more targeted refresh

src/lib/timeline-refresh.test.ts

@@ -0,0 +1,24 @@
+import { describe, expect, it, vi } from 'vitest'
+import { TimelineRefreshController } from './timeline-refresh'
+
+describe('TimelineRefreshController', () => {
+  it('refreshes only the currently registered route target', () => {
+    const controller = new TimelineRefreshController()
+    const first = vi.fn()
+    const second = vi.fn()
+    const unregisterFirst = controller.register(first)
+    const unregisterSecond = controller.register(second)
+
+    expect(controller.refresh()).toBe(true)
+    expect(first).not.toHaveBeenCalled()
+    expect(second).toHaveBeenCalledOnce()
+
+    // A stale route cleanup cannot remove the current route's target.
+    unregisterFirst()
+    expect(controller.refresh()).toBe(true)
+    expect(second).toHaveBeenCalledTimes(2)
+
+    unregisterSecond()
+    expect(controller.refresh()).toBe(false)
+  })
+})

src/lib/timeline-refresh.ts

@@ -0,0 +1,40 @@
+/**
+ * The active route's primary timeline refresh.
+ *
+ * App owns one controller and routes register while mounted. The guarded
+ * cleanup matters during navigation: an old route must not clear a newer
+ * route's callback if Svelte mounts the replacement before destroying it.
+ */
+import { getContext, setContext } from 'svelte'
+
+export type TimelineRefresh = () => void
+
+export class TimelineRefreshController {
+  private current: TimelineRefresh | null = null
+
+  register(refresh: TimelineRefresh): () => void {
+    this.current = refresh
+    return () => {
+      if (this.current === refresh) this.current = null
+    }
+  }
+
+  refresh(): boolean {
+    if (!this.current) return false
+    this.current()
+    return true
+  }
+}
+
+export const TIMELINE_REFRESH = Symbol('plspace.timeline-refresh')
+
+export function provideTimelineRefresh(): TimelineRefreshController {
+  const controller = new TimelineRefreshController()
+  setContext(TIMELINE_REFRESH, controller)
+  return controller
+}
+
+/** Routes remain independently renderable in tests without this context. */
+export function useTimelineRefresh(): TimelineRefreshController | null {
+  return getContext<TimelineRefreshController | undefined>(TIMELINE_REFRESH) ?? null
+}