#!/usr/bin/env bun
/**
 * link-polyfill.ts — Reactive local link for the @ng-eventually/polyfill polyfill.
 *
 * WHY a copy-overlay and not a symlink:
 *   The committed prod dependency installs @ng-eventually/polyfill from Gitea (git+https)
 *   into pnpm's store WITHOUT its own node_modules/@ng-org → @ng-org/web resolves up to
 *   Festipod → ONE @ng-org instance (one verifier). The local polyfill CHECKOUT, however,
 *   carries its own node_modules/@ng-org/* (symlinks into the ng-eventually-js monorepo
 *   store). Symlinking node_modules/@ng-eventually/polyfill to that checkout puts the
 *   checkout's @ng-org in the resolution path → a SECOND @ng-org instance → broken SDK
 *   (two verifiers). So we overlay a real directory that contains ONLY the polyfill's
 *   source (no node_modules) and keep it in sync by copying — @ng-org still resolves to
 *   Festipod, single instance preserved.
 *
 * WHAT IT DOES:
 *   1. Replaces node_modules/@ng-eventually/polyfill (the pnpm store symlink) with a real
 *      directory holding the local polyfill's package.json + src (NO node_modules).
 *   2. Asserts the single-instance invariant (same @ng-org/web realpath from Festipod and
 *      from the overlay) — aborts if it would break.
 *   3. Watches the local polyfill src and copies each change into the overlay, so
 *      `bun --hot` (bun run dev) reloads the edited file live.
 *
 * USAGE (reactive dev):
 *   Terminal 1:  pnpm run link:polyfill      # overlays local source, then watches
 *   Terminal 2:  bun run dev                 # portless festipod bun --hot src/index.ts
 *   Edit files under packages/polyfill/src → they land in node_modules → bun --hot reloads.
 *
 *   pnpm run link:polyfill --once            # overlay + verify, no watch (CI / one-shot)
 *   Return to the committed git-installed dependency:  pnpm install
 *
 * Override the local checkout path with NG_EVENTUALLY_LOCAL=/path/to/packages/polyfill.
 */
import { existsSync, lstatSync, mkdirSync, rmSync, cpSync, copyFileSync, realpathSync } from "node:fs";
import { watch } from "node:fs";
import { join, dirname } from "node:path";

const FESTIPOD = realpathSync(join(import.meta.dir, ".."));
const LOCAL =
  process.env.NG_EVENTUALLY_LOCAL ??
  "/home/sylvain/projects/nextgraph/ng-eventually-js/packages/polyfill";
const TARGET = join(FESTIPOD, "node_modules", "@ng-eventually", "polyfill");
const SRC_LOCAL = join(LOCAL, "src");
const SRC_TARGET = join(TARGET, "src");
const ONCE = process.argv.includes("--once");

function fail(msg: string): never {
  console.error(`✖ link:polyfill — ${msg}`);
  process.exit(1);
}

if (!existsSync(join(LOCAL, "package.json"))) {
  fail(`local polyfill not found at ${LOCAL} (set NG_EVENTUALLY_LOCAL to override)`);
}

// 1. Replace the pnpm store symlink with a real overlay dir (metadata + src, NO node_modules).
console.log(`→ overlaying local polyfill: ${LOCAL}`);
if (existsSync(TARGET) || lstatSync(TARGET, { throwIfNoEntry: false })) {
  rmSync(TARGET, { recursive: true, force: true });
}
mkdirSync(TARGET, { recursive: true });
for (const meta of ["package.json", "tsconfig.json", "README.md"]) {
  const from = join(LOCAL, meta);
  if (existsSync(from)) copyFileSync(from, join(TARGET, meta));
}
// Copy src fresh (NEVER a node_modules dir — that is what guarantees single @ng-org instance).
cpSync(SRC_LOCAL, SRC_TARGET, { recursive: true });

// 2. Assert the single-instance invariant.
const fromFestipod = realpathSync(Bun.resolveSync("@ng-org/web", FESTIPOD));
const overlayReal = realpathSync(TARGET);
const fromPolyfill = realpathSync(Bun.resolveSync("@ng-org/web", overlayReal));
console.log(`  @ng-org/web (Festipod): ${fromFestipod}`);
console.log(`  @ng-org/web (overlay) : ${fromPolyfill}`);
if (fromFestipod !== fromPolyfill) {
  fail(
    "single-instance invariant BROKEN — @ng-org/web resolves to two different realpaths.\n" +
      "  The overlay must not contain its own node_modules/@ng-org. Aborting.",
  );
}
console.log("✓ single @ng-org/web instance preserved");

if (ONCE) {
  console.log("✓ overlay ready (--once, not watching)");
  process.exit(0);
}

// 3. Watch and copy on change so `bun --hot` sees live edits.
console.log(`👀 watching ${SRC_LOCAL} → ${SRC_TARGET} (Ctrl-C to stop)`);
watch(SRC_LOCAL, { recursive: true }, (_event, filename) => {
  if (!filename) return;
  const from = join(SRC_LOCAL, filename);
  const to = join(SRC_TARGET, filename);
  try {
    if (existsSync(from)) {
      mkdirSync(dirname(to), { recursive: true });
      copyFileSync(from, to);
      console.log(`  ↻ ${filename}`);
    } else if (existsSync(to)) {
      rmSync(to, { force: true });
      console.log(`  ✗ ${filename} (removed)`);
    }
  } catch (err) {
    console.error(`  ! failed to sync ${filename}:`, err);
  }
});