salix/modules/order/back/methods/order/getTaxes.js

const ParameterizedSQL = require('loopback-connector').ParameterizedSQL;

module.exports = Self => {
    Self.remoteMethod('getTaxes', {
        description: 'Gets the taxes of a given order',
        accessType: 'READ',
        accepts: [{
            arg: 'id',
            type: 'number',
            required: true,
            description: 'order id',
            http: {source: 'path'}
        }],
        returns: {
            type: 'object',
            root: true
        },
        http: {
            path: `/:id/getTaxes`,
            verb: 'GET'
        }
    });

    Self.getTaxes = async(orderFk, options) => {
        const conn = Self.dataSource.connector;
        const stmts = [];
        let stmt;
        const myOptions = {};

        if (typeof options == 'object')
            Object.assign(myOptions, options);

        stmts.push('DROP TEMPORARY TABLE IF EXISTS tmp.order');

        stmt = new ParameterizedSQL(`
            CREATE TEMPORARY TABLE tmp.order
                (INDEX (orderFk))
                ENGINE = MEMORY
                    SELECT ? AS orderFk`, [orderFk]);
        stmts.push(stmt);

        stmts.push('CALL hedera.order_getTax()');

        const orderTaxIndex = stmts.push('SELECT * FROM tmp.orderAmount') - 1;

        stmts.push(`
            DROP TEMPORARY TABLE 
                tmp.order, 
                tmp.orderTax`);

        const sql = ParameterizedSQL.join(stmts, ';');
        const result = await conn.executeStmt(sql, myOptions);

        return result[orderTaxIndex];
    };
};