import { expect, test } from "bun:test"
import { readdirSync, readFileSync, statSync } from "node:fs"
import { join } from "node:path"

// The engine is the reusable, content-agnostic layer: it must import nothing from
// game (content) or app (browser glue). game -> engine and app -> game -> engine are
// fine; the reverse is the violation. This freezes the Stage-3 seam so a stray import
// can't quietly re-couple the layers.
function tsFiles(dir: string): string[] {
  const out: string[] = []
  for (const name of readdirSync(dir)) {
    const p = join(dir, name)
    if (statSync(p).isDirectory()) {
      out.push(...tsFiles(p))
    } else if (p.endsWith(".ts")) {
      out.push(p)
    }
  }
  return out
}

test("engine imports nothing from game or app", () => {
  const engineDir = new URL("../engine", import.meta.url).pathname
  const offenders = tsFiles(engineDir).filter((f) => /from\s+["'][^"']*\/(?:game|app)\//.test(readFileSync(f, "utf8")))
  expect(offenders).toEqual([])
})

test("game imports nothing from app", () => {
  const gameDir = new URL("../game", import.meta.url).pathname
  const offenders = tsFiles(gameDir).filter((f) => /from\s+["'][^"']*\/app\//.test(readFileSync(f, "utf8")))
  expect(offenders).toEqual([])
})