From 690c84236bf8b8b2a7be83bf25814bdd15029dd3 Mon Sep 17 00:00:00 2001
From: Robby6Strings <rausten93@gmail.com>
Date: Thu, 26 Sep 2024 04:58:08 +1200
Subject: [PATCH] lib - initial implementation of "lazy" components

---
 packages/lib/src/dom.ts                 |  2 +-
 packages/lib/src/index.ts               |  1 +
 packages/lib/src/lazy.ts                | 35 +++++++++++++++++++++++++
 sandbox/csr/src/App.tsx                 |  9 ++++---
 sandbox/csr/src/components/Counter.tsx  |  4 ++-
 sandbox/csr/src/components/LazyDemo.tsx | 26 ++++++++++++++++++
 6 files changed, 72 insertions(+), 5 deletions(-)
 create mode 100644 packages/lib/src/lazy.ts
 create mode 100644 sandbox/csr/src/components/LazyDemo.tsx

diff --git a/packages/lib/src/dom.ts b/packages/lib/src/dom.ts
index fdb10262..098a32bc 100644
--- a/packages/lib/src/dom.ts
+++ b/packages/lib/src/dom.ts
@@ -337,7 +337,7 @@ function placeDom(
       const n = stack.pop()!
       const _isPortal = isPortal(n)
       if (n.dom === dom) break // once we meet the dom we're placing, stop
-      if (!_isPortal && n.dom) prevDom = n.dom
+      if (!_isPortal && n.dom?.isConnected) prevDom = n.dom
       if (n.sibling) stack.push(n.sibling)
       if (!_isPortal && !n.dom && n.child) stack.push(n.child)
     }
diff --git a/packages/lib/src/index.ts b/packages/lib/src/index.ts
index 501b7417..643b0349 100644
--- a/packages/lib/src/index.ts
+++ b/packages/lib/src/index.ts
@@ -8,6 +8,7 @@ export * from "./context.js"
 export * from "./cloneVNode.js"
 export * from "./element.js"
 export * from "./hooks/index.js"
+export * from "./lazy.js"
 export * from "./memo.js"
 export * from "./portal.js"
 export * from "./renderToString.js"
diff --git a/packages/lib/src/lazy.ts b/packages/lib/src/lazy.ts
new file mode 100644
index 00000000..ce1e5e74
--- /dev/null
+++ b/packages/lib/src/lazy.ts
@@ -0,0 +1,35 @@
+import { createElement } from "./element.js"
+import { useRequestUpdate } from "./hooks/utils.js"
+
+const lazyCache = new WeakMap<() => Promise<Kaioken.FC>, Kaioken.FC | null>()
+
+type LazyComponentProps<T extends Kaioken.FC> = Kaioken.InferProps<T> & {
+  fallback?: JSX.Element
+}
+
+export function lazy<T extends Kaioken.FC>(
+  componentPromise: () => Promise<T>
+): Kaioken.FC<LazyComponentProps<T>> {
+  function LazyComponent(props: LazyComponentProps<T>) {
+    const { fallback = null, ...rest } = props
+    const requestUpdate = useRequestUpdate()
+    if (!lazyCache.has(componentPromise)) {
+      lazyCache.set(componentPromise, null)
+      componentPromise().then((component) => {
+        lazyCache.set(componentPromise, component)
+        requestUpdate()
+      })
+      return fallback
+    }
+
+    const component: Kaioken.FC<LazyComponentProps<T>> | null =
+      lazyCache.get(componentPromise)!
+    if (component === null) {
+      componentPromise().then(requestUpdate)
+      return fallback
+    }
+    return createElement(component, rest)
+  }
+  LazyComponent.displayName = "Kaioken.lazy"
+  return LazyComponent
+}
diff --git a/sandbox/csr/src/App.tsx b/sandbox/csr/src/App.tsx
index 1f917863..f177b618 100644
--- a/sandbox/csr/src/App.tsx
+++ b/sandbox/csr/src/App.tsx
@@ -1,6 +1,6 @@
 import { Router, Route, useRouter, useState } from "kaioken"
 import { Todos } from "./components/ToDos"
-import { Counter } from "./components/Counter"
+//import { Counter } from "./components/Counter"
 import { ProductPage } from "./components/Product"
 import { Link } from "./components/atoms/Link"
 import { GithubIcon } from "./components/GithubIcon"
@@ -16,6 +16,7 @@ import { UseSyncExternalStoreExample } from "./components/UseSyncExternalStoreEx
 import { UseModelExample } from "./components/useModelExample"
 import { GlobalComputedExample } from "./components/ComputedExample"
 import { LocalComputedExample } from "./components/ComputedExample"
+import { LazyDemo } from "./components/LazyDemo"
 
 function Home() {
   return <h1>Home</h1>
@@ -26,10 +27,11 @@ function Nav() {
     <nav className=" min-h-screen p-2  mb-5 h-full">
       <div className="sticky top-0 flex flex-col gap-2">
         <Link to="/">Home</Link>
+        <Link to="/lazy">Lazy</Link>
         <Link to="/useModel">UseModel</Link>
         <Link to="/todos">Todos (state, model, memo)</Link>
         <Link to="/todos-with-store">Todos (with store)</Link>
-        <Link to="/counter">Counter (store)</Link>
+        {/* <Link to="/counter">Counter (store)</Link> */}
         <Link to="/query?id=1">Query (useAsync)</Link>
         <Link to="/transitions">Dialogs (transitions, portal)</Link>
         <Link to="/memo">Memo demo</Link>
@@ -54,13 +56,14 @@ export function App() {
       <main className="flex items-center justify-center flex-grow w-full">
         <Router>
           <Route path="/" element={<Home />} />
+          <Route path="/lazy" element={<LazyDemo />} />
           <Route path="/useModel" element={<UseModelExample />} />
           <Route path="/big-list" element={<BigListComponent />} />
           <Route path="/router-test/:id" element={<RouterTest />} fallthrough />
           <Route path="/memo" element={<MemoDemo />} />
           <Route path="/todos" element={<Todos />} />
           <Route path="/todos-with-store" element={<TodosWithStore />} />
-          <Route path="/counter" element={<Counter />} />
+          {/* <Route path="/counter" element={<Counter />} /> */}
           <Route path="/query" element={<ProductPage />} />
           <Route path="/transitions" element={<Transitions />} />
           <Route path="/filtered-list" element={<FilteredList />} />
diff --git a/sandbox/csr/src/components/Counter.tsx b/sandbox/csr/src/components/Counter.tsx
index 3732278a..92c67336 100644
--- a/sandbox/csr/src/components/Counter.tsx
+++ b/sandbox/csr/src/components/Counter.tsx
@@ -2,7 +2,7 @@ import { Button } from "./atoms/Button"
 import { Container } from "./atoms/Container"
 import { useCountStore } from "../store"
 
-export function Counter() {
+export function Counter({ test, children }: { test?: string; children?: any }) {
   const { value: count, increment, decrement } = useCountStore()
 
   return (
@@ -13,6 +13,8 @@ export function Counter() {
         {count % 2 === 0 ? <a href="#">Test</a> : <a className="asd">Testw</a>}
         <Button onclick={increment}>+1</Button>
       </Container>
+      <div>{children}</div>
+      <div>{test}</div>
     </div>
   )
 }
diff --git a/sandbox/csr/src/components/LazyDemo.tsx b/sandbox/csr/src/components/LazyDemo.tsx
new file mode 100644
index 00000000..ad2ea12e
--- /dev/null
+++ b/sandbox/csr/src/components/LazyDemo.tsx
@@ -0,0 +1,26 @@
+import { lazy, signal } from "kaioken"
+
+const sleep = async (ms: number) =>
+  new Promise((resolve) => setTimeout(resolve, ms))
+
+function MiniCounter() {
+  const count = signal(0)
+  return <button onclick={() => count.value++}>Increment {count}</button>
+}
+
+const LazyCounter = lazy(() => {
+  console.log("loading Counter")
+  return sleep(1000).then(() =>
+    import("./Counter").then(({ Counter }) => Counter)
+  )
+})
+
+export function LazyDemo() {
+  return (
+    <div className="flex flex-col">
+      <h1>Lazy Demo</h1>
+      <LazyCounter fallback={<MiniCounter />}>sdsd</LazyCounter>
+      <LazyCounter fallback={"TEST"}>sdsd</LazyCounter>
+    </div>
+  )
+}