import * as api from '../../client/src/api';
import { EndpointError, EndpointHandler, catchUnhandledErrors } from './types';
import Knex from 'knex';

export const MergeTagEndpointHandler: EndpointHandler = async (req: any, res: any, knex: Knex) => {
    if (!api.checkMergeTagRequest(req)) {
        const e: EndpointError = {
            internalMessage: 'Invalid MergeTag request: ' + JSON.stringify(req.body),
            httpStatus: 400
        };
        throw e;
    }
    const reqObject: api.DeleteTagRequest = req.body;
    const { id: userId } = req.user;

    console.log("User ", userId, ": Merge Tag ", reqObject);
    const fromId = req.params.id;
    const toId = req.params.toId;

    await knex.transaction(async (trx) => {
        try {
            // Start retrieving the "from" tag.
            const fromTagPromise = trx.select('id')
                .from('tags')
                .where({ 'user': userId })
                .where({ id: fromId })
                .then((r: any) => (r && r[0]) ? r[0]['id'] : undefined)

            // Start retrieving the "to" tag.
            const toTagPromise = trx.select('id')
                .from('tags')
                .where({ 'user': userId })
                .where({ id: toId })
                .then((r: any) => (r && r[0]) ? r[0]['id'] : undefined)

            // Wait for the requests to finish.
            var [fromTag, toTag] = await Promise.all([fromTagPromise, toTagPromise]);

            // Check that we found all objects we need.
            if (!fromTag || !toTag) {
                const e: EndpointError = {
                    internalMessage: 'Source or target tag does not exist for MergeTag request: ' + JSON.stringify(req.body),
                    httpStatus: 400
                };
                throw e;
            }

            // Assign new tag ID to any objects referencing the to-be-merged tag.
            const cPromise = trx('tags')
                .where({ 'user': userId })
                .where({ 'parentId': fromId })
                .update({ 'parentId': toId });
            const sPromise = trx('songs_tags')
                .where({ 'tagId': fromId })
                .update({ 'tagId': toId });
            const arPromise = trx('artists_tags')
                .where({ 'tagId': fromId })
                .update({ 'tagId': toId });
            const alPromise = trx('albums_tags')
                .where({ 'tagId': fromId })
                .update({ 'tagId': toId });
            await Promise.all([sPromise, arPromise, alPromise, cPromise]);

            // Delete the original tag.
            await trx('tags')
                .where({ 'user': userId })
                .where({ 'id': fromId })
                .del();

            // Respond to the request.
            res.status(200).send();

        } catch (e) {
            catchUnhandledErrors(e);
            trx.rollback();
        }
    })
}