package connection

import (
	"hash/fnv"
	"sync"
	"sync/atomic"
	"time"

	"github.com/noahlann/nnet/pkg/errors"
)

// ShardedManager 分段连接管理器（减少锁竞争）
type ShardedManager struct {
	shards     []*shard
	shardCount int
	maxConns   int
	totalConns atomic.Int64
	// 分组策略注册表（共享，不需要分片）
	strategies map[string]GroupStrategy
	strategyMu sync.RWMutex
}

// shard 分片
type shard struct {
	connections map[string]ConnectionInterface
	groups      map[string]map[string]ConnectionInterface
	// 索引系统：indexKey -> indexValue -> connID
	indexes map[string]map[string]string
	// 反向索引：connID -> indexKey -> indexValue（用于快速删除）
	reverseIndexes map[string]map[string]string
	mu             sync.RWMutex
}

// NewShardedManager 创建分段连接管理器
func NewShardedManager(maxConns int, shardCount int) *ShardedManager {
	if shardCount <= 0 {
		shardCount = 16 // 默认16个分片
	}
	if shardCount > 256 {
		shardCount = 256 // 最大256个分片
	}

	shards := make([]*shard, shardCount)
	for i := range shards {
		shards[i] = &shard{
			connections:    make(map[string]ConnectionInterface),
			groups:         make(map[string]map[string]ConnectionInterface),
			indexes:        make(map[string]map[string]string),
			reverseIndexes: make(map[string]map[string]string),
		}
	}

	return &ShardedManager{
		shards:     shards,
		shardCount: shardCount,
		maxConns:   maxConns,
		strategies: make(map[string]GroupStrategy),
	}
}

// getShard 获取连接对应的分片
func (m *ShardedManager) getShard(connID string) *shard {
	h := fnv.New32a()
	h.Write([]byte(connID))
	idx := h.Sum32() % uint32(m.shardCount)
	return m.shards[idx]
}

// Add 添加连接
func (m *ShardedManager) Add(conn ConnectionInterface) error {
	if conn == nil {
		return errors.New("connection cannot be nil")
	}

	shard := m.getShard(conn.ID())
	shard.mu.Lock()
	defer shard.mu.Unlock()

	// 检查是否已存在（避免重复添加）
	if _, exists := shard.connections[conn.ID()]; exists {
		return errors.New("connection already exists")
	}

	if m.maxConns > 0 {
		for {
			current := m.totalConns.Load()
			if int(current) >= m.maxConns {
				return errors.New("max connections exceeded")
			}
			if m.totalConns.CompareAndSwap(current, current+1) {
				break
			}
		}
	} else {
		m.totalConns.Add(1)
	}

	shard.connections[conn.ID()] = conn
	return nil
}

// Remove 移除连接
func (m *ShardedManager) Remove(connID string) error {
	shard := m.getShard(connID)
	shard.mu.Lock()
	defer shard.mu.Unlock()

	conn, ok := shard.connections[connID]
	if !ok {
		return errors.ErrConnectionNotFound
	}

	delete(shard.connections, connID)
	m.totalConns.Add(-1)

	// 从所有分组中移除
	for groupID := range shard.groups {
		delete(shard.groups[groupID], connID)
		if len(shard.groups[groupID]) == 0 {
			delete(shard.groups, groupID)
		}
	}

	// 从所有索引中移除
	if indexKeys, exists := shard.reverseIndexes[connID]; exists {
		for indexKey, indexValue := range indexKeys {
			if indexMap, exists := shard.indexes[indexKey]; exists {
				delete(indexMap, indexValue)
				if len(indexMap) == 0 {
					delete(shard.indexes, indexKey)
				}
			}
		}
		delete(shard.reverseIndexes, connID)
	}

	// 关闭连接
	return conn.Close()
}

// Get 获取连接
func (m *ShardedManager) Get(connID string) (ConnectionInterface, error) {
	shard := m.getShard(connID)
	shard.mu.RLock()
	defer shard.mu.RUnlock()

	conn, ok := shard.connections[connID]
	if !ok {
		return nil, errors.ErrConnectionNotFound
	}

	return conn, nil
}

// Count 获取连接数
func (m *ShardedManager) Count() int {
	return int(m.totalConns.Load())
}

// GetAll 获取所有连接
func (m *ShardedManager) GetAll() []ConnectionInterface {
	total := m.Count()
	if total < 0 {
		total = 0
	}
	allConns := make([]ConnectionInterface, 0, total)

	for _, shard := range m.shards {
		shard.mu.RLock()
		for _, conn := range shard.connections {
			allConns = append(allConns, conn)
		}
		shard.mu.RUnlock()
	}

	return allConns
}

// AddToGroup 将连接添加到分组
func (m *ShardedManager) AddToGroup(groupID string, connID string) error {
	shard := m.getShard(connID)
	shard.mu.Lock()
	defer shard.mu.Unlock()

	conn, ok := shard.connections[connID]
	if !ok {
		return errors.ErrConnectionNotFound
	}

	if shard.groups[groupID] == nil {
		shard.groups[groupID] = make(map[string]ConnectionInterface)
	}

	shard.groups[groupID][connID] = conn
	return nil
}

// RemoveFromGroup 从分组中移除连接
func (m *ShardedManager) RemoveFromGroup(groupID string, connID string) error {
	shard := m.getShard(connID)
	shard.mu.Lock()
	defer shard.mu.Unlock()

	if shard.groups[groupID] == nil {
		return nil
	}

	delete(shard.groups[groupID], connID)
	if len(shard.groups[groupID]) == 0 {
		delete(shard.groups, groupID)
	}

	return nil
}

// GetGroup 获取分组
func (m *ShardedManager) GetGroup(groupID string) []ConnectionInterface {
	var conns []ConnectionInterface

	// 需要在所有分片中查找（因为分组可能跨分片）
	for _, shard := range m.shards {
		shard.mu.RLock()
		if shard.groups[groupID] != nil {
			for _, conn := range shard.groups[groupID] {
				conns = append(conns, conn)
			}
		}
		shard.mu.RUnlock()
	}

	return conns
}

// BroadcastToGroup 向分组广播消息
func (m *ShardedManager) BroadcastToGroup(groupID string, data []byte) error {
	if groupID == "" {
		return nil
	}

	var wg sync.WaitGroup
	var mu sync.Mutex
	var errs []error

	for _, shard := range m.shards {
		shard.mu.RLock()
		group := shard.groups[groupID]
		if len(group) == 0 {
			shard.mu.RUnlock()
			continue
		}

		conns := make([]ConnectionInterface, 0, len(group))
		for _, conn := range group {
			conns = append(conns, conn)
		}
		shard.mu.RUnlock()

		if len(conns) == 0 {
			continue
		}

		wg.Add(1)
		go func(connections []ConnectionInterface) {
			defer wg.Done()
			var localErrs []error
			for _, conn := range connections {
		if err := conn.Write(data); err != nil {
					localErrs = append(localErrs, err)
				}
			}
			if len(localErrs) > 0 {
				mu.Lock()
				errs = append(errs, localErrs...)
				mu.Unlock()
		}
		}(conns)
	}

	wg.Wait()

	if len(errs) > 0 {
		return errors.Newf("broadcast failed: %d errors", len(errs))
	}

	return nil
}

// CleanupInactive 清理非活动连接
func (m *ShardedManager) CleanupInactive(timeout interface{}) {
	timeoutDuration, ok := timeout.(time.Duration)
	if !ok {
		return
	}
	now := time.Now()

	for _, shard := range m.shards {
		shard.mu.Lock()
		for connID, conn := range shard.connections {
			// 检查连接是否有LastActive方法
			if activeConn, ok := conn.(interface{ LastActive() time.Time }); ok {
				if now.Sub(activeConn.LastActive()) > timeoutDuration {
					delete(shard.connections, connID)
					conn.Close()
					m.totalConns.Add(-1)

					// 从所有分组中移除
					for groupID := range shard.groups {
						delete(shard.groups[groupID], connID)
						if len(shard.groups[groupID]) == 0 {
							delete(shard.groups, groupID)
						}
					}

					// 从所有索引中移除
					if indexKeys, exists := shard.reverseIndexes[connID]; exists {
						for indexKey, indexValue := range indexKeys {
							if indexMap, exists := shard.indexes[indexKey]; exists {
								delete(indexMap, indexValue)
								if len(indexMap) == 0 {
									delete(shard.indexes, indexKey)
								}
							}
						}
						delete(shard.reverseIndexes, connID)
					}
				}
			}
		}
		shard.mu.Unlock()
	}
}

// AddIndex 添加索引（通过业务数据查询连接）
func (m *ShardedManager) AddIndex(key, value string, connID string) error {
	shard := m.getShard(connID)
	shard.mu.Lock()
	defer shard.mu.Unlock()

	// 验证连接存在
	if _, exists := shard.connections[connID]; !exists {
		return errors.ErrConnectionNotFound
	}

	// 创建索引映射（如果不存在）
	if shard.indexes[key] == nil {
		shard.indexes[key] = make(map[string]string)
	}

	// 添加索引（如果值已存在，会覆盖）
	shard.indexes[key][value] = connID

	// 维护反向索引
	if shard.reverseIndexes[connID] == nil {
		shard.reverseIndexes[connID] = make(map[string]string)
	}
	shard.reverseIndexes[connID][key] = value

	return nil
}

// RemoveIndex 移除索引
func (m *ShardedManager) RemoveIndex(key, value string, connID string) error {
	shard := m.getShard(connID)
	shard.mu.Lock()
	defer shard.mu.Unlock()

	// 从索引中移除
	if indexMap, exists := shard.indexes[key]; exists {
		delete(indexMap, value)
		if len(indexMap) == 0 {
			delete(shard.indexes, key)
		}
	}

	// 从反向索引中移除
	if reverseIndex, exists := shard.reverseIndexes[connID]; exists {
		delete(reverseIndex, key)
		if len(reverseIndex) == 0 {
			delete(shard.reverseIndexes, connID)
		}
	}

	return nil
}

// FindByIndex 通过索引查找连接（需要遍历所有分片）
func (m *ShardedManager) FindByIndex(key, value string) (ConnectionInterface, error) {
	// 需要在所有分片中查找
	for _, shard := range m.shards {
		shard.mu.RLock()
		indexMap, exists := shard.indexes[key]
		if exists {
			if connID, exists := indexMap[value]; exists {
				if conn, exists := shard.connections[connID]; exists {
					shard.mu.RUnlock()
					return conn, nil
				}
			}
		}
		shard.mu.RUnlock()
	}

	return nil, errors.ErrConnectionNotFound
}

// FindByIndexKey 通过索引键查找所有连接（需要遍历所有分片）
func (m *ShardedManager) FindByIndexKey(key string) ([]ConnectionInterface, error) {
	var conns []ConnectionInterface
	seen := make(map[string]bool) // 去重

	// 需要在所有分片中查找
	for _, shard := range m.shards {
		shard.mu.RLock()
		indexMap, exists := shard.indexes[key]
		if exists {
			for _, connID := range indexMap {
				if seen[connID] {
					continue
				}
				if conn, exists := shard.connections[connID]; exists {
					conns = append(conns, conn)
					seen[connID] = true
				}
			}
		}
		shard.mu.RUnlock()
	}

	return conns, nil
}

// AddToGroupByStrategy 使用分组策略将连接添加到分组
func (m *ShardedManager) AddToGroupByStrategy(groupID string, connID string, strategy GroupStrategy) error {
	shard := m.getShard(connID)
	shard.mu.Lock()
	defer shard.mu.Unlock()

	conn, ok := shard.connections[connID]
	if !ok {
		return errors.ErrConnectionNotFound
	}

	// 如果策略支持自动分组，使用策略获取分组ID
	if strategy != nil {
		if autoGroupID := strategy.GetGroupID(conn); autoGroupID != "" {
			groupID = autoGroupID
		}
	}

	if shard.groups[groupID] == nil {
		shard.groups[groupID] = make(map[string]ConnectionInterface)
	}

	shard.groups[groupID][connID] = conn
	return nil
}

// GetGroupByStrategy 使用分组策略获取分组（需要遍历所有分片）
func (m *ShardedManager) GetGroupByStrategy(groupID string, strategy GroupStrategy) []ConnectionInterface {
	var conns []ConnectionInterface

	// 如果使用策略，通过策略匹配所有连接（需要遍历所有分片）
	if strategy != nil {
		for _, shard := range m.shards {
			shard.mu.RLock()
			for _, conn := range shard.connections {
				if strategy.Match(conn, groupID) {
					conns = append(conns, conn)
				}
			}
			shard.mu.RUnlock()
		}
		return conns
	}

	// 否则使用传统的字符串分组（需要遍历所有分片）
	for _, shard := range m.shards {
		shard.mu.RLock()
		if shard.groups[groupID] != nil {
			for _, conn := range shard.groups[groupID] {
				conns = append(conns, conn)
			}
		}
		shard.mu.RUnlock()
	}

	return conns
}

// RegisterGroupStrategy 注册分组策略
func (m *ShardedManager) RegisterGroupStrategy(name string, strategy GroupStrategy) {
	m.strategyMu.Lock()
	defer m.strategyMu.Unlock()

	if m.strategies == nil {
		m.strategies = make(map[string]GroupStrategy)
	}
	m.strategies[name] = strategy
}

// GetGroupStrategy 获取已注册的分组策略
func (m *ShardedManager) GetGroupStrategy(name string) GroupStrategy {
	m.strategyMu.RLock()
	defer m.strategyMu.RUnlock()

	return m.strategies[name]
}