package storage

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

	"chorus.services/bzzz/pkg/dht"
	"chorus.services/bzzz/pkg/types"
)

// DistributedStorageImpl implements the DistributedStorage interface
type DistributedStorageImpl struct {
	mu          sync.RWMutex
	dht         dht.DHT
	nodeID      string
	metrics     *DistributedStorageStats
	replicas    map[string][]string // key -> replica node IDs
	heartbeat   *HeartbeatManager
	consensus   *ConsensusManager
	options     *DistributedStorageOptions
}

// HeartbeatManager manages node heartbeats and health
type HeartbeatManager struct {
	mu           sync.RWMutex
	nodes        map[string]*NodeHealth
	heartbeatInterval time.Duration
	timeoutThreshold  time.Duration
	stopCh       chan struct{}
}

// NodeHealth tracks the health of a distributed storage node
type NodeHealth struct {
	NodeID       string    `json:"node_id"`
	LastSeen     time.Time `json:"last_seen"`
	Latency      time.Duration `json:"latency"`
	IsActive     bool      `json:"is_active"`
	FailureCount int       `json:"failure_count"`
	Load         float64   `json:"load"`
}

// ConsensusManager handles consensus operations for distributed storage
type ConsensusManager struct {
	mu             sync.RWMutex
	pendingOps     map[string]*ConsensusOperation
	votingTimeout  time.Duration
	quorumSize     int
}

// ConsensusOperation represents a distributed operation requiring consensus
type ConsensusOperation struct {
	ID          string                 `json:"id"`
	Type        string                 `json:"type"`
	Key         string                 `json:"key"`
	Data        interface{}            `json:"data"`
	Initiator   string                 `json:"initiator"`
	Votes       map[string]bool        `json:"votes"`
	CreatedAt   time.Time              `json:"created_at"`
	Status      ConsensusStatus        `json:"status"`
	Callback    func(bool, error)      `json:"-"`
}

// ConsensusStatus represents the status of a consensus operation
type ConsensusStatus string

const (
	ConsensusPending   ConsensusStatus = "pending"
	ConsensusApproved  ConsensusStatus = "approved"
	ConsensusRejected  ConsensusStatus = "rejected"
	ConsensusTimeout   ConsensusStatus = "timeout"
)

// NewDistributedStorage creates a new distributed storage implementation
func NewDistributedStorage(
	dht dht.DHT,
	nodeID string,
	options *DistributedStorageOptions,
) *DistributedStorageImpl {
	if options == nil {
		options = &DistributedStoreOptions{
			ReplicationFactor: 3,
			ConsistencyLevel:  ConsistencyQuorum,
			Timeout:          30 * time.Second,
			PreferLocal:      true,
			SyncMode:         SyncAsync,
		}
	}

	ds := &DistributedStorageImpl{
		dht:      dht,
		nodeID:   nodeID,
		options:  options,
		replicas: make(map[string][]string),
		metrics: &DistributedStorageStats{
			LastRebalance: time.Now(),
		},
		heartbeat: &HeartbeatManager{
			nodes:            make(map[string]*NodeHealth),
			heartbeatInterval: 30 * time.Second,
			timeoutThreshold:  90 * time.Second,
			stopCh:           make(chan struct{}),
		},
		consensus: &ConsensusManager{
			pendingOps:    make(map[string]*ConsensusOperation),
			votingTimeout: 10 * time.Second,
			quorumSize:    (options.ReplicationFactor / 2) + 1,
		},
	}

	// Start background processes
	go ds.heartbeat.start()
	go ds.consensusMonitor()
	go ds.rebalanceMonitor()

	return ds
}

// Store stores data in the distributed DHT with replication
func (ds *DistributedStorageImpl) Store(
	ctx context.Context,
	key string,
	data interface{},
	options *DistributedStoreOptions,
) error {
	start := time.Now()

	if options == nil {
		options = ds.options
	}

	// Serialize data
	dataBytes, err := json.Marshal(data)
	if err != nil {
		return fmt.Errorf("failed to marshal data: %w", err)
	}

	// Create distributed entry
	entry := &DistributedEntry{
		Key:               key,
		Data:              dataBytes,
		ReplicationFactor: options.ReplicationFactor,
		ConsistencyLevel:  options.ConsistencyLevel,
		CreatedAt:         time.Now(),
		Version:           1,
		Checksum:          ds.calculateChecksum(dataBytes),
	}

	// Determine target nodes for replication
	targetNodes, err := ds.selectReplicationNodes(key, options.ReplicationFactor)
	if err != nil {
		return fmt.Errorf("failed to select replication nodes: %w", err)
	}

	// Store based on consistency level
	switch options.ConsistencyLevel {
	case ConsistencyEventual:
		return ds.storeEventual(ctx, entry, targetNodes)
	case ConsistencyStrong:
		return ds.storeStrong(ctx, entry, targetNodes)
	case ConsistencyQuorum:
		return ds.storeQuorum(ctx, entry, targetNodes)
	default:
		return fmt.Errorf("unsupported consistency level: %s", options.ConsistencyLevel)
	}
}

// Retrieve retrieves data from the distributed DHT
func (ds *DistributedStorageImpl) Retrieve(
	ctx context.Context,
	key string,
) (interface{}, error) {
	start := time.Now()
	defer func() {
		ds.updateLatencyMetrics(time.Since(start))
	}()

	// Try local first if prefer local is enabled
	if ds.options.PreferLocal {
		if localData, err := ds.dht.Get(key); err == nil {
			return ds.deserializeEntry(localData)
		}
	}

	// Get replica nodes for this key
	replicas, err := ds.getReplicationNodes(key)
	if err != nil {
		return nil, fmt.Errorf("failed to get replication nodes: %w", err)
	}

	// Retrieve from replicas
	return ds.retrieveFromReplicas(ctx, key, replicas)
}

// Delete removes data from the distributed DHT
func (ds *DistributedStorageImpl) Delete(
	ctx context.Context,
	key string,
) error {
	// Get replica nodes
	replicas, err := ds.getReplicationNodes(key)
	if err != nil {
		return fmt.Errorf("failed to get replication nodes: %w", err)
	}

	// Create consensus operation for deletion
	opID := ds.generateOperationID()
	op := &ConsensusOperation{
		ID:        opID,
		Type:      "delete",
		Key:       key,
		Initiator: ds.nodeID,
		Votes:     make(map[string]bool),
		CreatedAt: time.Now(),
		Status:    ConsensusPending,
	}

	// Execute consensus deletion
	return ds.executeConsensusOperation(ctx, op, replicas)
}

// Exists checks if data exists in the DHT
func (ds *DistributedStorageImpl) Exists(
	ctx context.Context,
	key string,
) (bool, error) {
	// Try local first
	if ds.options.PreferLocal {
		if exists, err := ds.dht.Exists(key); err == nil {
			return exists, nil
		}
	}

	// Check replicas
	replicas, err := ds.getReplicationNodes(key)
	if err != nil {
		return false, fmt.Errorf("failed to get replication nodes: %w", err)
	}

	for _, nodeID := range replicas {
		if exists, err := ds.checkExistsOnNode(ctx, nodeID, key); err == nil && exists {
			return true, nil
		}
	}

	return false, nil
}

// Replicate ensures data is replicated across nodes
func (ds *DistributedStorageImpl) Replicate(
	ctx context.Context,
	key string,
	replicationFactor int,
) error {
	// Get current replicas
	currentReplicas, err := ds.getReplicationNodes(key)
	if err != nil {
		return fmt.Errorf("failed to get current replicas: %w", err)
	}

	// If we already have enough replicas, return
	if len(currentReplicas) >= replicationFactor {
		return nil
	}

	// Get the data to replicate
	data, err := ds.Retrieve(ctx, key)
	if err != nil {
		return fmt.Errorf("failed to retrieve data for replication: %w", err)
	}

	// Select additional nodes for replication
	neededReplicas := replicationFactor - len(currentReplicas)
	newNodes, err := ds.selectAdditionalNodes(key, currentReplicas, neededReplicas)
	if err != nil {
		return fmt.Errorf("failed to select additional nodes: %w", err)
	}

	// Replicate to new nodes
	for _, nodeID := range newNodes {
		if err := ds.replicateToNode(ctx, nodeID, key, data); err != nil {
			// Log but continue with other nodes
			fmt.Printf("Failed to replicate to node %s: %v\n", nodeID, err)
			continue
		}
		currentReplicas = append(currentReplicas, nodeID)
	}

	// Update replica tracking
	ds.mu.Lock()
	ds.replicas[key] = currentReplicas
	ds.mu.Unlock()

	return nil
}

// FindReplicas finds all replicas of data
func (ds *DistributedStorageImpl) FindReplicas(
	ctx context.Context,
	key string,
) ([]string, error) {
	return ds.getReplicationNodes(key)
}

// Sync synchronizes with other DHT nodes
func (ds *DistributedStorageImpl) Sync(ctx context.Context) error {
	start := time.Now()
	defer func() {
		ds.metrics.LastRebalance = time.Now()
	}()

	// Get list of active nodes
	activeNodes := ds.heartbeat.getActiveNodes()

	// Sync with each active node
	for _, nodeID := range activeNodes {
		if nodeID == ds.nodeID {
			continue // Skip self
		}

		if err := ds.syncWithNode(ctx, nodeID); err != nil {
			// Log but continue with other nodes
			fmt.Printf("Failed to sync with node %s: %v\n", nodeID, err)
			continue
		}
	}

	return nil
}

// GetDistributedStats returns distributed storage statistics
func (ds *DistributedStorageImpl) GetDistributedStats() (*DistributedStorageStats, error) {
	ds.mu.RLock()
	defer ds.mu.RUnlock()

	// Update current stats
	activeNodes := ds.heartbeat.getActiveNodes()
	ds.metrics.ActiveNodes = len(activeNodes)
	ds.metrics.TotalNodes = len(ds.heartbeat.nodes)
	ds.metrics.FailedNodes = ds.metrics.TotalNodes - ds.metrics.ActiveNodes

	// Calculate replica health
	totalReplicas := int64(0)
	healthyReplicas := int64(0)
	underReplicated := int64(0)

	for key, replicas := range ds.replicas {
		totalReplicas += int64(len(replicas))
		healthy := 0
		for _, nodeID := range replicas {
			if ds.heartbeat.isNodeHealthy(nodeID) {
				healthy++
			}
		}
		healthyReplicas += int64(healthy)
		if healthy < ds.options.ReplicationFactor {
			underReplicated++
		}
	}

	ds.metrics.TotalReplicas = totalReplicas
	ds.metrics.HealthyReplicas = healthyReplicas
	ds.metrics.UnderReplicated = underReplicated

	// Return copy
	statsCopy := *ds.metrics
	return &statsCopy, nil
}

// DistributedEntry represents a distributed storage entry
type DistributedEntry struct {
	Key               string          `json:"key"`
	Data              []byte          `json:"data"`
	ReplicationFactor int             `json:"replication_factor"`
	ConsistencyLevel  ConsistencyLevel `json:"consistency_level"`
	CreatedAt         time.Time       `json:"created_at"`
	UpdatedAt         time.Time       `json:"updated_at"`
	Version           int64           `json:"version"`
	Checksum          string          `json:"checksum"`
}

// Helper methods implementation

func (ds *DistributedStorageImpl) selectReplicationNodes(key string, replicationFactor int) ([]string, error) {
	// Get active nodes
	activeNodes := ds.heartbeat.getActiveNodes()
	if len(activeNodes) < replicationFactor {
		return nil, fmt.Errorf("insufficient active nodes: need %d, have %d", replicationFactor, len(activeNodes))
	}

	// Use consistent hashing to determine primary replicas
	// This is a simplified version - production would use proper consistent hashing
	nodes := make([]string, 0, replicationFactor)
	hash := ds.calculateKeyHash(key)
	
	// Select nodes in a deterministic way based on key hash
	for i := 0; i < replicationFactor && i < len(activeNodes); i++ {
		nodeIndex := (int(hash) + i) % len(activeNodes)
		nodes = append(nodes, activeNodes[nodeIndex])
	}

	return nodes, nil
}

func (ds *DistributedStorageImpl) storeEventual(ctx context.Context, entry *DistributedEntry, nodes []string) error {
	// Store asynchronously on all nodes
	errCh := make(chan error, len(nodes))
	
	for _, nodeID := range nodes {
		go func(node string) {
			err := ds.storeOnNode(ctx, node, entry)
			errorCh <- err
		}(nodeID)
	}

	// Don't wait for all nodes - eventual consistency
	// Just ensure at least one succeeds
	select {
	case err := <-errCh:
		if err == nil {
			return nil // First success
		}
	case <-time.After(5 * time.Second):
		return fmt.Errorf("timeout waiting for eventual store")
	}

	// If first failed, try to get at least one success
	timer := time.NewTimer(10 * time.Second)
	defer timer.Stop()
	
	for i := 1; i < len(nodes); i++ {
		select {
		case err := <-errCh:
			if err == nil {
				return nil
			}
		case <-timer.C:
			return fmt.Errorf("timeout waiting for eventual store success")
		}
	}

	return fmt.Errorf("failed to store on any node")
}

func (ds *DistributedStorageImpl) storeStrong(ctx context.Context, entry *DistributedEntry, nodes []string) error {
	// Store synchronously on all nodes
	errCh := make(chan error, len(nodes))
	
	for _, nodeID := range nodes {
		go func(node string) {
			err := ds.storeOnNode(ctx, node, entry)
			errorCh <- err
		}(nodeID)
	}

	// Wait for all nodes to complete
	var errors []error
	for i := 0; i < len(nodes); i++ {
		select {
		case err := <-errCh:
			if err != nil {
				errors = append(errors, err)
			}
		case <-time.After(30 * time.Second):
			return fmt.Errorf("timeout waiting for strong consistency store")
		}
	}

	if len(errors) > 0 {
		return fmt.Errorf("strong consistency store failed: %v", errors)
	}

	return nil
}

func (ds *DistributedStorageImpl) storeQuorum(ctx context.Context, entry *DistributedEntry, nodes []string) error {
	// Store on quorum of nodes
	quorumSize := (len(nodes) / 2) + 1
	errCh := make(chan error, len(nodes))
	
	for _, nodeID := range nodes {
		go func(node string) {
			err := ds.storeOnNode(ctx, node, entry)
			errorCh <- err
		}(nodeID)
	}

	// Wait for quorum
	successCount := 0
	errorCount := 0
	
	for i := 0; i < len(nodes); i++ {
		select {
		case err := <-errCh:
			if err == nil {
				successCount++
				if successCount >= quorumSize {
					return nil // Quorum achieved
				}
			} else {
				errorCount++
				if errorCount > len(nodes)-quorumSize {
					return fmt.Errorf("quorum store failed: too many errors")
				}
			}
		case <-time.After(20 * time.Second):
			return fmt.Errorf("timeout waiting for quorum store")
		}
	}

	return fmt.Errorf("quorum store failed")
}

// Additional helper method implementations would continue here...
// This is a substantial implementation showing the architecture

func (ds *DistributedStorageImpl) calculateChecksum(data []byte) string {
	// Simple checksum calculation - would use proper hashing in production
	return fmt.Sprintf("%x", len(data)) // Placeholder
}

func (ds *DistributedStorageImpl) calculateKeyHash(key string) uint32 {
	// Simple hash function - would use proper consistent hashing in production
	hash := uint32(0)
	for _, c := range key {
		hash = hash*31 + uint32(c)
	}
	return hash
}

func (ds *DistributedStorageImpl) generateOperationID() string {
	return fmt.Sprintf("%s-%d", ds.nodeID, time.Now().UnixNano())
}

func (ds *DistributedStorageImpl) updateLatencyMetrics(latency time.Duration) {
	ds.mu.Lock()
	defer ds.mu.Unlock()
	
	if ds.metrics.NetworkLatency == 0 {
		ds.metrics.NetworkLatency = latency
	} else {
		// Exponential moving average
		ds.metrics.NetworkLatency = time.Duration(
			float64(ds.metrics.NetworkLatency)*0.8 + float64(latency)*0.2,
		)
	}
}

// Placeholder implementations for remaining methods

func (ds *DistributedStorageImpl) getReplicationNodes(key string) ([]string, error) {
	ds.mu.RLock()
	defer ds.mu.RUnlock()
	
	if replicas, exists := ds.replicas[key]; exists {
		return replicas, nil
	}
	
	// Fall back to consistent hashing
	return ds.selectReplicationNodes(key, ds.options.ReplicationFactor)
}

func (ds *DistributedStorageImpl) retrieveFromReplicas(ctx context.Context, key string, replicas []string) (interface{}, error) {
	// Try each replica until success
	for _, nodeID := range replicas {
		if data, err := ds.retrieveFromNode(ctx, nodeID, key); err == nil {
			return ds.deserializeEntry(data)
		}
	}
	return nil, fmt.Errorf("failed to retrieve from any replica")
}

func (ds *DistributedStorageImpl) deserializeEntry(data interface{}) (interface{}, error) {
	// Deserialize distributed entry
	return data, nil // Placeholder
}

// Heartbeat manager methods

func (hm *HeartbeatManager) start() {
	ticker := time.NewTicker(hm.heartbeatInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			hm.checkNodeHealth()
		case <-hm.stopCh:
			return
		}
	}
}

func (hm *HeartbeatManager) getActiveNodes() []string {
	hm.mu.RLock()
	defer hm.mu.RUnlock()

	var activeNodes []string
	for nodeID, health := range hm.nodes {
		if health.IsActive {
			activeNodes = append(activeNodes, nodeID)
		}
	}
	return activeNodes
}

func (hm *HeartbeatManager) isNodeHealthy(nodeID string) bool {
	hm.mu.RLock()
	defer hm.mu.RUnlock()

	health, exists := hm.nodes[nodeID]
	return exists && health.IsActive
}

func (hm *HeartbeatManager) checkNodeHealth() {
	// Placeholder implementation
	// Would send heartbeats and update node health
}

// Consensus monitor and other background processes

func (ds *DistributedStorageImpl) consensusMonitor() {
	ticker := time.NewTicker(5 * time.Second)
	defer ticker.Stop()

	for range ticker.C {
		ds.cleanupExpiredOperations()
	}
}

func (ds *DistributedStorageImpl) rebalanceMonitor() {
	ticker := time.NewTicker(1 * time.Hour)
	defer ticker.Stop()

	for range ticker.C {
		ds.rebalanceReplicas()
	}
}

func (ds *DistributedStorageImpl) cleanupExpiredOperations() {
	// Cleanup expired consensus operations
}

func (ds *DistributedStorageImpl) rebalanceReplicas() {
	// Rebalance replicas across healthy nodes
}

// Placeholder method stubs for remaining functionality

func (ds *DistributedStorageImpl) storeOnNode(ctx context.Context, nodeID string, entry *DistributedEntry) error {
	// Store entry on specific node
	return nil
}

func (ds *DistributedStorageImpl) retrieveFromNode(ctx context.Context, nodeID string, key string) (interface{}, error) {
	// Retrieve from specific node
	return nil, nil
}

func (ds *DistributedStorageImpl) checkExistsOnNode(ctx context.Context, nodeID string, key string) (bool, error) {
	// Check if key exists on specific node
	return false, nil
}

func (ds *DistributedStorageImpl) replicateToNode(ctx context.Context, nodeID string, key string, data interface{}) error {
	// Replicate data to specific node
	return nil
}

func (ds *DistributedStorageImpl) selectAdditionalNodes(key string, currentReplicas []string, needed int) ([]string, error) {
	// Select additional nodes for replication
	return nil, nil
}

func (ds *DistributedStorageImpl) syncWithNode(ctx context.Context, nodeID string) error {
	// Sync with specific node
	return nil
}

func (ds *DistributedStorageImpl) executeConsensusOperation(ctx context.Context, op *ConsensusOperation, nodes []string) error {
	// Execute consensus operation across nodes
	return nil
}
