Idempotency

curl https://api.saasybill.com/v1/subscriptions \
  -H "Authorization: Bearer $SAASYBILL_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: signup_8f3a2c1d" \
  -d '{ "customer_code": "ACME-001", "plan_code": "TEAM-MONTHLY", "units": 10 }'

async function createSubscription(body, idempotencyKey) {
  for (let attempt = 0; attempt < 5; attempt++) {
    try {
      const response = await fetch("https://api.saasybill.com/v1/subscriptions", {
        method: "POST",
        headers: {
          Authorization: `Bearer ${process.env.SAASYBILL_API_KEY}`,
          "Content-Type": "application/json",
          "Idempotency-Key": idempotencyKey,
        },
        body: JSON.stringify(body),
      });

      const retryable = response.status === 429 || response.status >= 500 || response.status === 409;
      if (!retryable) return response;

      // 409 is only worth retrying while the first request is still running.
      if (response.status === 409) {
        const { error } = await response.clone().json();
        if (error.code !== "request_in_progress") return response;
      }

      const wait = Number(response.headers.get("Retry-After")) || 2 ** attempt;
      await new Promise((resolve) => setTimeout(resolve, wait * 1000));
    } catch {
      // A network error or timeout: the request may have gone through. Retry with the same key.
      await new Promise((resolve) => setTimeout(resolve, 2 ** attempt * 1000));
    }
  }
  throw new Error("Saasybill did not respond after 5 attempts");
}