PICO-8 Node Build Script

/*
 * Simple build script for PICO-8 carts.
 * Looks for a config file in the directory it's run in and
 * tries to jam all the included lua files into the given cart.
*/
const fs = require('fs');

const START_MARKER = '__lua__';
const END_MARKER = '__gfx__';
const INCLUDE_MARKER = '#include ';

const alreadyLoaded = [];
let newCart = '';
const isValidIndex = (value) => typeof value === 'number' && value >= 0;
const loadForCart = (file) => {
   const lines = fs.readFileSync(file, 'utf-8').split('\n');
   lines.forEach(line => {
      const includeIndex = line.indexOf('#include');
      if (isValidIndex(includeIndex)) {
         // This file includes another, so go and load that first.
         const includedFile = line.slice(INCLUDE_MARKER.length, line.length).trim();
         if (!alreadyLoaded.includes(includedFile)) {
            loadForCart(includedFile);
            alreadyLoaded.push(includedFile);
         }
      }
      else {
         newCart += line + '\n';
      }
   });
}

/*
* Loading the config here. The config must have three fields defined:
* - output: The output DIRECTORY for the final cart.
* - entryPoint: The name of the 'main' file for your cart.
* - cartName: The name of your cart. The outputted file will be [cartName].p8.
*/
const config = JSON.parse(fs.readFileSync('config.json', 'utf8'));
if (!config.output || !config.entryPoint || !config.cartName) {
   console.log('ERROR :: Config must define an output directory, entry point and a cart name.');
}

// Get existing cart file.
console.log(`INFO :: Reading existing cart...`);
let existingCart = fs.readFileSync(`${config.output}/${config.cartName}.p8`, 'utf-8');
if (!existingCart) {
   console.log('ERROR :: The cart file must have been created in PICO-8 first.');
}
const startOfCode = existingCart.indexOf(START_MARKER) + START_MARKER.length;
const endOfCode = existingCart.indexOf(END_MARKER);

// Amalgamate source files and create the new cart.
console.log(`INFO :: Concatenating source files...`);
newCart = existingCart.slice(0, startOfCode) + '\n';
loadForCart(config.entryPoint);
newCart += '\n' + existingCart.slice(endOfCode, existingCart.length);

console.log(`INFO :: Saving new cart...`);
fs.writeFileSync(`${config.output}/${config.cartName}.p8`, newCart, 'utf-8');
console.log("INFO :: Done!");