import db from "../../db.server";

/**
 * Minimal shape of the Prisma client surface we use — declared inline so
 * the helper can be unit-tested with a tiny stub instead of pulling in a
 * real database.
 */
export interface DedupeDeps {
  db: {
    processedWebhook: {
      create: (args: {
        data: { webhookId: string; topic: string; shopDomain: string };
      }) => Promise<unknown>;
    };
  };
}

/**
 * Returns `true` when this Shopify webhook delivery has already been
 * processed and the caller should short-circuit without doing the work.
 *
 * Shopify retries webhook deliveries when it doesn't receive a 200 within
 * its (~5s) timeout window. Without dedupe this caused us to email an
 * invoice twice for the same order: the first slow delivery completed its
 * work but Shopify timed out and re-sent the webhook, which then ran the
 * automation a second time.
 *
 * We key on the `X-Shopify-Webhook-Id` header — Shopify guarantees the same
 * value for retries of the same delivery, but a new value for genuinely
 * new events. The insert is the lock: a unique-constraint violation
 * (Prisma error code `P2002`) means another delivery already claimed this
 * id.
 */
export async function isDuplicateWebhook(
  request: Request,
  shop: string,
  topic: string,
  deps: DedupeDeps = { db },
): Promise<boolean> {
  const webhookId = request.headers.get("x-shopify-webhook-id");
  if (!webhookId) {
    // Defensive: in unit tests / non-Shopify callers there is no id.
    // Don't dedupe — that would silently drop legitimate calls.
    return false;
  }
  try {
    await deps.db.processedWebhook.create({
      data: { webhookId, topic, shopDomain: shop },
    });
    return false;
  } catch (err) {
    // Duck-typed P2002 check so callers can stub the db without pulling
    // in the real `Prisma` namespace.
    if ((err as { code?: string } | null)?.code === "P2002") {
      console.log(
        `dedupe: skipping duplicate ${topic} delivery for ${shop} (webhookId=${webhookId})`,
      );
      return true;
    }
    // Don't fail the webhook on a logging-table issue; just process it.
    console.warn(
      `dedupe: failed to record webhook ${webhookId} (${topic}/${shop}):`,
      err,
    );
    return false;
  }
}