package proxy

import (
	"context"
	"fmt"
	"net"
	"net/url"
	"sync"
	"sync/atomic"
	"time"

	"golang.org/x/net/proxy"
)

// manager 代理管理器实现
type manager struct {
	config *ProxyConfig
	stats  *ProxyStats
	mu     sync.RWMutex
	
	// 连接池
	dialerCache map[string]Dialer
	cacheExpiry time.Time
	cacheMu     sync.RWMutex
}

// NewProxyManager 创建新的代理管理器
func NewProxyManager(config *ProxyConfig) ProxyManager {
	if config == nil {
		config = DefaultProxyConfig()
	}
	
	return &manager{
		config: config,
		stats: &ProxyStats{
			ProxyType:    config.Type.String(),
			ProxyAddress: config.Address,
		},
		dialerCache: make(map[string]Dialer),
		cacheExpiry: time.Now().Add(5 * time.Minute),
	}
}

// GetDialer 获取普通拨号器
func (m *manager) GetDialer() (Dialer, error) {
	m.mu.RLock()
	config := m.config
	m.mu.RUnlock()
	
	switch config.Type {
	case ProxyTypeNone:
		return m.createDirectDialer(), nil
	case ProxyTypeSOCKS5:
		return m.createSOCKS5Dialer()
	case ProxyTypeHTTP, ProxyTypeHTTPS:
		return m.createHTTPDialer()
	default:
		return nil, NewProxyError(ErrTypeConfig, "不支持的代理类型", 1001, nil)
	}
}

// GetTLSDialer 获取TLS拨号器
func (m *manager) GetTLSDialer() (TLSDialer, error) {
	dialer, err := m.GetDialer()
	if err != nil {
		return nil, err
	}
	
	return &tlsDialerWrapper{
		dialer: dialer,
		config: m.config,
		stats:  m.stats,
	}, nil
}

// UpdateConfig 更新配置
func (m *manager) UpdateConfig(config *ProxyConfig) error {
	if config == nil {
		return NewProxyError(ErrTypeConfig, "配置不能为空", 1002, nil)
	}
	
	m.mu.Lock()
	defer m.mu.Unlock()
	
	m.config = config
	m.stats.ProxyType = config.Type.String()
	m.stats.ProxyAddress = config.Address
	
	// 清理缓存
	m.cacheMu.Lock()
	m.dialerCache = make(map[string]Dialer)
	m.cacheExpiry = time.Now().Add(5 * time.Minute)
	m.cacheMu.Unlock()
	
	return nil
}

// Close 关闭管理器
func (m *manager) Close() error {
	m.cacheMu.Lock()
	defer m.cacheMu.Unlock()
	
	m.dialerCache = make(map[string]Dialer)
	return nil
}

// Stats 获取统计信息
func (m *manager) Stats() *ProxyStats {
	m.mu.RLock()
	defer m.mu.RUnlock()
	
	// 返回副本以避免并发问题
	statsCopy := *m.stats
	return &statsCopy
}

// createDirectDialer 创建直连拨号器
func (m *manager) createDirectDialer() Dialer {
	return &directDialer{
		timeout: m.config.Timeout,
		stats:   m.stats,
	}
}

// createSOCKS5Dialer 创建SOCKS5拨号器
func (m *manager) createSOCKS5Dialer() (Dialer, error) {
	// 检查缓存
	cacheKey := fmt.Sprintf("socks5_%s", m.config.Address)
	m.cacheMu.RLock()
	if time.Now().Before(m.cacheExpiry) {
		if cached, exists := m.dialerCache[cacheKey]; exists {
			m.cacheMu.RUnlock()
			return cached, nil
		}
	}
	m.cacheMu.RUnlock()
	
	// 解析代理地址
	proxyURL := fmt.Sprintf("socks5://%s", m.config.Address)
	if m.config.Username != "" {
		proxyURL = fmt.Sprintf("socks5://%s:%s@%s", 
			m.config.Username, m.config.Password, m.config.Address)
	}
	
	u, err := url.Parse(proxyURL)
	if err != nil {
		return nil, NewProxyError(ErrTypeConfig, "SOCKS5代理地址解析失败", 2001, err)
	}
	
	// 创建基础拨号器
	baseDial := &net.Dialer{
		Timeout:   m.config.Timeout,
		KeepAlive: m.config.KeepAlive,
	}
	
	// 创建SOCKS5拨号器
	var auth *proxy.Auth
	if u.User != nil {
		auth = &proxy.Auth{
			User: u.User.Username(),
		}
		if password, hasPassword := u.User.Password(); hasPassword {
			auth.Password = password
		}
	}
	
	socksDialer, err := proxy.SOCKS5("tcp", u.Host, auth, baseDial)
	if err != nil {
		return nil, NewProxyError(ErrTypeConnection, "SOCKS5拨号器创建失败", 2002, err)
	}
	
	dialer := &socks5Dialer{
		dialer: socksDialer,
		config: m.config,
		stats:  m.stats,
	}
	
	// 更新缓存
	m.cacheMu.Lock()
	m.dialerCache[cacheKey] = dialer
	m.cacheExpiry = time.Now().Add(5 * time.Minute)
	m.cacheMu.Unlock()
	
	return dialer, nil
}

// createHTTPDialer 创建HTTP代理拨号器
func (m *manager) createHTTPDialer() (Dialer, error) {
	// 检查缓存
	cacheKey := fmt.Sprintf("http_%s", m.config.Address)
	m.cacheMu.RLock()
	if time.Now().Before(m.cacheExpiry) {
		if cached, exists := m.dialerCache[cacheKey]; exists {
			m.cacheMu.RUnlock()
			return cached, nil
		}
	}
	m.cacheMu.RUnlock()
	
	dialer := &httpDialer{
		config: m.config,
		stats:  m.stats,
		baseDial: &net.Dialer{
			Timeout:   m.config.Timeout,
			KeepAlive: m.config.KeepAlive,
		},
	}
	
	// 更新缓存
	m.cacheMu.Lock()
	m.dialerCache[cacheKey] = dialer
	m.cacheExpiry = time.Now().Add(5 * time.Minute)
	m.cacheMu.Unlock()
	
	return dialer, nil
}

// directDialer 直连拨号器
type directDialer struct {
	timeout time.Duration
	stats   *ProxyStats
}

func (d *directDialer) Dial(network, address string) (net.Conn, error) {
	return d.DialContext(context.Background(), network, address)
}

func (d *directDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
	start := time.Now()
	atomic.AddInt64(&d.stats.TotalConnections, 1)
	
	dialer := &net.Dialer{
		Timeout: d.timeout,
	}
	
	conn, err := dialer.DialContext(ctx, network, address)
	
	duration := time.Since(start)
	d.stats.LastConnectTime = start
	
	if err != nil {
		atomic.AddInt64(&d.stats.FailedConnections, 1)
		d.stats.LastError = err.Error()
		return nil, NewProxyError(ErrTypeConnection, "直连失败", 3001, err)
	}
	
	atomic.AddInt64(&d.stats.ActiveConnections, 1)
	d.updateAverageConnectTime(duration)
	
	return &trackedConn{
		Conn:  conn,
		stats: d.stats,
	}, nil
}

// socks5Dialer SOCKS5拨号器
type socks5Dialer struct {
	dialer proxy.Dialer
	config *ProxyConfig
	stats  *ProxyStats
}

func (s *socks5Dialer) Dial(network, address string) (net.Conn, error) {
	return s.DialContext(context.Background(), network, address)
}

func (s *socks5Dialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
	start := time.Now()
	atomic.AddInt64(&s.stats.TotalConnections, 1)
	
	// 创建一个带超时的上下文
	dialCtx, cancel := context.WithTimeout(ctx, s.config.Timeout)
	defer cancel()
	
	// 使用goroutine处理拨号，以支持取消
	connChan := make(chan struct {
		conn net.Conn
		err  error
	}, 1)
	
	go func() {
		conn, err := s.dialer.Dial(network, address)
		select {
		case <-dialCtx.Done():
			if conn != nil {
				conn.Close()
			}
		case connChan <- struct {
			conn net.Conn
			err  error
		}{conn, err}:
		}
	}()
	
	select {
	case <-dialCtx.Done():
		atomic.AddInt64(&s.stats.FailedConnections, 1)
		s.stats.LastError = dialCtx.Err().Error()
		return nil, NewProxyError(ErrTypeTimeout, "SOCKS5连接超时", 3002, dialCtx.Err())
	case result := <-connChan:
		duration := time.Since(start)
		s.stats.LastConnectTime = start
		
		if result.err != nil {
			atomic.AddInt64(&s.stats.FailedConnections, 1)
			s.stats.LastError = result.err.Error()
			return nil, NewProxyError(ErrTypeConnection, "SOCKS5连接失败", 3003, result.err)
		}
		
		atomic.AddInt64(&s.stats.ActiveConnections, 1)
		s.updateAverageConnectTime(duration)
		
		return &trackedConn{
			Conn:  result.conn,
			stats: s.stats,
		}, nil
	}
}

// updateAverageConnectTime 更新平均连接时间
func (d *directDialer) updateAverageConnectTime(duration time.Duration) {
	// 简单的移动平均
	if d.stats.AverageConnectTime == 0 {
		d.stats.AverageConnectTime = duration
	} else {
		d.stats.AverageConnectTime = (d.stats.AverageConnectTime + duration) / 2
	}
}

func (s *socks5Dialer) updateAverageConnectTime(duration time.Duration) {
	// 简单的移动平均
	if s.stats.AverageConnectTime == 0 {
		s.stats.AverageConnectTime = duration
	} else {
		s.stats.AverageConnectTime = (s.stats.AverageConnectTime + duration) / 2
	}
}