#!/usr/bin/env node
// Assemble rendered slide PNGs into a 16:9 PPTX: one full-bleed image per slide,
// native speaker notes, document metadata.
//
// Usage:
//   node build.mjs <pngdir> <out.pptx> [--notes notes.json] [--title T] [--author A] [--subject S]
import { createRequire } from 'node:module';
import { existsSync, readdirSync, readFileSync } from 'node:fs';
import path from 'node:path';

const require = createRequire(import.meta.url);
const PptxGenJS = require('pptxgenjs');

const args = process.argv.slice(2);
if (!args[0] || !args[1]) {
  console.error(
    'usage: node build.mjs <pngdir> <out.pptx> [--notes notes.json] [--title T] [--author A] [--subject S]',
  );
  process.exit(1);
}

const invocationDir = process.env.INIT_CWD || process.cwd();
const dir = path.resolve(invocationDir, args[0]);
const out = path.resolve(invocationDir, args[1]);
const opt = (flag, fallback) => {
  const index = args.indexOf(flag);
  return index >= 0 ? args[index + 1] : fallback;
};

const presentation = new PptxGenJS();
presentation.layout = 'LAYOUT_WIDE'; // 13.333 x 7.5 in
presentation.title = opt('--title', path.basename(out, '.pptx'));
presentation.author = opt('--author', 'ThothII');
presentation.subject = opt('--subject', '');

const notesOption = opt('--notes', null);
const notesPath = notesOption
  ? path.resolve(invocationDir, notesOption)
  : path.join(dir, 'notes.json');
const notes = existsSync(notesPath)
  ? JSON.parse(readFileSync(notesPath, 'utf8'))
  : {};

const pngs = readdirSync(dir)
  .filter(file => /^\d+\.png$/.test(file))
  .sort((left, right) => Number.parseInt(left, 10) - Number.parseInt(right, 10));
if (pngs.length === 0) {
  console.error('no NN.png files in ' + dir);
  process.exit(1);
}

for (const file of pngs) {
  const slideNumber = Number.parseInt(file, 10);
  const slide = presentation.addSlide();
  slide.background = { color: 'FCFAFA' };
  slide.addImage({
    path: path.join(dir, file),
    x: 0,
    y: 0,
    w: 13.333,
    h: 7.5,
  });
  if (notes[slideNumber]) {
    slide.addNotes(notes[slideNumber]);
  }
}

await presentation.writeFile({ fileName: out });
console.log('built', out, '-', pngs.length, 'slides');