// process_manager.go
// frpc-console 进程管理模块
// 2.6-preview: 端口检测 + 单实例锁定 + 状态自述

package main

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"time"

	"golang.org/x/sys/unix"
)

// ================================================================
// 常量定义
// ================================================================

const (
	LockFileName       = ".frpc.lock"
	PortCheckTimeout   = 500 * time.Millisecond
	StartWaitTime      = 500 * time.Millisecond
	StopMaxWaitTime    = 5 * time.Second
	LockAcquireTimeout = 30 * time.Second
	LockRetryInterval  = 100 * time.Millisecond
	APITimeout         = 2 * time.Second
)

// ================================================================
// 数据结构
// ================================================================

type PortStatus struct {
	Port       int    `json:"port"`
	Occupied   bool   `json:"occupied"`
	PID        int    `json:"pid"`
	IsFRPC     bool   `json:"is_frpc"`
	ProcessCmd string `json:"process_cmd,omitempty"`
}

type ProcessStatus struct {
	State   string `json:"state"`
	PID     int    `json:"pid"`
	Port    int    `json:"port"`
	Uptime  string `json:"uptime,omitempty"`
	Version string `json:"version,omitempty"`
	Error   string `json:"error,omitempty"`
}

type FRPCStatus struct {
	Version string `json:"version"`
	RunID   string `json:"run_id"`
	Proxies []struct {
		Name      string `json:"name"`
		Type      string `json:"type"`
		Status    string `json:"status"`
		LocalAddr string `json:"local_addr"`
	} `json:"proxies"`
}

// ================================================================
// ProcessManager 主结构
// ================================================================

type ProcessManager struct {
	mu          sync.Mutex
	dataDir     string
	configPath  string
	frpcBinPath string
	adminPort   int
	lockFile    *os.File
	locked      bool
}

func NewProcessManager(dataDir, configPath, frpcBinPath string) *ProcessManager {
	return &ProcessManager{
		dataDir:     dataDir,
		configPath:  configPath,
		frpcBinPath: frpcBinPath,
		adminPort:   0,
	}
}

// ================================================================
// 配置读取
// ================================================================

func (pm *ProcessManager) LoadConfig() error {
	content, err := os.ReadFile(pm.configPath)
	if err != nil {
		return fmt.Errorf("读取配置文件失败: %w", err)
	}
	if port := extractIntValue(string(content), "admin_port"); port > 0 {
		pm.adminPort = port
		return nil
	}
	if port := extractIntValueFromSection(string(content), "webServer", "port"); port > 0 {
		pm.adminPort = port
		return nil
	}
	return fmt.Errorf("未找到 admin_port 或 webServer.port 配置")
}

func extractIntValue(content, key string) int {
	lines := strings.Split(content, "\n")
	for _, line := range lines {
		trimmed := strings.TrimSpace(line)
		if strings.HasPrefix(trimmed, key) {
			parts := strings.SplitN(trimmed, "=", 2)
			if len(parts) == 2 {
				val := strings.TrimSpace(parts[1])
				val = strings.Trim(val, `"`)
				if port, err := strconv.Atoi(val); err == nil && port > 0 {
					return port
				}
			}
		}
	}
	return 0
}

func extractIntValueFromSection(content, section, key string) int {
	lines := strings.Split(content, "\n")
	inSection := false
	for _, line := range lines {
		trimmed := strings.TrimSpace(line)
		if strings.HasPrefix(trimmed, "[") && strings.HasSuffix(trimmed, "]") {
			inSection = strings.Trim(trimmed, "[]") == section
			continue
		}
		if inSection && strings.HasPrefix(trimmed, key) {
			parts := strings.SplitN(trimmed, "=", 2)
			if len(parts) == 2 {
				val := strings.TrimSpace(parts[1])
				val = strings.Trim(val, `"`)
				if port, err := strconv.Atoi(val); err == nil && port > 0 {
					return port
				}
			}
		}
	}
	return 0
}

// ================================================================
// 端口检测
// ================================================================

func (pm *ProcessManager) CheckPort() (bool, error) {
	if pm.adminPort <= 0 {
		return false, fmt.Errorf("admin_port 未配置")
	}
	conn, err := net.DialTimeout("tcp", fmt.Sprintf("127.0.0.1:%d", pm.adminPort), PortCheckTimeout)
	if err != nil {
		return false, nil
	}
	conn.Close()
	return true, nil
}

func (pm *ProcessManager) GetPortStatus() (*PortStatus, error) {
	status := &PortStatus{Port: pm.adminPort, Occupied: false, PID: 0, IsFRPC: false}
	occupied, err := pm.CheckPort()
	if err != nil {
		return status, err
	}
	status.Occupied = occupied
	if !occupied {
		return status, nil
	}

	pid, err := pm.getPIDByPort(pm.adminPort)
	if err != nil {
		if pidFromFile := pm.readPIDFile(); pidFromFile > 0 {
			if pm.isProcessListeningOnPort(pidFromFile, pm.adminPort) {
				status.PID = pidFromFile
			}
		}
	} else {
		status.PID = pid
	}
	if status.PID == 0 {
		return status, nil
	}
	isFRPC, cmd := pm.isFRPCProcess(status.PID)
	status.IsFRPC = isFRPC
	status.ProcessCmd = cmd
	return status, nil
}

func (pm *ProcessManager) getPIDByPort(port int) (int, error) {
	if pid, err := pm.getPIDBySS(port); err == nil && pid > 0 {
		return pid, nil
	}
	if pid, err := pm.getPIDByNetstat(port); err == nil && pid > 0 {
		return pid, nil
	}
	if pid, err := pm.getPIDByLsof(port); err == nil && pid > 0 {
		return pid, nil
	}
	return 0, fmt.Errorf("无法通过端口反查 PID")
}

func (pm *ProcessManager) getPIDBySS(port int) (int, error) {
	cmd := exec.Command("ss", "-lpn", "state", "listening")
	out, err := cmd.Output()
	if err != nil {
		return 0, err
	}
	scanner := bufio.NewScanner(bytes.NewReader(out))
	for scanner.Scan() {
		line := scanner.Text()
		if !strings.Contains(line, fmt.Sprintf(":%d", port)) {
			continue
		}
		if idx := strings.Index(line, "pid="); idx != -1 {
			end := strings.Index(line[idx:], ",")
			if end == -1 {
				end = strings.Index(line[idx:], ")")
			}
			if end == -1 {
				continue
			}
			pidStr := line[idx+4 : idx+end]
			pidStr = strings.TrimSpace(pidStr)
			if pid, err := strconv.Atoi(pidStr); err == nil && pid > 0 {
				return pid, nil
			}
		}
	}
	return 0, fmt.Errorf("未找到监听端口 %d 的进程", port)
}

func (pm *ProcessManager) getPIDByNetstat(port int) (int, error) {
	cmd := exec.Command("netstat", "-tulpn")
	out, err := cmd.Output()
	if err != nil {
		return 0, err
	}
	scanner := bufio.NewScanner(bytes.NewReader(out))
	for scanner.Scan() {
		line := scanner.Text()
		if !strings.Contains(line, fmt.Sprintf(":%d", port)) {
			continue
		}
		parts := strings.Fields(line)
		if len(parts) < 7 {
			continue
		}
		last := parts[len(parts)-1]
		if idx := strings.Index(last, "/"); idx != -1 {
			pidStr := last[:idx]
			if pid, err := strconv.Atoi(pidStr); err == nil && pid > 0 {
				return pid, nil
			}
		}
	}
	return 0, fmt.Errorf("未找到监听端口 %d 的进程", port)
}

func (pm *ProcessManager) getPIDByLsof(port int) (int, error) {
	cmd := exec.Command("lsof", "-i", fmt.Sprintf(":%d", port), "-sTCP:LISTEN")
	out, err := cmd.Output()
	if err != nil {
		return 0, err
	}
	scanner := bufio.NewScanner(bytes.NewReader(out))
	for scanner.Scan() {
		line := scanner.Text()
		if strings.Contains(line, "frpc") {
			parts := strings.Fields(line)
			if len(parts) >= 2 {
				if pid, err := strconv.Atoi(parts[1]); err == nil && pid > 0 {
					return pid, nil
				}
			}
		}
	}
	return 0, fmt.Errorf("未找到监听端口 %d 的 frpc 进程", port)
}

func (pm *ProcessManager) isProcessListeningOnPort(pid, port int) bool {
	cmd := exec.Command("lsof", "-p", strconv.Itoa(pid), "-a", "-i", fmt.Sprintf(":%d", port), "-sTCP:LISTEN")
	out, err := cmd.Output()
	if err != nil {
		return false
	}
	return strings.Contains(string(out), "LISTEN")
}

func (pm *ProcessManager) isFRPCProcess(pid int) (bool, string) {
	cmdlinePath := fmt.Sprintf("/proc/%d/cmdline", pid)
	if data, err := os.ReadFile(cmdlinePath); err == nil {
		cmd := strings.ReplaceAll(string(data), "\x00", " ")
		if strings.Contains(cmd, "frpc") {
			return true, cmd
		}
	}
	cmd := exec.Command("ps", "-p", strconv.Itoa(pid), "-o", "args=")
	out, err := cmd.Output()
	if err == nil {
		args := strings.TrimSpace(string(out))
		if strings.Contains(args, "frpc") {
			return true, args
		}
	}
	return false, ""
}

// ================================================================
// 互斥锁 (flock)
// ================================================================

func (pm *ProcessManager) Lock() error {
	pm.mu.Lock()
	defer pm.mu.Unlock()
	if pm.locked {
		return nil
	}
	lockPath := filepath.Join(pm.dataDir, LockFileName)
	if err := os.MkdirAll(pm.dataDir, 0755); err != nil {
		return fmt.Errorf("创建数据目录失败: %w", err)
	}
	file, err := os.OpenFile(lockPath, os.O_CREATE|os.O_RDWR, 0644)
	if err != nil {
		return fmt.Errorf("打开锁文件失败: %w", err)
	}
	start := time.Now()
	for {
		err := unix.Flock(int(file.Fd()), unix.LOCK_EX|unix.LOCK_NB)
		if err == nil {
			pm.lockFile = file
			pm.locked = true
			return nil
		}
		if err != syscall.EWOULDBLOCK {
			file.Close()
			return fmt.Errorf("获取锁失败: %w", err)
		}
		if time.Since(start) > LockAcquireTimeout {
			file.Close()
			return fmt.Errorf("获取锁超时 (超过 %v)", LockAcquireTimeout)
		}
		time.Sleep(LockRetryInterval)
	}
}

func (pm *ProcessManager) Unlock() error {
	pm.mu.Lock()
	defer pm.mu.Unlock()
	if !pm.locked {
		return nil
	}
	if pm.lockFile != nil {
		unix.Flock(int(pm.lockFile.Fd()), unix.LOCK_UN)
		pm.lockFile.Close()
		pm.lockFile = nil
	}
	pm.locked = false
	return nil
}

// ================================================================
// PID 文件操作
// ================================================================

func (pm *ProcessManager) pidFilePath() string {
	return filepath.Join(pm.dataDir, "frpc.pid")
}

func (pm *ProcessManager) readPIDFile() int {
	data, err := os.ReadFile(pm.pidFilePath())
	if err != nil {
		return 0
	}
	pid, err := strconv.Atoi(strings.TrimSpace(string(data)))
	if err != nil || pid <= 0 {
		return 0
	}
	return pid
}

func (pm *ProcessManager) writePIDFile(pid int) error {
	return os.WriteFile(pm.pidFilePath(), []byte(strconv.Itoa(pid)), 0644)
}

func (pm *ProcessManager) deletePIDFile() error {
	err := os.Remove(pm.pidFilePath())
	if os.IsNotExist(err) {
		return nil
	}
	return err
}

// ================================================================
// 状态查询
// ================================================================

func (pm *ProcessManager) Status() (*ProcessStatus, error) {
	status := &ProcessStatus{State: "unknown", PID: 0, Port: pm.adminPort}
	if pm.adminPort <= 0 {
		status.Error = "admin_port 未配置"
		return status, nil
	}
	portStatus, err := pm.GetPortStatus()
	if err != nil {
		status.Error = err.Error()
		return status, nil
	}
	if !portStatus.Occupied {
		pm.deletePIDFile()
		status.State = "stopped"
		return status, nil
	}
	if !portStatus.IsFRPC {
		status.State = "conflict"
		status.PID = portStatus.PID
		status.Error = fmt.Sprintf("端口 %d 被非 frpc 进程占用 (PID: %d)", pm.adminPort, portStatus.PID)
		return status, nil
	}
	status.State = "running"
	status.PID = portStatus.PID
	pm.writePIDFile(portStatus.PID)
	if info := pm.getFRPCStatus(portStatus.PID); info != nil {
		status.Version = info.Version
	}
	return status, nil
}

// ================================================================
// API 回源 (2.7-preview 预留)
// ================================================================

func (pm *ProcessManager) getFRPCStatus(pid int) *FRPCStatus {
	if pid <= 0 || pm.adminPort <= 0 {
		return nil
	}
	url := fmt.Sprintf("http://127.0.0.1:%d/api/status", pm.adminPort)
	ctx, cancel := context.WithTimeout(context.Background(), APITimeout)
	defer cancel()
	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return nil
	}
	client := &http.Client{Timeout: APITimeout}
	resp, err := client.Do(req)
	if err != nil {
		return nil
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		return nil
	}
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil
	}
	var status FRPCStatus
	if err := json.Unmarshal(body, &status); err != nil {
		return nil
	}
	return &status
}

// ================================================================
// 操作执行 (Start / Stop / Restart)
// ================================================================

func (pm *ProcessManager) Start(ctx context.Context) error {
	if err := pm.Lock(); err != nil {
		return fmt.Errorf("获取锁失败: %w", err)
	}
	defer pm.Unlock()
	return pm.startLocked(ctx)
}

func (pm *ProcessManager) startLocked(ctx context.Context) error {
	portStatus, err := pm.GetPortStatus()
	if err != nil {
		return fmt.Errorf("检测端口状态失败: %w", err)
	}
	if portStatus.Occupied {
		if portStatus.IsFRPC {
			pm.writePIDFile(portStatus.PID)
			return nil
		}
		return fmt.Errorf("端口 %d 被非 frpc 进程占用 (PID: %d)", pm.adminPort, portStatus.PID)
	}

	cmd := exec.CommandContext(ctx, pm.frpcBinPath, "-c", pm.configPath)

	// 根据平台设置 SysProcAttr
	setProcessAttributes(cmd)

	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	if err := cmd.Start(); err != nil {
		return fmt.Errorf("启动 frpc 失败: %w", err)
	}
	time.Sleep(StartWaitTime)
	occupied, err := pm.CheckPort()
	if err != nil {
		return fmt.Errorf("验证启动状态失败: %w", err)
	}
	if !occupied {
		return fmt.Errorf("frpc 启动失败: 端口未监听")
	}
	pid, _ := pm.getPIDByPort(pm.adminPort)
	if pid > 0 {
		pm.writePIDFile(pid)
	}
	return nil
}

func (pm *ProcessManager) Stop(ctx context.Context) error {
	if err := pm.Lock(); err != nil {
		return fmt.Errorf("获取锁失败: %w", err)
	}
	defer pm.Unlock()
	return pm.stopLocked(ctx)
}

func (pm *ProcessManager) stopLocked(ctx context.Context) error {
	portStatus, err := pm.GetPortStatus()
	if err != nil {
		return fmt.Errorf("检测端口状态失败: %w", err)
	}
	if !portStatus.Occupied {
		pm.deletePIDFile()
		return nil
	}
	var pid int
	if portStatus.IsFRPC {
		pid = portStatus.PID
	} else {
		return fmt.Errorf("端口 %d 被非 frpc 进程占用, 无法安全停止", pm.adminPort)
	}
	if pid <= 0 {
		pid = pm.readPIDFile()
		if pid <= 0 {
			return fmt.Errorf("无法确定 frpc 进程 PID")
		}
	}
	proc, err := os.FindProcess(pid)
	if err != nil {
		pm.deletePIDFile()
		return nil
	}
	if err := proc.Signal(syscall.SIGTERM); err != nil {
		pm.deletePIDFile()
		return nil
	}
	start := time.Now()
	for time.Since(start) < StopMaxWaitTime {
		occupied, _ := pm.CheckPort()
		if !occupied {
			pm.deletePIDFile()
			return nil
		}
		time.Sleep(200 * time.Millisecond)
	}
	proc.Kill()
	time.Sleep(500 * time.Millisecond)
	if occupied, _ := pm.CheckPort(); occupied {
		return fmt.Errorf("强制停止失败: 端口仍被占用")
	}
	pm.deletePIDFile()
	return nil
}

func (pm *ProcessManager) Restart(ctx context.Context) error {
	if err := pm.Lock(); err != nil {
		return fmt.Errorf("获取锁失败: %w", err)
	}
	defer pm.Unlock()
	if err := pm.stopLocked(ctx); err != nil {
		return fmt.Errorf("停止失败: %w", err)
	}
	if err := pm.startLocked(ctx); err != nil {
		return fmt.Errorf("启动失败: %w", err)
	}
	return nil
}

// ================================================================
// 健康检查
// ================================================================

func (pm *ProcessManager) HealthCheck() map[string]interface{} {
	result := map[string]interface{}{"admin_port": pm.adminPort}
	status, err := pm.Status()
	if err != nil {
		result["state"] = "error"
		result["error"] = err.Error()
		return result
	}
	result["state"] = status.State
	result["pid"] = status.PID
	if status.Version != "" {
		result["version"] = status.Version
	}
	if status.Error != "" {
		result["error"] = status.Error
	}
	return result
}