rollup.config.js

// @ts-check

import babel from '@rollup/plugin-babel';
import commonjs from '@rollup/plugin-commonjs';
import resolve from '@rollup/plugin-node-resolve';
import replace from '@rollup/plugin-replace';
import url from '@rollup/plugin-url';
import copy from 'rollup-plugin-copy';
import pkg from './package.json' with { type: 'json' };

const extensions = ['.js', '.jsx', '.ts', '.tsx'];

const pluginTransformConstToLet = () => ({
  renderChunk(chunk) {
    return chunk.replace(/\bconst\b/g, 'let');
  },
});

// Replace well-known string constants with shorter, yet unique, names!
const pluginShortenKnownStrings = () => ({
  renderChunk(chunk) {
    const pairs = [
      ['v-movement', 'mv'],
      ['draw-console', 'dc'],
      ['viewport', 'vp'],
      ['drag-state', 'ds'],
      ['pointer-target', 'pt'],
      ['spring-constraint', 'sc'],
      ['bounding-box', 'bb'],
      ['circle-shape', 'cs'],
      ['user-controlled', 'uc'],
      ['debug-drawable-circle', 'ddc'],
      ['debug-drawable-rect', 'ddr'],
      ['enemy-miasma', 'em'],
      ['enemy-targetable', 'et'],
      ['impedance-value', 'imv'],
      ['health-value', 'hv'],
      ['enemy-impedance', 'eim'],
    ];

    const shorts = new Set();

    for (const [long, short] of pairs) {
      if (shorts.has(short))
        throw new Error(`Need a unique short name! Got ${short}`);
      shorts.add(short);
      chunk = chunk.replace(
        new RegExp(`['"]${long}['"]`, 'g'),
        JSON.stringify(short),
      );
    }

    return chunk;
  },
});

// Replace typescript assertions. Hacky to do it via regex, but it's well-known
// and easier than writing a rollup plugin. Note that this uses a negative
// lookbehind to avoid targeting the function definition itself, only supported
// in V8.
const pluginRemoveTypescriptAssertions = () => ({
  renderChunk(chunk) {
    return chunk.replace(
      /(?<!function )(assertDefinedFatal|assertExhaustive|assertSpatialHandleIsInt)\([^)]+\)/g,
      '',
    );
  },
});

export default {
  input: './src/index.ts',

  plugins: [
    resolve({ extensions }),

    // Copy imported static files into the dist folder
    // limit is the number of bytes before the image is copied instead of inlined.
    // 0 means always copy.
    // Probably want to tweak this, depending on the size and format of the image.
    url({
      limit: 0,
      include: [
        '**/*.svg',
        '**/*.png',
        '**/*.jpg',
        '**/*.gif',
        '**/*.mp4',
        '**/*.mp3',
        '**/*.ttf',
      ],
    }),

    commonjs(),

    babel({
      extensions,
      babelHelpers: 'bundled',
      include: ['src/**/*', 'assets/**/*.ts'],
    }),

    replace({
      preventAssignment: true,
      'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV),
    }),

    ...(process.env.NODE_ENV === 'production'
      ? [
          pluginTransformConstToLet(),
          pluginShortenKnownStrings(),
          pluginRemoveTypescriptAssertions(),
        ]
      : []),

    copy({ targets: [{ src: 'src/index.html', dest: 'dist/' }] }),
  ],

  output: [
    {
      file: 'dist/bundle.js',
      format: 'iife',
    },
  ],
};