Config

Gator is a multi-user CLI application. There's no server (other than the database), so it's only intended for local use, but just like games in the 90's and early 2000's, that doesn't mean we can't have multiplayer functionality on a single device!

We'll use a single JSON file to keep track of two things:

Who is currently logged in
The connection credentials for the PostgreSQL database

The JSON file should have this structure (when prettified):

{
  "db_url": "connection_string_goes_here",
  "current_user_name": "username_goes_here"
}

Note: There's no user-based authentication for this app. If someone has the database credentials, they can act as any user. We'll cover auth in other courses. We want to focus on SQL, CLIs and long-running services for this project.

Assignment

Manually create a config file in your home directory, ~/.gatorconfig.json, with the following content:

{
  "db_url": "postgres://example"
}

Don't worry about adding current_user_name, that will be set by the application.

Create a config.ts file. This is where we'll handle reading and writing the JSON file.
Create a Config type that represents the JSON file structure. Keep the fields in camelCase even though the JSON keys are snake_case.

This file should have the following functionality exported:

Export a setUser function that writes a Config object to the JSON file after setting the current_user_name field.
Export a readConfig function that reads the JSON file found at ~/.gatorconfig.json and returns a Config object. It should read the file from the HOME directory, then decode the JSON string into a new Config object.

I used os.homedir to get the location of HOME.

I also wrote a few non-exported helper functions.

getConfigFilePath(): string
writeConfig(cfg: Config): void
validateConfig(rawConfig: any): Config - used by readConfig to validate the result of JSON.parse.

JSON.parse is typed as any because it can return any type of object. We need to validate the object to ensure it has the correct structure.

I imported the fs, os, and path modules:

import fs from "fs";
import os from "os";
import path from "path";

fs is the file system module, which allows you to read and write files.
os provides operating system-related utility methods.
path provides utilities for working with file and directory paths.

But you can implement the internals however you like.

If you want additional help, see the Tips section below.

Update the main function to:
- Set the current user to "Lane" (actually, you should use your name instead) and update the config file on disk.
- Read the config file again, parse it into a config object and print it to the terminal.

Run and submit the CLI tests from the root of your project.

Tips

To read and write to JSON, I used:

fs.readFileSync(path[,options]) and set the encoding to 'utf-8'.
fs.writeFileSync(file, data[, options]) after using JSON.stringify

To get the path to read and write to, I used:

path.join([...paths]) and os.homedir