package main

import (
	"context"
	"flag"
	"log"
	"os"
	"os/signal"
	"sync/atomic"
	"syscall"
	"time"

	"incudal-agent/internal/config"
	"incudal-agent/internal/panel"
	"incudal-agent/internal/report"
	"incudal-agent/internal/upgrade"
)

var version = "dev"

func main() {
	configPath := flag.String("config", "/etc/incudal-agent/config.yaml", "agent config file")
	once := flag.Bool("once", false, "send one heartbeat and exit")
	flag.Parse()

	cfg, err := config.Load(*configPath)
	if err != nil {
		log.Fatalf("load config: %v", err)
	}

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

	client := panel.New(cfg)
	if *once {
		if _, err := sendHeartbeat(ctx, client, cfg.HeartbeatIntervalSeconds); err != nil {
			log.Fatalf("heartbeat: %v", err)
		}
		return
	}

	log.Printf("incudal-agent started: panel=%s interval=%s", cfg.PanelURL, cfg.HeartbeatInterval)
	upgradeRunner := upgrade.DefaultRunner(cfg)
	var upgradeInProgress atomic.Bool
	if result, err := sendHeartbeat(ctx, client, cfg.HeartbeatIntervalSeconds); err != nil {
		log.Printf("heartbeat failed: %v", err)
	} else {
		scheduleAgentUpgrade(ctx, upgradeRunner, result, &upgradeInProgress)
	}

	ticker := time.NewTicker(cfg.HeartbeatInterval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			log.Printf("incudal-agent stopped")
			return
		case <-ticker.C:
			if result, err := sendHeartbeat(ctx, client, cfg.HeartbeatIntervalSeconds); err != nil {
				log.Printf("heartbeat failed: %v", err)
			} else {
				scheduleAgentUpgrade(ctx, upgradeRunner, result, &upgradeInProgress)
			}
		}
	}
}

func sendHeartbeat(ctx context.Context, client *panel.Client, heartbeatIntervalSeconds int) (panel.HeartbeatResult, error) {
	result, err := client.Heartbeat(ctx, report.HeartbeatPayload(version, heartbeatIntervalSeconds))
	if err != nil {
		return result, err
	}
	upgradeAvailable := result.Upgrade != nil && result.Upgrade.Available
	log.Printf("heartbeat ok: status=%d latencyMs=%d upgrade=%t", result.StatusCode, result.LatencyMs, upgradeAvailable)
	return result, nil
}

func scheduleAgentUpgrade(ctx context.Context, runner *upgrade.Runner, result panel.HeartbeatResult, upgradeInProgress *atomic.Bool) {
	if result.Upgrade == nil || !result.Upgrade.Available {
		return
	}
	if !upgradeInProgress.CompareAndSwap(false, true) {
		log.Printf("agent upgrade already scheduled: version=%s", result.Upgrade.Version)
		return
	}

	instruction := *result.Upgrade
	log.Printf("agent upgrade scheduled: version=%s", instruction.Version)
	go func() {
		defer upgradeInProgress.Store(false)

		if delay := upgrade.RandomJitter(5 * time.Minute); delay > 0 {
			timer := time.NewTimer(delay)
			select {
			case <-ctx.Done():
				timer.Stop()
				return
			case <-timer.C:
			}
		}

		upgradeCtx, cancel := context.WithTimeout(context.Background(), 10*time.Minute)
		defer cancel()
		if err := runner.Apply(upgradeCtx, instruction, version); err != nil {
			log.Printf("agent upgrade failed: version=%s error=%v", instruction.Version, err)
			return
		}
		log.Printf("agent upgrade applied: version=%s", instruction.Version)
	}()
}