From e12618a688905b7ae9394fb80625aa6a2d414028 Mon Sep 17 00:00:00 2001
From: MasterGordon <gologo.x@gmail.com>
Date: Fri, 6 Mar 2026 21:12:24 +0100
Subject: [PATCH] wip added hooks and some basic debugging

---
 examples/client-renderer/src/cr.ts    | 94 ++++++++++++++++++++++-----
 examples/client-renderer/src/main.tsx |  9 ++-
 examples/client-renderer/src/types.ts |  8 +++
 3 files changed, 93 insertions(+), 18 deletions(-)

diff --git a/examples/client-renderer/src/cr.ts b/examples/client-renderer/src/cr.ts
index 3cc8dc3..4c59442 100644
--- a/examples/client-renderer/src/cr.ts
+++ b/examples/client-renderer/src/cr.ts
@@ -4,6 +4,7 @@ import {
   EffectTag,
   isFunctionFiber,
   isHostFiber,
+  StateHook,
   type Child,
   type FiberNode,
   type FunctionFiber,
@@ -90,16 +91,44 @@ function createFiberFromElement(element: JSXElement): FiberNode {
     effectTag: EffectTag.NoEffect,
     alternate: null,
     nextEffect: null,
+    actions: null,
+    pendingChildren: [],
   };
 }
 
+function canBailout(fiber: FiberNode) {
+  const alternate = fiber.alternate;
+  if (!alternate) {
+    return false;
+  }
+  if (fiber.actions) {
+    return false;
+  }
+  const propKeys = Object.keys(fiber.pendingProps);
+  const pendingPropKeys = Object.keys(alternate.pendingProps);
+  if (propKeys.length !== pendingPropKeys.length) {
+    return false;
+  }
+  if (
+    propKeys.some(
+      (key) => fiber.pendingProps[key] !== alternate.pendingProps[key],
+    )
+  )
+    return false;
+  return true;
+}
+
 function updateFunctionComponent(fiber: FunctionFiber) {
   wipFiber = fiber;
   hookIndex = 0;
   wipFiber.hooks = [];
   wipFiber.effectTag = EffectTag.NoEffect;
-  const children = [fiber.type(fiber.pendingProps)];
-  reconcileChildren(fiber, children);
+  if (fiber.alternate && canBailout(fiber)) {
+    fiber.pendingChildren = fiber.alternate.pendingChildren;
+  } else {
+    fiber.pendingChildren = [fiber.type(fiber.pendingProps)];
+  }
+  reconcileChildren(fiber, fiber.pendingChildren);
 }
 
 function updateHostComponent(fiber: HostFiber) {
@@ -128,6 +157,26 @@ function pushEffect(fiber: FiberNode) {
   wipRoot.lastEffect = fiber;
 }
 
+function createAlternate(oldFiber: FiberNode): FiberNode {
+  return {
+    $$typeof: FiberNodeSymbol,
+    type: oldFiber.type,
+    key: null,
+    child: null,
+    sibling: null,
+    parent: wipFiber,
+    index: 0,
+    dom: oldFiber.dom,
+    hooks: [],
+    pendingProps: oldFiber.pendingProps,
+    effectTag: EffectTag.Update,
+    alternate: oldFiber,
+    nextEffect: null,
+    actions: null,
+    pendingChildren: [],
+  };
+}
+
 function reconcileChildren(
   wipFiber: FiberNode | RootFiber,
   children: Child[] = [],
@@ -150,21 +199,9 @@ function reconcileChildren(
 
     const isSameType = oldFiber && element && element.type === oldFiber.type;
     if (isSameType && oldFiber) {
-      newFiber = {
-        $$typeof: FiberNodeSymbol,
-        type: oldFiber.type,
-        key: element.key ?? null,
-        child: null,
-        sibling: null,
-        parent: wipFiber,
-        index: 0,
-        dom: oldFiber.dom,
-        hooks: [],
-        pendingProps: element.props,
-        effectTag: EffectTag.Update,
-        alternate: oldFiber,
-        nextEffect: null,
-      };
+      newFiber = createAlternate(oldFiber);
+      newFiber.key = element.key ?? null;
+      newFiber.pendingProps = element.props;
       pushEffect(newFiber);
     }
 
@@ -183,6 +220,8 @@ function reconcileChildren(
         effectTag: EffectTag.Placement,
         alternate: null,
         nextEffect: null,
+        actions: null,
+        pendingChildren: [],
       };
       pushEffect(newFiber);
     }
@@ -394,6 +433,8 @@ export function createRootFiber(root: HTMLElement): RootFiber {
     isRoot: true,
     firstEffect: null,
     lastEffect: null,
+    actions: null,
+    pendingChildren: [],
   };
   const rootFiber: RootFiber = {
     $$typeof: FiberNodeSymbol,
@@ -412,6 +453,8 @@ export function createRootFiber(root: HTMLElement): RootFiber {
     isRoot: true,
     firstEffect: null,
     lastEffect: null,
+    actions: null,
+    pendingChildren: [],
   };
   alternate.alternate = rootFiber;
   for (const event of events) {
@@ -432,3 +475,20 @@ export function render(rootFiber: RootFiber, element: JSXElement) {
   };
   unitOfWork = wipRoot;
 }
+
+export function logFiber(label: string) {
+  console.log(label, unitOfWork);
+}
+
+export function useState<T>(initialValue: T) {
+  if (!unitOfWork)
+    throw new Error("useState can only be used inside of a component!");
+  const fiber = unitOfWork;
+  const alternate = fiber.alternate?.hooks[hookIndex];
+  if (alternate && alternate.type !== StateHook)
+    throw new Error("Hook order changed smth.");
+  const value: T = alternate ? alternate.value : initialValue;
+  const setValue = (newValue: T) => {
+    fiber.hooks[hookIndex];
+  };
+}
diff --git a/examples/client-renderer/src/main.tsx b/examples/client-renderer/src/main.tsx
index 6434902..6026028 100644
--- a/examples/client-renderer/src/main.tsx
+++ b/examples/client-renderer/src/main.tsx
@@ -1,7 +1,13 @@
-import { createRootFiber, render, scheduleRerender } from "./cr";
+import { createRootFiber, logFiber, render, scheduleRerender } from "./cr";
 import { domFiber } from "./symbols";
 
 let renderCount = 0;
+
+const Child = () => {
+  logFiber("Child");
+  return <div>Child</div>;
+};
+
 const App = () => {
   console.log("render");
   const items = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
@@ -15,6 +21,7 @@ const App = () => {
       }}
     >
       Hello world {String(++renderCount)}
+      <Child />
     </div>
   );
 };
diff --git a/examples/client-renderer/src/types.ts b/examples/client-renderer/src/types.ts
index 848aba4..c675da3 100644
--- a/examples/client-renderer/src/types.ts
+++ b/examples/client-renderer/src/types.ts
@@ -42,11 +42,17 @@ export const EffectHook = Symbol.for("cr.effect-hook");
 type Hook =
   | {
       type: typeof StateHook;
+      value: any;
     }
   | {
       type: typeof EffectHook;
     };
 
+type Action = {
+  execute: (fiber: FiberNode) => void;
+  nextAction: null | Action;
+};
+
 export interface FiberNode {
   $$typeof: typeof FiberNodeSymbol;
   // Identity
@@ -63,12 +69,14 @@ export interface FiberNode {
   dom: Node | null;
   hooks: Hook[];
   pendingProps: any;
+  pendingChildren: Child[];
 
   effectTag: EffectTag;
 
   // Used for double buffering
   alternate: FiberNode | null;
   nextEffect: FiberNode | null;
+  actions: Action | null;
 }
 
 export type FunctionFiber = FiberNode & {