//go:build windows

// Command xui-agent-windows is the standalone Windows build of the
// 3x-ui node agent. Windows nodes are probe-only by design: the agent
// reports host facts/metrics and runs latency probes, but no xray or
// sing-box core is ever fetched or started here (the agent core
// machinery stays the master's Linux fleet concern; the local
// agent.json carries "probeOnly": true, written by
// install-agent.ps1).
//
// Usage:
//
//	xui-agent-windows.exe [-config C:\x-ui\agent.json]      run (service or console)
//	xui-agent-windows.exe install [-config <path>]          register the service
//	xui-agent-windows.exe uninstall                         remove the service
//	xui-agent-windows.exe start | stop                      control the service
//
// The agent lifecycle wiring (config load, baseline derivation,
// logger init, graceful stop) mirrors main.go's agent branch — the
// same internal/agent package does the work either way.
package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"path/filepath"
	"syscall"
	"time"

	"github.com/mhsanaei/3x-ui/v3/internal/agent"
	"github.com/mhsanaei/3x-ui/v3/internal/logger"

	"github.com/op/go-logging"
	"golang.org/x/sys/windows/svc"
	"golang.org/x/sys/windows/svc/mgr"
)

const (
	serviceName    = "x-ui-agent"
	defaultCfgPath = `C:\x-ui\agent.json`
)

func main() {
	log.SetPrefix("[x-ui-agent] ")
	args := os.Args[1:]

	// Management subcommands come first; anything else is a run.
	if len(args) > 0 {
		switch args[0] {
		case "install", "uninstall", "start", "stop":
			cfgPath := parseConfigFlag("xui-agent-windows "+args[0], args[1:])
			if err := runControl(args[0], cfgPath); err != nil {
				log.Fatalf("%s: %v", args[0], err)
			}
			return
		}
	}

	cfgPath := parseConfigFlag("xui-agent-windows", args)

	isService, err := svc.IsWindowsService()
	if err != nil {
		log.Fatalf("detect service environment: %v", err)
	}
	if isService {
		if err := svc.Run(serviceName, &agentHandler{cfgPath: cfgPath}); err != nil {
			log.Fatalf("service run: %v", err)
		}
		return
	}

	// Interactive run: console foreground, Ctrl+C stops gracefully.
	running, err := startAgent(cfgPath)
	if err != nil {
		log.Fatalf("start agent: %v", err)
	}
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, os.Interrupt, syscall.SIGTERM)
	select {
	case <-sigCh:
		log.Println("Shutting down agent...")
		running.Stop()
		<-running.done
	case err := <-running.done:
		if err != nil {
			log.Fatalf("Agent error: %v", err)
		}
	}
}

func parseConfigFlag(name string, args []string) string {
	fs := flag.NewFlagSet(name, flag.ExitOnError)
	cfg := fs.String("config", defaultCfgPath, "Path to agent config file")
	_ = fs.Parse(args)
	return *cfg
}

// runningAgent is one started agent plus its completion signal.
type runningAgent struct {
	ag   *agent.Agent
	done chan error
}

func (r *runningAgent) Stop() { r.ag.Stop() }

// startAgent performs the same setup as main.go's agent branch and
// launches the agent loop in the background.
func startAgent(cfgPath string) (*runningAgent, error) {
	// Agent mode uses the panel's directory layout for core binaries
	// and configs; on a probe-only Windows node nothing consumes it,
	// but keep the wiring identical to the Linux entry so behaviour
	// cannot drift between the two.
	if os.Getenv("XUI_BIN_FOLDER") == "" {
		_ = os.Setenv("XUI_BIN_FOLDER", agent.DefaultBinFolder)
	}

	cfg, err := agent.LoadConfig(cfgPath)
	if err != nil {
		return nil, fmt.Errorf("load agent config from %s: %w", cfgPath, err)
	}
	// The acknowledged traffic baseline persists next to the agent
	// config (its state home), unless the config names a path.
	if cfg.BaselinePath == "" {
		cfg.BaselinePath = filepath.Join(filepath.Dir(cfgPath), "agent-traffic-baseline.json")
	}

	logger.InitLogger(logging.INFO)
	log.Printf("Starting 3x-ui agent (node: %s)", cfg.NodeName)

	ag := agent.New(cfg)
	r := &runningAgent{ag: ag, done: make(chan error, 1)}
	go func() { r.done <- ag.Run() }()
	return r, nil
}

// agentHandler adapts the agent loop to the SCM protocol.
type agentHandler struct {
	cfgPath string
}

func (h *agentHandler) Execute(_ []string, r <-chan svc.ChangeRequest, status chan<- svc.Status) (bool, uint32) {
	const accepted = svc.AcceptStop | svc.AcceptShutdown
	status <- svc.Status{State: svc.StartPending}
	running, err := startAgent(h.cfgPath)
	if err != nil {
		log.Printf("start agent: %v", err)
		return false, 1
	}
	status <- svc.Status{State: svc.Running, Accepts: accepted}
	for {
		select {
		case err := <-running.done:
			// The agent loop ended on its own (e.g. fatal run error).
			if err != nil {
				log.Printf("agent exited: %v", err)
				return false, 1
			}
			return false, 0
		case c := <-r:
			switch c.Cmd {
			case svc.Interrogate:
				status <- c.CurrentStatus
			case svc.Stop, svc.Shutdown:
				status <- svc.Status{State: svc.StopPending}
				running.Stop()
				<-running.done
				return false, 0
			default:
				log.Printf("unexpected service command: %v", c.Cmd)
			}
		}
	}
}

// runControl implements the install/uninstall/start/stop subcommands
// through the service control manager.
func runControl(cmd, cfgPath string) error {
	m, err := mgr.ConnectRemote("")
	if err != nil {
		return fmt.Errorf("connect to service manager: %w", err)
	}
	defer m.Disconnect()

	switch cmd {
	case "install":
		exePath, err := os.Executable()
		if err != nil {
			return fmt.Errorf("locate own binary: %w", err)
		}
		absCfg, err := filepath.Abs(cfgPath)
		if err != nil {
			return fmt.Errorf("resolve config path: %w", err)
		}
		if s, err := m.OpenService(serviceName); err == nil {
			s.Close()
			return fmt.Errorf("service %s already exists (uninstall first)", serviceName)
		}
		s, err := m.CreateService(serviceName, exePath, mgr.Config{
			DisplayName:  "3x-ui Agent",
			Description:  "3x-ui probe-only node agent (facts, metrics and latency probes; runs no proxy core).",
			StartType:    mgr.StartAutomatic,
			ErrorControl: mgr.ErrorNormal,
		}, "-config", absCfg)
		if err != nil {
			return fmt.Errorf("create service: %w", err)
		}
		defer s.Close()
		log.Printf("service %s installed (config: %s)", serviceName, absCfg)
		return nil

	case "uninstall":
		s, err := openService(m)
		if err != nil {
			return err
		}
		defer s.Close()
		// Stop first so the binary is not locked when the operator
		// deletes or replaces it; an already-stopped service is fine.
		_, _ = s.Control(svc.Stop)
		deadline := time.Now().Add(15 * time.Second)
		for time.Now().Before(deadline) {
			st, err := s.Query()
			if err != nil || st.State == svc.Stopped {
				break
			}
			time.Sleep(300 * time.Millisecond)
		}
		if err := s.Delete(); err != nil {
			return fmt.Errorf("delete service: %w", err)
		}
		log.Printf("service %s removed", serviceName)
		return nil

	case "start":
		s, err := openService(m)
		if err != nil {
			return err
		}
		defer s.Close()
		if err := s.Start(); err != nil {
			return fmt.Errorf("start service: %w", err)
		}
		log.Printf("service %s started", serviceName)
		return nil

	case "stop":
		s, err := openService(m)
		if err != nil {
			return err
		}
		defer s.Close()
		if _, err := s.Control(svc.Stop); err != nil {
			return fmt.Errorf("stop service: %w", err)
		}
		log.Printf("service %s stop requested", serviceName)
		return nil
	}
	return fmt.Errorf("unknown subcommand %q", cmd)
}

func openService(m *mgr.Mgr) (*mgr.Service, error) {
	s, err := m.OpenService(serviceName)
	if err != nil {
		return nil, fmt.Errorf("open service %s: %w", serviceName, err)
	}
	return s, nil
}