feat: integrate Sensei Spook mascot in 4 stances, speech bubbles, and style updates

lib/rate-limit.ts

@@ -0,0 +1,58 @@
+interface DeviceUsage {
+  count: number;
+  firstUsedAt: number;
+}
+
+// In-memory usage map (or keyed by hashed client token)
+const usageStore = new Map<string, DeviceUsage>();
+
+export interface RateLimitResult {
+  allowed: boolean;
+  remaining: number;
+  resetMinutes: number;
+}
+
+export function checkRateLimit(
+  clientId: string,
+  maxAllowed: number,
+  cooldownMinutes: number
+): RateLimitResult {
+  if (!maxAllowed || maxAllowed <= 0) {
+    return { allowed: true, remaining: 999999, resetMinutes: 0 };
+  }
+
+  const now = Date.now();
+  const cooldownMs = cooldownMinutes * 60 * 1000;
+  const usage = usageStore.get(clientId);
+
+  if (!usage) {
+    return { allowed: true, remaining: maxAllowed, resetMinutes: 0 };
+  }
+
+  // Check if cooldown period has elapsed since first use
+  if (now - usage.firstUsedAt > cooldownMs) {
+    usageStore.delete(clientId);
+    return { allowed: true, remaining: maxAllowed, resetMinutes: 0 };
+  }
+
+  const remaining = Math.max(0, maxAllowed - usage.count);
+  const remainingCooldownMs = cooldownMs - (now - usage.firstUsedAt);
+  const resetMinutes = Math.ceil(remainingCooldownMs / (60 * 1000));
+
+  return {
+    allowed: usage.count < maxAllowed,
+    remaining,
+    resetMinutes,
+  };
+}
+
+export function incrementRateLimit(clientId: string): void {
+  const now = Date.now();
+  const usage = usageStore.get(clientId);
+
+  if (!usage) {
+    usageStore.set(clientId, { count: 1, firstUsedAt: now });
+  } else {
+    usage.count += 1;
+  }
+}