import { randomBytes, createHash } from "node:crypto";

function base64url(input: Buffer): string {
  return input
    .toString("base64")
    .replace(/\+/g, "-")
    .replace(/\//g, "_")
    .replace(/=+$/, "");
}

export function generateCodeVerifier(): string {
  return base64url(randomBytes(48));
}

export function generateCodeChallenge(verifier: string): string {
  return base64url(createHash("sha256").update(verifier).digest());
}

export function generateState(): string {
  return base64url(randomBytes(16));
}

interface PendingAuth {
  platform: string;
  codeVerifier: string;
  redirectUri: string;
  requestedScope?: string;
  expiresAt: number;
}

const PENDING_TTL_MS = 10 * 60 * 1000;
const pendingAuths = new Map<string, PendingAuth>();

export function storePendingAuth(state: string, entry: Omit<PendingAuth, "expiresAt">): void {
  for (const [key, value] of pendingAuths) {
    if (value.expiresAt < Date.now()) pendingAuths.delete(key);
  }
  pendingAuths.set(state, { ...entry, expiresAt: Date.now() + PENDING_TTL_MS });
}

export function consumePendingAuth(state: string): PendingAuth | null {
  const entry = pendingAuths.get(state);
  if (!entry) return null;
  pendingAuths.delete(state);
  if (entry.expiresAt < Date.now()) return null;
  return entry;
}