import { describe, expect, test } from "bun:test";
import { join } from "node:path";
import { fitHintToBudget, normalizeHint } from "../src/lib/hint";

// D-WS2a: the server engine truncates the hint in Python (server-py/sidecar.py,
// with faster-whisper's tokenizer) and the browser engine in TypeScript
// (src/lib/hint.ts, with the Transformers.js tokenizer). Both must apply the
// same rule; with the same deterministic fake tokenizer they must agree
// exactly. sidecar.py imports faster-whisper only inside main(), so the
// helpers import without it.

const SIDECAR = join(import.meta.dir, "../server-py/sidecar.py");

const CASES: { hint: string; budget: number }[] = [
  { hint: "", budget: 223 },
  { hint: " \n\t ", budget: 223 },
  { hint: "Maxwell\nVoices of the Void", budget: 223 },
  { hint: "  Århus\r\n\r\nÆrø,  Festuge \n", budget: 223 },
  { hint: "Max\u0000well\u0007", budget: 223 },
  { hint: "alpha, beta gamma", budget: 10 },
  { hint: "alpha; beta; gamma; delta", budget: 14 },
  { hint: "x".repeat(50), budget: 10 },
  { hint: "Maxwell, ".repeat(300), budget: 223 },
  { hint: Array.from({ length: 400 }, (_, i) => `term${i}`).join("\n"), budget: 223 },
];

/** One token per UTF-16 code unit — the same function on both sides. */
const charEncode = (text: string) => [...text].map((c) => c.charCodeAt(0));

const PYTHON = `
import importlib.util, json, sys
spec = importlib.util.spec_from_file_location("sidecar", sys.argv[1])
sidecar = importlib.util.module_from_spec(spec)
spec.loader.exec_module(sidecar)
encode = lambda text: [ord(c) for c in text]
cases = json.load(sys.stdin)
print(json.dumps([
    {"normalized": sidecar.normalize_hint(c["hint"]),
     "ids": sidecar.fit_prompt_ids(c["hint"], encode, c["budget"])}
    for c in cases
]))
`;

describe("hint truncation parity: TypeScript vs sidecar.py", () => {
  test("normalize_hint / fit_prompt_ids match normalizeHint / fitHintToBudget", () => {
    const proc = Bun.spawnSync(["python3", "-I", "-c", PYTHON, SIDECAR], {
      stdin: new TextEncoder().encode(JSON.stringify(CASES)),
      stdout: "pipe",
      stderr: "pipe",
    });
    expect(proc.stderr.toString()).toBe("");
    const python = JSON.parse(proc.stdout.toString()) as { normalized: string; ids: number[] }[];
    expect(python).toEqual(
      CASES.map(({ hint, budget }) => ({
        normalized: normalizeHint(hint),
        ids: fitHintToBudget(hint, charEncode, budget),
      })),
    );
  });
});