// Investor Flow — tRPC context + auth/session (DESIGN.md §2.2 auth/session seam).
// Signed session cookies (HMAC), scrypt password hashing (design specified argon2id;
// adapted to built-in scrypt — reversible, OWASP-approved).
import { randomUUID, randomBytes, scryptSync, timingSafeEqual, createHmac } from 'node:crypto';
import type { DatabaseSync } from 'node:sqlite';
import type { CacheRepository } from '../cache/CacheRepository.ts';
import type { AdapterQueue } from '../queue/AdapterQueue.ts';
import type { XCookieAdapter } from '../adapters/XCookieAdapter.ts';

export const SESSION_COOKIE = 'iflow_session';
export const OAUTH_STATE_COOKIE = 'iflow_oauth_state';
// Fail-fast: refuse to run with the unsafe default secret outside dev.
const isDev = process.env.NODE_ENV === 'development' || process.env.NODE_ENV === undefined;
if (!process.env.IFLOW_SESSION_SECRET && !isDev) {
  throw new Error('IFLOW_SESSION_SECRET is not set and NODE_ENV is not "development". The default dev secret must never be used in production.');
}

const SESSION_SECRET = process.env.IFLOW_SESSION_SECRET ?? 'dev-secret-change-me';
const SESSION_TTL_MS = 30 * 24 * 60 * 60 * 1000; // 30 days

export interface Context {
  db: DatabaseSync;
  cache: CacheRepository;
  queue: AdapterQueue;
  xAdapter: XCookieAdapter | null;
  resHeaders: Headers; // mutable; procedures append Set-Cookie here (applied to Response by the fetch adapter)
  userId: string | null; // resolved from the session cookie; null = unauthenticated
  cookies: Record<string, string>; // parsed request cookies (session + oauth state)
}
export interface CreateContextOpts { req: Request; resHeaders: Headers; info: unknown; }

// ----- signed token (HMAC) -----
function sign(token: string): string { return `${token}.${createHmac('sha256', SESSION_SECRET).update(token).digest('hex')}`; }
function unsign(signed: string): string | null {
  const idx = signed.lastIndexOf('.');
  if (idx <= 0) return null;
  const token = signed.slice(0, idx);
  const mac = signed.slice(idx + 1);
  const expected = createHmac('sha256', SESSION_SECRET).update(token).digest('hex');
  const a = Buffer.from(mac); const b = Buffer.from(expected);
  return a.length === b.length && timingSafeEqual(a, b) ? token : null;
}

export function sessionCookie(sessionId: string): string {
  return `${SESSION_COOKIE}=${sign(sessionId)}; HttpOnly; SameSite=Lax; Path=/; Max-Age=${SESSION_TTL_MS / 1000}`;
}
export function clearCookie(): string { return `${SESSION_COOKIE}=; HttpOnly; SameSite=Lax; Path=/; Max-Age=0`; }

// OAuth CSRF state cookie (short-lived): signs provider:state:redirectUri.
export function oauthStateCookie(provider: string, state: string, redirectUri: string): string {
  return `${OAUTH_STATE_COOKIE}=${sign(`${provider}:${state}:${redirectUri}`)}; HttpOnly; SameSite=Lax; Path=/; Max-Age=600`;
}
export function verifyOAuthState(cookieValue: string | undefined, provider: string, state: string, redirectUri: string): boolean {
  if (!cookieValue) return false;
  const token = unsign(cookieValue);
  return token !== null && token === `${provider}:${state}:${redirectUri}`;
}

export function parseCookies(req: Request): Record<string, string> {
  const header = req.headers.get('cookie') ?? '';
  const out: Record<string, string> = {};
  for (const part of header.split(';')) {
    const eq = part.indexOf('=');
    if (eq < 0) continue;
    const k = part.slice(0, eq).trim(); const v = part.slice(eq + 1).trim();
    if (k) out[k] = v;
  }
  return out;
}

export function createSession(database: DatabaseSync, userId: string): { sessionId: string; cookie: string } {
  const sessionId = randomUUID();
  const now = new Date().toISOString();
  const expires = new Date(Date.now() + SESSION_TTL_MS).toISOString();
  database.prepare('INSERT INTO sessions (id,user_id,expires_at,created_at) VALUES (?,?,?,?)').run(sessionId, userId, expires, now);
  return { sessionId, cookie: sessionCookie(sessionId) };
}

export function resolveSessionUserId(database: DatabaseSync, req: Request): string | null {
  const cookies = parseCookies(req);
  const signed = cookies[SESSION_COOKIE];
  if (!signed) return null;
  const token = unsign(signed);
  if (!token) return null;
  const row = database.prepare('SELECT user_id, expires_at FROM sessions WHERE id=?').get(token) as { user_id: string; expires_at: string } | undefined;
  if (!row) return null;
  if (Date.parse(row.expires_at) < Date.now()) return null;
  return row.user_id;
}

// ----- password hashing (scrypt) -----
export function hashPassword(pw: string): string {
  const salt = randomBytes(16);
  const hash = scryptSync(pw, salt, 64);
  return `scrypt$${salt.toString('hex')}$${hash.toString('hex')}`;
}
export function verifyPassword(pw: string, stored: string): boolean {
  const parts = stored.split('$');
  if (parts.length !== 3 || parts[0] !== 'scrypt') return false;
  const salt = Buffer.from(parts[1], 'hex');
  const hash = Buffer.from(parts[2], 'hex');
  const test = scryptSync(pw, salt, 64);
  return hash.length === test.length && timingSafeEqual(hash, test);
}

// ----- context factory: 1f wires real db+cache; tests inject in-memory -----
export function makeCreateContext(opts: { db: DatabaseSync; cache: CacheRepository; queue: AdapterQueue; xAdapter?: XCookieAdapter | null }) {
  return ({ req, resHeaders }: CreateContextOpts): Context => {
    const cookies = parseCookies(req);
    return {
      db: opts.db,
      cache: opts.cache,
      queue: opts.queue,
      xAdapter: opts.xAdapter ?? null,
      resHeaders,
      cookies,
      userId: resolveSessionUserId(opts.db, req),
    };
  };
}
// Backward-compat helper for tests that build a context from a cookie map.
export function userIdFromCookies(database: DatabaseSync, cookies: Record<string, string>): string | null {
  const signed = cookies[SESSION_COOKIE];
  if (!signed) return null;
  const token = unsign(signed);
  if (!token) return null;
  const row = database.prepare('SELECT user_id, expires_at FROM sessions WHERE id=?').get(token) as { user_id: string; expires_at: string } | undefined;
  if (!row || Date.parse(row.expires_at) < Date.now()) return null;
  return row.user_id;
}