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packages/web/src/routes/api/usage-events.ts

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+import { createFileRoute } from "@tanstack/react-router"
+import { flowglad } from "@/lib/flowglad"
+import { getAuth } from "@/lib/auth"
+import { findUsagePriceByMeterSlug } from "@/lib/billing-helpers"
+
+const json = (data: unknown, status = 200) =>
+  new Response(JSON.stringify(data), {
+    status,
+    headers: { "content-type": "application/json" },
+  })
+
+/**
+ * POST /api/usage-events
+ *
+ * Creates a usage event for the current customer.
+ *
+ * Body: {
+ *   usageMeterSlug: string;  // e.g., 'ai_requests'
+ *   amount: number;          // e.g., 1
+ *   transactionId?: string;  // Optional: for idempotency
+ * }
+ */
+export const Route = createFileRoute("/api/usage-events")({
+  server: {
+    handlers: {
+      POST: async ({ request }) => {
+        try {
+          // Authenticate user
+          const session = await getAuth().api.getSession({
+            headers: request.headers,
+          })
+
+          if (!session?.user) {
+            return json({ error: "Unauthorized" }, 401)
+          }
+
+          const userId = session.user.id
+
+          // Parse and validate request body
+          const body = await request.json().catch(() => ({}))
+
+          const { usageMeterSlug, amount, transactionId } = body as {
+            usageMeterSlug?: string
+            amount?: number
+            transactionId?: string
+          }
+
+          if (!usageMeterSlug || typeof usageMeterSlug !== "string") {
+            return json({ error: "usageMeterSlug is required" }, 400)
+          }
+
+          if (typeof amount !== "number" || amount <= 0 || !Number.isInteger(amount)) {
+            return json({ error: "amount must be a positive integer" }, 400)
+          }
+
+          // Get Flowglad server
+          const flowgladServer = flowglad(userId)
+          if (!flowgladServer) {
+            return json({ error: "Billing not configured" }, 500)
+          }
+
+          // Get billing info
+          const billing = await flowgladServer.getBilling()
+
+          if (!billing.customer) {
+            return json({ error: "Customer not found" }, 404)
+          }
+
+          // Get current subscription
+          const currentSubscription = billing.currentSubscriptions?.[0]
+          if (!currentSubscription) {
+            return json({ error: "No active subscription found" }, 404)
+          }
+
+          // Find usage price for the meter
+          const usagePrice = findUsagePriceByMeterSlug(
+            usageMeterSlug,
+            billing.pricingModel,
+          )
+
+          if (!usagePrice) {
+            return json(
+              {
+                error: `Usage price not found for meter: ${usageMeterSlug}`,
+              },
+              404,
+            )
+          }
+
+          // Generate transaction ID if not provided (for idempotency)
+          const finalTransactionId =
+            transactionId ??
+            `usage_${Date.now()}_${Math.random().toString(36).substring(7)}`
+
+          // Create usage event
+          const usageEvent = await flowgladServer.createUsageEvent({
+            subscriptionId: currentSubscription.id,
+            priceSlug: usagePrice.slug!,
+            amount,
+            transactionId: finalTransactionId,
+          })
+
+          return json({
+            success: true,
+            usageEvent,
+          })
+        } catch (error) {
+          console.error("[usage-events] Error:", error)
+          return json(
+            {
+              error: error instanceof Error ? error.message : "Failed to create usage event",
+            },
+            500,
+          )
+        }
+      },
+    },
+  },
+})