The controllers for the routes

courseController.js

const client = require("../db/db_config");

const getCourses = async (req, res) => {
    const allCourses = await client.query('SELECT * FROM mydb.courses');

    res.send({ allCourses });
};

const getSpecificCourse = async (req, res) => {
    const course = await client.query(`SELECT * FROM mydb.courses WHERE id="${req.params.id}"`);

    res.send({ course });
};

const addCourse = async (req, res) => {
    const allProperties = Object.keys(req.body).length;

    if (allProperties !== 4) {
        res.code(400).send({ 
            error: 'Some properties are missing! Add the name, description, author and link!' 
        });

        return;
    }

    try {
        const newCourse = await client.insert({
            table: 'courses',
            records: [
                {
                    name: req.body.name,
                    description: req.body.description,
                    author: req.body.author,
                    link: req.body.link
                }
            ]
        });

        res.send({ newCourse });
    } catch (error) {
        res.send({ error });
    }
};

const editCourse = async (req, res) => {
    const updates = Object.keys(req.body);
    const allowedUpdates = ['name', 'description', 'author', 'link'];
    const isValidOperation = updates.every((update) => allowedUpdates.includes(update));

    if (!isValidOperation) {
        res.code(400).send({ error: 'Not a valid operation! '});

        return;
    }

    try {
        const updatedCourse = await client.update({
            table: 'courses',
            records: [
                {
                    id: req.params.id,
                    name: req.body.name,
                    description: req.body.description,
                    author: req.body.author,
                    link: req.body.link
                }
            ]
        });

        res.send({ updatedCourse });
    } catch (error) {
        res.send({ error });
    }
};

const deleteCourse = async (req, res) => {
    const course = await client.query(`DELETE FROM mydb.courses WHERE id="${req.params.id}"`);

    res.send({ 
        message: 'Course deleted!',
        deleteCourse: course
     });
};

module.exports = {
    getCourses,
    getSpecificCourse,
    addCourse,
    editCourse,
    deleteCourse
}