// 虛擬節點結構定義
interface VNode {
    type: string | ComponentClass; // 節點類型
    key: string | number;         // 唯一標識
    props: Object;               // 屬性對象
    children: VNode[];           // 子節點
    instance: any;               // 對應的組件實例
    depth: number;               // 節點深度
}

// 差異比較結果
interface DiffResult {
    type: 'CREATE' | 'UPDATE' | 'DELETE' | 'MOVE';
    node: VNode;
    oldNode?: VNode;
    moves?: PatchMove[];
}

class Differ {
    private oldTree: VNode;
    private newTree: VNode;
    
    // 執行差異比較
    diff(oldTree: VNode, newTree: VNode): DiffResult[] {
        const patches: DiffResult[] = [];
        this.oldTree = oldTree;
        this.newTree = newTree;
        
        // 深度優先遍歷比較
        this.walk(oldTree, newTree, patches, 0);
        
        return this.optimizePatches(patches);
    }
    
    // 節點比較算法
    private walk(oldNode: VNode, newNode: VNode, patches: DiffResult[], index: number): void {
        if (!oldNode && newNode) {
            // 新增節點
            patches.push({
                type: 'CREATE',
                node: newNode
            });
        } else if (oldNode && !newNode) {
            // 刪除節點
            patches.push({
                type: 'DELETE',
                node: oldNode
            });
        } else if (this.isSameType(oldNode, newNode)) {
            // 相同類型節點，比較屬性和子節點
            if (this.isKeyed(oldNode) && oldNode.key !== newNode.key) {
                // key不同，視為移動操作
                patches.push({
                    type: 'MOVE',
                    node: newNode,
                    oldNode: oldNode
                });
            } else {
                // 比較屬性差異
                const propPatches = this.diffProps(oldNode.props, newNode.props);
                if (propPatches.length > 0) {
                    patches.push({
                        type: 'UPDATE',
                        node: newNode,
                        oldNode: oldNode
                    });
                }
                
                // 遞歸比較子節點
                this.diffChildren(oldNode.children, newNode.children, patches);
            }
        } else {
            // 節點類型不同，完全替換
            patches.push({
                type: 'DELETE',
                node: oldNode
            });
            patches.push({
                type: 'CREATE',
                node: newNode
            });
        }
    }
    
    // 子節點差異比較優化
    private diffChildren(oldChildren: VNode[], newChildren: VNode[], patches: DiffResult[]): void {
        const oldMap = this.createKeyIndexMap(oldChildren);
        const newMap = this.createKeyIndexMap(newChildren);
        
        // 識別移動、新增、刪除的節點
        const moves = this.calculateMoves(oldMap, newMap);
        patches.push(...moves);
        
        // 對相同key的節點進行深度比較
        for (const key in newMap) {
            if (oldMap[key] !== undefined) {
                this.walk(oldChildren[oldMap[key]], newChildren[newMap[key]], patches, 0);
            }
        }
    }
    
    // 基於key的移動檢測算法
    private calculateMoves(oldMap: Map<string, number>, newMap: Map<string, number>): PatchMove[] {
        const moves: PatchMove[] = [];
        const used: Set<string> = new Set();
        
        // 第一遍：識別位置變化的節點
        for (const [key, newIndex] of newMap) {
            const oldIndex = oldMap.get(key);
            if (oldIndex !== undefined && oldIndex !== newIndex) {
                moves.push({
                    from: oldIndex,
                    to: newIndex,
                    key: key
                });
                used.add(key);
            }
        }
        
        return moves;
    }
}

// 更新調度器
class UpdateScheduler {
    private dirtyComponents: Set<Component> = new Set();
    private isBatchUpdating: boolean = false;
    private frameCallbackId: number = 0;
    
    // 標記組件需要更新
    scheduleUpdate(component: Component): void {
        this.dirtyComponents.add(component);
        
        if (!this.isBatchUpdating) {
            this.requestFrameUpdate();
        }
    }
    
    // 請求動畫幀更新
    private requestFrameUpdate(): void {
        if (this.frameCallbackId === 0) {
            this.frameCallbackId = requestAnimationFrame(() => {
                this.performUpdate();
            });
        }
    }
    
    // 執行批量更新
    private performUpdate(): void {
        this.isBatchUpdating = true;
        this.frameCallbackId = 0;
        
        // 當前幀處理的組件快照
        const componentsToUpdate = new Set(this.dirtyComponents);
        this.dirtyComponents.clear();
        
        // 分組處理：按組件深度和優先級排序
        const sortedComponents = this.sortComponentsByPriority(componentsToUpdate);
        
        // 執行更新
        for (const component of sortedComponents) {
            if (component.shouldUpdate()) {
                component.performUpdate();
            }
        }
        
        this.isBatchUpdating = false;
        
        // 如果更新過程中又產生了新的髒組件，繼續下一幀更新
        if (this.dirtyComponents.size > 0) {
            this.requestFrameUpdate();
        }
    }
    
    // 開啓批量更新模式
    batchedUpdates<T>(callback: () => T): T {
        const wasBatchUpdating = this.isBatchUpdating;
        this.isBatchUpdating = true;
        
        try {
            return callback();
        } finally {
            this.isBatchUpdating = wasBatchUpdating;
            if (!wasBatchUpdating && this.dirtyComponents.size > 0) {
                this.requestFrameUpdate();
            }
        }
    }
}

// 組件鍵優化管理器
class KeyOptimizationManager {
    private keyCache: Map<string, string> = new Map();
    private staticReuseThreshold: number = 0.8;
    
    // 生成優化鍵
    generateOptimizedKey(component: Component, data: any): string {
        // 場景1：列表項基於數據ID生成鍵
        if (data?.id) {
            return `item_${data.id}`;
        }
        
        // 場景2：基於內容哈希生成鍵（適合靜態內容）
        if (this.isStaticContent(component)) {
            const contentHash = this.generateContentHash(component);
            return `static_${contentHash}`;
        }
        
        // 場景3：基於位置索引生成鍵（最後手段）
        return `index_${component.index}`;
    }
    
    // 鍵穩定性檢測
    detectKeyStability(oldKeys: string[], newKeys: string[]): StabilityReport {
        const stableKeys = this.findCommonKeys(oldKeys, newKeys);
        const addedKeys = this.findAddedKeys(oldKeys, newKeys);
        const removedKeys = this.findRemovedKeys(oldKeys, newKeys);
        
        const stabilityScore = stableKeys.length / Math.max(oldKeys.length, newKeys.length);
        
        return {
            stabilityScore,
            stableKeys,
            addedKeys,
            removedKeys,
            recommendation: this.generateOptimizationRecommendation(stabilityScore)
        };
    }
    
    // 智能鍵分配策略
    assignSmartKeys(components: Component[], dataList: any[]): KeyAssignment[] {
        const assignments: KeyAssignment[] = [];
        
        // 優先使用數據中的穩定標識符
        for (let i = 0; i < dataList.length; i++) {
            const data = dataList[i];
            const component = components[i];
            
            let key: string;
            if (data.uniqueId) {
                key = `data_${data.uniqueId}`;
            } else if (data.contentHash) {
                key = `hash_${data.contentHash}`;
            } else {
                // 生成基於內容的鍵
                key = this.generateContentBasedKey(data);
            }
            
            assignments.push({ component, key, confidence: this.calculateKeyConfidence(key) });
        }
        
        return assignments.sort((a, b) => b.confidence - a.confidence);
    }
}

// 組件實例池
class ComponentInstancePool {
    private pools: Map<string, Component[]> = new Map();
    private maxPoolSize: number = 50;
    private stats: Map<string, PoolStatistics> = new Map();
    
    // 獲取可複用組件實例
    acquire(componentType: string, props: any): Component | null {
        const poolKey = this.getPoolKey(componentType, props);
        
        if (!this.pools.has(poolKey)) {
            this.pools.set(poolKey, []);
            this.stats.set(poolKey, { hits: 0, misses: 0, creations: 0 });
        }
        
        const pool = this.pools.get(poolKey)!;
        const stats = this.stats.get(poolKey)!;
        
        if (pool.length > 0) {
            const instance = pool.pop()!;
            stats.hits++;
            
            // 重置組件狀態
            this.recycleInstance(instance, props);
            return instance;
        }
        
        stats.misses++;
        return null;
    }
    
    // 歸還組件實例到池中
    release(instance: Component): void {
        const poolKey = this.getPoolKey(instance.constructor.name, instance.props);
        
        if (!this.pools.has(poolKey)) {
            this.pools.set(poolKey, []);
        }
        
        const pool = this.pools.get(poolKey)!;
        
        // 池大小限制
        if (pool.length < this.maxPoolSize) {
            // 清理組件狀態
            this.cleanupInstance(instance);
            pool.push(instance);
        } else {
            // 池已滿，直接銷燬
            instance.destroy();
        }
    }
    
    // 智能池清理策略
    cleanupIdlePools(): void {
        const now = Date.now();
        const idleThreshold = 30000; // 30秒
        
        for (const [poolKey, pool] of this.pools) {
            // 清理長時間未使用的池
            if (now - this.getLastUsedTime(poolKey) > idleThreshold) {
                for (const instance of pool) {
                    instance.destroy();
                }
                this.pools.delete(poolKey);
            }
        }
    }
}

// 虛擬滾動控制器
class VirtualScrollController {
    private viewport: { width: number; height: number };
    private itemSize: number | ((index: number) => number);
    private scrollTop: number = 0;
    private visibleRange: { start: number; end: number } = { start: 0, end: 0 };
    private overscan: number = 5; // 預渲染項目數
    
    // 計算可視區域
    calculateVisibleRange(totalCount: number): { start: number; end: number } {
        const startIndex = Math.max(0, Math.floor(this.scrollTop / this.getItemSize(0)) - this.overscan);
        const endIndex = Math.min(
            totalCount - 1,
            Math.floor((this.scrollTop + this.viewport.height) / this.getItemSize(0)) + this.overscan
        );
        
        return { start: startIndex, end: endIndex };
    }
    
    // 獲取項目尺寸
    private getItemSize(index: number): number {
        return typeof this.itemSize === 'function' ? this.itemSize(index) : this.itemSize;
    }
    
    // 滾動事件處理
    handleScroll(scrollTop: number, totalCount: number): boolean {
        const oldRange = this.visibleRange;
        this.scrollTop = scrollTop;
        this.visibleRange = this.calculateVisibleRange(totalCount);
        
        // 只有可見範圍發生變化時才觸發更新
        return this.hasRangeChanged(oldRange, this.visibleRange);
    }
    
    // 獲取需要渲染的項目數據
    getVisibleItems<T>(allItems: T[]): Array<{ data: T; index: number; offset: number }> {
        const { start, end } = this.visibleRange;
        const visibleItems: Array<{ data: T; index: number; offset: number }> = [];
        
        for (let i = start; i <= end; i++) {
            if (i >= 0 && i < allItems.length) {
                const offset = this.calculateItemOffset(i);
                visibleItems.push({
                    data: allItems[i],
                    index: i,
                    offset: offset
                });
            }
        }
        
        return visibleItems;
    }
}

// 智能數據加載器
class SmartDataLoader<T> {
    private pageSize: number = 20;
    private loadedPages: Map<number, T[]> = new Map();
    private loadingState: Map<number, 'loading' | 'loaded' | 'error'> = new Map();
    private prefetchThreshold: number = 0.7; // 預加載閾值
    
    // 按需加載數據
    async loadDataForIndex(index: number): Promise<T[]> {
        const pageIndex = Math.floor(index / this.pageSize);
        
        // 如果數據已加載，直接返回
        if (this.loadedPages.has(pageIndex)) {
            return this.loadedPages.get(pageIndex)!;
        }
        
        // 如果正在加載，等待完成
        if (this.loadingState.get(pageIndex) === 'loading') {
            await this.waitForPageLoad(pageIndex);
            return this.loadedPages.get(pageIndex)!;
        }
        
        // 開始加載
        this.loadingState.set(pageIndex, 'loading');
        
        try {
            const data = await this.fetchPageData(pageIndex);
            this.loadedPages.set(pageIndex, data);
            this.loadingState.set(pageIndex, 'loaded');
            
            // 預加載相鄰頁面
            this.prefetchAdjacentPages(pageIndex);
            
            return data;
        } catch (error) {
            this.loadingState.set(pageIndex, 'error');
            throw error;
        }
    }
    
    // 預加載策略
    private prefetchAdjacentPages(currentPage: number): void {
        const prefetchPages = [currentPage - 1, currentPage + 1];
        
        for (const page of prefetchPages) {
            if (page >= 0 && !this.loadedPages.has(page) && 
                !this.loadingState.has(page)) {
                // 異步預加載，不阻塞當前操作
                this.loadDataForIndex(page * this.pageSize).catch(() => {
                    // 預加載失敗可忽略，用户滾動到時再重試
                });
            }
        }
    }
    
    // 內存管理：清理不可見頁面
    cleanupInvisiblePages(visibleRange: { start: number; end: number }): void {
        const visibleStartPage = Math.floor(visibleRange.start / this.pageSize);
        const visibleEndPage = Math.floor(visibleRange.end / this.pageSize);
        const keepPageRange = 3; // 保留前後3頁
        
        for (const [pageIndex] of this.loadedPages) {
            if (pageIndex < visibleStartPage - keepPageRange || 
                pageIndex > visibleEndPage + keepPageRange) {
                this.loadedPages.delete(pageIndex);
                this.loadingState.delete(pageIndex);
            }
        }
    }
}

// 幀率控制器
class FrameRateController {
    private targetFPS: number = 60;
    private frameInterval: number = 1000 / this.targetFPS;
    private lastFrameTime: number = 0;
    private frameDurations: number[] = [];
    private droppedFrames: number = 0;
    
    // VSync同步渲染
    async renderWithVSync(renderCallback: () => void): Promise<void> {
        const currentTime = performance.now();
        const elapsed = currentTime - this.lastFrameTime;
        
        // 檢查是否應該跳過本幀以保持幀率
        if (elapsed < this.frameInterval) {
            await this.delay(this.frameInterval - elapsed);
            return;
        }
        
        // 記錄幀時間
        this.recordFrameDuration(elapsed);
        
        // 檢查掉幀
        if (this.detectFrameDrop(elapsed)) {
            this.droppedFrames++;
            this.adaptToFrameDrop();
        }
        
        // 執行渲染
        this.lastFrameTime = performance.now();
        renderCallback();
        
        // 動態調整幀率
        this.adaptFrameRateIfNeeded();
    }
    
    // 掉幀檢測算法
    private detectFrameDuration(elapsed: number): boolean {
        // 如果幀時間超過理想幀時間的150%，認為掉幀
        return elapsed > this.frameInterval * 1.5;
    }
    
    // 幀率自適應策略
    private adaptFrameRateIfNeeded(): void {
        const avgFrameTime = this.getAverageFrameTime();
        const currentFPS = 1000 / avgFrameTime;
        
        // 如果平均FPS低於目標值，考慮降低渲染質量
        if (currentFPS < this.targetFPS * 0.8) {
            this.reduceRenderingQuality();
        }
    }
    
    // 降低渲染質量以保持幀率
    private reduceRenderingQuality(): void {
        // 策略1：減少重渲染範圍
        this.reduceRerenderScope();
        
        // 策略2：降低動畫精度
        this.reduceAnimationPrecision();
        
        // 策略3：延遲非關鍵渲染任務
        this.deferNonCriticalRendering();
    }
}

@Component
struct HighPerformanceList {
    @State @Watch('onDataChange') listData: ListItem[] = [];
    @State visibleRange: { start: number; end: number } = { start: 0, end: 20 };
    
    private virtualScroll: VirtualScrollController = new VirtualScrollController();
    private dataLoader: SmartDataLoader<ListItem> = new SmartDataLoader();
    private componentPool: ComponentInstancePool = new ComponentInstancePool();
    private updateScheduler: UpdateScheduler = new UpdateScheduler();
    
    // 數據變化監聽
    onDataChange(): void {
        this.updateScheduler.batchedUpdates(() => {
            this.updateVisibleItems();
        });
    }
    
    // 滾動事件處理
    handleScroll(event: ScrollEvent): void {
        if (this.virtualScroll.handleScroll(event.scrollTop, this.listData.length)) {
            this.updateVisibleRange();
        }
    }
    
    // 更新可見區域
    private updateVisibleRange(): void {
        const newRange = this.virtualScroll.calculateVisibleRange(this.listData.length);
        
        if (this.hasRangeChanged(this.visibleRange, newRange)) {
            this.visibleRange = newRange;
            this.updateVisibleItems();
            
            // 預加載即將進入視圖的數據
            this.prefetchData(newRange);
        }
    }
    
    // 渲染可見項目
    build() {
        Stack({ align: Alignment.TopStart }) {
            // 容器用於正確計算滾動位置
            Scroll(this.scrollArea) {
                Column() {
                    // 上方空白區域
                    BlankSpace({ height: this.virtualScroll.getOffsetTop(this.visibleRange.start) })
                    
                    // 可見項目渲染
                    ForEach(this.getVisibleItems(), (item: ListItem, index: number) => {
                        this.renderListItem(item, index)
                    })
                    
                    // 下方空白區域
                    BlankSpace({ height: this.virtualScroll.getOffsetBottom(
                        this.visibleRange.end, 
                        this.listData.length
                    ) })
                }
            }
            .onScroll((event: ScrollEvent) => this.handleScroll(event))
            .scrollable(ScrollDirection.Vertical)
        }
    }
    
    // 優化的列表項渲染
    @OptimizeRender
    renderListItem(item: ListItem, index: number): void {
        // 嘗試從組件池獲取可複用實例
        let listItem = this.componentPool.acquire('ListItem', item);
        
        if (!listItem) {
            listItem = new ListItemComponent();
        }
        
        // 應用差異更新
        if (listItem.needsUpdate(item)) {
            listItem.applyUpdate(item);
        }
        
        return listItem;
    }
}

// 渲染性能分析器
class RenderingProfiler {
    private metrics: RenderMetrics[] = [];
    private samplingRate: number = 1000; // 採樣率（毫秒）
    private isProfiling: boolean = false;
    
    // 開始性能分析
    startProfiling(): void {
        this.isProfiling = true;
        this.metrics = [];
        this.samplingInterval = setInterval(() => {
            this.recordMetrics();
        }, this.samplingRate);
    }
    
    // 記錄性能指標
    private recordMetrics(): void {
        const metrics: RenderMetrics = {
            timestamp: Date.now(),
            fps: this.calculateFPS(),
            memoryUsage: this.getMemoryUsage(),
            componentCount: this.getComponentCount(),
            updateCount: this.getUpdateCount(),
            layoutTime: this.getLayoutTime(),
            renderTime: this.getRenderTime()
        };
        
        this.metrics.push(metrics);
        
        // 性能告警
        if (this.detectPerformanceIssues(metrics)) {
            this.triggerPerformanceAlert(metrics);
        }
    }
    
    // 生成性能報告
    generatePerformanceReport(): PerformanceReport {
        return {
            averageFPS: this.calculateAverageFPS(),
            frameDrops: this.countFrameDrops(),
            memoryPeak: this.findMemoryPeak(),
            recommendations: this.generateOptimizationRecommendations()
        };
    }
    
    // 性能問題檢測
    private detectPerformanceIssues(metrics: RenderMetrics): boolean {
        // 幀率過低告警
        if (metrics.fps < 30) {
            return true;
        }
        
        // 內存使用過高告警
        if (metrics.memoryUsage > 100 * 1024 * 1024) { // 100MB
            return true;
        }
        
        // 渲染時間過長告警
        if (metrics.renderTime > 16) { // 超過16ms
            return true;
        }
        
        return false;
    }
}