app.js

//import database setup utils
const createDB = require("./database/utils/createDB");
const seedDB = require("./database/utils/seedDB");

// use cors policy to allow heroku api
var cors = require("cors");

//import Sequelize instance
const db = require("./database");

//sync and seed
const syncDatabase = async () => {
  try {
    //the {force: true} option will clear the database tables
    await db.sync({ force: true });
    //every time we restart the server
    //remove the option if you want the data to persist, ie:
    // await db.sync();
    console.log("------Synced to db--------");
    await seedDB();
    console.log("--------Successfully seeded db--------");
  } catch (err) {
    console.error("syncDB error:", err);
  }
};

//import express library
const express = require("express");

//create express server
const app = express();
  
//set cors policy
app.use(cors())


//express router: import routes we defined
const apiRouter = require("./routes");

//initialize express server
const configureApp = async () => {
  // handle request data
  app.use(express.json());
  app.use(express.urlencoded({ extended: false }));
  //ignore browser requests for favicon file
  app.get("/favicon.ico", (req, res) => res.status(204));
  //define a route
  app.get("/", (request, response) => {
    response.send("Hello world! Want to use my API to keep track of your classes?");
  });

  // Mount apiRouter
  app.use("/api", apiRouter);

  // Handle page not found:
  // gets triggered when a request is made to
  // an undefined route
  app.use((req, res, next) => {
    const error = new Error("Not Found, Please Check URL!");
    error.status = 404;
    next(error);
  });

  // Error-handling middleware:
  // all express errors get passed to this
  // when next(error) is called
  app.use((err, req, res, next) => {
    console.error(err);
    console.log(req.originalUrl);
    res.status(err.status || 500).send(err.message || "Internal server error.");
  });
};

const bootApp = async () => {
  //creates local database if it doesn't exist
  !process.env.DATABASE_URL && (await createDB());

  //calls sync which is a Sequelize method that creates the database tables
  //calls seedDB which will insert initial data into the tables
  await syncDatabase();

  //express setup - define routes and middleware
  await configureApp();
};

// PROGRAM STARTS HERE

bootApp();

const PORT = process.env.PORT || 5000;
app.listen(PORT, console.log(`Server started on ${PORT}`));