/**
 * Writes the backend's seed fixture from the frontend's seed module.
 *
 *   node scripts/seed-fixture.mjs           # check: exits non-zero if stale
 *   node scripts/seed-fixture.mjs --write   # regenerate
 *
 * `src/api/seed.js` is the authored source: it has the helpers, the reasoning in
 * comments, and the values a person edits. `seed/fixtures/seed.json` is what the
 * Go seeder loads. They used to be maintained in parallel with nothing checking
 * them, which is a duplication that only fails quietly — the demo and the API
 * would answer the same question differently, and the first symptom would be a
 * number on a page disagreeing with a number from an agent.
 *
 * `ShiftRecord` is deliberately not carried across. Its dates are anchored to
 * the day the seeder runs rather than to this file's fixed calendar, so the Go
 * side generates it (internal/seeder/shifts.go, a port of attendanceSeed.js).
 * A frozen snapshot of it would read as permanently empty a fortnight later.
 */
import { createServer } from 'vite';
import { readFileSync, writeFileSync, existsSync } from 'node:fs';
import { join } from 'node:path';
import { pathToFileURL } from 'node:url';

export const FIXTURE_PATH = join(process.cwd(), '..', 'krow-backend', 'seed', 'fixtures', 'seed.json');

/** The fixture the frontend seed implies. Pure — takes the loaded module. */
export const GENERATED_NOTE =
  'Generated from krow-demo/src/api/seed.js — do not edit by hand. ' +
  'Regenerate with: npm run seed:fixture';

export function fixtureFrom(seedModule) {
  const { ShiftRecord, ...entities } = seedModule.seedData;
  /* First key, so it is the first thing anyone opening the file reads. The Go
     loader unmarshals into a struct of demoUser + entities and ignores the
     rest, so this costs nothing on the reading side. */
  return { _generated: GENERATED_NOTE, demoUser: seedModule.DEMO_USER, entities };
}

/** Serialised exactly as the committed file is: 2-space indent, no trailing newline. */
export const serialise = (fixture) => JSON.stringify(fixture, null, 2);

export async function buildFixture(server) {
  return serialise(fixtureFrom(await server.ssrLoadModule('/src/api/seed.js')));
}

/* ── CLI ──────────────────────────────────────────────────────────────────── */
/* pathToFileURL, not string concatenation: this repo lives under a path with a
   space in it, and import.meta.url percent-encodes it while `file://${path}`
   does not — the guard silently never fires and the script does nothing. */
if (import.meta.url === pathToFileURL(process.argv[1]).href) {
  const server = await createServer({
    root: process.cwd(), server: { middlewareMode: true }, appType: 'custom', logLevel: 'error',
  });
  const built = await buildFixture(server);
  await server.close();

  if (process.argv.includes('--write')) {
    writeFileSync(FIXTURE_PATH, built);
    const { entities } = JSON.parse(built);
    const n = Object.values(entities).reduce((s, v) => s + v.length, 0);
    console.log(`seed.json written — ${Object.keys(entities).length} collections, ${n} records.`);
  } else if (!existsSync(FIXTURE_PATH)) {
    console.error('seed.json is missing. Run: node scripts/seed-fixture.mjs --write');
    process.exit(1);
  } else if (readFileSync(FIXTURE_PATH, 'utf8') !== built) {
    console.error('seed.json is stale — it no longer matches src/api/seed.js.');
    console.error('Run: node scripts/seed-fixture.mjs --write');
    process.exit(1);
  } else {
    console.log('seed.json is in step with src/api/seed.js.');
  }
}