Authenticating with the 4invoices API

bash
curl -sS -X POST https://api.4invoices.net/v1/auth/token \
  -H 'Content-Type: application/json' \
  -d '{
    "grant_type": "client_credentials",
    "client_id": "cli_XXXXXXXXXXXX",
    "client_secret": "sec_XXXXXXXXXXXXXXXXXXXX"
  }'

# → {"access_token":"eyJ...","token_type":"Bearer","expires_in":3600,
#    "scope":"invoices:read invoices:write efactura:submit"}

bash
curl -sS https://api.4invoices.net/v1/me \
  -H "Authorization: Bearer $ACCESS_TOKEN"

# → tenant, granted scopes and the current rate-limit buckets

javascript
// Cache the token; do not mint one per request.
let cached = { token: "", expiresAt: 0 };

async function getToken() {
  if (cached.token && Date.now() < cached.expiresAt - 60_000) return cached.token;

  const res = await fetch("https://api.4invoices.net/v1/auth/token", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({
      grant_type: "client_credentials",
      client_id: process.env.FOURINVOICES_CLIENT_ID,
      client_secret: process.env.FOURINVOICES_CLIENT_SECRET,
    }),
  });
  if (!res.ok) throw new Error(`token ${res.status}`);

  const data = await res.json();
  cached = { token: data.access_token, expiresAt: Date.now() + data.expires_in * 1000 };
  return cached.token;
}