#!/usr/bin/env node
/**
 * One-shot patch: dither visitor photos before they go on the badge canvas.
 *
 *   node scripts/dither-badge-photos.mjs          # patch
 *   node scripts/dither-badge-photos.mjs --check  # report only
 *
 * A thermal head has no grey. Drawn straight, a photo gets thresholded by the
 * plane conversion and most of a face lands on one side of that threshold, so
 * it prints as a solid black mass. This inserts a Floyd-Steinberg pass at
 * exactly the size the photo will occupy.
 *
 * Idempotent, writes printer.js.bak, refuses to run if the anchor is missing.
 */

import fs from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

const here = path.dirname(fileURLToPath(import.meta.url));
const target = path.resolve(here, '..', 'src', 'printer.js');
const checkOnly = process.argv.includes('--check');

function fail(message) {
  console.error(`\n  FAILED: ${message}\n`);
  console.error('  Nothing was changed.\n');
  process.exit(1);
}

if (!fs.existsSync(target)) fail(`${target} does not exist. Run this from the repo root.`);

let source = fs.readFileSync(target, 'utf8');
const original = source;

if (source.includes('ditherPhoto(')) {
  console.log('\n  Already patched — printer.js dithers photos. Nothing to do.\n');
  process.exit(0);
}

const changes = [];

/* -- 1. Import ---------------------------------------------------- */

const importAnchor = "import { photoAbsolutePath } from './photos.js';";
if (!source.includes(importAnchor)) fail('could not find the photos.js import');

source = source.replace(
  importAnchor,
  `${importAnchor}\nimport { ditherPhoto } from './printing/dither.js';`
);
changes.push('added the ditherPhoto import');

/* -- 2. Dither once, at final size, before either draw site ------- */

// Matches the existing line regardless of the exact multipliers, so tweaking
// the photo size later doesn't break this patch.
const sizeAnchor = /const photoSize = photo \? Math\.round\([^;]+\) : 0;/;
const match = source.match(sizeAnchor);
if (!match) fail('could not find the photoSize calculation in drawBadge');

const insertion = `${match[0]}

  // Thermal heads print pure black or nothing, so a photo has to be reduced to
  // 1-bit before it lands on the canvas — otherwise the plane conversion
  // thresholds it into a solid blob. Done once here rather than at each draw
  // site, and at exactly photoSize: rescaling a dithered image resamples the
  // dot pattern back into greys and undoes the whole thing.
  //
  // Skipped on the measuring pass, which never paints.
  if (photo && photoSize > 0 && startY !== null) {
    photo = ditherPhoto(photo, photoSize);
  }`;

source = source.replace(sizeAnchor, insertion);
changes.push('drawBadge dithers the photo at its final size');

/* -- 3. Sanity check ---------------------------------------------- */

if (!/let photo = null;/.test(source)) {
  fail('photo is not declared with let — it cannot be reassigned. Patch by hand.');
}

console.log('\n  Changes to src/printer.js:');
for (const c of changes) console.log(`    - ${c}`);

if (checkOnly) {
  console.log('\n  --check given, nothing written.\n');
  process.exit(0);
}

if (source === original) fail('nothing actually changed');

fs.writeFileSync(`${target}.bak`, original);
fs.writeFileSync(target, source);

console.log(`\n  Wrote ${target}`);
console.log(`  Backup at ${target}.bak`);
console.log('\n  Next: docker compose build && docker compose up -d\n');