import { Router } from "express";
import crypto from "crypto";
import fs from "fs";
import path from "path";

const router = Router();

const LICENSE_FILE = path.join(process.cwd(), "license.json");
const SECRET = process.env.LICENSE_SECRET || "";

function validateKey(key: string): { valid: boolean; expiry?: string; error?: string } {
  // Format: DENTAL-{24-char-signature}-{YYYY-MM-DD}
  const parts = key.trim().split("-");
  if (parts.length !== 5 || parts[0] !== "DENTAL") {
    return { valid: false, error: "Invalid license key format" };
  }

  const signature = parts[1];
  const expiryStr = `${parts[2]}-${parts[3]}-${parts[4]}`;

  // Verify signature
  const payload = `DENTAL:${expiryStr}`;
  const expectedSig = crypto
    .createHmac("sha256", SECRET)
    .update(payload)
    .digest("hex")
    .substring(0, 24)
    .toUpperCase();

  if (signature !== expectedSig) {
    return { valid: false, error: "Invalid license key" };
  }

  // Check expiry
  const expiry = new Date(expiryStr);
  if (isNaN(expiry.getTime())) {
    return { valid: false, error: "Invalid expiry date in key" };
  }

  if (new Date() > expiry) {
    return { valid: false, expiry: expiryStr, error: "License key has expired" };
  }

  return { valid: true, expiry: expiryStr };
}

function loadLicense(): { key: string; expiry: string } | null {
  try {
    if (!fs.existsSync(LICENSE_FILE)) return null;
    return JSON.parse(fs.readFileSync(LICENSE_FILE, "utf8"));
  } catch {
    return null;
  }
}

function saveLicense(key: string, expiry: string) {
  fs.writeFileSync(LICENSE_FILE, JSON.stringify({ key, expiry }, null, 2));
}

// GET /api/license/status
router.get("/status", (req, res) => {
  const stored = loadLicense();
  if (!stored) {
    return res.json({ activated: false, expired: false, expiry: null, daysLeft: null });
  }

  const result = validateKey(stored.key);
  if (!result.valid && result.expiry) {
    return res.json({ activated: true, expired: true, expiry: stored.expiry, daysLeft: 0 });
  }
  if (!result.valid) {
    return res.json({ activated: false, expired: false, expiry: null, daysLeft: null });
  }

  const expiry = new Date(stored.expiry);
  const daysLeft = Math.ceil((expiry.getTime() - Date.now()) / (1000 * 60 * 60 * 24));

  return res.json({ activated: true, expired: false, expiry: stored.expiry, daysLeft });
});

// POST /api/license/activate
router.post("/activate", (req, res) => {
  const { key } = req.body;
  if (!key) {
    return res.status(400).json({ error: "License key is required" });
  }

  const result = validateKey(key);
  if (!result.valid) {
    return res.status(400).json({ error: result.error });
  }

  saveLicense(key.trim(), result.expiry!);
  return res.json({ success: true, expiry: result.expiry });
});

export default router;