// Bundles the content script and the modules it imports into one classic script.
//
// Content scripts cannot be ES modules, and loading modules with a dynamic import() makes Chrome log
// "Unsafe attempt to load URL chrome-extension://..." on every YouTube page, which piles up in the
// extension's error list. A single classic file avoids both.
//
// Supported source style: one-line `import ... from './x.js';`, and `export` only before
// const / let / function / class. Top-level names must be unique across the bundled modules.
import { readFileSync, writeFileSync } from 'node:fs';
import { basename, dirname, resolve } from 'node:path';
import { fileURLToPath, pathToFileURL } from 'node:url';

const IMPORT = /^import\s+(?:[^'"]*?\s+from\s+)?'([^']+)';?[ \t]*\r?\n/gm;
const EXPORT_DECLARATION = /^export\s+(?=(?:async\s+function|function|const|let|class)\b)/gm;
const UNSUPPORTED_EXPORT = /^export\s+(?!(?:async\s+function|function|const|let|class)\b)/m;
const TOP_LEVEL_NAME = /^(?:async\s+)?(?:function\*?|const|let|class)\s+([A-Za-z_$][\w$]*)/gm;

const HEADER =
  '// GENERATED by tools/build-content.js from src/content/main.js and the modules it imports.\n' +
  '// Edit those files and run `npm run build`; do not edit this file by hand.\n';

export function bundle(entry) {
  const order = [];
  const seen = new Set();
  const visit = (file) => {
    if (seen.has(file)) return;
    seen.add(file);
    for (const [, specifier] of readFileSync(file, 'utf8').matchAll(IMPORT)) visit(resolve(dirname(file), specifier));
    order.push(file);
  };
  visit(resolve(entry));

  const owner = new Map();
  const parts = order.map((file) => {
    const source = readFileSync(file, 'utf8');
    if (UNSUPPORTED_EXPORT.test(source)) {
      throw new Error(`${file}: only "export const/let/function/class" declarations are supported`);
    }
    const code = source.replace(IMPORT, '').replace(EXPORT_DECLARATION, '').trim();
    for (const [, name] of code.matchAll(TOP_LEVEL_NAME)) {
      if (owner.has(name)) throw new Error(`Duplicate top-level name "${name}" in ${file} and ${owner.get(name)}`);
      owner.set(name, file);
    }
    return `// ---- ${basename(file)} ----\n${code}\n`;
  });

  return `${HEADER}(() => {\n'use strict';\n\n${parts.join('\n')}})();\n`;
}

const isMain = process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href;
if (isMain) {
  const root = resolve(dirname(fileURLToPath(import.meta.url)), '..');
  writeFileSync(resolve(root, 'src/content.js'), bundle(resolve(root, 'src/content/main.js')));
  console.log('Wrote src/content.js');
}