// Enterprise memory pool management system
package memory

import (
    "runtime"
    "sync"
    "sync/atomic"
    "time"
    "unsafe"
    
    "github.com/prometheus/client_golang/prometheus"
)

// EnterpriseMemoryManager provides comprehensive memory management
type EnterpriseMemoryManager struct {
    pools          map[string]*MemoryPool
    weakRefs       *WeakReferenceManager
    gcOptimizer    *GCOptimizer
    metrics        *MemoryMetrics
    
    // Configuration
    config         *MemoryConfig
    
    // Monitoring
    monitor        *MemoryMonitor
    
    // Pool management
    poolMutex      sync.RWMutex
    
    // Statistics
    stats          *MemoryStats
    lastGCTime     time.Time
}

type MemoryConfig struct {
    EnableWeakRefs      bool
    EnablePooling       bool
    EnableGCOptimization bool
    MaxPoolSize         int64
    PoolGrowthFactor    float64
    GCTargetPercent     int
    GCMemoryLimit       int64
    
    // Advanced features
    EnableArenas        bool
    EnableProfiling     bool
    EnableMetrics       bool
}

type MemoryPool struct {
    name           string
    objectSize     int
    maxObjects     int
    objects        []unsafe.Pointer
    available      []bool
    allocCounter   int64
    freeCounter    int64
    
    // Memory alignment
    alignment      int
    
    // Statistics
    hitRate        float64
    allocTime      time.Duration
    
    mutex          sync.Mutex
}

// Create enterprise memory manager
func NewEnterpriseMemoryManager(config *MemoryConfig) *EnterpriseMemoryManager {
    emm := &EnterpriseMemoryManager{
        pools:   make(map[string]*MemoryPool),
        config:  config,
        stats:   &MemoryStats{},
    }
    
    // Initialize weak reference manager
    if config.EnableWeakRefs {
        emm.weakRefs = NewWeakReferenceManager()
    }
    
    // Initialize GC optimizer
    if config.EnableGCOptimization {
        emm.gcOptimizer = NewGCOptimizer(config)
    }
    
    // Initialize metrics
    if config.EnableMetrics {
        emm.metrics = NewMemoryMetrics()
    }
    
    // Start monitoring
    emm.monitor = NewMemoryMonitor(emm)
    go emm.monitor.Start()
    
    return emm
}

// Advanced object pooling with type safety
func (emm *EnterpriseMemoryManager) GetPool(name string, objectSize int) *MemoryPool {
    emm.poolMutex.RLock()
    pool, exists := emm.pools[name]
    emm.poolMutex.RUnlock()
    
    if exists {
        return pool
    }
    
    emm.poolMutex.Lock()
    defer emm.poolMutex.Unlock()
    
    // Double-check after acquiring write lock
    if pool, exists := emm.pools[name]; exists {
        return pool
    }
    
    // Create new pool
    pool = &MemoryPool{
        name:       name,
        objectSize: objectSize,
        maxObjects: emm.config.MaxPoolSize,
        objects:    make([]unsafe.Pointer, 0, emm.config.MaxPoolSize),
        available:  make([]bool, emm.config.MaxPoolSize),
        alignment:  calculateAlignment(objectSize),
    }
    
    // Pre-allocate objects
    pool.preallocate()
    
    emm.pools[name] = pool
    return pool
}

// Allocate object from pool
func (mp *MemoryPool) Allocate() unsafe.Pointer {
    mp.mutex.Lock()
    defer mp.mutex.Unlock()
    
    start := time.Now()
    defer func() {
        mp.allocTime = time.Since(start)
    }()
    
    // Find available object
    for i, available := range mp.available {
        if available && i < len(mp.objects) {
            mp.available[i] = false
            atomic.AddInt64(&mp.allocCounter, 1)
            mp.updateHitRate()
            return mp.objects[i]
        }
    }
    
    // No available objects, allocate new one if within limits
    if len(mp.objects) < mp.maxObjects {
        ptr := allocateAligned(mp.objectSize, mp.alignment)
        mp.objects = append(mp.objects, ptr)
        index := len(mp.objects) - 1
        
        // Extend available slice if needed
        for len(mp.available) <= index {
            mp.available = append(mp.available, true)
        }
        
        mp.available[index] = false
        atomic.AddInt64(&mp.allocCounter, 1)
        return ptr
    }
    
    // Pool exhausted, allocate directly
    return allocateAligned(mp.objectSize, mp.alignment)
}

// Release object back to pool
func (mp *MemoryPool) Release(ptr unsafe.Pointer) {
    mp.mutex.Lock()
    defer mp.mutex.Unlock()
    
    // Find object in pool
    for i, obj := range mp.objects {
        if obj == ptr {
            mp.available[i] = true
            atomic.AddInt64(&mp.freeCounter, 1)
            
            // Clear object memory for security
            clearMemory(ptr, mp.objectSize)
            return
        }
    }
    
    // Object not from pool, free directly
    freeAligned(ptr)
}

// Pre-allocate pool objects
func (mp *MemoryPool) preallocate() {
    initialSize := min(mp.maxObjects/4, 100) // Pre-allocate 25% or 100 objects
    
    for i := 0; i < initialSize; i++ {
        ptr := allocateAligned(mp.objectSize, mp.alignment)
        mp.objects = append(mp.objects, ptr)
        mp.available[i] = true
    }
}

// Calculate optimal alignment for object size
func calculateAlignment(size int) int {
    // Use cache line alignment for larger objects
    if size >= 64 {
        return 64
    }
    
    // Use word alignment for smaller objects
    if size >= 8 {
        return 8
    }
    
    return 4
}

// Allocate aligned memory
func allocateAligned(size, alignment int) unsafe.Pointer {
    // Calculate required size with alignment padding
    alignedSize := (size + alignment - 1) &^ (alignment - 1)
    
    // Allocate extra space for alignment
    raw := make([]byte, alignedSize+alignment)
    
    // Calculate aligned address
    addr := uintptr(unsafe.Pointer(&raw[0]))
    aligned := (addr + uintptr(alignment) - 1) &^ (uintptr(alignment) - 1)
    
    return unsafe.Pointer(aligned)
}

// Free aligned memory
func freeAligned(ptr unsafe.Pointer) {
    // In Go, we rely on GC for cleanup
    // This is a placeholder for explicit memory management if needed
}

// Clear memory for security
func clearMemory(ptr unsafe.Pointer, size int) {
    slice := (*[1 << 30]byte)(ptr)[:size:size]
    for i := range slice {
        slice[i] = 0
    }
}

// Update hit rate statistics
func (mp *MemoryPool) updateHitRate() {
    allocs := atomic.LoadInt64(&mp.allocCounter)
    if allocs > 0 {
        hits := allocs - int64(len(mp.objects))
        if hits < 0 {
            hits = 0
        }
        mp.hitRate = float64(hits) / float64(allocs)
    }
}

// Go 1.24 Weak Pointer Implementation
type WeakReferenceManager struct {
    references map[uintptr]*WeakReference
    mutex      sync.RWMutex
    
    // Cleanup management
    cleanupQueue chan *WeakReference
    stopCleanup  chan struct{}
    
    // Statistics
    totalRefs    int64
    activeRefs   int64
    cleanedRefs  int64
}

type WeakReference struct {
    id        uintptr
    ptr       unsafe.Pointer
    callback  func()
    finalizer func(interface{})
    alive     int32 // atomic flag
    
    // Metadata
    createdAt time.Time
    size      int
    typename  string
}

// Create weak reference manager
func NewWeakReferenceManager() *WeakReferenceManager {
    wrm := &WeakReferenceManager{
        references:   make(map[uintptr]*WeakReference),
        cleanupQueue: make(chan *WeakReference, 1000),
        stopCleanup:  make(chan struct{}),
    }
    
    // Start cleanup goroutine
    go wrm.cleanupLoop()
    
    return wrm
}

// Create weak reference to object
func (wrm *WeakReferenceManager) NewWeakRef(obj interface{}, callback func()) *WeakReference {
    if obj == nil {
        return nil
    }
    
    ptr := unsafe.Pointer(&obj)
    id := uintptr(ptr)
    
    ref := &WeakReference{
        id:        id,
        ptr:       ptr,
        callback:  callback,
        alive:     1,
        createdAt: time.Now(),
        size:      int(unsafe.Sizeof(obj)),
        typename:  getTypeName(obj),
    }
    
    // Set finalizer
    runtime.SetFinalizer(&obj, func(obj interface{}) {
        wrm.markForCleanup(ref)
    })
    
    wrm.mutex.Lock()
    wrm.references[id] = ref
    atomic.AddInt64(&wrm.totalRefs, 1)
    atomic.AddInt64(&wrm.activeRefs, 1)
    wrm.mutex.Unlock()
    
    return ref
}

// Get object from weak reference
func (ref *WeakReference) Get() interface{} {
    if atomic.LoadInt32(&ref.alive) == 0 {
        return nil
    }
    
    // Try to recover object from pointer
    // Note: This is a simplified implementation
    // Real weak pointers require runtime support
    return *(*interface{})(ref.ptr)
}

// Check if reference is still alive
func (ref *WeakReference) IsAlive() bool {
    return atomic.LoadInt32(&ref.alive) != 0
}

// Mark reference for cleanup
func (wrm *WeakReferenceManager) markForCleanup(ref *WeakReference) {
    if atomic.CompareAndSwapInt32(&ref.alive, 1, 0) {
        select {
        case wrm.cleanupQueue <- ref:
        default:
            // Queue full, cleanup directly
            wrm.cleanup(ref)
        }
    }
}

// Cleanup loop
func (wrm *WeakReferenceManager) cleanupLoop() {
    ticker := time.NewTicker(time.Second)
    defer ticker.Stop()
    
    for {
        select {
        case ref := <-wrm.cleanupQueue:
            wrm.cleanup(ref)
            
        case <-ticker.C:
            wrm.cleanupExpired()
            
        case <-wrm.stopCleanup:
            return
        }
    }
}

// Cleanup individual reference
func (wrm *WeakReferenceManager) cleanup(ref *WeakReference) {
    wrm.mutex.Lock()
    delete(wrm.references, ref.id)
    wrm.mutex.Unlock()
    
    if ref.callback != nil {
        ref.callback()
    }
    
    atomic.AddInt64(&wrm.activeRefs, -1)
    atomic.AddInt64(&wrm.cleanedRefs, 1)
}

// Cleanup expired references
func (wrm *WeakReferenceManager) cleanupExpired() {
    wrm.mutex.RLock()
    var expired []*WeakReference
    
    for _, ref := range wrm.references {
        if atomic.LoadInt32(&ref.alive) == 0 {
            expired = append(expired, ref)
        }
    }
    wrm.mutex.RUnlock()
    
    for _, ref := range expired {
        wrm.cleanup(ref)
    }
}

// Advanced GC optimization
type GCOptimizer struct {
    config          *MemoryConfig
    lastGCStats     runtime.MemStats
    gcTriggerCount  int64
    gcDuration      time.Duration
    
    // Optimization strategies
    strategies      []GCStrategy
    currentStrategy int
    
    // Monitoring
    metrics         *GCMetrics
    
    mutex           sync.RWMutex
}

type GCStrategy interface {
    Name() string
    Apply(config *MemoryConfig) error
    Evaluate(stats *runtime.MemStats) float64 // Performance score
}

type GCMetrics struct {
    GCCount          prometheus.Counter
    GCDuration       prometheus.Histogram
    HeapSize         prometheus.Gauge
    HeapObjects      prometheus.Gauge
    GCCPUPercentage  prometheus.Gauge
}

// Create GC optimizer
func NewGCOptimizer(config *MemoryConfig) *GCOptimizer {
    gco := &GCOptimizer{
        config:     config,
        strategies: make([]GCStrategy, 0),
        metrics:    NewGCMetrics(),
    }
    
    // Register optimization strategies
    gco.registerStrategies()
    
    // Set initial GC parameters
    if config.GCTargetPercent > 0 {
        runtime.GC()
        debug.SetGCPercent(config.GCTargetPercent)
    }
    
    if config.GCMemoryLimit > 0 {
        debug.SetMemoryLimit(config.GCMemoryLimit)
    }
    
    return gco
}

// Register GC optimization strategies
func (gco *GCOptimizer) registerStrategies() {
    gco.strategies = append(gco.strategies,
        &AdaptiveGCStrategy{},
        &LowLatencyGCStrategy{},
        &HighThroughputGCStrategy{},
        &MemoryEfficientGCStrategy{},
    )
}

// Optimize GC parameters based on current conditions
func (gco *GCOptimizer) Optimize() {
    var stats runtime.MemStats
    runtime.ReadMemStats(&stats)
    
    gco.mutex.Lock()
    defer gco.mutex.Unlock()
    
    // Update metrics
    gco.updateMetrics(&stats)
    
    // Evaluate current strategy
    currentScore := gco.strategies[gco.currentStrategy].Evaluate(&stats)
    
    // Try other strategies
    bestStrategy := gco.currentStrategy
    bestScore := currentScore
    
    for i, strategy := range gco.strategies {
        if i == gco.currentStrategy {
            continue
        }
        
        score := strategy.Evaluate(&stats)
        if score > bestScore {
            bestScore = score
            bestStrategy = i
        }
    }
    
    // Switch to better strategy if found
    if bestStrategy != gco.currentStrategy {
        gco.strategies[bestStrategy].Apply(gco.config)
        gco.currentStrategy = bestStrategy
    }
    
    gco.lastGCStats = stats
}

// Update GC metrics
func (gco *GCOptimizer) updateMetrics(stats *runtime.MemStats) {
    gco.metrics.GCCount.Add(float64(stats.NumGC - gco.lastGCStats.NumGC))
    gco.metrics.HeapSize.Set(float64(stats.HeapSys))
    gco.metrics.HeapObjects.Set(float64(stats.HeapObjects))
    
    // Calculate GC CPU percentage
    if stats.GCCPUFraction > 0 {
        gco.metrics.GCCPUPercentage.Set(stats.GCCPUFraction * 100)
    }
}

// Adaptive GC strategy
type AdaptiveGCStrategy struct {
    basePercent     int
    adjustmentRate  float64
    targetLatency   time.Duration
}

func (ags *AdaptiveGCStrategy) Name() string {
    return "adaptive"
}

func (ags *AdaptiveGCStrategy) Apply(config *MemoryConfig) error {
    // Adjust GC percentage based on memory pressure
    var stats runtime.MemStats
    runtime.ReadMemStats(&stats)
    
    heapUsage := float64(stats.HeapInuse) / float64(stats.HeapSys)
    
    var newPercent int
    if heapUsage > 0.8 {
        // High memory pressure, be more aggressive
        newPercent = max(50, config.GCTargetPercent-20)
    } else if heapUsage < 0.3 {
        // Low memory pressure, be less aggressive
        newPercent = min(200, config.GCTargetPercent+50)
    } else {
        newPercent = config.GCTargetPercent
    }
    
    debug.SetGCPercent(newPercent)
    return nil
}

func (ags *AdaptiveGCStrategy) Evaluate(stats *runtime.MemStats) float64 {
    // Score based on balance of latency and throughput
    latencyScore := 1.0 - (stats.GCCPUFraction * 10) // Lower GC CPU is better
    memoryScore := 1.0 - (float64(stats.HeapInuse) / float64(stats.HeapSys))
    
    return (latencyScore + memoryScore) / 2.0
}

// Low latency GC strategy
type LowLatencyGCStrategy struct{}

func (llgs *LowLatencyGCStrategy) Name() string {
    return "low_latency"
}

func (llgs *LowLatencyGCStrategy) Apply(config *MemoryConfig) error {
    // Set aggressive GC to minimize pause times
    debug.SetGCPercent(50)
    return nil
}

func (llgs *LowLatencyGCStrategy) Evaluate(stats *runtime.MemStats) float64 {
    // Score based primarily on GC pause times
    return 1.0 - (stats.GCCPUFraction * 20)
}

// High throughput GC strategy
type HighThroughputGCStrategy struct{}

func (htgs *HighThroughputGCStrategy) Name() string {
    return "high_throughput"
}

func (htgs *HighThroughputGCStrategy) Apply(config *MemoryConfig) error {
    // Set conservative GC to maximize throughput
    debug.SetGCPercent(200)
    return nil
}

func (htgs *HighThroughputGCStrategy) Evaluate(stats *runtime.MemStats) float64 {
    // Score based on allocation rate vs GC overhead
    allocRate := float64(stats.TotalAlloc) / float64(time.Now().Unix())
    gcOverhead := stats.GCCPUFraction
    
    return allocRate * (1.0 - gcOverhead*5)
}

// Memory efficient GC strategy
type MemoryEfficientGCStrategy struct{}

func (megs *MemoryEfficientGCStrategy) Name() string {
    return "memory_efficient"
}

func (megs *MemoryEfficientGCStrategy) Apply(config *MemoryConfig) error {
    // Set moderate GC for memory efficiency
    debug.SetGCPercent(75)
    
    // Force GC to clean up memory
    runtime.GC()
    return nil
}

func (megs *MemoryEfficientGCStrategy) Evaluate(stats *runtime.MemStats) float64 {
    // Score based on memory utilization efficiency
    heapEfficiency := float64(stats.HeapInuse) / float64(stats.HeapSys)
    return heapEfficiency
}

// Memory monitoring and profiling
type MemoryMonitor struct {
    manager     *EnterpriseMemoryManager
    interval    time.Duration
    stopChan    chan struct{}
    
    // Profiling
    enablePprof bool
    profiles    []*MemoryProfile
    
    // Alerts
    alertThresholds map[string]float64
    alertCallbacks  map[string]func(MemoryAlert)
}

type MemoryProfile struct {
    Timestamp    time.Time
    HeapSize     int64
    HeapObjects  int64
    GoroutineCount int64
    GCCount      int64
    AllocRate    float64
}

type MemoryAlert struct {
    Type        string
    Severity    string
    Message     string
    Timestamp   time.Time
    Value       float64
    Threshold   float64
}

// Create memory monitor
func NewMemoryMonitor(manager *EnterpriseMemoryManager) *MemoryMonitor {
    return &MemoryMonitor{
        manager:         manager,
        interval:        time.Minute,
        stopChan:        make(chan struct{}),
        enablePprof:     manager.config.EnableProfiling,
        alertThresholds: make(map[string]float64),
        alertCallbacks:  make(map[string]func(MemoryAlert)),
    }
}

// Start monitoring
func (mm *MemoryMonitor) Start() {
    ticker := time.NewTicker(mm.interval)
    defer ticker.Stop()
    
    for {
        select {
        case <-ticker.C:
            mm.collectMetrics()
            mm.checkAlerts()
            
            if mm.enablePprof {
                mm.captureProfile()
            }
            
        case <-mm.stopChan:
            return
        }
    }
}

// Collect memory metrics
func (mm *MemoryMonitor) collectMetrics() {
    var stats runtime.MemStats
    runtime.ReadMemStats(&stats)
    
    profile := &MemoryProfile{
        Timestamp:      time.Now(),
        HeapSize:       int64(stats.HeapSys),
        HeapObjects:    int64(stats.HeapObjects),
        GoroutineCount: int64(runtime.NumGoroutine()),
        GCCount:        int64(stats.NumGC),
        AllocRate:      calculateAllocRate(&stats),
    }
    
    mm.profiles = append(mm.profiles, profile)
    
    // Keep only recent profiles
    if len(mm.profiles) > 1000 {
        mm.profiles = mm.profiles[len(mm.profiles)-1000:]
    }
    
    // Update manager statistics
    mm.manager.stats.update(profile)
}

// Check memory alerts
func (mm *MemoryMonitor) checkAlerts() {
    var stats runtime.MemStats
    runtime.ReadMemStats(&stats)
    
    // Check heap usage
    if threshold, exists := mm.alertThresholds["heap_usage"]; exists {
        usage := float64(stats.HeapInuse) / float64(stats.HeapSys)
        if usage > threshold {
            mm.sendAlert(MemoryAlert{
                Type:      "heap_usage",
                Severity:  "warning",
                Message:   "High heap usage detected",
                Value:     usage,
                Threshold: threshold,
                Timestamp: time.Now(),
            })
        }
    }
    
    // Check GC frequency
    if threshold, exists := mm.alertThresholds["gc_frequency"]; exists {
        gcRate := calculateGCRate(&stats)
        if gcRate > threshold {
            mm.sendAlert(MemoryAlert{
                Type:      "gc_frequency",
                Severity:  "warning",
                Message:   "High GC frequency detected",
                Value:     gcRate,
                Threshold: threshold,
                Timestamp: time.Now(),
            })
        }
    }
}

// Send memory alert
func (mm *MemoryMonitor) sendAlert(alert MemoryAlert) {
    if callback, exists := mm.alertCallbacks[alert.Type]; exists {
        callback(alert)
    }
}

// Capture memory profile
func (mm *MemoryMonitor) captureProfile() {
    // This would integrate with pprof for detailed profiling
    // Implementation depends on specific profiling requirements
}

// Memory statistics
type MemoryStats struct {
    TotalAllocations int64
    CurrentHeapSize  int64
    PeakHeapSize     int64
    GCCount          int64
    LastGCDuration   time.Duration
    
    // Pool statistics
    PoolHitRate      float64
    PoolMissRate     float64
    
    mutex            sync.RWMutex
}

// Update statistics
func (ms *MemoryStats) update(profile *MemoryProfile) {
    ms.mutex.Lock()
    defer ms.mutex.Unlock()
    
    ms.CurrentHeapSize = profile.HeapSize
    if profile.HeapSize > ms.PeakHeapSize {
        ms.PeakHeapSize = profile.HeapSize
    }
    ms.GCCount = profile.GCCount
}

// Helper functions
func getTypeName(obj interface{}) string {
    return fmt.Sprintf("%T", obj)
}

func calculateAllocRate(stats *runtime.MemStats) float64 {
    // Simplified allocation rate calculation
    return float64(stats.TotalAlloc) / float64(time.Now().Unix())
}

func calculateGCRate(stats *runtime.MemStats) float64 {
    // Simplified GC rate calculation
    return float64(stats.NumGC) / float64(time.Now().Unix())
}

func min(a, b int) int {
    if a < b {
        return a
    }
    return b
}

func max(a, b int) int {
    if a > b {
        return a
    }
    return b
}

// Metrics initialization
func NewMemoryMetrics() *MemoryMetrics {
    return &MemoryMetrics{
        PoolHitRate: prometheus.NewGaugeVec(
            prometheus.GaugeOpts{
                Name: "memory_pool_hit_rate",
                Help: "Memory pool hit rate percentage",
            },
            []string{"pool_name"},
        ),
        PoolSize: prometheus.NewGaugeVec(
            prometheus.GaugeOpts{
                Name: "memory_pool_size",
                Help: "Current memory pool size",
            },
            []string{"pool_name"},
        ),
        WeakReferences: prometheus.NewGauge(
            prometheus.GaugeOpts{
                Name: "weak_references_active",
                Help: "Number of active weak references",
            },
        ),
    }
}

func NewGCMetrics() *GCMetrics {
    return &GCMetrics{
        GCCount: prometheus.NewCounter(
            prometheus.CounterOpts{
                Name: "gc_collections_total",
                Help: "Total number of GC collections",
            },
        ),
        GCDuration: prometheus.NewHistogram(
            prometheus.HistogramOpts{
                Name: "gc_duration_seconds",
                Help: "GC pause duration in seconds",
                Buckets: prometheus.ExponentialBuckets(0.0001, 2, 15),
            },
        ),
        HeapSize: prometheus.NewGauge(
            prometheus.GaugeOpts{
                Name: "heap_size_bytes",
                Help: "Current heap size in bytes",
            },
        ),
        HeapObjects: prometheus.NewGauge(
            prometheus.GaugeOpts{
                Name: "heap_objects_total",
                Help: "Number of objects in heap",
            },
        ),
        GCCPUPercentage: prometheus.NewGauge(
            prometheus.GaugeOpts{
                Name: "gc_cpu_percentage",
                Help: "GC CPU usage percentage",
            },
        ),
    }
}

type MemoryMetrics struct {
    PoolHitRate     *prometheus.GaugeVec
    PoolSize        *prometheus.GaugeVec
    WeakReferences  prometheus.Gauge
}

// Go 1.24 weak pointer implementation
package weakptr

import (
    "reflect"
    "runtime"
    "sync"
    "sync/atomic"
    "unsafe"
)

// WeakPointer represents a weak reference that doesn't prevent garbage collection
type WeakPointer[T any] struct {
    ptr     unsafe.Pointer
    id      uintptr
    cleanup func()
    valid   int32 // atomic flag
    
    // Type information
    typeInfo *TypeInfo
    
    // Metadata
    metadata *WeakPtrMetadata
}

type TypeInfo struct {
    Type     reflect.Type
    Size     uintptr
    Align    uintptr
    Kind     reflect.Kind
}

type WeakPtrMetadata struct {
    CreatedAt    int64  // Unix timestamp
    AccessCount  int64  // Atomic counter
    LastAccess   int64  // Unix timestamp
    SourceInfo   string // Debug information
}

// Global weak pointer registry
var (
    globalRegistry = &WeakPtrRegistry{
        pointers: make(map[uintptr]*WeakPointerEntry),
        cleanup:  make(chan *WeakPointerEntry, 1000),
    }
)

type WeakPtrRegistry struct {
    pointers map[uintptr]*WeakPointerEntry
    cleanup  chan *WeakPointerEntry
    mutex    sync.RWMutex
    
    // Statistics
    totalCreated int64
    totalCleaned int64
    activeCount  int64
}

type WeakPointerEntry struct {
    id       uintptr
    weakPtr  interface{} // Actual weak pointer
    finalizer func()
    typeInfo *TypeInfo
}

// Create new weak pointer
func NewWeakPointer[T any](obj *T) *WeakPointer[T] {
    if obj == nil {
        return nil
    }
    
    ptr := unsafe.Pointer(obj)
    id := uintptr(ptr)
    
    // Get type information
    typeInfo := &TypeInfo{
        Type:  reflect.TypeOf(*obj),
        Size:  unsafe.Sizeof(*obj),
        Align: unsafe.Alignof(*obj),
        Kind:  reflect.TypeOf(*obj).Kind(),
    }
    
    // Create metadata
    metadata := &WeakPtrMetadata{
        CreatedAt:  time.Now().Unix(),
        SourceInfo: getCallerInfo(),
    }
    
    weak := &WeakPointer[T]{
        ptr:      ptr,
        id:       id,
        valid:    1,
        typeInfo: typeInfo,
        metadata: metadata,
    }
    
    // Register with global registry
    globalRegistry.register(weak)
    
    // Set up finalizer for the original object
    runtime.SetFinalizer(obj, func(obj *T) {
        weak.invalidate()
        globalRegistry.markForCleanup(id)
    })
    
    return weak
}

// Get the referenced object
func (wp *WeakPointer[T]) Get() *T {
    if !wp.IsValid() {
        return nil
    }
    
    // Update access statistics
    atomic.AddInt64(&wp.metadata.AccessCount, 1)
    atomic.StoreInt64(&wp.metadata.LastAccess, time.Now().Unix())
    
    // Attempt to recover the object
    // Note: This requires runtime support for true weak pointers
    return (*T)(wp.ptr)
}

// Check if the weak pointer is still valid
func (wp *WeakPointer[T]) IsValid() bool {
    return atomic.LoadInt32(&wp.valid) != 0
}

// Invalidate the weak pointer
func (wp *WeakPointer[T]) invalidate() {
    if atomic.CompareAndSwapInt32(&wp.valid, 1, 0) {
        if wp.cleanup != nil {
            wp.cleanup()
        }
    }
}

// Set cleanup callback
func (wp *WeakPointer[T]) SetCleanup(cleanup func()) {
    wp.cleanup = cleanup
}

// Get metadata
func (wp *WeakPointer[T]) Metadata() *WeakPtrMetadata {
    return wp.metadata
}

// Get type information
func (wp *WeakPointer[T]) TypeInfo() *TypeInfo {
    return wp.typeInfo
}

// Register weak pointer with global registry
func (wpr *WeakPtrRegistry) register(weak interface{}) {
    wpr.mutex.Lock()
    defer wpr.mutex.Unlock()
    
    var id uintptr
    switch w := weak.(type) {
    case *WeakPointer[any]:
        id = w.id
    default:
        // Handle other weak pointer types
        return
    }
    
    entry := &WeakPointerEntry{
        id:      id,
        weakPtr: weak,
    }
    
    wpr.pointers[id] = entry
    atomic.AddInt64(&wpr.totalCreated, 1)
    atomic.AddInt64(&wpr.activeCount, 1)
}

// Mark weak pointer for cleanup
func (wpr *WeakPtrRegistry) markForCleanup(id uintptr) {
    wpr.mutex.RLock()
    entry, exists := wpr.pointers[id]
    wpr.mutex.RUnlock()
    
    if exists {
        select {
        case wpr.cleanup <- entry:
        default:
            // Cleanup queue full, clean immediately
            wpr.cleanupEntry(entry)
        }
    }
}

// Cleanup entry
func (wpr *WeakPtrRegistry) cleanupEntry(entry *WeakPointerEntry) {
    wpr.mutex.Lock()
    delete(wpr.pointers, entry.id)
    wpr.mutex.Unlock()
    
    if entry.finalizer != nil {
        entry.finalizer()
    }
    
    atomic.AddInt64(&wpr.totalCleaned, 1)
    atomic.AddInt64(&wpr.activeCount, -1)
}

// Advanced weak pointer patterns for caches
type WeakCache[K comparable, V any] struct {
    entries map[K]*WeakCacheEntry[V]
    mutex   sync.RWMutex
    
    // Statistics
    hits   int64
    misses int64
    
    // Configuration
    maxSize     int
    ttl         time.Duration
    onEvict     func(K, *V)
}

type WeakCacheEntry[V any] struct {
    weakPtr   *WeakPointer[V]
    createdAt time.Time
    lastAccess time.Time
    hitCount   int64
}

// Create new weak cache
func NewWeakCache[K comparable, V any](maxSize int, ttl time.Duration) *WeakCache[K, V] {
    cache := &WeakCache[K, V]{
        entries: make(map[K]*WeakCacheEntry[V]),
        maxSize: maxSize,
        ttl:     ttl,
    }
    
    // Start cleanup goroutine
    go cache.cleanupLoop()
    
    return cache
}

// Store value in weak cache
func (wc *WeakCache[K, V]) Store(key K, value *V) {
    if value == nil {
        return
    }
    
    wc.mutex.Lock()
    defer wc.mutex.Unlock()
    
    // Create weak pointer
    weakPtr := NewWeakPointer(value)
    if weakPtr == nil {
        return
    }
    
    // Set cleanup callback to remove from cache
    weakPtr.SetCleanup(func() {
        wc.remove(key)
    })
    
    // Create cache entry
    entry := &WeakCacheEntry[V]{
        weakPtr:    weakPtr,
        createdAt:  time.Now(),
        lastAccess: time.Now(),
    }
    
    // Store in cache
    wc.entries[key] = entry
    
    // Enforce size limit
    if len(wc.entries) > wc.maxSize {
        wc.evictOldest()
    }
}

// Load value from weak cache
func (wc *WeakCache[K, V]) Load(key K) (*V, bool) {
    wc.mutex.RLock()
    entry, exists := wc.entries[key]
    wc.mutex.RUnlock()
    
    if !exists {
        atomic.AddInt64(&wc.misses, 1)
        return nil, false
    }
    
    // Get value from weak pointer
    value := entry.weakPtr.Get()
    if value == nil {
        // Object was garbage collected
        wc.remove(key)
        atomic.AddInt64(&wc.misses, 1)
        return nil, false
    }
    
    // Update access statistics
    wc.mutex.Lock()
    entry.lastAccess = time.Now()
    atomic.AddInt64(&entry.hitCount, 1)
    wc.mutex.Unlock()
    
    atomic.AddInt64(&wc.hits, 1)
    return value, true
}

// Remove entry from cache
func (wc *WeakCache[K, V]) remove(key K) {
    wc.mutex.Lock()
    defer wc.mutex.Unlock()
    
    if entry, exists := wc.entries[key]; exists {
        delete(wc.entries, key)
        
        if wc.onEvict != nil && entry.weakPtr.IsValid() {
            if value := entry.weakPtr.Get(); value != nil {
                wc.onEvict(key, value)
            }
        }
    }
}

// Evict oldest entry
func (wc *WeakCache[K, V]) evictOldest() {
    var oldestKey K
    var oldestTime time.Time
    first := true
    
    for key, entry := range wc.entries {
        if first || entry.lastAccess.Before(oldestTime) {
            oldestKey = key
            oldestTime = entry.lastAccess
            first = false
        }
    }
    
    if !first {
        wc.remove(oldestKey)
    }
}

// Cleanup loop for expired entries
func (wc *WeakCache[K, V]) cleanupLoop() {
    ticker := time.NewTicker(wc.ttl / 4)
    defer ticker.Stop()
    
    for range ticker.C {
        now := time.Now()
        
        wc.mutex.RLock()
        var expired []K
        for key, entry := range wc.entries {
            if now.Sub(entry.lastAccess) > wc.ttl {
                expired = append(expired, key)
            }
        }
        wc.mutex.RUnlock()
        
        for _, key := range expired {
            wc.remove(key)
        }
    }
}

// Get cache statistics
func (wc *WeakCache[K, V]) Stats() CacheStats {
    wc.mutex.RLock()
    defer wc.mutex.RUnlock()
    
    return CacheStats{
        Size:     len(wc.entries),
        Hits:     atomic.LoadInt64(&wc.hits),
        Misses:   atomic.LoadInt64(&wc.misses),
        HitRatio: float64(wc.hits) / float64(wc.hits + wc.misses),
    }
}

type CacheStats struct {
    Size     int
    Hits     int64
    Misses   int64
    HitRatio float64
}

// Weak reference observer pattern
type WeakObserver[T any] struct {
    observers map[uintptr]*WeakPointer[Observer[T]]
    mutex     sync.RWMutex
}

type Observer[T any] interface {
    OnNext(value T)
    OnError(err error)
    OnComplete()
}

// Create new weak observer
func NewWeakObserver[T any]() *WeakObserver[T] {
    return &WeakObserver[T]{
        observers: make(map[uintptr]*WeakPointer[Observer[T]]),
    }
}

// Subscribe observer
func (wo *WeakObserver[T]) Subscribe(observer Observer[T]) {
    wo.mutex.Lock()
    defer wo.mutex.Unlock()
    
    weakObs := NewWeakPointer(&observer)
    if weakObs != nil {
        wo.observers[weakObs.id] = weakObs
        
        // Set cleanup to remove from observers
        weakObs.SetCleanup(func() {
            wo.mutex.Lock()
            delete(wo.observers, weakObs.id)
            wo.mutex.Unlock()
        })
    }
}

// Notify all observers
func (wo *WeakObserver[T]) Notify(value T) {
    wo.mutex.RLock()
    defer wo.mutex.RUnlock()
    
    for _, weakObs := range wo.observers {
        if obs := weakObs.Get(); obs != nil {
            (*obs).OnNext(value)
        }
    }
}

// Utility functions
func getCallerInfo() string {
    _, file, line, ok := runtime.Caller(2)
    if !ok {
        return "unknown"
    }
    return fmt.Sprintf("%s:%d", file, line)
}

// Initialize global registry cleanup
func init() {
    go func() {
        for entry := range globalRegistry.cleanup {
            globalRegistry.cleanupEntry(entry)
        }
    }()
}