import type { NextRequest } from "next/server";
import { NextResponse } from "next/server";

const SESSION_COOKIE = "inven_session";

function getAuthSecret() {
  return process.env.AUTH_SECRET || "dev-insecure-auth-secret";
}

async function sign(value: string) {
  const key = await crypto.subtle.importKey(
    "raw",
    new TextEncoder().encode(getAuthSecret()),
    { name: "HMAC", hash: "SHA-256" },
    false,
    ["sign"]
  );

  const signature = await crypto.subtle.sign("HMAC", key, new TextEncoder().encode(value));
  return Array.from(new Uint8Array(signature))
    .map((byte) => byte.toString(16).padStart(2, "0"))
    .join("");
}

function decodeBase64Url(value: string) {
  const normalized = value.replace(/-/g, "+").replace(/_/g, "/");
  const padded = normalized.padEnd(Math.ceil(normalized.length / 4) * 4, "=");
  return atob(padded);
}

async function hasValidSession(request: NextRequest) {
  const raw = request.cookies.get(SESSION_COOKIE)?.value;
  if (!raw) {
    return false;
  }

  const [base, signature] = raw.split(".");
  if (!base || !signature || (await sign(base)) !== signature) {
    return false;
  }

  try {
    const payload = JSON.parse(decodeBase64Url(base)) as { expiresAt?: number };
    return typeof payload.expiresAt === "number" && payload.expiresAt > Date.now();
  } catch {
    return false;
  }
}

export async function proxy(request: NextRequest) {
  const { pathname } = request.nextUrl;
  const isPublic =
    pathname === "/login" ||
    pathname.startsWith("/_next") ||
    pathname.startsWith("/favicon") ||
    pathname === "/api/health";

  const authenticated = await hasValidSession(request);

  if (!authenticated && !isPublic) {
    const url = request.nextUrl.clone();
    url.pathname = "/login";
    return NextResponse.redirect(url);
  }

  if (authenticated && pathname === "/login") {
    const url = request.nextUrl.clone();
    url.pathname = "/";
    return NextResponse.redirect(url);
  }

  return NextResponse.next();
}

export const config = {
  matcher: ["/((?!.*\\..*).*)"]
};