chore: refactoring and tests, splitting up files (#12495)

packages/app/src/pages/session/message-gesture.test.ts

@@ -0,0 +1,62 @@
+import { describe, expect, test } from "bun:test"
+import { normalizeWheelDelta, shouldMarkBoundaryGesture } from "./message-gesture"
+
+describe("normalizeWheelDelta", () => {
+  test("converts line mode to px", () => {
+    expect(normalizeWheelDelta({ deltaY: 3, deltaMode: 1, rootHeight: 500 })).toBe(120)
+  })
+
+  test("converts page mode to container height", () => {
+    expect(normalizeWheelDelta({ deltaY: -1, deltaMode: 2, rootHeight: 600 })).toBe(-600)
+  })
+
+  test("keeps pixel mode unchanged", () => {
+    expect(normalizeWheelDelta({ deltaY: 16, deltaMode: 0, rootHeight: 600 })).toBe(16)
+  })
+})
+
+describe("shouldMarkBoundaryGesture", () => {
+  test("marks when nested scroller cannot scroll", () => {
+    expect(
+      shouldMarkBoundaryGesture({
+        delta: 20,
+        scrollTop: 0,
+        scrollHeight: 300,
+        clientHeight: 300,
+      }),
+    ).toBe(true)
+  })
+
+  test("marks when scrolling beyond top boundary", () => {
+    expect(
+      shouldMarkBoundaryGesture({
+        delta: -40,
+        scrollTop: 10,
+        scrollHeight: 1000,
+        clientHeight: 400,
+      }),
+    ).toBe(true)
+  })
+
+  test("marks when scrolling beyond bottom boundary", () => {
+    expect(
+      shouldMarkBoundaryGesture({
+        delta: 50,
+        scrollTop: 580,
+        scrollHeight: 1000,
+        clientHeight: 400,
+      }),
+    ).toBe(true)
+  })
+
+  test("does not mark when nested scroller can consume movement", () => {
+    expect(
+      shouldMarkBoundaryGesture({
+        delta: 20,
+        scrollTop: 200,
+        scrollHeight: 1000,
+        clientHeight: 400,
+      }),
+    ).toBe(false)
+  })
+})