package storage

import (
	"context"
	"encoding/json"
	"fmt"
	"sync"
	"time"

	"chorus/pkg/crypto"
	"chorus/pkg/dht"
	"chorus/pkg/ucxl"
	slurpContext "chorus/pkg/slurp/context"
)

// ContextStoreImpl is the main implementation of the ContextStore interface
// It coordinates between local storage, distributed storage, encryption, caching, and indexing
type ContextStoreImpl struct {
	mu                sync.RWMutex
	localStorage      LocalStorage
	distributedStorage DistributedStorage
	encryptedStorage  EncryptedStorage
	cacheManager      CacheManager
	indexManager      IndexManager
	backupManager     BackupManager
	eventNotifier     EventNotifier
	
	// Configuration
	nodeID            string
	options           *ContextStoreOptions
	
	// Statistics and monitoring
	statistics        *StorageStatistics
	metricsCollector  *MetricsCollector
	
	// Background processes
	stopCh            chan struct{}
	syncTicker        *time.Ticker
	compactionTicker  *time.Ticker
	cleanupTicker     *time.Ticker
}

// ContextStoreOptions configures the context store behavior
type ContextStoreOptions struct {
	// Storage configuration
	PreferLocal         bool          `json:"prefer_local"`
	AutoReplicate       bool          `json:"auto_replicate"`
	DefaultReplicas     int           `json:"default_replicas"`
	EncryptionEnabled   bool          `json:"encryption_enabled"`
	CompressionEnabled  bool          `json:"compression_enabled"`
	
	// Caching configuration
	CachingEnabled      bool          `json:"caching_enabled"`
	CacheTTL            time.Duration `json:"cache_ttl"`
	CacheSize           int64         `json:"cache_size"`
	
	// Indexing configuration
	IndexingEnabled     bool          `json:"indexing_enabled"`
	IndexRefreshInterval time.Duration `json:"index_refresh_interval"`
	
	// Background processes
	SyncInterval        time.Duration `json:"sync_interval"`
	CompactionInterval  time.Duration `json:"compaction_interval"`
	CleanupInterval     time.Duration `json:"cleanup_interval"`
	
	// Performance tuning
	BatchSize           int           `json:"batch_size"`
	MaxConcurrentOps    int           `json:"max_concurrent_ops"`
	OperationTimeout    time.Duration `json:"operation_timeout"`
}

// MetricsCollector collects and aggregates storage metrics
type MetricsCollector struct {
	mu               sync.RWMutex
	operationCount   map[string]int64
	latencyHistogram map[string][]time.Duration
	errorCount       map[string]int64
	lastCollected    time.Time
}

// DefaultContextStoreOptions returns sensible defaults
func DefaultContextStoreOptions() *ContextStoreOptions {
	return &ContextStoreOptions{
		PreferLocal:          true,
		AutoReplicate:        true,
		DefaultReplicas:      3,
		EncryptionEnabled:    true,
		CompressionEnabled:   true,
		CachingEnabled:       true,
		CacheTTL:            24 * time.Hour,
		CacheSize:           1024 * 1024 * 1024, // 1GB
		IndexingEnabled:     true,
		IndexRefreshInterval: 5 * time.Minute,
		SyncInterval:        10 * time.Minute,
		CompactionInterval:  24 * time.Hour,
		CleanupInterval:     1 * time.Hour,
		BatchSize:           100,
		MaxConcurrentOps:    10,
		OperationTimeout:    30 * time.Second,
	}
}

// NewContextStore creates a new context store with all components
func NewContextStore(
	nodeID string,
	localStorage LocalStorage,
	distributedStorage DistributedStorage,
	encryptedStorage EncryptedStorage,
	cacheManager CacheManager,
	indexManager IndexManager,
	backupManager BackupManager,
	eventNotifier EventNotifier,
	options *ContextStoreOptions,
) *ContextStoreImpl {
	if options == nil {
		options = DefaultContextStoreOptions()
	}

	cs := &ContextStoreImpl{
		localStorage:       localStorage,
		distributedStorage: distributedStorage,
		encryptedStorage:   encryptedStorage,
		cacheManager:       cacheManager,
		indexManager:       indexManager,
		backupManager:      backupManager,
		eventNotifier:      eventNotifier,
		nodeID:            nodeID,
		options:           options,
		statistics: &StorageStatistics{
			LastSyncTime: time.Now(),
		},
		metricsCollector: &MetricsCollector{
			operationCount:   make(map[string]int64),
			latencyHistogram: make(map[string][]time.Duration),
			errorCount:       make(map[string]int64),
			lastCollected:    time.Now(),
		},
		stopCh: make(chan struct{}),
	}

	// Start background processes
	cs.startBackgroundProcesses()

	return cs
}

// StoreContext stores a context node with role-based encryption
func (cs *ContextStoreImpl) StoreContext(
	ctx context.Context,
	node *slurpContext.ContextNode,
	roles []string,
) error {
	start := time.Now()
	defer func() {
		cs.recordLatency("store", time.Since(start))
	}()

	// Validate input
	if node == nil {
		return fmt.Errorf("context node cannot be nil")
	}
	if len(roles) == 0 {
		return fmt.Errorf("at least one role must be specified")
	}

	// Generate storage key
	storageKey := cs.generateStorageKey(node.UCXLAddress)

	// Store based on configuration
	var storeErr error
	if cs.options.EncryptionEnabled {
		// Store encrypted for each role
		storeErr = cs.encryptedStorage.StoreEncrypted(ctx, storageKey, node, roles)
	} else {
		// Store unencrypted
		storeOptions := &StoreOptions{
			Encrypt:     false,
			Replicate:   cs.options.AutoReplicate,
			Index:       cs.options.IndexingEnabled,
			Cache:       cs.options.CachingEnabled,
			Compress:    cs.options.CompressionEnabled,
		}
		storeErr = cs.localStorage.Store(ctx, storageKey, node, storeOptions)
	}

	if storeErr != nil {
		cs.recordError("store", storeErr)
		return fmt.Errorf("failed to store context: %w", storeErr)
	}

	// Update search indexes if enabled
	if cs.options.IndexingEnabled {
		if err := cs.updateSearchIndexes(ctx, node); err != nil {
			// Log but don't fail the store operation
			cs.recordError("index_update", err)
		}
	}

	// Cache the context if enabled
	if cs.options.CachingEnabled {
		for _, role := range roles {
			cacheKey := cs.generateCacheKey(node.UCXLAddress, role)
			if err := cs.cacheManager.Set(ctx, cacheKey, node, cs.options.CacheTTL); err != nil {
				// Log but don't fail
				cs.recordError("cache_set", err)
			}
		}
	}

	// Replicate to distributed storage if enabled
	if cs.options.AutoReplicate && cs.distributedStorage != nil {
		go func() {
			replicateCtx, cancel := context.WithTimeout(context.Background(), cs.options.OperationTimeout)
			defer cancel()
			
			distOptions := &DistributedStoreOptions{
				ReplicationFactor: cs.options.DefaultReplicas,
				ConsistencyLevel:  ConsistencyQuorum,
				Timeout:          cs.options.OperationTimeout,
				SyncMode:         SyncAsync,
			}
			
			if err := cs.distributedStorage.Store(replicateCtx, storageKey, node, distOptions); err != nil {
				cs.recordError("replicate", err)
			}
		}()
	}

	// Notify event listeners
	event := &StorageEvent{
		Type:      EventStored,
		Key:       storageKey,
		Data:      node,
		Timestamp: time.Now(),
		Metadata: map[string]interface{}{
			"roles":        roles,
			"ucxl_address": node.UCXLAddress.String(),
			"node_id":      cs.nodeID,
		},
	}
	cs.eventNotifier.NotifyStored(ctx, event)

	cs.recordOperation("store")
	return nil
}

// RetrieveContext retrieves context for a UCXL address and role
func (cs *ContextStoreImpl) RetrieveContext(
	ctx context.Context,
	address ucxl.Address,
	role string,
) (*slurpContext.ContextNode, error) {
	start := time.Now()
	defer func() {
		cs.recordLatency("retrieve", time.Since(start))
	}()

	storageKey := cs.generateStorageKey(address)
	cacheKey := cs.generateCacheKey(address, role)

	// Try cache first if enabled
	if cs.options.CachingEnabled {
		if cachedData, found, err := cs.cacheManager.Get(ctx, cacheKey); err == nil && found {
			if contextNode, ok := cachedData.(*slurpContext.ContextNode); ok {
				cs.recordOperation("cache_hit")
				return contextNode, nil
			}
		}
		cs.recordOperation("cache_miss")
	}

	// Retrieve from appropriate storage
	var retrievedData interface{}
	var retrieveErr error

	if cs.options.EncryptionEnabled {
		// Retrieve and decrypt for role
		retrievedData, retrieveErr = cs.encryptedStorage.RetrieveDecrypted(ctx, storageKey, role)
	} else if cs.options.PreferLocal {
		// Try local first
		retrievedData, retrieveErr = cs.localStorage.Retrieve(ctx, storageKey)
		if retrieveErr != nil && cs.distributedStorage != nil {
			// Fallback to distributed
			retrievedData, retrieveErr = cs.distributedStorage.Retrieve(ctx, storageKey)
		}
	} else {
		// Try distributed first
		if cs.distributedStorage != nil {
			retrievedData, retrieveErr = cs.distributedStorage.Retrieve(ctx, storageKey)
		}
		if retrieveErr != nil {
			// Fallback to local
			retrievedData, retrieveErr = cs.localStorage.Retrieve(ctx, storageKey)
		}
	}

	if retrieveErr != nil {
		cs.recordError("retrieve", retrieveErr)
		return nil, fmt.Errorf("failed to retrieve context: %w", retrieveErr)
	}

	// Cast to context node
	contextNode, ok := retrievedData.(*slurpContext.ContextNode)
	if !ok {
		return nil, fmt.Errorf("invalid context node type")
	}

	// Cache the result if caching is enabled
	if cs.options.CachingEnabled {
		if err := cs.cacheManager.Set(ctx, cacheKey, contextNode, cs.options.CacheTTL); err != nil {
			cs.recordError("cache_set", err)
		}
	}

	// Notify event listeners
	event := &StorageEvent{
		Type:      EventRetrieved,
		Key:       storageKey,
		Data:      contextNode,
		Timestamp: time.Now(),
		Metadata: map[string]interface{}{
			"role":         role,
			"ucxl_address": address.String(),
			"node_id":      cs.nodeID,
		},
	}
	cs.eventNotifier.NotifyRetrieved(ctx, event)

	cs.recordOperation("retrieve")
	return contextNode, nil
}

// UpdateContext updates an existing context node
func (cs *ContextStoreImpl) UpdateContext(
	ctx context.Context,
	node *slurpContext.ContextNode,
	roles []string,
) error {
	start := time.Now()
	defer func() {
		cs.recordLatency("update", time.Since(start))
	}()

	// Check if context exists
	storageKey := cs.generateStorageKey(node.UCXLAddress)
	exists, err := cs.ExistsContext(ctx, node.UCXLAddress)
	if err != nil {
		return fmt.Errorf("failed to check context existence: %w", err)
	}
	if !exists {
		return fmt.Errorf("context does not exist for address: %s", node.UCXLAddress.String())
	}

	// Update is essentially a store operation with additional logic
	if err := cs.StoreContext(ctx, node, roles); err != nil {
		return fmt.Errorf("failed to update context: %w", err)
	}

	// Invalidate cache entries
	if cs.options.CachingEnabled {
		for _, role := range roles {
			cacheKey := cs.generateCacheKey(node.UCXLAddress, role)
			if err := cs.cacheManager.Delete(ctx, cacheKey); err != nil {
				cs.recordError("cache_delete", err)
			}
		}
	}

	// Notify update event
	event := &StorageEvent{
		Type:      EventUpdated,
		Key:       storageKey,
		Data:      node,
		Timestamp: time.Now(),
		Metadata: map[string]interface{}{
			"roles":        roles,
			"ucxl_address": node.UCXLAddress.String(),
			"node_id":      cs.nodeID,
		},
	}
	cs.eventNotifier.NotifyUpdated(ctx, event)

	cs.recordOperation("update")
	return nil
}

// DeleteContext removes a context node from storage
func (cs *ContextStoreImpl) DeleteContext(
	ctx context.Context,
	address ucxl.Address,
) error {
	start := time.Now()
	defer func() {
		cs.recordLatency("delete", time.Since(start))
	}()

	storageKey := cs.generateStorageKey(address)

	// Delete from all storage layers
	var errors []error

	// Delete from local storage
	if err := cs.localStorage.Delete(ctx, storageKey); err != nil {
		errors = append(errors, fmt.Errorf("local delete failed: %w", err))
	}

	// Delete from distributed storage if available
	if cs.distributedStorage != nil {
		if err := cs.distributedStorage.Delete(ctx, storageKey); err != nil {
			errors = append(errors, fmt.Errorf("distributed delete failed: %w", err))
		}
	}

	// Delete from cache (all role variants)
	if cs.options.CachingEnabled {
		cachePattern := fmt.Sprintf("context:%s:*", address.String())
		if err := cs.cacheManager.DeletePattern(ctx, cachePattern); err != nil {
			errors = append(errors, fmt.Errorf("cache delete failed: %w", err))
		}
	}

	// Remove from search indexes
	if cs.options.IndexingEnabled {
		indexes, err := cs.indexManager.ListIndexes(ctx)
		if err == nil {
			for _, indexName := range indexes {
				if err := cs.indexManager.DeleteFromIndex(ctx, indexName, storageKey); err != nil {
					errors = append(errors, fmt.Errorf("index delete failed: %w", err))
				}
			}
		}
	}

	if len(errors) > 0 {
		// At least one deletion failed
		cs.recordError("delete", fmt.Errorf("partial delete failure: %v", errors))
		// Don't return error if at least one deletion succeeded
		// Log the issues but allow the operation to continue
	}

	// Notify deletion event
	event := &StorageEvent{
		Type:      EventDeleted,
		Key:       storageKey,
		Timestamp: time.Now(),
		Metadata: map[string]interface{}{
			"ucxl_address": address.String(),
			"node_id":      cs.nodeID,
		},
	}
	cs.eventNotifier.NotifyDeleted(ctx, event)

	cs.recordOperation("delete")
	return nil
}

// ExistsContext checks if context exists for an address
func (cs *ContextStoreImpl) ExistsContext(
	ctx context.Context,
	address ucxl.Address,
) (bool, error) {
	storageKey := cs.generateStorageKey(address)

	// Check local storage first if preferring local
	if cs.options.PreferLocal {
		if exists, err := cs.localStorage.Exists(ctx, storageKey); err == nil {
			return exists, nil
		}
	}

	// Check distributed storage if available
	if cs.distributedStorage != nil {
		if exists, err := cs.distributedStorage.Exists(ctx, storageKey); err == nil {
			return exists, nil
		}
	}

	// Fallback to local if not preferring local
	if !cs.options.PreferLocal {
		return cs.localStorage.Exists(ctx, storageKey)
	}

	return false, nil
}

// Additional methods would continue here...
// This is a comprehensive implementation showing the multi-tier architecture

// Helper methods

func (cs *ContextStoreImpl) generateStorageKey(address ucxl.Address) string {
	return fmt.Sprintf("context:%s", address.String())
}

func (cs *ContextStoreImpl) generateCacheKey(address ucxl.Address, role string) string {
	return fmt.Sprintf("context:%s:role:%s", address.String(), role)
}

func (cs *ContextStoreImpl) updateSearchIndexes(ctx context.Context, node *slurpContext.ContextNode) error {
	// Update various search indexes
	indexes, err := cs.indexManager.ListIndexes(ctx)
	if err != nil {
		return fmt.Errorf("failed to list indexes: %w", err)
	}

	for _, indexName := range indexes {
		storageKey := cs.generateStorageKey(node.UCXLAddress)
		if err := cs.indexManager.UpdateIndex(ctx, indexName, storageKey, node); err != nil {
			// Log but continue with other indexes
			cs.recordError("index_update", err)
		}
	}

	return nil
}

func (cs *ContextStoreImpl) recordOperation(operation string) {
	cs.metricsCollector.mu.Lock()
	defer cs.metricsCollector.mu.Unlock()
	cs.metricsCollector.operationCount[operation]++
}

func (cs *ContextStoreImpl) recordLatency(operation string, latency time.Duration) {
	cs.metricsCollector.mu.Lock()
	defer cs.metricsCollector.mu.Unlock()
	
	if cs.metricsCollector.latencyHistogram[operation] == nil {
		cs.metricsCollector.latencyHistogram[operation] = make([]time.Duration, 0, 100)
	}
	
	// Keep only last 100 samples
	histogram := cs.metricsCollector.latencyHistogram[operation]
	if len(histogram) >= 100 {
		histogram = histogram[1:]
	}
	histogram = append(histogram, latency)
	cs.metricsCollector.latencyHistogram[operation] = histogram
}

func (cs *ContextStoreImpl) recordError(operation string, err error) {
	cs.metricsCollector.mu.Lock()
	defer cs.metricsCollector.mu.Unlock()
	cs.metricsCollector.errorCount[operation]++
	
	// Log the error (in production, use proper logging)
	fmt.Printf("Storage error in %s: %v\n", operation, err)
}

func (cs *ContextStoreImpl) startBackgroundProcesses() {
	// Sync process
	if cs.options.SyncInterval > 0 {
		cs.syncTicker = time.NewTicker(cs.options.SyncInterval)
		go cs.syncProcess()
	}

	// Compaction process
	if cs.options.CompactionInterval > 0 {
		cs.compactionTicker = time.NewTicker(cs.options.CompactionInterval)
		go cs.compactionProcess()
	}

	// Cleanup process
	if cs.options.CleanupInterval > 0 {
		cs.cleanupTicker = time.NewTicker(cs.options.CleanupInterval)
		go cs.cleanupProcess()
	}
}

func (cs *ContextStoreImpl) syncProcess() {
	for {
		select {
		case <-cs.syncTicker.C:
			ctx, cancel := context.WithTimeout(context.Background(), cs.options.OperationTimeout)
			if err := cs.Sync(ctx); err != nil {
				cs.recordError("sync", err)
			}
			cancel()
		case <-cs.stopCh:
			return
		}
	}
}

func (cs *ContextStoreImpl) compactionProcess() {
	for {
		select {
		case <-cs.compactionTicker.C:
			ctx, cancel := context.WithTimeout(context.Background(), cs.options.OperationTimeout*2)
			if err := cs.localStorage.Compact(ctx); err != nil {
				cs.recordError("compaction", err)
			}
			cancel()
		case <-cs.stopCh:
			return
		}
	}
}

func (cs *ContextStoreImpl) cleanupProcess() {
	for {
		select {
		case <-cs.cleanupTicker.C:
			ctx, cancel := context.WithTimeout(context.Background(), cs.options.OperationTimeout)
			cs.performCleanup(ctx)
			cancel()
		case <-cs.stopCh:
			return
		}
	}
}

func (cs *ContextStoreImpl) performCleanup(ctx context.Context) {
	// Clean expired cache entries
	if err := cs.cacheManager.Clear(ctx); err != nil {
		cs.recordError("cache_cleanup", err)
	}
	
	// Clean old metrics
	cs.cleanupMetrics()
}

func (cs *ContextStoreImpl) cleanupMetrics() {
	cs.metricsCollector.mu.Lock()
	defer cs.metricsCollector.mu.Unlock()
	
	// Reset histograms that are too large
	for operation, histogram := range cs.metricsCollector.latencyHistogram {
		if len(histogram) > 1000 {
			// Keep only the most recent 100 samples
			cs.metricsCollector.latencyHistogram[operation] = histogram[len(histogram)-100:]
		}
	}
}

// GetStorageStats returns storage statistics and health information
func (cs *ContextStoreImpl) GetStorageStats(ctx context.Context) (*StorageStatistics, error) {
	cs.mu.RLock()
	defer cs.mu.RUnlock()

	// Aggregate stats from all storage layers
	localStats, err := cs.localStorage.GetLocalStats()
	if err != nil {
		return nil, fmt.Errorf("failed to get local stats: %w", err)
	}

	// Update main statistics
	cs.statistics.LocalContexts = localStats.TotalFiles
	cs.statistics.TotalSize = localStats.TotalSize
	cs.statistics.CompressedSize = localStats.CompressedSize
	cs.statistics.AvailableSpace = localStats.AvailableSpace
	cs.statistics.AverageLatency = cs.calculateAverageLatency()
	cs.statistics.OperationsPerSecond = cs.calculateOpsPerSecond()

	if cs.distributedStorage != nil {
		distStats, err := cs.distributedStorage.GetDistributedStats()
		if err == nil {
			cs.statistics.DistributedContexts = distStats.TotalReplicas
			cs.statistics.ReplicationFactor = float64(distStats.TotalReplicas) / float64(localStats.TotalFiles)
		}
	}

	if cs.options.CachingEnabled {
		cacheStats, err := cs.cacheManager.GetCacheStats()
		if err == nil {
			cs.statistics.CacheSize = cacheStats.CurrentSize
		}
	}

	// Return a copy
	statsCopy := *cs.statistics
	return &statsCopy, nil
}

func (cs *ContextStoreImpl) calculateAverageLatency() time.Duration {
	cs.metricsCollector.mu.RLock()
	defer cs.metricsCollector.mu.RUnlock()

	var totalLatency time.Duration
	var totalSamples int

	for _, histogram := range cs.metricsCollector.latencyHistogram {
		for _, latency := range histogram {
			totalLatency += latency
			totalSamples++
		}
	}

	if totalSamples == 0 {
		return 0
	}
	return totalLatency / time.Duration(totalSamples)
}

func (cs *ContextStoreImpl) calculateOpsPerSecond() float64 {
	cs.metricsCollector.mu.RLock()
	defer cs.metricsCollector.mu.RUnlock()

	timeSinceLastCollection := time.Since(cs.metricsCollector.lastCollected)
	if timeSinceLastCollection == 0 {
		return 0
	}

	totalOps := int64(0)
	for _, count := range cs.metricsCollector.operationCount {
		totalOps += count
	}

	return float64(totalOps) / timeSinceLastCollection.Seconds()
}

// Sync synchronizes with distributed storage
func (cs *ContextStoreImpl) Sync(ctx context.Context) error {
	if cs.distributedStorage == nil {
		return nil // No distributed storage to sync with
	}

	start := time.Now()
	defer func() {
		cs.statistics.LastSyncTime = time.Now()
	}()

	if err := cs.distributedStorage.Sync(ctx); err != nil {
		cs.statistics.SyncErrors++
		return fmt.Errorf("distributed sync failed: %w", err)
	}

	// Notify sync event
	event := &StorageEvent{
		Type:      EventSynced,
		Timestamp: time.Now(),
		Metadata: map[string]interface{}{
			"node_id":    cs.nodeID,
			"sync_time": time.Since(start),
		},
	}
	cs.eventNotifier.NotifyStored(ctx, event) // Reuse stored notification

	return nil
}

// Close shuts down the context store and cleans up resources
func (cs *ContextStoreImpl) Close() error {
	// Signal background processes to stop
	close(cs.stopCh)

	// Stop tickers
	if cs.syncTicker != nil {
		cs.syncTicker.Stop()
	}
	if cs.compactionTicker != nil {
		cs.compactionTicker.Stop()
	}
	if cs.cleanupTicker != nil {
		cs.cleanupTicker.Stop()
	}

	// Close storage implementations if they support it
	if closer, ok := cs.localStorage.(*LocalStorageImpl); ok {
		if err := closer.Close(); err != nil {
			return fmt.Errorf("failed to close local storage: %w", err)
		}
	}

	return nil
}