import 'server-only';
import { sql } from '@/lib/db';
import { db } from '@/lib/db';

/**
 * Fixed-window counter stored in Postgres so limits hold across PM2 instances.
 * Returns whether the call is allowed and the seconds until the window resets.
 */
export async function rateLimit(key: string, limit: number, windowSeconds: number): Promise<{ ok: boolean; remaining: number; retryAfterSeconds: number }> {
  const now = new Date();
  const resetAt = new Date(now.getTime() + windowSeconds * 1000);
  const nowIso = now.toISOString();
  const resetIso = resetAt.toISOString();
  const rows = (await db().execute(sql`
    insert into rate_limits (key, count, reset_at) values (${key}, 1, ${resetIso}::timestamptz)
    on conflict (key) do update set
      count = case when rate_limits.reset_at <= ${nowIso}::timestamptz then 1 else rate_limits.count + 1 end,
      reset_at = case when rate_limits.reset_at <= ${nowIso}::timestamptz then ${resetIso}::timestamptz else rate_limits.reset_at end
    returning count, reset_at
  `)) as unknown as Array<{ count: number; reset_at: Date | string }>;
  const row = rows[0]!;
  const count = Number(row.count);
  const reset = new Date(row.reset_at);
  return { ok: count <= limit, remaining: Math.max(0, limit - count), retryAfterSeconds: Math.max(1, Math.ceil((reset.getTime() - now.getTime()) / 1000)) };
}

export class RateLimited extends Error {
  constructor(public retryAfterSeconds: number) {
    super(`Too many attempts. Try again in ${retryAfterSeconds}s.`);
  }
}

export async function enforce(key: string, limit: number, windowSeconds: number): Promise<void> {
  const r = await rateLimit(key, limit, windowSeconds);
  if (!r.ok) throw new RateLimited(r.retryAfterSeconds);
}