package welcome

import (
	"context"
	"os"
	"os/signal"
	"path/filepath"
	"strings"
	"syscall"
	"time"

	"bash_go_service/shared/pkg/constants"
	"bash_go_service/shared/pkg/logger"

	"github.com/fsnotify/fsnotify"
)

type Service struct {
	watcher  *fsnotify.Watcher
	sigChan  chan os.Signal
	stopChan chan struct{}
}

func NewService() (*Service, error) {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return nil, err
	}

	return &Service{
		watcher:  watcher,
		sigChan:  make(chan os.Signal, 1),
		stopChan: make(chan struct{}),
	}, nil
}

func (s *Service) checkExistingTerminals() {
	entries, err := os.ReadDir(constants.UtmpDir)
	if err != nil {
		logger.Error("Error reading %s: %v", constants.UtmpDir, err)
		return
	}

	for _, entry := range entries {
		if !entry.IsDir() {
			path := filepath.Join(constants.UtmpDir, entry.Name())
			if isValidTerminal(path) {
				go s.handleNewTerminal(path)
			}
		}
	}
}

func (s *Service) Start() error {
	err := s.watcher.Add(constants.UtmpDir)
	if err != nil {
		return err
	}

	signal.Notify(s.sigChan, syscall.SIGINT, syscall.SIGTERM)

	s.checkExistingTerminals()

	logger.Info("Service started")

	go s.watch()

	return nil
}

func (s *Service) Stop() {
	close(s.stopChan)
	s.watcher.Close()
	signal.Stop(s.sigChan)
}

func (s *Service) watch() {
	for {
		select {
		case event, ok := <-s.watcher.Events:
			if !ok {
				return
			}
			if event.Op&fsnotify.Create == fsnotify.Create {
				go s.handleNewTerminal(event.Name)
			}

		case err, ok := <-s.watcher.Errors:
			if !ok {
				return
			}
			logger.Error("Watcher error: %v", err)

		case sig := <-s.sigChan:
			logger.Debug("Received signal: %v", sig)
			return

		case <-s.stopChan:
			return
		}
	}
}

// 判断是否为有效的终端设备
func isValidTerminal(path string) bool {
	// 只处理 tty 和 pts 设备
	basename := filepath.Base(path)

	// 如果是tty设备,直接返回true
	if strings.HasPrefix(basename, "tty") {
		return true
	}

	// 检查设备文件是否真实存在且可写
	info, err := os.Stat(path)
	if err != nil {
		return false
	}

	// 检查是否为字符设备
	if stat, ok := info.Sys().(*syscall.Stat_t); ok {
		// 检查是否为字符设备(参考 Linux 设备文件类型)
		return (stat.Mode & syscall.S_IFMT) == syscall.S_IFCHR
	}

	return false
}

func (s *Service) handleNewTerminal(path string) {
	// 首先检查是否为虚拟终端
	if !isValidTerminal(path) {
		logger.Debug("Skipping no valied terminal: %s", path)
		return
	}

	// 创建一个带超时的context
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()

	// 使用channel来控制任务完成
	done := make(chan bool)

	go func() {
		defer close(done)

		// 尝试读取欢迎文件内容
		content, err := readWelcomeFile()
		if err != nil {
			logger.Error("Failed to read welcome file: %v", err)
			return
		}

		// 尝试打开终端
		f, err := os.OpenFile(path, os.O_WRONLY, 0)
		if err != nil {
			logger.Error("Error opening terminal %s: %v", path, err)
			return
		}
		defer f.Close()

		// 写入文件内容
		if _, err = f.WriteString(content); err != nil {
			logger.Error("Error writing to terminal %s: %v", path, err)
			return
		}

		// 写入换行符
		if _, err = f.Write([]byte{'\n'}); err != nil {
			logger.Error("Error sending newline to terminal %s: %v", path, err)
			return
		}

		logger.Info("Welcome message sent to %s", path)
		done <- true
	}()

	// 等待任务完成或超时
	select {
	case <-ctx.Done():
		logger.Error("Timeout while sending welcome message to %s", path)
		return
	case <-done:
		return
	}
}

// 读取欢迎文件内容的辅助函数
func readWelcomeFile() (string, error) {
	// 检查文件是否存在
	if _, err := os.Stat(constants.WelcomeFilePath); os.IsNotExist(err) {
		return "已连接到北溟服务，您执行的命令将由北溟提供帮助", nil
	}

	// 读取文件内容
	content, err := os.ReadFile(constants.WelcomeFilePath)
	if err != nil {
		return "已连接到北溟服务，您执行的命令将由北溟提供帮助", nil
	}

	// 去除多余的空白字符
	return strings.TrimSpace(string(content)), nil
}