feat: add fiber-based hook implementations

Add useState, useEffect, useRef, useMemo, useCallback, useReducer,
and useContext hooks on the fiber architecture. Update context module
to use fiber tree traversal for value lookup.

Author: MarcelOlsen

src/context/index.ts

@@ -3,41 +3,17 @@
 /* ***************** */
 
 import { createElement } from "../core";
-import type {
-	AnyMiniReactElement,
-	FunctionalComponent,
-	VDOMInstance,
-} from "../core/types";
+import type { AnyMiniReactElement, FunctionalComponent } from "../core/types";
+import { getCurrentlyRenderingFiber } from "../fiber/fiberHooks";
+import type { Fiber } from "../fiber/types";
 import type { MiniReactContext } from "./types";
 
-// Context system - Track context providers in the render tree
-const contextStack: Map<symbol, unknown>[] = [];
-
-// Hook state management
-let currentRenderInstance: VDOMInstance | null = null;
-
-/**
- * Sets the current render instance for context hooks
- * @param instance The current VDOM instance
- */
-export function setContextRenderInstance(instance: VDOMInstance | null): void {
-	currentRenderInstance = instance;
-}
-
-/**
- * Pushes a context value onto the context stack
- * @param contextValues The context values to push
- */
-export function pushContextValues(contextValues: Map<symbol, unknown>): void {
-	contextStack.push(contextValues);
-}
-
-/**
- * Pops a context value from the context stack
- */
-export function popContextValues(): void {
-	contextStack.pop();
-}
+// Map from Provider function to its context object
+// Used to identify Provider fibers when traversing the tree
+const providerToContext = new WeakMap<
+	FunctionalComponent<{ value: unknown; children?: AnyMiniReactElement[] }>,
+	MiniReactContext<unknown>
+>();
 
 /**
  * createContext function - Creates a new context object with default value
@@ -61,14 +37,6 @@ export function createContext<T>(defaultValue: T): MiniReactContext<T> {
 		// Update the context's current value to keep it in sync
 		context._currentValue = value;
 
-		// Store context value in the current instance so reconciler can manage context stack
-		if (currentRenderInstance) {
-			if (!currentRenderInstance.contextValues) {
-				currentRenderInstance.contextValues = new Map();
-			}
-			currentRenderInstance.contextValues.set(contextId, value);
-		}
-
 		// Render children
 		let result: AnyMiniReactElement | null = null;
 		if (!children || children.length === 0) {
@@ -89,28 +57,60 @@ export function createContext<T>(defaultValue: T): MiniReactContext<T> {
 	// Set the Provider function on the context object
 	context.Provider = Provider;
 
+	// Register Provider function with its context for fiber traversal lookup
+	providerToContext.set(
+		Provider as FunctionalComponent<{
+			value: unknown;
+			children?: AnyMiniReactElement[];
+		}>,
+		context as MiniReactContext<unknown>,
+	);
+
 	return context;
 }
 
+/**
+ * Finds the context value by traversing up the fiber tree.
+ * Returns the value from the nearest Provider or the default value.
+ */
+function findContextValue<T>(fiber: Fiber, context: MiniReactContext<T>): T {
+	let currentFiber: Fiber | null = fiber.return;
+
+	while (currentFiber !== null) {
+		// Check if this fiber is a Provider for our context
+		const fiberType = currentFiber.type;
+		if (typeof fiberType === "function") {
+			const providerContext = providerToContext.get(
+				fiberType as FunctionalComponent<{
+					value: unknown;
+					children?: AnyMiniReactElement[];
+				}>,
+			);
+			if (providerContext === (context as MiniReactContext<unknown>)) {
+				// Found the Provider! Get the value from its props
+				const props = currentFiber.memoizedProps ?? currentFiber.pendingProps;
+				if (props && "value" in props) {
+					return props["value"] as T;
+				}
+			}
+		}
+		currentFiber = currentFiber.return;
+	}
+
+	// No Provider found, return default value
+	return context._defaultValue;
+}
+
 /**
  * useContext hook implementation
  * @param context The context object created by createContext
  * @returns The current context value
  */
 export function useContext<T>(context: MiniReactContext<T>): T {
-	if (!currentRenderInstance) {
+	const currentFiber = getCurrentlyRenderingFiber();
+	if (currentFiber === null) {
 		throw new Error("useContext must be called inside a functional component");
 	}
 
-	// Check the global context stack for active context values
-	for (let i = contextStack.length - 1; i >= 0; i--) {
-		const contextMap = contextStack[i];
-		if (contextMap.has(context._contextId)) {
-			const value = contextMap.get(context._contextId) as T;
-			return value;
-		}
-	}
-
-	// Return default value if no provider found
-	return context._defaultValue;
+	return findContextValue(currentFiber, context);
 }