import crypto from "node:crypto";
import { promisify } from "node:util";
import type { NextFunction, Request, Response } from "express";
import { query } from "./db.js";

const scrypt = promisify(crypto.scrypt);
const sessionCookieName = "tickettracker_session";
const sessionMaxAgeMs = Number(process.env.SESSION_MAX_AGE_MS ?? 1000 * 60 * 60 * 24 * 14);

export type UserRole = "admin" | "user";

export type AuthUser = {
  id: string;
  username: string;
  display_name: string;
  role: UserRole;
  active: boolean;
};

declare global {
  namespace Express {
    interface Request {
      user?: AuthUser;
      authSessionHash?: string;
    }
  }
}

export async function hashPassword(password: string) {
  const salt = crypto.randomBytes(16).toString("base64url");
  const key = (await scrypt(password, salt, 64)) as Buffer;
  return `scrypt$${salt}$${key.toString("base64url")}`;
}

export async function verifyPassword(password: string, storedHash: string) {
  const [algorithm, salt, expected] = storedHash.split("$");

  if (algorithm !== "scrypt" || !salt || !expected) {
    return false;
  }

  const expectedBuffer = Buffer.from(expected, "base64url");
  const actualBuffer = (await scrypt(password, salt, expectedBuffer.length)) as Buffer;

  return expectedBuffer.length === actualBuffer.length && crypto.timingSafeEqual(expectedBuffer, actualBuffer);
}

export function hashToken(token: string) {
  return crypto.createHash("sha256").update(token).digest("hex");
}

function readCookie(req: Request, name: string) {
  const rawCookie = req.headers.cookie;

  if (!rawCookie) {
    return null;
  }

  const cookies = rawCookie.split(";").map((part) => part.trim());
  const prefix = `${name}=`;
  const match = cookies.find((cookie) => cookie.startsWith(prefix));

  if (!match) {
    return null;
  }

  return decodeURIComponent(match.slice(prefix.length));
}

function publicUser(user: AuthUser) {
  return {
    id: user.id,
    username: user.username,
    display_name: user.display_name,
    role: user.role,
    active: user.active
  };
}

export async function createAuthSession(res: Response, userId: string) {
  const token = crypto.randomBytes(32).toString("base64url");
  const tokenHash = hashToken(token);
  const expiresAt = new Date(Date.now() + sessionMaxAgeMs);

  await query(
    `
      INSERT INTO auth_sessions (token_hash, user_id, expires_at)
      VALUES ($1, $2, $3);
    `,
    [tokenHash, userId, expiresAt.toISOString()]
  );

  res.cookie(sessionCookieName, token, {
    httpOnly: true,
    sameSite: "lax",
    secure: process.env.COOKIE_SECURE === "true",
    maxAge: sessionMaxAgeMs,
    path: "/"
  });
}

export async function clearAuthSession(req: Request, res: Response) {
  if (req.authSessionHash) {
    await query("DELETE FROM auth_sessions WHERE token_hash = $1;", [req.authSessionHash]);
  }

  res.clearCookie(sessionCookieName, {
    sameSite: "lax",
    secure: process.env.COOKIE_SECURE === "true",
    path: "/"
  });
}

export async function requireAuth(req: Request, res: Response, next: NextFunction) {
  try {
    const token = readCookie(req, sessionCookieName);

    if (!token) {
      res.status(401).json({ error: "Nicht angemeldet" });
      return;
    }

    const tokenHash = hashToken(token);
    const result = await query<AuthUser>(
      `
        SELECT u.id, u.username, u.display_name, u.role, u.active
        FROM auth_sessions s
        JOIN users u ON u.id = s.user_id
        WHERE s.token_hash = $1
          AND s.expires_at > now()
          AND u.active = true;
      `,
      [tokenHash]
    );

    if (result.rows.length === 0) {
      res.status(401).json({ error: "Sitzung ist abgelaufen" });
      return;
    }

    req.user = publicUser(result.rows[0]);
    req.authSessionHash = tokenHash;
    next();
  } catch (error) {
    next(error);
  }
}

export function requireAdmin(req: Request, res: Response, next: NextFunction) {
  if (req.user?.role !== "admin") {
    res.status(403).json({ error: "Adminrechte erforderlich" });
    return;
  }

  next();
}

export function requireUser(req: Request, res: Response, next: NextFunction) {
  if (req.user?.role !== "user") {
    res.status(403).json({ error: "Dieser Bereich ist nur für Benutzerkonten vorgesehen" });
    return;
  }

  next();
}

export function currentUser(req: Request) {
  if (!req.user) {
    throw Object.assign(new Error("Nicht angemeldet"), { status: 401 });
  }

  return req.user;
}