package main

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"os/signal"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"syscall"
	"time"
)

// ==================== 配置 ====================

type Config struct {
	Server  ServerConfig `json:"server"`
	Remote  RemoteConfig `json:"remote"`
	Timing  TimingConfig `json:"timing"`
	Log     LogConfig    `json:"log"`
	Reverse bool         `json:"reverse"` // true=正(翻转发送逻辑), false=反(默认)
}

type ServerConfig struct {
	Port int `json:"port"` // 本机 TCP 监听端口
}

type RemoteConfig struct {
	Host        string `json:"host"`                  // 远端 TCP 服务地址
	Port        int    `json:"port"`                   // 远端 TCP 服务端口
	DialTimeout int    `json:"dial_timeout_seconds"`   // 连接超时
}

type TimingConfig struct {
	StartupDelaySeconds int `json:"startup_delay_seconds"` // 启动后延迟发送
	ResendDelaySeconds  int `json:"resend_delay_seconds"`  // 收到后重发延迟
}

type LogConfig struct {
	Dir          string `json:"dir"`           // 日志目录
	Level        string `json:"level"`         // debug/info/warn/error
	KeepDays     int    `json:"keep_days"`     // 日志保留天数
}

func defaultConfig() Config {
	return Config{
		Server: ServerConfig{Port: 9600},
		Remote: RemoteConfig{
			Host:        "127.0.0.1",
			Port:        9000,
			DialTimeout: 5,
		},
		Timing: TimingConfig{
			StartupDelaySeconds: 180,
			ResendDelaySeconds:  180,
		},
		Log: LogConfig{
			Dir:      "logs",
			Level:    "info",
			KeepDays: 60,
		},
		Reverse: false,
	}
}

func loadConfig(path string) (*Config, error) {
	cfg := defaultConfig()

	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			log.Printf("[WARN] 配置文件 %s 不存在，使用默认配置", path)
			return &cfg, nil
		}
		return nil, fmt.Errorf("读取配置文件失败: %w", err)
	}

	if err := json.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("解析配置文件失败: %w", err)
	}

	if cfg.Server.Port <= 0 || cfg.Server.Port > 65535 {
		return nil, fmt.Errorf("无效的服务端口: %d", cfg.Server.Port)
	}
	if cfg.Remote.Port <= 0 || cfg.Remote.Port > 65535 {
		return nil, fmt.Errorf("无效的远端端口: %d", cfg.Remote.Port)
	}
	if cfg.Log.KeepDays <= 0 {
		cfg.Log.KeepDays = 60
	}
	if cfg.Log.Dir == "" {
		cfg.Log.Dir = "logs"
	}

	return &cfg, nil
}

// ==================== 按天滚动日志 ====================

type DailyLogger struct {
	dir      string
	level    string
	keepDays int
	logger   *log.Logger
	mu       sync.Mutex
	date     string // 当前日志日期
	file     *os.File
}

func NewDailyLogger(dir, level string, keepDays int) *DailyLogger {
	os.MkdirAll(dir, 0755)
	dl := &DailyLogger{
		dir:      dir,
		level:    level,
		keepDays: keepDays,
	}
	dl.rotate()
	return dl
}

func (dl *DailyLogger) rotate() {
	today := time.Now().Format("2006-01-02")
	if dl.date == today && dl.logger != nil {
		return
	}

	// 关闭旧文件
	if dl.file != nil {
		dl.file.Close()
	}

	dl.date = today
	filename := filepath.Join(dl.dir, fmt.Sprintf("tcp_service_%s.log", today))

	f, err := os.OpenFile(filename, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		log.Printf("[ERROR] 无法创建日志文件 %s: %v", filename, err)
		dl.logger = log.New(os.Stdout, "", log.LstdFlags|log.Lmicroseconds)
		dl.file = nil
		return
	}

	dl.file = f
	multiWriter := io.MultiWriter(os.Stdout, f)
	dl.logger = log.New(multiWriter, "", log.LstdFlags|log.Lmicroseconds)

	// 清理过期日志
	go dl.cleanOldLogs()
}

func (dl *DailyLogger) cleanOldLogs() {
	entries, err := os.ReadDir(dl.dir)
	if err != nil {
		return
	}

	cutoff := time.Now().AddDate(0, 0, -dl.keepDays)
	var expired []string

	for _, e := range entries {
		if e.IsDir() || !strings.HasPrefix(e.Name(), "tcp_service_") {
			continue
		}
		// 从文件名提取日期: tcp_service_2006-01-02.log
		name := e.Name()
		dateStr := strings.TrimPrefix(name, "tcp_service_")
		dateStr = strings.TrimSuffix(dateStr, ".log")

		t, err := time.Parse("2006-01-02", dateStr)
		if err != nil {
			continue
		}
		if t.Before(cutoff) {
			expired = append(expired, filepath.Join(dl.dir, name))
		}
	}

	sort.Strings(expired)
	for _, p := range expired {
		os.Remove(p)
		dl.Logf("[INFO] 清理过期日志: %s", filepath.Base(p))
	}
}

// Logf 写日志（自动检查日期滚动）
func (dl *DailyLogger) Logf(format string, args ...interface{}) {
	dl.mu.Lock()
	defer dl.mu.Unlock()

	today := time.Now().Format("2006-01-02")
	if dl.date != today {
		dl.rotate()
	}

	msg := fmt.Sprintf(format, args...)
	dl.logger.Println(msg)
}

// ==================== 远端 TCP 客户端 ====================

type TCPClient struct {
	host    string
	port    int
	timeout time.Duration
	log     *DailyLogger

	mu     sync.Mutex
	conn   net.Conn
	writer *bufio.Writer
	ctx    context.Context
	cancel context.CancelFunc
}

func NewTCPClient(host string, port int, dialTimeoutSec int, log *DailyLogger) *TCPClient {
	ctx, cancel := context.WithCancel(context.Background())
	return &TCPClient{
		host:    host,
		port:    port,
		timeout: time.Duration(dialTimeoutSec) * time.Second,
		log:     log,
		ctx:     ctx,
		cancel:  cancel,
	}
}

func (c *TCPClient) Connect() error {
	c.mu.Lock()
	defer c.mu.Unlock()

	if c.conn != nil {
		c.conn.Close()
	}

	addr := fmt.Sprintf("%s:%d", c.host, c.port)
	c.log.Logf("[INFO] 正在连接远端 %s ...", addr)

	d := net.Dialer{Timeout: c.timeout}
	conn, err := d.DialContext(c.ctx, "tcp", addr)
	if err != nil {
		return fmt.Errorf("连接远端 %s 失败: %w", addr, err)
	}

	conn.SetDeadline(time.Time{})
	c.conn = conn
	c.writer = bufio.NewWriter(conn)
	c.log.Logf("[INFO] 已连接远端 %s", addr)

	go c.receiveLoop()
	return nil
}

func (c *TCPClient) Send(msg string) error {
	// 最多重试 2 次（首次 + 1次重连重试）
	for attempt := 0; attempt < 2; attempt++ {
		// 确保连接存在
		c.mu.Lock()
		needConnect := c.conn == nil
		c.mu.Unlock()

		if needConnect {
			if err := c.Connect(); err != nil {
				return err
			}
		}

		c.mu.Lock()
		if c.conn == nil {
			c.mu.Unlock()
			continue
		}

		c.log.Logf("[INFO] >>> 发送远端: %s", msg)

		_, err := c.writer.WriteString(msg)
		if err != nil {
			c.log.Logf("[ERROR] 发送失败: %v, 重试中...", err)
			c.closeLocked()
			c.mu.Unlock()
			continue
		}

		if err := c.writer.Flush(); err != nil {
			c.log.Logf("[ERROR] Flush失败: %v, 重试中...", err)
			c.closeLocked()
			c.mu.Unlock()
			continue
		}

		c.mu.Unlock()
		return nil
	}

	return fmt.Errorf("发送失败: 重试次数已用完")
}

func (c *TCPClient) receiveLoop() {
	c.mu.Lock()
	conn := c.conn
	c.mu.Unlock()

	if conn == nil {
		return
	}

	reader := bufio.NewReader(conn)
	for {
		select {
		case <-c.ctx.Done():
			return
		default:
		}

		line, err := reader.ReadString('\n')
		if err != nil {
			if err == io.EOF {
				c.log.Logf("[WARN] 远端关闭了连接")
			} else {
				c.log.Logf("[WARN] 远端接收错误: %v", err)
			}
			// 只关闭自己的连接，避免误关已被替换的新连接
			c.mu.Lock()
			if c.conn == conn {
				c.closeLocked()
			} else {
				conn.Close()
			}
			c.mu.Unlock()
			return
		}
		c.log.Logf("[INFO] <<< 远端返回: %s", strings.TrimRight(line, "\r\n"))
	}
}

func (c *TCPClient) closeLocked() {
	if c.conn != nil {
		c.conn.Close()
		c.conn = nil
		c.writer = nil
	}
}

func (c *TCPClient) Close() {
	c.cancel()
	c.mu.Lock()
	defer c.mu.Unlock()
	c.closeLocked()
}

// ==================== TCP 服务端 ====================

type TCPServer struct {
	port         int
	client       *TCPClient
	cfg          *TimingConfig
	log          *DailyLogger
	reverse      bool
	ctx          context.Context
	cancel       context.CancelFunc
	autoOffTimer *time.Timer // 自动关灯定时器
	timerMu      sync.Mutex
}

func NewTCPServer(port int, client *TCPClient, cfg *TimingConfig, reverse bool, log *DailyLogger) *TCPServer {
	ctx, cancel := context.WithCancel(context.Background())
	return &TCPServer{
		port:    port,
		client:  client,
		cfg:     cfg,
		log:     log,
		reverse: reverse,
		ctx:     ctx,
		cancel:  cancel,
	}
}

// sendMsg 发送消息（根据 reverse 参数翻转）
func (s *TCPServer) sendMsg(msg string) error {
	if s.reverse {
		msg = flipMsg(msg)
	}
	return s.client.Send(msg)
}

// flipMsg 翻转消息内容 <1,0,post> ↔ <1,1,post>
func flipMsg(msg string) string {
	switch msg {
	case "<1,0,post>":
		return "<1,1,post>"
	case "<1,1,post>":
		return "<1,0,post>"
	default:
		return msg
	}
}

// flipMsgCond 根据条件翻转（用于 main 等非 TCPServer 上下文）
func flipMsgCond(msg string, reverse bool) string {
	if reverse {
		return flipMsg(msg)
	}
	return msg
}

func (s *TCPServer) Start() error {
	addr := fmt.Sprintf(":%d", s.port)
	listener, err := net.Listen("tcp", addr)
	if err != nil {
		return fmt.Errorf("TCP 监听 %s 失败: %w", addr, err)
	}

	s.log.Logf("[INFO] TCP 服务监听 %s", addr)

	go func() {
		<-s.ctx.Done()
		listener.Close()
	}()

	for {
		conn, err := listener.Accept()
		if err != nil {
			select {
			case <-s.ctx.Done():
				return nil
			default:
				s.log.Logf("[ERROR] Accept 失败: %v", err)
				continue
			}
		}
		go s.handleConn(conn)
	}
}

func (s *TCPServer) handleConn(conn net.Conn) {
	defer conn.Close()

	remoteAddr := conn.RemoteAddr().String()
	s.log.Logf("[INFO] 新连接: %s", remoteAddr)

	reader := bufio.NewReader(conn)
	for {
		select {
		case <-s.ctx.Done():
			return
		default:
		}

		line, err := reader.ReadString('>')
		if err != nil {
			if err != io.EOF {
				s.log.Logf("[WARN] 读取 %s 错误: %v", remoteAddr, err)
			}
			s.log.Logf("[INFO] 连接断开: %s", remoteAddr)
			return
		}

		cmd := strings.TrimSpace(line)
		switch cmd {
		case "<1,0,post>":
			s.log.Logf("[INFO] <<< 收到命令 [%s]: %s 关灯命令", remoteAddr, cmd)
			go s.handleCmd1_0()
		case "<1,1,post>":
			s.log.Logf("[INFO] <<< 收到命令 [%s]: %s 开灯命令", remoteAddr, cmd)
			go s.handleCmd1_1()
		default:
			s.log.Logf("[WARN] 未知命令: %s", cmd)
			continue
		}
	}
}

// cancelAutoOffTimer 取消自动关灯定时器（如果有的话）
func (s *TCPServer) cancelAutoOffTimer() {
	s.timerMu.Lock()
	defer s.timerMu.Unlock()
	if s.autoOffTimer != nil {
		s.autoOffTimer.Stop()
		s.autoOffTimer = nil
		s.log.Logf("[INFO] 已取消自动关灯定时器")
	}
}

// resetAutoOffTimer 重置自动关灯定时器（先取消旧的，再创建新的）
func (s *TCPServer) resetAutoOffTimer() {
	s.timerMu.Lock()
	if s.autoOffTimer != nil {
		s.autoOffTimer.Stop()
	}

	delay := time.Duration(s.cfg.ResendDelaySeconds) * time.Second
	msg := s.effectiveMsg("<1,1,post>")
	s.log.Logf("[INFO] 重置自动关灯定时器: %v 后发送 %s", delay, msg)

	s.autoOffTimer = time.AfterFunc(delay, func() {
		s.timerMu.Lock()
		s.autoOffTimer = nil
		s.timerMu.Unlock()
		s.log.Logf("[INFO] 自动关灯触发: 发送 %s", msg)
		if err := s.sendMsg("<1,1,post>"); err != nil {
			s.log.Logf("[ERROR] 自动关灯发送失败: %v", err)
		}
	})
	s.timerMu.Unlock()
}

// handleCmd1_0: 收到 <1,0,post>（关灯命令）→ 远端发送 <1,1,post>，并取消自动关灯定时器
func (s *TCPServer) handleCmd1_0() {
	s.cancelAutoOffTimer() // 关灯了就不用再自动关了
	s.log.Logf("[INFO] 处理 <1,0,post>: 向远端发送 %s", s.effectiveMsg("<1,1,post>"))
	if err := s.sendMsg("<1,1,post>"); err != nil {
		s.log.Logf("[ERROR] 发送失败: %v", err)
	}
}

func (s *TCPServer) effectiveMsg(msg string) string {
	if s.reverse {
		return flipMsg(msg)
	}
	return msg
}

// handleCmd1_1: 收到 <1,1,post>（开灯命令）→ 远端发送 <1,0,post>，重置自动关灯定时器
func (s *TCPServer) handleCmd1_1() {
	s.log.Logf("[INFO] 处理 <1,1,post>: 向远端发送 %s", s.effectiveMsg("<1,0,post>"))
	if err := s.sendMsg("<1,0,post>"); err != nil {
		s.log.Logf("[ERROR] 发送失败: %v", err)
	}

	// 重置自动关灯定时器（如果之前有旧的会被取消）
	s.resetAutoOffTimer()
}

// ==================== 主函数 ====================

func main() {
	configPath := "config.json"
	if len(os.Args) > 1 {
		configPath = os.Args[1]
	}

	cfg, err := loadConfig(configPath)
	if err != nil {
		log.Fatalf("[FATAL] %v", err)
	}

	// 初始化按天滚动日志
	dailyLog := NewDailyLogger(cfg.Log.Dir, cfg.Log.Level, cfg.Log.KeepDays)
	dailyLog.Logf("[INFO] ======== TCP 转发服务启动 ========")
	dailyLog.Logf("[INFO] 配置: 监听端口=%d, 远端=%s:%d, 启动延迟=%ds, 重发延迟=%ds, 正反=%v, 日志保留=%d天",
		cfg.Server.Port,
		cfg.Remote.Host, cfg.Remote.Port,
		cfg.Timing.StartupDelaySeconds, cfg.Timing.ResendDelaySeconds,
		cfg.Reverse,
		cfg.Log.KeepDays)

	// 创建远端 TCP 客户端
	remoteClient := NewTCPClient(cfg.Remote.Host, cfg.Remote.Port, cfg.Remote.DialTimeout, dailyLog)
	defer remoteClient.Close()

	// 启动时连接远端
	if err := remoteClient.Connect(); err != nil {
		dailyLog.Logf("[WARN] 启动时连接远端失败: %v (将在收到命令时自动重连)", err)
	}

	// 启动延迟 → 自动发送 <1,1,post>（正模式时翻转）
	startupDelay := time.Duration(cfg.Timing.StartupDelaySeconds) * time.Second
	startupMsg := flipMsgCond("<1,1,post>", cfg.Reverse)
	dailyLog.Logf("[INFO] 将在 %v 后自动发送 %s", startupDelay, startupMsg)
	time.AfterFunc(startupDelay, func() {
		dailyLog.Logf("[INFO] 启动定时触发: 发送 %s", startupMsg)
		if err := remoteClient.Send(startupMsg); err != nil {
			dailyLog.Logf("[ERROR] 启动定时发送失败: %v", err)
		}
	})

	// 启动 TCP 服务端
	server := NewTCPServer(cfg.Server.Port, remoteClient, &cfg.Timing, cfg.Reverse, dailyLog)

	// 优雅关闭
	go func() {
		sigCh := make(chan os.Signal, 1)
		signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
		<-sigCh
		dailyLog.Logf("[INFO] 收到退出信号，正在关闭...")
		shutdownMsg := flipMsgCond("<1,1,post>", cfg.Reverse)
		dailyLog.Logf("[INFO] 退出前发送 %s", shutdownMsg)
		if err := remoteClient.Send(shutdownMsg); err != nil {
			dailyLog.Logf("[ERROR] 退出发送失败: %v", err)
		}
		server.cancel()
		remoteClient.Close()
		os.Exit(0)
	}()

	if err := server.Start(); err != nil {
		dailyLog.Logf("[FATAL] 服务启动失败: %v", err)
		os.Exit(1)
	}
}