/**
 * TASK-0102 DoD: "Status machine enforced; only valid transitions possible
 * (test)." The full transition table — valid and invalid — is pinned here.
 */
import { describe, expect, it } from "vitest";
import {
  ALLOWED_TRANSITIONS,
  assertTransition,
  isValidTransition,
  InvalidTransitionError
} from "../status.js";
import type { FileStatus } from "@prisma/client";

const ALL: FileStatus[] = ["UPLOADING", "SCANNING", "READY", "VIRUS_DETECTED", "FAILED"];

describe("files status machine (TASK-0102 §2)", () => {
  it("allows exactly the spec transitions", () => {
    expect(ALLOWED_TRANSITIONS.UPLOADING).toEqual(["SCANNING"]);
    expect(ALLOWED_TRANSITIONS.SCANNING).toEqual(["READY", "VIRUS_DETECTED", "FAILED"]);
    expect(ALLOWED_TRANSITIONS.READY).toEqual(["FAILED"]); // re-scan only
    expect(ALLOWED_TRANSITIONS.VIRUS_DETECTED).toEqual([]);
    expect(ALLOWED_TRANSITIONS.FAILED).toEqual([]);
  });

  it("isValidTransition matches the table for every (from,to) pair", () => {
    for (const from of ALL) {
      for (const to of ALL) {
        expect(isValidTransition(from, to)).toBe(ALLOWED_TRANSITIONS[from].includes(to));
      }
    }
  });

  it("assertTransition passes on legal transitions", () => {
    expect(() => assertTransition("UPLOADING", "SCANNING")).not.toThrow();
    expect(() => assertTransition("SCANNING", "READY")).not.toThrow();
    expect(() => assertTransition("SCANNING", "VIRUS_DETECTED")).not.toThrow();
    expect(() => assertTransition("SCANNING", "FAILED")).not.toThrow();
    expect(() => assertTransition("READY", "FAILED")).not.toThrow();
  });

  it("assertTransition throws InvalidTransitionError on every illegal transition", () => {
    for (const from of ALL) {
      for (const to of ALL) {
        if (ALLOWED_TRANSITIONS[from].includes(to)) continue;
        expect(() => assertTransition(from, to), `${from} → ${to}`).toThrow(
          InvalidTransitionError
        );
        expect(() => assertTransition(from, to), `${from} → ${to}`).toThrow(
          new RegExp(`${from} → ${to}`)
        );
      }
    }
  });

  it("terminal states have no outgoing transitions", () => {
    for (const t of ["VIRUS_DETECTED", "FAILED"] as FileStatus[]) {
      for (const to of ALL) {
        expect(isValidTransition(t, to)).toBe(false);
      }
    }
  });

  it("READY is terminal for the pipeline (only a later re-scan → FAILED)", () => {
    expect(isValidTransition("READY", "READY")).toBe(false);
    expect(isValidTransition("READY", "SCANNING")).toBe(false);
    expect(isValidTransition("READY", "VIRUS_DETECTED")).toBe(false);
    expect(isValidTransition("READY", "FAILED")).toBe(true);
  });
});