/**
 * localAuth.ts — local authentication routes (AUTH-LOCAL-03, AUTH-LOCAL-06).
 *
 * Routes:
 *   POST /api/auth/local/login  — rate-limited credential verify + session cookie issue
 *   POST /api/auth/local/logout — clear local-session cookie
 *   GET  /api/auth/local/logout — alias for POST /logout (some browsers prefer GET)
 *
 * Mounted in index.ts as app.route('/api/auth', localAuthRouter) BEFORE any auth middleware.
 * This means POST /api/auth/local/login is reachable without a session (pre-auth, per D-01).
 *
 * Security (T-19-11, T-19-12, T-19-14):
 *   - noEchoHook on login: Zod errors NEVER return received values (T-19-14 / Pitfall 7).
 *   - Dummy-hash timing defense: verifyPassword is always called, even for unknown usernames,
 *     to prevent timing-oracle username enumeration attacks (T-19-12 / RESEARCH Pitfall 2).
 *   - Same 401 body for wrong password AND unknown username — no field discrimination (T-19-12).
 *   - Per-USERNAME in-memory rate-limiting: 5 failures → 429; 10 failures → 423 (T-19-11).
 *   - Lockout (423) auto-expires after LOCKOUT_TTL_MS (CR-04) so a single attacker cannot
 *     permanently deny login for the whole household, and no process restart is needed to
 *     recover. Admin password reset still clears it immediately (resetLoginAttempts).
 *
 * CR-04: the limiter is keyed on the submitted username, NOT the client IP. In this
 * deployment all household traffic egresses the Pangolin tunnel with the same
 * X-Forwarded-For first hop, so IP-keying made one bad actor (or one fat-fingered user)
 * able to lock out every member, and X-Forwarded-For is attacker-spoofable. Username-keying
 * scopes the lockout to the identity actually under attack and the TTL makes it self-healing.
 */

import { Hono } from 'hono';
import type { Context } from 'hono';
import { zValidator } from '@hono/zod-validator';
import { z } from 'zod';
import { eq } from 'drizzle-orm';
import { db } from '../db/client.js';
import { localCredentials } from '../db/schema.js';
import { verifyPassword, hashPassword } from '../auth/localCredentials.js';
import { issueLocalSessionCookie, clearLocalSessionCookie } from '../auth/localSession.js';

export const localAuthRouter = new Hono();

// ---------------------------------------------------------------------------
// noEchoHook — NEVER return Zod validation error details for the login route.
// Zod's error object contains issues[].received which may echo the submitted password.
// Always return { error: 'Invalid request' } 400, no other fields (T-19-14).
// ---------------------------------------------------------------------------

const noEchoHook = (result: { success: boolean }, c: Context) => {
  if (!result.success) {
    return c.json({ error: 'Invalid request' }, 400);
  }
};

// ---------------------------------------------------------------------------
// Zod schema for login body
// ---------------------------------------------------------------------------

const loginSchema = z.object({
  username: z.string().min(1).max(128).trim(),
  password: z.string().min(1).max(1000),
});

// ---------------------------------------------------------------------------
// Per-USERNAME rate-limiting state (in-memory Map — household scale, no Redis needed).
//
// State shape per username: { count, lockedUntil (epoch ms), lockedOut (bool), lockedAt (epoch ms) }
//   count >= RATE_WINDOW_FAILURES AND Date.now() < lockedUntil → 429
//   count >= LOCKOUT_FAILURES → 423 (until LOCKOUT_TTL_MS elapses OR admin reset)
//   Success → delete entry (clears counter)
//
// RATE_WINDOW_FAILURES: 5 failures → 60s cooldown (429)
// LOCKOUT_FAILURES:    10 failures → account locked (423)
// LOCKOUT_TTL_MS:      15 min after which a 423 lockout auto-expires (CR-04)
//
// CR-04: keyed on the validated username (not the client IP) so a lockout is scoped to
// the identity under attack, and self-heals after LOCKOUT_TTL_MS without a restart.
// ---------------------------------------------------------------------------

export const loginAttempts = new Map<
  string,
  { count: number; lockedUntil: number; lockedOut: boolean; lockedAt: number }
>();

const RATE_WINDOW_FAILURES = 5;
const RATE_WINDOW_SECS = 60;
const LOCKOUT_FAILURES = 10;
const LOCKOUT_TTL_MS = 15 * 60 * 1000; // CR-04: 423 lockout auto-expires after 15 minutes

/**
 * Immediately clear any rate-limit / lockout state for a username (CR-04).
 *
 * Called by the admin password-reset path so a reset is an instant unlock and the
 * lockout is not "unrecoverable without a process restart". Safe to call for an
 * unknown username (no-op). Normalizes the username the same way the login schema
 * does (trim) so the key matches what the limiter stored.
 */
export function resetLoginAttempts(username: string): void {
  loginAttempts.delete(username.trim());
}

/**
 * IN-03: evict stale rate-limit entries to bound the in-memory map size.
 *
 * An entry is stale (and safe to drop) when it is neither inside an active rate-limit
 * window nor inside an active lockout TTL:
 *   - locked-out entries expire LOCKOUT_TTL_MS after lockedAt
 *   - non-locked entries expire once their lockedUntil window has passed
 *
 * Called opportunistically at the top of each login request. Dropping an entry is
 * behaviourally identical to the entry having naturally expired, so eviction never
 * weakens the brute-force defense — it only reclaims memory for identities no longer
 * under active rate-limiting.
 */
function evictStaleLoginAttempts(now: number): void {
  for (const [k, v] of loginAttempts) {
    const lockoutExpired = v.lockedOut ? now - v.lockedAt >= LOCKOUT_TTL_MS : true;
    const windowExpired = now >= v.lockedUntil;
    if (lockoutExpired && windowExpired) {
      loginAttempts.delete(k);
    }
  }
}

// Pre-computed dummy hash used to run verifyPassword on unknown-username paths
// (timing defense — prevents timing-oracle username enumeration, RESEARCH Pitfall 2).
// WR-03: hashPassword is now async. Kick off the computation once at module load and keep
// the PROMISE; the login handler awaits it. The value is never used for auth — only to make
// the unknown-username path perform the same scrypt work as the known-username path.
const dummyHashPromise: Promise<string> = hashPassword('dummy-constant-time-filler-xyzzy');

// ---------------------------------------------------------------------------
// POST /local/login  →  POST /api/auth/local/login
// ---------------------------------------------------------------------------

localAuthRouter.post('/local/login', zValidator('json', loginSchema, noEchoHook), async (c) => {
  // CR-04: the rate-limit / lockout key is the validated, normalized username — NOT the
  // client IP. zValidator has already run, so c.req.valid('json') is available here.
  const { username, password } = c.req.valid('json');
  const key = username; // loginSchema .trim()s the username; the map key matches resetLoginAttempts

  const now = Date.now();
  // IN-03: opportunistically reclaim memory from entries that are no longer actively
  // rate-limited or locked out. Cheap at household scale; bounds the map under input churn.
  evictStaleLoginAttempts(now);
  const attempt = loginAttempts.get(key);

  // 423: account locked (>= LOCKOUT_FAILURES failures). CR-04: the lockout auto-expires
  // after LOCKOUT_TTL_MS so a single attacker cannot deny login indefinitely and no restart
  // is required to recover. On expiry, drop the entry so the next attempt starts clean.
  if (attempt?.lockedOut) {
    if (now - attempt.lockedAt >= LOCKOUT_TTL_MS) {
      loginAttempts.delete(key);
    } else {
      return c.json({ error: 'Account locked' }, 423);
    }
  }

  // Re-read after a possible expiry-delete above.
  const live = loginAttempts.get(key);

  // 429: rate window — >= RATE_WINDOW_FAILURES failures within the cooldown window.
  // Increment the counter even on 429 so continued brute-force accumulates toward lockout.
  if (live && live.count >= RATE_WINDOW_FAILURES && now < live.lockedUntil) {
    live.count += 1;
    // WR-06: do NOT extend lockedUntil here. This request was itself REJECTED by the window;
    // re-arming the cooldown on every blocked attempt let an attacker who keeps hammering the
    // endpoint slide the window forward forever, so a legitimate user behind the same identity
    // could never get back in even after pausing. The window stays anchored to when it was
    // first armed (in the failure path below); it expires on schedule regardless of rejected
    // traffic. The lockout (423) still triggers once the failure count crosses the threshold.
    live.lockedOut = live.count >= LOCKOUT_FAILURES;
    if (live.lockedOut && live.lockedAt === 0) live.lockedAt = now;
    loginAttempts.set(key, live);
    if (live.lockedOut) {
      return c.json({ error: 'Account locked' }, 423);
    }
    return c.json({ error: 'Too many attempts' }, 429);
  }

  // Look up local_credentials by username
  let cred: { userId: number; passwordHash: string } | undefined;
  try {
    const [found] = await db
      .select({ userId: localCredentials.userId, passwordHash: localCredentials.passwordHash })
      .from(localCredentials)
      .where(eq(localCredentials.username, username))
      .limit(1);
    cred = found;
  } catch (err) {
    console.error(
      '[localAuth/POST /local/login] DB error:',
      err instanceof Error ? err.message : String(err),
    );
    return c.json({ error: 'Service unavailable' }, 503);
  }

  // ALWAYS run verifyPassword — even for unknown usernames — to prevent timing-oracle
  // username enumeration (T-19-12 / RESEARCH Pitfall 2). Use a pre-computed dummy hash
  // so the scrypt work is always performed regardless of whether username was found.
  // WR-03: verifyPassword is async (threadpool scrypt) — await it.
  const valid = cred
    ? await verifyPassword(cred.passwordHash, password)
    : await verifyPassword(await dummyHashPromise, password);

  if (!valid || !cred) {
    // Increment failure counter (keyed on username)
    const cur = loginAttempts.get(key) ?? {
      count: 0,
      lockedUntil: 0,
      lockedOut: false,
      lockedAt: 0,
    };
    cur.count += 1;
    cur.lockedUntil = Date.now() + RATE_WINDOW_SECS * 1000;
    cur.lockedOut = cur.count >= LOCKOUT_FAILURES;
    if (cur.lockedOut && cur.lockedAt === 0) cur.lockedAt = Date.now();
    loginAttempts.set(key, cur);
    // Same 401 body for wrong password AND unknown username — no field discrimination (T-19-12)
    return c.json({ error: 'Invalid credentials' }, 401);
  }

  // Success: clear failure counter, issue the local-session JWT cookie, return ok
  loginAttempts.delete(key);
  try {
    await issueLocalSessionCookie(c, cred.userId);
  } catch (err) {
    console.error(
      '[localAuth/POST /local/login] Cookie issue error:',
      err instanceof Error ? err.message : String(err),
    );
    return c.json({ error: 'Service unavailable' }, 503);
  }
  return c.json({ ok: true }, 200);
});

// ---------------------------------------------------------------------------
// POST /local/logout  →  POST /api/auth/local/logout
// GET  /local/logout  →  GET  /api/auth/local/logout (browser-redirect alias)
// ---------------------------------------------------------------------------

function handleLogout(c: Context) {
  clearLocalSessionCookie(c);
  return c.json({ ok: true }, 200);
}

localAuthRouter.post('/local/logout', handleLogout);
localAuthRouter.get('/local/logout', handleLogout);