import { NextRequest } from 'next/server';
import { db } from '@/lib/db';
import { createHmac, randomBytes } from 'crypto';

// ============================================================
// JWT-like Token Management (Simple HMAC-based)
// ============================================================

const JWT_SECRET = process.env.JWT_SECRET || 'socialconnect-secret-key-2024';
const TOKEN_EXPIRY = 24 * 60 * 60 * 1000; // 24 hours
const REFRESH_TOKEN_EXPIRY = 7 * 24 * 60 * 60 * 1000; // 7 days

interface TokenPayload {
  userId: string;
  email: string;
  role: string;
  exp: number;
  type: 'access' | 'refresh';
}

function base64UrlEncode(data: string): string {
  return Buffer.from(data).toString('base64url');
}

function base64UrlDecode(data: string): string {
  return Buffer.from(data, 'base64url').toString();
}

export function generateToken(payload: Omit<TokenPayload, 'exp' | 'type'>, type: 'access' | 'refresh' = 'access'): string {
  const exp = Date.now() + (type === 'refresh' ? REFRESH_TOKEN_EXPIRY : TOKEN_EXPIRY);
  const fullPayload: TokenPayload = { ...payload, exp, type };
  const header = base64UrlEncode(JSON.stringify({ alg: 'HS256', typ: 'JWT' }));
  const payloadStr = base64UrlEncode(JSON.stringify(fullPayload));
  const signature = createHmac('sha256', JWT_SECRET).update(`${header}.${payloadStr}`).digest('base64url');
  return `${header}.${payloadStr}.${signature}`;
}

export function verifyToken(token: string): TokenPayload | null {
  try {
    const parts = token.split('.');
    if (parts.length !== 3) return null;

    const [header, payload, signature] = parts;
    const expectedSignature = createHmac('sha256', JWT_SECRET).update(`${header}.${payload}`).digest('base64url');

    if (signature !== expectedSignature) return null;

    const decoded = JSON.parse(base64UrlDecode(payload)) as TokenPayload;

    if (decoded.exp < Date.now()) return null;

    return decoded;
  } catch {
    return null;
  }
}

// ============================================================
// Password Hashing
// ============================================================

export function hashPassword(password: string): string {
  const salt = randomBytes(16).toString('hex');
  const hash = createHmac('sha256', salt).update(password).digest('hex');
  return `${salt}:${hash}`;
}

export function verifyPassword(password: string, stored: string): boolean {
  const [salt, hash] = stored.split(':');
  const verifyHash = createHmac('sha256', salt).update(password).digest('hex');
  return hash === verifyHash;
}

// ============================================================
// Auth Middleware Helper
// ============================================================

export interface AuthUser {
  userId: string;
  email: string;
  role: string;
}

export async function getAuthUser(request: NextRequest): Promise<AuthUser | null> {
  const authHeader = request.headers.get('authorization');
  if (!authHeader?.startsWith('Bearer ')) return null;

  const token = authHeader.substring(7);
  const payload = verifyToken(token);
  if (!payload) return null;

  // Verify user still exists and is active
  const user = await db.user.findUnique({ where: { id: payload.userId } });
  if (!user || !user.isActive) return null;

  return { userId: user.id, email: user.email, role: user.role };
}

export function requireRole(user: AuthUser | null, roles: string[]): AuthUser {
  if (!user) throw new Error('Authentication required');
  if (!roles.includes(user.role)) throw new Error('Insufficient permissions');
  return user;
}