import { randomBytes } from "node:crypto";
import type { FastifyReply, FastifyRequest } from "fastify";
import { eq, rolePermissions, type Db } from "@parking/db";
import { ADMIN_ROLE_ID, PERMISSIONS, type Permission } from "@parking/shared";

// Local JWT auth helpers — fully local, no external identity provider
// (offline-first). The JWT is carried in an HttpOnly cookie (JS can't read it);
// a separate readable CSRF cookie + matching header defends mutations
// (double-submit). See wiki/entities/local-jwt-auth.md.
//
// Authorization is DYNAMIC RBAC: the token carries the user's `roleId`, and each
// guarded route resolves that role's PERMISSION SET (cached in memory) and checks
// the permission it requires. Editing a role takes effect on the next request —
// no re-login, no token bloat, no stale perms. See @parking/shared PERMISSIONS.

declare module "@fastify/jwt" {
  interface FastifyJWT {
    payload: { sub: string; username: string; roleId: string; csrf: string };
    user: { sub: string; username: string; roleId: string; csrf: string };
  }
}

export const TOKEN_COOKIE = "parking_token";
export const CSRF_COOKIE = "parking_csrf";
export const CSRF_HEADER = "x-csrf-token";

// Session lifetime: the JWT has NO expiry — a login is valid until explicit
// logout. Booth reality breaks any fixed clock (relief late/absent, forced double
// shifts), and a shift is a separate explicit boundary, not the token's lifetime.
// See wiki/entities/local-jwt-auth.md + wiki/concepts/shift.md.
//
// The cookie still needs a maxAge so it survives a browser restart (a session
// cookie would log out an active operator on browser close — the opposite of
// "until logout"). Use a long fixed window; the server clears it on logout.
export const COOKIE_MAX_AGE_SECONDS = 30 * 24 * 60 * 60; // 30 days

/**
 * Resolve the JWT signing secret, refusing to start without a strong one.
 * There is deliberately no fallback default — a missing, short, or placeholder
 * secret throws so the server never runs with forgeable tokens.
 */
export function requireJwtSecret(): string {
  const secret = process.env.JWT_SECRET;
  if (!secret || secret.length < 32 || /change.?me|insecure|dev-only/i.test(secret)) {
    throw new Error(
      "JWT_SECRET must be set to a strong random value (>=32 chars). " +
        "Generate one with: openssl rand -hex 32",
    );
  }
  return secret;
}

/**
 * Whether to set the `Secure` flag on the auth/CSRF cookies. FAIL-SAFE: default is
 * `true` (Secure) — a misconfigured/forgotten env can only ever make cookies MORE
 * restrictive, never silently drop the flag.
 *
 * The previous gate keyed off `NODE_ENV === "production"`, which meant an appliance
 * deployed without that var leaked cookies over plain HTTP. Now `Secure` is the
 * default and is dropped ONLY for an explicit, deliberate opt-out — `COOKIE_SECURE`
 * set to a falsey value (`0/false/no/off`), or the legacy `NODE_ENV !== production`
 * signal kept as a fallback so existing dev setups still work over http://localhost.
 *
 * The parking appliance often serves the SPA same-origin over the LAN with no TLS;
 * THAT box sets `COOKIE_SECURE=0` on purpose (a Secure cookie would never be sent
 * over its http origin and would lock operators out). Everything else stays secure.
 */
export function secureCookies(): boolean {
  const override = process.env.COOKIE_SECURE;
  if (override !== undefined) {
    return !/^(0|false|no|off)$/i.test(override.trim());
  }
  // No explicit override: secure unless this is an obvious local-dev run.
  return process.env.NODE_ENV !== "development";
}

export function newCsrfToken(): string {
  return randomBytes(32).toString("hex");
}

/** Set the auth (HttpOnly) + CSRF (readable) cookies after a successful login. */
export function setAuthCookies(reply: FastifyReply, jwt: string, csrf: string): void {
  const secure = secureCookies();
  reply.setCookie(TOKEN_COOKIE, jwt, {
    httpOnly: true,
    sameSite: "strict",
    secure,
    path: "/",
    maxAge: COOKIE_MAX_AGE_SECONDS,
  });
  // Readable by JS so the SPA can echo it back in the CSRF header (double-submit).
  reply.setCookie(CSRF_COOKIE, csrf, {
    httpOnly: false,
    sameSite: "strict",
    secure,
    path: "/",
    maxAge: COOKIE_MAX_AGE_SECONDS,
  });
}

export function clearAuthCookies(reply: FastifyReply): void {
  reply.clearCookie(TOKEN_COOKIE, { path: "/" });
  reply.clearCookie(CSRF_COOKIE, { path: "/" });
}

const MUTATING = new Set(["POST", "PUT", "PATCH", "DELETE"]);

/**
 * Double-submit CSRF check: the X-CSRF-Token header must match the CSRF cookie.
 * The CSRF token is bound into the JWT at login, so a stolen/forged cookie pair
 * still can't pass unless it matches the signed token. Only enforced on
 * state-changing methods (safe reads are exempt).
 */
function assertCsrf(req: FastifyRequest): void {
  if (!MUTATING.has(req.method)) return;
  const header = req.headers[CSRF_HEADER];
  const cookie = req.cookies[CSRF_COOKIE];
  const tokenCsrf = (req.user as { csrf?: string } | undefined)?.csrf;
  if (!header || !cookie || header !== cookie || (tokenCsrf && header !== tokenCsrf)) {
    throw Object.assign(new Error("invalid CSRF token"), { statusCode: 403 });
  }
}

// --- Permission resolution + cache -------------------------------------------
// A role's permission set is read from `role_permissions` and cached in memory.
// SQLite is single-writer/single-process here, so a module-level Map is a correct
// cache: every role / role-permission mutation calls bumpPermsCache() to clear it,
// and the next request re-reads. The built-in `admin` role always resolves to the
// FULL permission set in code (never trusts the DB rows for it), so administration
// can't be accidentally narrowed.

const ADMIN_PERMS: ReadonlySet<Permission> = new Set(PERMISSIONS);
const permsCache = new Map<string, ReadonlySet<Permission>>();

// The DB handle the permission resolver reads from. Set ONCE at startup via
// initAuth() so route guards don't each have to thread `db` (several route
// modules only receive a monitor/service, not the db). Single-process server.
let authDb: Db | null = null;

/** Wire the permission resolver to the app's DB. Call once in buildServer(). */
export function initAuth(db: Db): void {
  authDb = db;
  permsCache.clear();
}

/** Clear the permission cache. Call after ANY write to roles / role_permissions
 *  (or a user's roleId) so the change takes effect on the next request. */
export function bumpPermsCache(): void {
  permsCache.clear();
}

/** The permission set for a role id, cached. `admin` is always the full set. */
export function permissionsFor(roleId: string): ReadonlySet<Permission> {
  if (roleId === ADMIN_ROLE_ID) return ADMIN_PERMS;
  const hit = permsCache.get(roleId);
  if (hit) return hit;
  if (!authDb) throw new Error("auth not initialised (call initAuth)");
  const rows = authDb
    .select({ permission: rolePermissions.permission })
    .from(rolePermissions)
    .where(eq(rolePermissions.roleId, roleId))
    .all();
  const set = new Set(rows.map((r) => r.permission as Permission));
  permsCache.set(roleId, set);
  return set;
}

/** True if the role grants every listed permission. */
export function roleHasPermissions(
  roleId: string,
  required: readonly Permission[],
): boolean {
  const granted = permissionsFor(roleId);
  return required.every((p) => granted.has(p));
}

/**
 * preHandler permission guard. Verifies the JWT (from the HttpOnly cookie),
 * enforces CSRF on mutations, then requires the user's role to grant ALL of the
 * listed permissions. Authorization is a per-route permission check against the
 * dynamic, admin-composed role grid — no Casbin/RBAC engine needed at this scale.
 */
export function requirePermission(...required: Permission[]) {
  return async (req: FastifyRequest, _reply: FastifyReply) => {
    await req.jwtVerify(); // reads the token cookie (configured in server.ts)
    assertCsrf(req);
    if (!req.user || !roleHasPermissions(req.user.roleId, required)) {
      throw Object.assign(new Error("forbidden"), { statusCode: 403 });
    }
  };
}

/**
 * preHandler that requires a valid signed-in session but NO specific permission —
 * for "about me" routes (/me, change own language) every authenticated user may
 * call regardless of role. Still enforces CSRF on mutations.
 */
export async function requireAuth(
  req: FastifyRequest,
  _reply: FastifyReply,
): Promise<void> {
  await req.jwtVerify();
  assertCsrf(req);
}