Initial Commit

packages/api-stack/api/api-sse-bun/src/limits/tenant-cap.ts

@@ -0,0 +1,62 @@
+import type { TenantId } from "@suaveplan/api-types/tenant";
+import { SSE_BUN_CODES, SseBunError } from "../error-codes/error-codes.js";
+
+/**
+ * Per-tenant connection counter the engine consults on every handshake.
+ *
+ * Implementations expose `tryAcquire(tenantId)` (returns `true` and
+ * increments on success, throws {@link SSE_BUN_CODES.TENANT_CAP_EXCEEDED}
+ * on cap breach) plus `release(tenantId)` called on graceful close.
+ */
+export interface TenantConnectionCap {
+    tryAcquire(tenantId: TenantId): true;
+    release(tenantId: TenantId): void;
+    count(tenantId: TenantId): number;
+    readonly total: number;
+}
+
+/**
+ * Build a tenant cap with the given per-tenant ceiling.
+ */
+export function createTenantConnectionCap(
+    maxConnectionsPerTenant: number
+): TenantConnectionCap {
+    const counts = new Map<TenantId, number>();
+    let total = 0;
+    return {
+        tryAcquire(tenantId): true {
+            const current = counts.get(tenantId) ?? 0;
+            if (current >= maxConnectionsPerTenant) {
+                throw new SseBunError(
+                    SSE_BUN_CODES.TENANT_CAP_EXCEEDED,
+                    "error.sse_bun.tenant_cap_exceeded",
+                    {
+                        context: {
+                            tenantId,
+                            limit: maxConnectionsPerTenant,
+                            current,
+                        },
+                    }
+                );
+            }
+            counts.set(tenantId, current + 1);
+            total += 1;
+            return true;
+        },
+        release(tenantId): void {
+            const current = counts.get(tenantId) ?? 0;
+            if (current <= 1) {
+                counts.delete(tenantId);
+            } else {
+                counts.set(tenantId, current - 1);
+            }
+            total = Math.max(0, total - 1);
+        },
+        count(tenantId): number {
+            return counts.get(tenantId) ?? 0;
+        },
+        get total() {
+            return total;
+        },
+    };
+}