Optimize max peak memory usage and add warnings on mobile for higher models

tests/mobileMemoryGuard.test.ts

@@ -0,0 +1,87 @@
+import { describe, test, expect } from "bun:test";
+import { isLikelyMobile, shouldWarnBeforeLoad } from "../src/lib/mobileMemoryGuard";
+
+// Pure UA/heuristic logic (D-027) — no browser, no navigator.
+
+const ANDROID_UA =
+  "Mozilla/5.0 (Linux; Android 13; Pixel 7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0 Mobile Safari/537.36";
+const IPHONE_UA =
+  "Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Mobile/15E148 Safari/604.1";
+const IPAD_DESKTOP_UA =
+  "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Safari/605.1.15";
+const DESKTOP_MAC_UA =
+  "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0 Safari/537.36";
+const DESKTOP_WINDOWS_UA =
+  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0 Safari/537.36";
+
+describe("isLikelyMobile", () => {
+  test("detects Android and iPhone user agents", () => {
+    expect(isLikelyMobile({ userAgent: ANDROID_UA, maxTouchPoints: 5 })).toBe(true);
+    expect(isLikelyMobile({ userAgent: IPHONE_UA, maxTouchPoints: 5 })).toBe(true);
+  });
+
+  test("detects iPadOS's desktop-Safari UA via touch points", () => {
+    expect(isLikelyMobile({ userAgent: IPAD_DESKTOP_UA, maxTouchPoints: 5 })).toBe(true);
+    // Same UA, no touch support reported — treat as a real desktop Mac.
+    expect(isLikelyMobile({ userAgent: IPAD_DESKTOP_UA, maxTouchPoints: 0 })).toBe(false);
+    expect(isLikelyMobile({ userAgent: IPAD_DESKTOP_UA, maxTouchPoints: undefined })).toBe(
+      false,
+    );
+  });
+
+  test("does not flag real desktop browsers", () => {
+    expect(isLikelyMobile({ userAgent: DESKTOP_MAC_UA, maxTouchPoints: 0 })).toBe(false);
+    expect(isLikelyMobile({ userAgent: DESKTOP_WINDOWS_UA, maxTouchPoints: 0 })).toBe(false);
+  });
+
+  test("undefined userAgent (SSR/tests) is never mobile", () => {
+    expect(isLikelyMobile({ userAgent: undefined, maxTouchPoints: 5 })).toBe(false);
+  });
+});
+
+describe("shouldWarnBeforeLoad", () => {
+  const MEDIUM_PEAK_BYTES = 555_000_000; // ~medium q4's estimated peak
+
+  test("never warns on desktop regardless of size or reported memory", () => {
+    expect(
+      shouldWarnBeforeLoad(
+        { userAgent: DESKTOP_WINDOWS_UA, maxTouchPoints: 0, deviceMemoryGB: 0.5 },
+        MEDIUM_PEAK_BYTES,
+      ),
+    ).toBe(false);
+  });
+
+  test("warns on mobile with low reported deviceMemory", () => {
+    // Safe budget = 1 GB * 0.5 = 500 MB, below the ~555 MB medium peak.
+    expect(
+      shouldWarnBeforeLoad(
+        { userAgent: ANDROID_UA, maxTouchPoints: 5, deviceMemoryGB: 1 },
+        MEDIUM_PEAK_BYTES,
+      ),
+    ).toBe(true);
+  });
+
+  test("does not warn on mobile with ample reported deviceMemory", () => {
+    expect(
+      shouldWarnBeforeLoad(
+        { userAgent: ANDROID_UA, maxTouchPoints: 5, deviceMemoryGB: 8 },
+        MEDIUM_PEAK_BYTES,
+      ),
+    ).toBe(false);
+  });
+
+  test("falls back to a flat threshold when deviceMemory is unreported (iOS)", () => {
+    expect(
+      shouldWarnBeforeLoad(
+        { userAgent: IPHONE_UA, maxTouchPoints: 5, deviceMemoryGB: undefined },
+        MEDIUM_PEAK_BYTES,
+      ),
+    ).toBe(true);
+    expect(
+      shouldWarnBeforeLoad(
+        { userAgent: IPHONE_UA, maxTouchPoints: 5, deviceMemoryGB: undefined },
+        50_000_000, // tiny model — well under the fallback threshold
+      ),
+    ).toBe(false);
+  });
+});