,
            //offset: reqObject.offset,
        })
        const artists = (reqObject.artistLimit > 0) && await models.Artist.findAll({
            // NOTE: have to disable limit and offset because of bug: https://github.com/sequelize/sequelize/issues/11938.
            // Custom pagination is implemented before responding.
            where: getSequelizeWhere(reqObject.query, QueryType.Artist),
            order: getSequelizeOrder(reqObject.ordering, QueryType.Artist),
            include: [models.Song, models.Album, models.Tag],
            //limit: reqObject.limit,
            //offset: reqObject.offset,
        })
        const tags = (reqObject.tagLimit > 0) && await models.Tag.findAll({
            // NOTE: have to disable limit and offset because of bug: https://github.com/sequelize/sequelize/issues/11938.
            // Custom pagination is implemented before responding.
            where: getSequelizeWhere(reqObject.query, QueryType.Tag),
            order: getSequelizeOrder(reqObject.ordering, QueryType.Tag),
            include: [models.Song, models.Album, models.Artist],
            //limit: reqObject.limit,
            //offset: reqObject.offset,
        })

        const response: api.QueryResponse = {
            songs: (reqObject.songLimit <= 0) ? [] : await Promise.all(songs.map(async (song: any) => {
                const artists = song.getArtists();
                const tags = song.getTags();
                const rankings = song.getRankings();
                return <api.SongDetails>{
                    songId: song.id,
                    title: song.title,
                    storeLinks: song.storeLinks,
                    artists: (await artists).map((artist: any) => {
                        return <api.ArtistDetails>{
                            artistId: artist.id,
                            name: artist.name,
                        }
                    }),
                    tags: (await tags).map((tag: any) => {
                        return <api.TagDetails>{
                            tagId: tag.id,
                            name: tag.name,
                        }
                    }),
                    rankings: await (await rankings).map(async (ranking: any) => {
                        const maybeTagContext: api.TagDetails | undefined = await ranking.getTagContext();
                        const maybeArtistContext: api.ArtistDetails | undefined = await ranking.getArtistContext();
                        const maybeContext = maybeTagContext || maybeArtistContext;
                        return <api.RankingDetails>{
                            rankingId: ranking.id,
                            type: api.ItemType.Song,
                            rankedId: song.id,
                            context: maybeContext,
                            value: ranking.value,
                        }
                    })
                };
            }).slice(reqObject.songOffset, reqObject.songOffset + reqObject.songLimit)),
            // TODO: custom pagination due to bug mentioned above
            artists: (reqObject.artistLimit <= 0) ? [] : await Promise.all(artists.map(async (artist: any) => {
                return <api.ArtistDetails>{
                    artistId: artist.id,
                    name: artist.name,
                };
            }).slice(reqObject.artistOffset, reqObject.artistOffset + reqObject.artistLimit)),
            tags: (reqObject.tagLimit <= 0) ? [] : await Promise.all(tags.map(async (tag: any) => {
                return <api.TagDetails>{
                    tagId: tag.id,
                    name: tag.name,
                };
            }).slice(reqObject.tagOffset, reqObject.tagOffset + reqObject.tagLimit)),
        };
        res.send(response);
    } catch (e) {
        catchUnhandledErrors(e);
    }
}