package main

import (
	"bytes"
	"embed"
	"fmt"
	"io"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"text/template"
)

//go:embed bin/*
var embeddedFrps embed.FS

//go:embed frps.tmpl
var FrpsTemplateContent string

var (
	cachedFrpsPath string
	frpsPathMutex  sync.Mutex
)

func getFrpsPath() (string, error) {
	frpsPathMutex.Lock()
	defer frpsPathMutex.Unlock()

	if cachedFrpsPath != "" {
		if _, err := os.Stat(cachedFrpsPath); err == nil {
			return cachedFrpsPath, nil
		}
		cachedFrpsPath = ""
	}

	var fileName string
	switch {
	case runtime.GOOS == "windows" && runtime.GOARCH == "amd64":
		fileName = "frps_windows_amd64.exe"
	case runtime.GOOS == "linux" && runtime.GOARCH == "amd64":
		fileName = "frps_linux_amd64"
	case runtime.GOOS == "linux" && runtime.GOARCH == "arm64":
		fileName = "frps_linux_arm64"
	case runtime.GOOS == "linux" && runtime.GOARCH == "arm":
		fileName = "frps_linux_arm_hf"
	default:
		path, err := exec.LookPath("frps")
		if err == nil {
			cachedFrpsPath = path
			return path, nil
		}
		return "", fmt.Errorf("不支持的平台: %s/%s", runtime.GOOS, runtime.GOARCH)
	}

	localPath := filepath.Join(".", "bin", fileName)
	if _, err := os.Stat(localPath); err == nil {
		cachedFrpsPath = localPath
		return localPath, nil
	}

	data, err := embeddedFrps.ReadFile("bin/" + fileName)
	if err == nil {
		tmpPath := filepath.Join(os.TempDir(), "frps")
		if runtime.GOOS == "windows" {
			tmpPath += ".exe"
		}
		if err := os.WriteFile(tmpPath, data, 0755); err == nil {
			cachedFrpsPath = tmpPath
			return tmpPath, nil
		}
		if _, statErr := os.Stat(tmpPath); statErr == nil {
			cachedFrpsPath = tmpPath
			return tmpPath, nil
		}
	}

	path, err := exec.LookPath("frps")
	if err == nil {
		cachedFrpsPath = path
		return path, nil
	}

	return "", fmt.Errorf("未找到 frps 文件")
}

func GenerateFrpsConfig() error {
	cfg, err := GetGlobalConfig()
	if err != nil {
		return fmt.Errorf("读取全局配置失败: %w", err)
	}

	// 直接使用 cfg，模板使用 frps.tmpl
	var tmplContent string
	if _, err := os.Stat("frps.tmpl"); err == nil {
		content, readErr := os.ReadFile("frps.tmpl")
		if readErr == nil {
			tmplContent = string(content)
		} else {
			tmplContent = FrpsTemplateContent
		}
	} else {
		tmplContent = FrpsTemplateContent
	}

	tmpl, err := template.New("frps").Parse(tmplContent)
	if err != nil {
		return fmt.Errorf("解析模板失败: %w", err)
	}

	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, cfg); err != nil {
		return fmt.Errorf("渲染模板失败: %w", err)
	}

	if err := os.MkdirAll("./data", 0755); err != nil {
		return fmt.Errorf("创建 data 目录失败: %w", err)
	}
	if err := os.WriteFile("./data/frps.toml", buf.Bytes(), 0644); err != nil {
		return fmt.Errorf("写入配置文件失败: %w", err)
	}

	return nil
}

func isFrpsRunning() bool {
	pidData, err := os.ReadFile("./data/frps.pid")
	if err != nil {
		return false
	}
	pid, err := strconv.Atoi(strings.TrimSpace(string(pidData)))
	if err != nil {
		return false
	}

	if runtime.GOOS == "windows" {
		cmd := exec.Command("tasklist", "/FI", "PID eq", strconv.Itoa(pid))
		output, err := cmd.CombinedOutput()
		if err != nil {
			return false
		}
		return strings.Contains(string(output), strconv.Itoa(pid))
	}

	process, err := os.FindProcess(pid)
	if err != nil {
		return false
	}
	return process.Signal(syscall.Signal(0)) == nil
}

func StartFrps() error {
	frpsPath, err := getFrpsPath()
	if err != nil {
		return fmt.Errorf("获取 frps 路径失败: %w", err)
	}

	if err := os.MkdirAll("./data", 0755); err != nil {
		return fmt.Errorf("创建 data 目录失败: %w", err)
	}

	if _, err := os.Stat("./data/frps.toml"); os.IsNotExist(err) {
		if err := GenerateFrpsConfig(); err != nil {
			return fmt.Errorf("生成配置文件失败: %w", err)
		}
	}

	if isFrpsRunning() {
		return nil
	}

	os.Remove("./data/frps.pid")

	cmd := exec.Command(frpsPath, "-c", "./data/frps.toml")
	setWindowHide(cmd)
	setSysProcAttr(cmd)

	logFile, err := os.OpenFile("./data/frps.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
	if err != nil {
		return fmt.Errorf("打开日志文件失败: %w", err)
	}
	cmd.Stdout = logFile
	cmd.Stderr = logFile

	if err := cmd.Start(); err != nil {
		return fmt.Errorf("启动 frps 失败: %w", err)
	}

	if err := os.WriteFile("./data/frps.pid", []byte(fmt.Sprintf("%d", cmd.Process.Pid)), 0644); err != nil {
		return fmt.Errorf("保存 PID 失败: %w", err)
	}

	return nil
}

func StopFrps() error {
	if runtime.GOOS == "windows" {
		cmd := exec.Command("taskkill", "/F", "/IM", "frps.exe")
		if err := cmd.Run(); err != nil && !strings.Contains(err.Error(), "not found") {
			return fmt.Errorf("停止 frps 失败: %w", err)
		}
		os.Remove("./data/frps.pid")
		return nil
	}

	pidData, err := os.ReadFile("./data/frps.pid")
	if err != nil {
		cmd := exec.Command("pkill", "-f", "frps")
		if err := cmd.Run(); err != nil && !strings.Contains(err.Error(), "no process") {
			return fmt.Errorf("停止 frps 失败: %w", err)
		}
		return nil
	}

	pid, _ := strconv.Atoi(strings.TrimSpace(string(pidData)))
	process, err := os.FindProcess(pid)
	if err != nil {
		os.Remove("./data/frps.pid")
		return nil
	}

	if err := process.Kill(); err != nil {
		return fmt.Errorf("杀死进程失败: %w", err)
	}

	os.Remove("./data/frps.pid")
	return nil
}

func GetFrpsStatus() (bool, error) {
	return isFrpsRunning(), nil
}

func ReloadFrps() error {
	running := isFrpsRunning()
	if !running {
		return StartFrps()
	}

	frpsPath, err := getFrpsPath()
	if err != nil {
		return fmt.Errorf("获取 frps 路径失败: %w", err)
	}

	cmd := exec.Command(frpsPath, "reload", "-c", "./data/frps.toml")
	_, err = cmd.CombinedOutput()
	if err != nil {
		log.Printf("⚠️  热加载失败 (%v)，自动降级为重启 frps", err)
		if stopErr := StopFrps(); stopErr != nil {
			return fmt.Errorf("停止 frps 失败: %w", stopErr)
		}
		if startErr := StartFrps(); startErr != nil {
			return fmt.Errorf("启动 frps 失败: %w", startErr)
		}
		return nil
	}
	return nil
}

// readTailLog 通用
func readTailLog(filePath string, n int) ([]string, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	info, err := file.Stat()
	if err != nil {
		return nil, err
	}
	fileSize := info.Size()
	if fileSize == 0 {
		return []string{}, nil
	}

	const chunkSize = 4096
	var lines []string
	var leftover []byte
	offset := fileSize

	for len(lines) < n && offset > 0 {
		readSize := chunkSize
		if offset < int64(chunkSize) {
			readSize = int(offset)
		}
		offset -= int64(readSize)

		buf := make([]byte, readSize)
		_, err := file.ReadAt(buf, offset)
		if err != nil && err != io.EOF {
			return nil, err
		}

		data := append(buf, leftover...)
		leftover = nil

		start := 0
		for i := len(data) - 1; i >= 0; i-- {
			if data[i] == '\n' {
				if i+1 < len(data) {
					line := string(data[i+1:])
					if line != "" {
						lines = append([]string{line}, lines...)
						if len(lines) >= n {
							break
						}
					}
				}
				start = i
			}
		}

		if len(lines) < n && start > 0 {
			leftover = data[:start]
		}
	}

	if len(lines) < n && len(leftover) > 0 {
		parts := strings.Split(string(leftover), "\n")
		for i := len(parts) - 1; i >= 0; i-- {
			if parts[i] != "" {
				lines = append([]string{parts[i]}, lines...)
				if len(lines) >= n {
					break
				}
			}
		}
	}

	return lines, nil
}