// Command agent is the Linux client installed on machines without a public IP.
// It runs as a root systemd service, dials the server over HTTP long-polling,
// and opens a root PTY when an admin requests a terminal in the web panel.
package main

import (
	"context"
	"log"
	"net"
	"net/url"
	"os"
	"os/signal"
	"strconv"
	"syscall"

	"github.com/x-grk/longpolling-remote-access/internal/agent"
	"github.com/x-grk/longpolling-remote-access/internal/tunnel"
)

func main() {
	host := envOr("HOST", "https://REDACTED:8445")
	cfg := agent.Config{
		Host:         host,
		EnrollSecret: os.Getenv("ENROLL_SECRET"),
		Name:         os.Getenv("AGENT_NAME"),
		StatePath:    envOr("STATE_PATH", "/etc/lpagent/state.json"),
		TunnelAddr:   tunnelAddr(host),
		// A locally set address wins over the one from the panel settings.
		TunnelPinned: os.Getenv("TUNNEL_ADDR") != "" || os.Getenv("TUNNEL_PORT") != "",
	}
	if cfg.EnrollSecret == "" {
		// Only required for the very first run (before enrollment).
		if _, err := os.Stat(cfg.StatePath); os.IsNotExist(err) {
			log.Fatal("ENROLL_SECRET is required for first enrollment")
		}
	}

	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stop()

	err := agent.New(cfg).Run(ctx)
	// Stopping (an update, a restart): hang the terminals up, so their shells
	// save their history instead of being killed.
	agent.CloseTerminals()
	if err != nil {
		log.Fatalf("agent: %v", err)
	}
}

func envOr(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}

// tunnelAddr derives the direct-tunnel address (host:port) from the server URL.
// It is only the starting point: the agent follows the host and port set in
// the panel settings, unless TUNNEL_ADDR (the whole address) or TUNNEL_PORT
// (just the port) pins it here. Set TUNNEL_ADDR=off to disable the tunnel.
func tunnelAddr(hostURL string) string {
	if v := os.Getenv("TUNNEL_ADDR"); v != "" {
		if v == "off" {
			return ""
		}
		return v
	}
	u, err := url.Parse(hostURL)
	if err != nil || u.Hostname() == "" {
		return ""
	}
	return net.JoinHostPort(u.Hostname(), envOr("TUNNEL_PORT", strconv.Itoa(tunnel.DefaultPort)))
}