package server

import (
	"context"
	"encoding/json"
	"io"
	"net/http"
	"sync"

	"github.com/noahlann/nnet/internal/connection"
	"github.com/noahlann/nnet/internal/logger"
	internalrouter "github.com/noahlann/nnet/internal/router"
	codecpkg "github.com/noahlann/nnet/pkg/codec"
	"github.com/noahlann/nnet/pkg/config"
	"github.com/noahlann/nnet/pkg/errors"
	"github.com/noahlann/nnet/pkg/health"
	metricspkg "github.com/noahlann/nnet/pkg/metrics"
	protocolpkg "github.com/noahlann/nnet/pkg/protocol"
	routerpkg "github.com/noahlann/nnet/pkg/router"
	"go.bug.st/serial"
)

// SerialServer 串口服务器
type SerialServer struct {
	config             *config.Config
	logger             logger.Logger
	connManager        connection.ManagerInterface
	router             routerpkg.Router
	port               serial.Port
	mu                 sync.RWMutex
	ctx                context.Context
	cancel             context.CancelFunc
	started            bool
	codecRegistry      codecpkg.Registry
	codecResolverChain *codecpkg.ResolverChain
	defaultCodec       string
	protocolManager    protocolpkg.Manager
	unpackerManager    *unpackerManager
	metrics            metricspkg.Metrics
	healthChecker      health.Checker
	msgHandler         *messageHandler
}

// NewSerialServer 创建串口服务器
func NewSerialServer(cfg *config.Config) (*SerialServer, error) {
	if cfg == nil {
		cfg = config.DefaultConfig()
	}

	if err := cfg.Validate(); err != nil {
		return nil, err
	}

	// 创建日志器
	var logConfig *logger.Config
	if cfg.Logger != nil {
		logConfig = &logger.Config{
			Level:  cfg.Logger.Level,
			Format: cfg.Logger.Format,
			Output: cfg.Logger.Output,
		}
	} else {
		logConfig = &logger.Config{
			Level:  "info",
			Format: "text",
			Output: "stdout",
		}
	}
	log := logger.New(logConfig)

	// 创建连接管理器（使用分段锁优化）
	shardCount := cfg.ConnectionManagerShards
	if shardCount <= 0 {
		shardCount = 16 // 默认16个分片
	}
	connManager := connection.NewShardedManager(cfg.MaxConnections, shardCount)

	// 创建路由器
	r := internalrouter.NewRouter()

	// 创建编解码器注册表
	codecRegistry := initCodecRegistry(cfg)

	// 创建协议管理器
	protocolManager := initProtocolManager()

	// 创建Codec解析器链（用户需要自己添加resolver）
	configHelper := newServerConfigHelper(cfg)
	defaultCodec := configHelper.DefaultCodec()
	codecResolverChain := codecpkg.NewResolverChain(codecRegistry, defaultCodec)

	metrics := metricspkg.NewMetrics()
	healthChecker := health.NewChecker()
	_ = healthChecker.Register("connections", &connectionHealthCheck{
		connManager: connManager,
		maxConns:    cfg.MaxConnections,
	})

	ctx, cancel := context.WithCancel(context.Background())

	cloneHeader := configHelper.CloneHeader()
	return &SerialServer{
		config:             cfg,
		logger:             log,
		connManager:        connManager,
		router:             r,
		codecRegistry:      codecRegistry,
		codecResolverChain: codecResolverChain,
		defaultCodec:       defaultCodec,
		protocolManager:    protocolManager,
		unpackerManager:    newUnpackerManager(),
		metrics:            metrics,
		healthChecker:      healthChecker,
		ctx:                ctx,
		cancel:             cancel,
		started:            false,
		msgHandler:         newMessageHandler(log, codecRegistry, codecResolverChain, defaultCodec, r, cloneHeader),
	}, nil
}

// Start 启动串口服务器
func (s *SerialServer) Start() error {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.started {
		return errors.ErrServerAlreadyStarted
	}

	// 解析串口地址
	addr := s.config.Addr
	if len(addr) >= 7 && addr[:7] == "serial:" {
		addr = addr[7:]
	}

	// 获取串口配置
	serialConfig := s.config.Serial
	if serialConfig == nil {
		serialConfig = &config.SerialConfig{
			BaudRate:     9600,
			DataBits:     8,
			StopBits:     1,
			Parity:       "None",
			ReadTimeout:  1000,
			WriteTimeout: 1000,
		}
	}

	// 验证和设置数据位（范围：5-8）
	dataBits := serialConfig.DataBits
	if dataBits < 5 || dataBits > 8 {
		dataBits = 8
	}

	// 验证和设置停止位（范围：1-2）
	stopBits := serialConfig.StopBits
	if stopBits < 1 || stopBits > 2 {
		stopBits = 1
	}

	// 设置校验位
	var parity serial.Parity
	switch serialConfig.Parity {
	case "Odd":
		parity = serial.OddParity
	case "Even":
		parity = serial.EvenParity
	case "Mark":
		parity = serial.MarkParity
	case "Space":
		parity = serial.SpaceParity
	case "None":
		parity = serial.NoParity
	default:
		parity = serial.NoParity
	}

	// 配置串口模式
	mode := &serial.Mode{
		BaudRate: serialConfig.BaudRate,
		DataBits: dataBits,
		StopBits: serial.StopBits(stopBits),
		Parity:   parity,
	}

	// 打开串口
	port, err := serial.Open(addr, mode)
	if err != nil {
		return errors.New("failed to open serial port").WithCause(err)
	}

	s.port = port
	s.started = true
	s.logger.Info("Serial server started on %s", addr)

	// 启动读取协程
	go s.handleConnection()

	return nil
}

// Stop 停止串口服务器
func (s *SerialServer) Stop() error {
	s.mu.Lock()
	defer s.mu.Unlock()

	if !s.started {
		return errors.ErrServerNotStarted
	}

	s.logger.Info("Stopping Serial server...")

	s.cancel()

	if s.port != nil {
		if err := s.port.Close(); err != nil {
			s.logger.Error("Failed to close serial port: %v", err)
		}
	}

	s.started = false
	s.logger.Info("Serial server stopped")
	return nil
}

// handleConnection 处理串口连接
func (s *SerialServer) handleConnection() {
	// 解析串口地址
	addr := s.config.Addr
	if len(addr) >= 7 && addr[:7] == "serial:" {
		addr = addr[7:]
	}
	if len(addr) == 0 {
		addr = "/dev/ttyUSB0" // 默认串口设备
	}

	// 创建串口连接包装器
	// 使用地址作为连接ID
	// 连接ID由NewSerialConnection自动生成xid
	serialConn := connection.NewSerialConnection("", s.port)
	connID := serialConn.ID()

	// 添加到连接管理器
	if err := s.connManager.Add(serialConn); err != nil {
		s.logger.Error("Failed to add connection: %v", err)
		return
	}
	s.metrics.IncConnections()
	defer func() {
		s.connManager.Remove(connID)
		s.unpackerManager.removeUnpacker(connID)
		s.metrics.DecConnections()
	}()

	// 获取协议和编解码器配置
	configHelper := newServerConfigHelper(s.config)
	enableProtocolEncode := configHelper.IsProtocolEncodeEnabled()
	var protocol protocolpkg.Protocol
	if enableProtocolEncode {
		protocol, _ = s.protocolManager.Get(s.config.ApplicationProtocol, "")
	}

	// 获取或创建连接的unpacker
	unpacker := s.unpackerManager.getOrCreateUnpacker(connID, protocol)

	// 转换为Context需要的Connection接口
	ctxConn := toContextConnection(serialConn)

	buffer := make([]byte, s.config.ReadBufferSize)

	for {
		select {
		case <-s.ctx.Done():
			return
		default:
			n, err := s.port.Read(buffer)
			if err != nil {
				if err == io.EOF {
					continue
				}
				s.logger.Debug("Serial read error: %v", err)
				return
			}

			if n == 0 {
				continue
			}
			s.metrics.AddBytesReceived(int64(n))

			data := make([]byte, n)
			copy(data, buffer[:n])

			// 使用unpacker处理数据
			messages, _, hasRemaining, err := processDataWithUnpacker(data, unpacker)
			if err != nil {
				s.logger.Error("Unpack error: %v", err)
				s.metrics.IncErrors()
				continue
			}

			// 如果没有完整消息，等待更多数据
			if len(messages) == 0 {
				if !hasRemaining {
					// 没有剩余数据，可能是错误
					s.logger.Debug("No messages and no remaining data")
				}
				continue
			}

			// 处理每个完整的消息
			handlerTimeout := newServerConfigHelper(s.config).HandlerTimeout()
			for _, message := range messages {
				s.metrics.IncRequests()
				s.msgHandler.handleMessageWithContext(
					context.Background(),
					ctxConn,
					message,
					protocol,
					s.codecRegistry,
					handlerTimeout,
				)
				// 注意：metrics错误计数在handleMessageWithContext内部处理
				// 如果需要更细粒度的错误处理，可以在handleMessageWithContext中回调
			}
		}
	}
}

// Router 获取路由器
func (s *SerialServer) Router() routerpkg.Router {
	return s.router
}

// ConnectionManager 获取连接管理器
func (s *SerialServer) ConnectionManager() connection.ManagerInterface {
	return s.connManager
}

// Config 获取配置
func (s *SerialServer) Config() *config.Config {
	return s.config
}

// Started 检查服务器是否已启动
func (s *SerialServer) Started() bool {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.started
}

// CodecRegistry 获取编解码器注册表
func (s *SerialServer) CodecRegistry() codecpkg.Registry {
	return s.codecRegistry
}

// ProtocolManager 获取协议管理器
func (s *SerialServer) ProtocolManager() protocolpkg.Manager {
	return s.protocolManager
}

// Metrics 返回指标收集器
func (s *SerialServer) Metrics() metricspkg.Metrics {
	return s.metrics
}

// HealthChecker 返回健康检查器
func (s *SerialServer) HealthChecker() health.Checker {
	return s.healthChecker
}

// ExportMetrics 以Prometheus格式导出指标
func (s *SerialServer) ExportMetrics(w io.Writer) error {
	exporter := metricspkg.NewPrometheusExporter(s.metrics)
	return exporter.Export(w)
}

// MetricsHandler 返回默认的Metrics HTTP处理器
func (s *SerialServer) MetricsHandler() http.Handler {
	return http.HandlerFunc(s.handleMetrics)
}

// HealthHandler 返回默认的健康检查HTTP处理器
func (s *SerialServer) HealthHandler() http.Handler {
	return http.HandlerFunc(s.handleHealth)
}

func (s *SerialServer) handleMetrics(w http.ResponseWriter, r *http.Request) {
	exporter := metricspkg.NewPrometheusExporter(s.metrics)
	w.Header().Set("Content-Type", "text/plain; version=0.0.4")
	if err := exporter.Export(w); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

func (s *SerialServer) handleHealth(w http.ResponseWriter, r *http.Request) {
	status, results := s.healthChecker.Check()
	w.Header().Set("Content-Type", "application/json")
	response := map[string]interface{}{
		"status":  status,
		"results": results,
	}

	switch status {
	case health.StatusHealthy, health.StatusDegraded:
		w.WriteHeader(http.StatusOK)
	default:
		w.WriteHeader(http.StatusServiceUnavailable)
	}

	_ = json.NewEncoder(w).Encode(response)
}