/**
 * Extension-agnostic SSR module loading, for the duration of the TypeScript
 * migration.
 *
 * Every script in here addresses modules by literal path — `ssrLoadModule(
 * '/src/lib/skills/registry.js')` — about a hundred and seventy times across
 * `skill-check.mjs`, `owliver-capture.mjs`, `render-page.mjs` and
 * `seed-fixture.mjs`. That is fine while every source file is JavaScript and
 * fatal the moment one is not: renaming `registry.js` to `registry.ts` turns
 * the check suite's very first load into a failure, and the suite is the only
 * evidence the Owliver flow still behaves the way it did.
 *
 * Rewriting all those call sites would be a large, noisy, error-prone diff
 * against the file that guards the migration — exactly the wrong thing to
 * disturb. So the loader is wrapped once instead and the call sites keep the
 * paths they already have, which stay readable as the names of real files.
 *
 * Resolution is by existence on disk, not by catching a failed load. A load
 * that fails for a real reason — a syntax error, a bad import inside the module
 * — must surface as itself; retrying under another extension would bury it
 * behind a second, more confusing error about a file that was never there.
 *
 * The path as written is always tried first, so while a module is still
 * JavaScript this changes nothing at all.
 *
 * This file is temporary. When `src` holds no `.js` or `.jsx` any more, the
 * call sites can be renamed in one pass and this wrapper deleted.
 */
import { existsSync } from 'node:fs';
import { join } from 'node:path';

/**
 * The candidate paths for one module specifier, in the order they are tried.
 *
 * Only `.js` and `.jsx` are rewritten. Anything else — a bare specifier, a
 * `.mjs` file, something under `/node_modules` — is returned untouched, because
 * nothing in this migration renames it.
 *
 * `.js` is allowed to become `.tsx` as well as `.ts`. Not because any `.js`
 * file here contains JSX today — none of the 93 does, checked with a parser
 * rather than a guess — but because one may be renamed that way: the only
 * `.js` under `src/pages` is `admin/positions/nodes.js`, sitting among seven
 * sibling `nodes.jsx` files, and whoever converts that directory will
 * reasonably want all eight to end in `.tsx`. The extra candidate costs one
 * `existsSync` that answers no.
 */
export function candidatesFor(path) {
  const specifier = String(path);
  if (!/\.jsx?$/.test(specifier)) return [specifier];
  const stem = specifier.replace(/\.jsx?$/, '');
  return [...new Set([specifier, `${stem}.ts`, `${stem}.tsx`])];
}

/**
 * Wraps `server.ssrLoadModule` so it finds a module whichever of the four
 * extensions it currently carries.
 *
 * Mutates and returns the server, so it reads as one line after `createServer`
 * and every later call — including the dynamically-built paths, which is why
 * this is done here rather than at the call sites — goes through it.
 *
 * `root` is where the leading-slash paths are rooted; it defaults to the
 * process's working directory, which is what every caller here uses.
 */
export function withSourceResolution(server, root = process.cwd()) {
  const load = server.ssrLoadModule.bind(server);

  server.ssrLoadModule = (path, options) => {
    for (const candidate of candidatesFor(path)) {
      if (existsSync(join(root, candidate.replace(/^\//, '')))) {
        return load(candidate, options);
      }
    }
    /* Nothing on disk under any extension. Load the path as written so the
       error names what the caller actually asked for. */
    return load(path, options);
  };

  return server;
}

/**
 * The same resolution, for source read as TEXT rather than loaded as a module.
 *
 * `skill-check.mjs` asserts structural facts by reading source files and
 * matching against their contents — "the panel imports no local suggestion
 * ranker", "no runtime path writes a definition". Those reads go through
 * `readFileSync`, not `ssrLoadModule`, so `withSourceResolution` above never
 * sees them: it wraps the loader, and this is a second, entirely separate
 * channel. Renaming `base44Client.js` to `.ts` is what surfaced the difference,
 * as an ENOENT in the middle of a suite that had been passing.
 *
 * Takes and returns a path RELATIVE to the project root, so the call site keeps
 * its `join(ROOT, …)` exactly as it was:
 *
 *     readFileSync(join(ROOT, resolveSourcePath('src/api/base44Client.js')), 'utf8')
 *
 * Unresolvable paths come back unchanged, so the resulting error still names
 * the file the caller asked for rather than a candidate it invented. That also
 * keeps the deliberately absent ones honest: a check asserting a file is GONE
 * gets the path it asked about, and `existsSync` still answers false.
 */
export function resolveSourcePath(path, root = process.cwd()) {
  for (const candidate of candidatesFor(path)) {
    if (existsSync(join(root, candidate))) return candidate;
  }
  return path;
}