parking_solution/apps/server/src/event-log.test.ts

import { afterEach, beforeEach, describe, expect, it } from "vitest";
import { createTestDb } from "@parking/db/testing";
import { ledgerEvents, eq, type Db } from "@parking/db";
import { EventLog, canonicalize, hashEvent } from "./event-log.js";
import { SoftwareSigner, buildVerifier } from "./signer.js";

// The append-only, hash-chained, signed event log is THE anti-fraud primitive
// (threat model: the operator at the booth). These tests pin every integrity rule:
// monotonic index, prevHash linkage, payload-in-signature, and that verifyChain()
// catches each class of tamper (content edit, reorder, deletion gap, forged sig,
// missing key). No live DB is touched — a fresh in-memory SQLite per test.

const SECRET = "test-event-signing-key-0123456789";

let db: Db;
let close: () => void;
let log: EventLog;

beforeEach(() => {
  const t = createTestDb();
  db = t.db;
  close = t.close;
  log = new EventLog(db, new SoftwareSigner(SECRET), buildVerifier);
});

afterEach(() => close());

describe("EventLog.append — chain construction", () => {
  it("assigns a monotonic index starting at 1", async () => {
    const a = await log.append({ type: "vehicle_entry", identity: "T1" });
    const b = await log.append({ type: "vehicle_exit", identity: "T1" });
    expect(a.index).toBe(1);
    expect(b.index).toBe(2);
  });

  it("genesis event has a null prevHash; the next chains to it", async () => {
    const a = await log.append({ type: "vehicle_entry", identity: "T1" });
    const b = await log.append({ type: "vehicle_exit", identity: "T1" });
    expect(a.prevHash).toBeNull();
    expect(b.prevHash).toBe(hashEvent(canonicalize(a)));
  });

  it("signs each row under the active keyId", async () => {
    const row = await log.append({ type: "payment", identity: "T1", payload: { amountMinor: 100 } });
    expect(row.keyId).toBe("sw-hmac-v2");
    expect(new SoftwareSigner(SECRET).verify(canonicalize(row), row.signature)).toBe(true);
  });

  it("serializes concurrent appends without index collisions", async () => {
    const rows = await Promise.all(
      Array.from({ length: 25 }, (_, i) => log.append({ type: "vehicle_entry", identity: `T${i}` })),
    );
    const indices = rows.map((r) => r.index).sort((a, b) => a - b);
    expect(indices).toEqual(Array.from({ length: 25 }, (_, i) => i + 1));
  });
});

describe("EventLog.verifyChain — integrity", () => {
  async function seed() {
    await log.append({ type: "vehicle_entry", identity: "T1", direction: "entry" });
    await log.append({ type: "payment", identity: "T1", payload: { amountMinor: 200, tariffVersionId: "tv1" } });
    await log.append({ type: "vehicle_exit", identity: "T1", direction: "exit" });
  }

  it("accepts an untampered chain", async () => {
    await seed();
    expect(log.verifyChain()).toEqual({ ok: true });
  });

  it("accepts an empty chain", () => {
    expect(log.verifyChain()).toEqual({ ok: true });
  });

  it("detects a tampered payload (the money amount)", async () => {
    await seed();
    // Rewrite the payment amount directly in the DB — exactly the booth-operator
    // fraud the signed payload defends against.
    db.update(ledgerEvents).set({ payload: { amountMinor: 1, tariffVersionId: "tv1" } }).where(eq(ledgerEvents.index, 2)).run();
    const r = log.verifyChain();
    expect(r.ok).toBe(false);
    if (!r.ok) {
      expect(r.index).toBe(2);
      expect(r.reason).toMatch(/signature invalid/);
    }
  });

  it("detects a deleted row as an index gap", async () => {
    await seed();
    db.delete(ledgerEvents).where(eq(ledgerEvents.index, 2)).run();
    const r = log.verifyChain();
    expect(r.ok).toBe(false);
    if (!r.ok) expect(r.reason).toMatch(/index gap/);
  });

  it("detects a broken prevHash link (reordering / re-chaining)", async () => {
    await seed();
    db.update(ledgerEvents).set({ prevHash: "0".repeat(64) }).where(eq(ledgerEvents.index, 3)).run();
    const r = log.verifyChain();
    expect(r.ok).toBe(false);
    if (!r.ok) {
      expect(r.index).toBe(3);
      expect(r.reason).toMatch(/prevHash/);
    }
  });

  it("detects an event signed under a key that is no longer configured", async () => {
    await seed();
    // Re-sign row 2 under an unknown keyId — buildVerifier can't resolve it.
    db.update(ledgerEvents).set({ keyId: "atecc608-slot9" }).where(eq(ledgerEvents.index, 2)).run();
    const r = log.verifyChain();
    expect(r.ok).toBe(false);
    if (!r.ok) expect(r.reason).toMatch(/no signer for keyId/);
  });
});

describe("canonicalize — byte-stability", () => {
  it("is independent of payload key order (sorted recursively)", () => {
    const base = { index: 1, type: "payment", direction: null, source: null, identity: "T1", occurredAt: "2026-06-21T10:00:00.000Z", prevHash: null };
    const a = canonicalize({ ...base, payload: { amountMinor: 100, tariffVersionId: "tv1" } });
    const b = canonicalize({ ...base, payload: { tariffVersionId: "tv1", amountMinor: 100 } });
    expect(a).toBe(b);
  });

  it("changes when any signed field changes", () => {
    const base = { index: 1, type: "payment" as const, direction: null, source: null, identity: "T1", payload: { amountMinor: 100 }, occurredAt: "2026-06-21T10:00:00.000Z", prevHash: null };
    expect(canonicalize(base)).not.toBe(canonicalize({ ...base, payload: { amountMinor: 101 } }));
    expect(canonicalize(base)).not.toBe(canonicalize({ ...base, identity: "T2" }));
  });
});