#!/usr/bin/env node
// ============================================================
// build-client.mjs — Compiles client/**/*.ts to public/dist/.
//
// Strangler-fig pattern: TS modules live under client/, legacy
// IIFE files stay under public/js/ until each is migrated.
// Each top-level .ts file in client/ becomes one ES-module bundle
// in public/dist/ that index.html can load via:
//   <script type="module" src="/dist/<name>.js"></script>
//
// Run:
//   npm run build:client          # one-shot
//   npm run build:client -- --watch   # rebuild on change
// ============================================================

import { build, context } from 'esbuild';
import { readdirSync, mkdirSync, existsSync } from 'node:fs';
import { resolve, dirname } from 'node:path';
import { fileURLToPath } from 'node:url';

const __dirname = dirname(fileURLToPath(import.meta.url));
const PROJECT_ROOT = resolve(__dirname, '..');
const SRC = resolve(PROJECT_ROOT, 'client');
const OUT = resolve(PROJECT_ROOT, 'public/dist');

const watch = process.argv.includes('--watch');

if (!existsSync(SRC)) {
  console.error(`[build-client] Source dir does not exist: ${SRC}`);
  process.exit(1);
}
mkdirSync(OUT, { recursive: true });

// Explicit entry list — every other .ts file in client/ is a sub-module
// imported by an entry. Add new entries here when a feature truly needs
// its own separate bundle (different DOM lifecycle, lazy-loaded route,
// etc.). For most modernization work, just import into main.ts.
const ENTRIES = [
  'main.ts',
];

const entryFiles = ENTRIES.map(name => {
  const p = resolve(SRC, name);
  if (!existsSync(p)) {
    console.error(`[build-client] Entry file does not exist: ${p}`);
    process.exit(1);
  }
  return p;
});

const buildOpts = {
  entryPoints: entryFiles,
  outdir: OUT,
  bundle: true,
  format: 'esm',
  target: 'es2022',
  platform: 'browser',
  sourcemap: true,
  minify: !watch, // unminified in watch mode for easier debugging
  logLevel: 'info',
};

if (watch) {
  const ctx = await context(buildOpts);
  await ctx.watch();
  console.log('[build-client] Watching for changes…');
} else {
  await build(buildOpts);
  console.log(`[build-client] Built ${entryFiles.length} entry point(s) → ${OUT}`);
}