import { SignJWT, jwtVerify } from "jose";
import { config } from "../config.js";

const secret = new TextEncoder().encode(config.JWT_SECRET);
const ISSUER = "stoat-mbot";

export interface SessionClaims {
  sub: string;
  username: string;
  /** "session" for the panel cookie, "link" for one-time links from chat. */
  typ: "session" | "link";
  /** Present on chat links: the server the link was issued for. */
  srv?: string;
}

export async function signSession(userId: string, username: string): Promise<string> {
  return new SignJWT({ username, typ: "session" })
    .setProtectedHeader({ alg: "HS256" })
    .setSubject(userId)
    .setIssuer(ISSUER)
    .setIssuedAt()
    .setExpirationTime(`${config.SESSION_TTL_HOURS}h`)
    .sign(secret);
}

export async function signPanelLink(
  userId: string,
  username: string,
  serverId: string,
): Promise<string> {
  return new SignJWT({ username, typ: "link", srv: serverId })
    .setProtectedHeader({ alg: "HS256" })
    .setSubject(userId)
    .setIssuer(ISSUER)
    .setIssuedAt()
    .setExpirationTime("10m")
    .sign(secret);
}

export async function verifyToken(token: string): Promise<SessionClaims | null> {
  try {
    const { payload } = await jwtVerify(token, secret, { issuer: ISSUER });
    if (!payload.sub || (payload["typ"] !== "session" && payload["typ"] !== "link")) return null;
    return {
      sub: payload.sub,
      username: String(payload["username"] ?? "unknown"),
      typ: payload["typ"] as "session" | "link",
      srv: typeof payload["srv"] === "string" ? payload["srv"] : undefined,
    };
  } catch {
    return null;
  }
}