Add useForesights to @foresightjs/react

packages/devpage-react/src/pages/home/index.tsx

@@ -1,5 +1,5 @@
-import { useState } from "react"
-import { useForesight } from "@foresightjs/react"
+import { useMemo, useState } from "react"
+import { useForesights } from "@foresightjs/react"
 import { useQuery, useQueryClient } from "@tanstack/react-query"
 import { pageQueryOptions, prefetchPage } from "./api"
 import { ForesightImageButton } from "./ForesightImageButton"
@@ -12,39 +12,6 @@ const PAGES = [
   { slug: "pricing", label: "Pricing" },
 ] as const
 
-type ForesightPageButtonProps = {
-  slug: string
-  label: string
-  isActive: boolean
-  onSelect: (slug: string) => void
-}
-
-const ForesightPageButton = ({ slug, label, isActive, onSelect }: ForesightPageButtonProps) => {
-  const queryClient = useQueryClient()
-  const reactivateAfter = useReactivateAfter()
-
-  const { elementRef, isPredicted } = useForesight<HTMLButtonElement>({
-    callback: () => prefetchPage(queryClient, slug),
-    name: slug,
-    hitSlop: 20,
-    reactivateAfter,
-  })
-
-  return (
-    <button
-      ref={elementRef}
-      onClick={() => onSelect(slug)}
-      className={`px-5 py-3 border text-sm font-medium transition-colors cursor-pointer ${
-        isActive
-          ? "border-gray-900 bg-gray-900 text-white"
-          : "border-gray-400 text-gray-800 hover:bg-gray-100"
-      } ${isPredicted ? "outline-1 outline-amber-500" : ""}`}
-    >
-      {label}
-    </button>
-  )
-}
-
 const PageContent = ({ slug }: { slug: string }) => {
   const { data, isLoading, isFetching } = useQuery(pageQueryOptions(slug))
 
@@ -123,25 +90,62 @@ const ImageSection = () => {
   )
 }
 
+const PageButtons = ({
+  activePage,
+  onSelect,
+}: {
+  activePage: string | null
+  onSelect: (slug: string) => void
+}) => {
+  const queryClient = useQueryClient()
+  const reactivateAfter = useReactivateAfter()
+
+  const options = useMemo(
+    () =>
+      PAGES.map(({ slug }) => ({
+        callback: () => prefetchPage(queryClient, slug),
+        name: slug,
+        hitSlop: 20 as const,
+        reactivateAfter,
+      })),
+    [queryClient, reactivateAfter]
+  )
+
+  const results = useForesights<HTMLButtonElement>(options)
+
+  return (
+    <nav className="flex gap-3">
+      {PAGES.map(({ slug, label }, i) => {
+        const { elementRef, isPredicted } = results[i]
+        const isActive = activePage === slug
+
+        return (
+          <button
+            key={slug}
+            ref={elementRef}
+            onClick={() => onSelect(slug)}
+            className={`px-5 py-3 border text-sm font-medium transition-colors cursor-pointer ${
+              isActive
+                ? "border-gray-900 bg-gray-900 text-white"
+                : "border-gray-400 text-gray-800 hover:bg-gray-100"
+            } ${isPredicted ? "outline-1 outline-amber-500" : ""}`}
+          >
+            {label}
+          </button>
+        )
+      })}
+    </nav>
+  )
+}
+
 const Home = () => {
   const [activePage, setActivePage] = useState<string | null>(null)
 
   return (
     <main className="max-w-4xl mx-auto px-6 py-8 space-y-8">
       <section className="space-y-4">
         <h1 className="text-xl font-semibold">Data prefetching</h1>
-        <nav className="flex gap-3">
-          {PAGES.map(({ slug, label }) => (
-            <ForesightPageButton
-              key={slug}
-              slug={slug}
-              label={label}
-              isActive={activePage === slug}
-              onSelect={setActivePage}
-            />
-          ))}
-        </nav>
-
+        <PageButtons activePage={activePage} onSelect={setActivePage} />
         {activePage && <PageContent slug={activePage} />}
       </section>
 

packages/foresightjs-react/src/hooks/useForesights.test.tsx

@@ -0,0 +1,185 @@
+import { act, render } from "@testing-library/react"
+import { beforeEach, describe, expect, it, vi } from "vitest"
+import {
+  createUnregisteredSnapshot,
+  type ForesightRegisterOptionsWithoutElement,
+} from "js.foresight"
+import { mockState, registerSpy, unregisterSpy } from "../tests/setup"
+import { useForesights } from "./useForesights"
+
+beforeEach(() => {
+  registerSpy.mockClear()
+  unregisterSpy.mockClear()
+  mockState.listeners = []
+  mockState.lastCallbackWrapper = null
+  mockState.currentSnapshot = createUnregisteredSnapshot(false)
+})
+
+type ProbeProps = {
+  optionsArray: ForesightRegisterOptionsWithoutElement[]
+}
+
+const MultiProbe = ({ optionsArray }: ProbeProps) => {
+  const results = useForesights<HTMLButtonElement>(optionsArray)
+
+  return (
+    <div>
+      {results.map((r, i) => (
+        <button
+          key={i}
+          data-testid={`el-${i}`}
+          data-predicted={r.isPredicted}
+          data-registered={r.isRegistered}
+          ref={r.elementRef}
+        />
+      ))}
+    </div>
+  )
+}
+
+describe("useForesights", () => {
+  it("registers all elements when refs attach", () => {
+    render(
+      <MultiProbe
+        optionsArray={[
+          { name: "a", callback: vi.fn() },
+          { name: "b", callback: vi.fn() },
+        ]}
+      />
+    )
+    expect(registerSpy).toHaveBeenCalledTimes(2)
+    expect(registerSpy.mock.calls[0][0].name).toBe("a")
+    expect(registerSpy.mock.calls[0][0].element).toBeInstanceOf(HTMLButtonElement)
+    expect(registerSpy.mock.calls[1][0].name).toBe("b")
+    expect(registerSpy.mock.calls[1][0].element).toBeInstanceOf(HTMLButtonElement)
+  })
+
+  it("unregisters all on unmount", () => {
+    const { unmount } = render(
+      <MultiProbe
+        optionsArray={[
+          { name: "a", callback: vi.fn() },
+          { name: "b", callback: vi.fn() },
+        ]}
+      />
+    )
+    unmount()
+    expect(unregisterSpy).toHaveBeenCalledTimes(2)
+  })
+
+  it("returns unregistered initial snapshot before nodes attach", () => {
+    const NoRefProbe = () => {
+      const results = useForesights([{ callback: vi.fn() }])
+
+      return <span data-testid="state" data-registered={results[0].isRegistered} />
+    }
+    const { getByTestId } = render(<NoRefProbe />)
+    expect(getByTestId("state").getAttribute("data-registered")).toBe("false")
+  })
+
+  it("reflects state updates pushed through subscribe", () => {
+    const { getByTestId } = render(
+      <MultiProbe
+        optionsArray={[
+          { name: "a", callback: vi.fn() },
+          { name: "b", callback: vi.fn() },
+        ]}
+      />
+    )
+
+    expect(getByTestId("el-0").getAttribute("data-predicted")).toBe("false")
+
+    act(() => {
+      mockState.currentSnapshot = { ...createUnregisteredSnapshot(false), isPredicted: true }
+      mockState.listeners.forEach(l => l())
+    })
+
+    expect(getByTestId("el-0").getAttribute("data-predicted")).toBe("true")
+  })
+
+  it("forwards the latest callback (no stale closure)", () => {
+    const cb1 = vi.fn()
+    const cb2 = vi.fn()
+    const { rerender } = render(<MultiProbe optionsArray={[{ name: "a", callback: cb1 }]} />)
+    rerender(<MultiProbe optionsArray={[{ name: "a", callback: cb2 }]} />)
+
+    const fired = { ...createUnregisteredSnapshot(false), isPredicted: true }
+    act(() => {
+      mockState.lastCallbackWrapper?.(fired)
+    })
+
+    expect(cb1).not.toHaveBeenCalled()
+    expect(cb2).toHaveBeenCalledWith(fired)
+  })
+
+  it("handles growing the array (new items added)", () => {
+    const { rerender } = render(<MultiProbe optionsArray={[{ name: "a", callback: vi.fn() }]} />)
+    expect(registerSpy).toHaveBeenCalledTimes(1)
+
+    registerSpy.mockClear()
+    rerender(
+      <MultiProbe
+        optionsArray={[
+          { name: "a", callback: vi.fn() },
+          { name: "b", callback: vi.fn() },
+        ]}
+      />
+    )
+
+    // Should register the new element (and possibly re-register existing)
+    const names = registerSpy.mock.calls.map(c => c[0].name)
+    expect(names).toContain("b")
+  })
+
+  it("handles shrinking the array (items removed)", () => {
+    const { rerender } = render(
+      <MultiProbe
+        optionsArray={[
+          { name: "a", callback: vi.fn() },
+          { name: "b", callback: vi.fn() },
+        ]}
+      />
+    )
+    unregisterSpy.mockClear()
+
+    rerender(<MultiProbe optionsArray={[{ name: "a", callback: vi.fn() }]} />)
+
+    // The removed element should be unregistered
+    expect(unregisterSpy).toHaveBeenCalled()
+  })
+
+  it("patches options without unregistering", () => {
+    const { rerender } = render(<MultiProbe optionsArray={[{ name: "a", callback: vi.fn() }]} />)
+    registerSpy.mockClear()
+    unregisterSpy.mockClear()
+
+    rerender(<MultiProbe optionsArray={[{ name: "b", callback: vi.fn() }]} />)
+
+    expect(registerSpy).toHaveBeenCalled()
+    const lastCall = registerSpy.mock.calls[registerSpy.mock.calls.length - 1]
+    expect(lastCall?.[0].name).toBe("b")
+    expect(unregisterSpy).not.toHaveBeenCalled()
+  })
+
+  it("works with an empty array", () => {
+    const { container } = render(<MultiProbe optionsArray={[]} />)
+    expect(registerSpy).not.toHaveBeenCalled()
+    expect(container.querySelectorAll("button")).toHaveLength(0)
+  })
+
+  it("registers three elements", () => {
+    render(
+      <MultiProbe
+        optionsArray={[
+          { name: "x", callback: vi.fn() },
+          { name: "y", callback: vi.fn() },
+          { name: "z", callback: vi.fn() },
+        ]}
+      />
+    )
+    expect(registerSpy).toHaveBeenCalledTimes(3)
+    expect(registerSpy.mock.calls[0][0].name).toBe("x")
+    expect(registerSpy.mock.calls[1][0].name).toBe("y")
+    expect(registerSpy.mock.calls[2][0].name).toBe("z")
+  })
+})