package main

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/appupdate"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/config"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/diagnostics"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/hetzner"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/ipresolve"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/scheduler"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/secure"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/store"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/updateagent"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/web"
)

func main() {
	command := commandForInvocation(os.Args)
	if command == "healthcheck" {
		os.Exit(healthcheck())
	}
	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelInfo}))
	var err error
	switch command {
	case "serve":
		err = run(logger)
	case "update-agent":
		ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
		defer stop()
		err = updateagent.Serve(ctx, updateagent.ServerConfigFromEnvironment(), logger)
	default:
		err = errors.New("unknown command; expected serve, healthcheck, or update-agent")
	}
	if err != nil {
		logger.Error("application stopped", "error", err)
		os.Exit(1)
	}
}

func commandForInvocation(arguments []string) string {
	if len(arguments) == 0 {
		return "invalid"
	}
	// v1.3 Compose files override the agent entrypoint and inherit the image's
	// default "serve" command. Keep that one-time manual upgrade path working
	// while the image itself still contains only one executable.
	if filepath.Base(arguments[0]) == "update-agent" && (len(arguments) == 1 || (len(arguments) == 2 && arguments[1] == "serve")) {
		return "update-agent"
	}
	if len(arguments) == 1 {
		return "serve"
	}
	if len(arguments) == 2 {
		return arguments[1]
	}
	return "invalid"
}

func run(logger *slog.Logger) error {
	startedAt := time.Now()
	// Credentials and session data must never inherit a permissive process umask.
	syscall.Umask(0o077)
	cfg, err := config.Load()
	if err != nil {
		return err
	}
	if err := diagnostics.Configure(filepath.Join(cfg.DataDir, "diagnostics.jsonl"), logger); err != nil {
		logger.Warn("diagnostic log unavailable")
	}
	diagnostics.Record(diagnostics.Event{Code: "startup", Network: diagnostics.CurrentNetwork()})
	cipher, err := secure.LoadOrCreateCipher(cfg.MasterKeyFile)
	if err != nil {
		return err
	}
	ctx := context.Background()
	database, err := store.Open(ctx, cfg.DatabasePath)
	if err != nil {
		return err
	}
	defer database.Close()
	if err := database.RecoverInterruptedRuns(ctx); err != nil {
		return fmt.Errorf("recover interrupted update runs: %w", err)
	}
	if err := database.Prune(ctx); err != nil {
		logger.Warn("prune old local data", "error", err)
	}
	provider := hetzner.New(cfg.HCloudBaseURL)
	updater := scheduler.New(database, provider, ipresolve.New(), cipher, logger)
	softwareUpdates, err := appupdate.New(database, cipher, cfg.UpdateAPIURL, cfg.UpdateAgentSock, cfg.UpdateInterval, logger)
	if err != nil {
		return err
	}
	settings, err := database.GetSettings(ctx)
	if err != nil {
		return err
	}
	if !settings.IPv6Enabled {
		cleanupCtx, cancel := context.WithTimeout(ctx, 10*time.Second)
		deleted, cleanupErr := updater.DisableIPv6(cleanupCtx)
		cancel()
		if cleanupErr != nil {
			logger.Warn("enforce disabled IPv6", "error", cleanupErr)
		} else if deleted > 0 {
			logger.Info("removed AAAA records for disabled IPv6", "count", deleted)
		}
	}
	restartRequested := make(chan struct{})
	var restartOnce sync.Once
	requestRestart := func() {
		restartOnce.Do(func() {
			// Docker applies restart policies only after a container has stayed up
			// long enough to be considered successfully started. Keep very early
			// UI requests alive until that safety window has passed.
			delay := time.Until(startedAt.Add(11 * time.Second))
			if delay > 0 {
				time.AfterFunc(delay, func() { close(restartRequested) })
				return
			}
			close(restartRequested)
		})
	}
	serverUI, err := web.New(cfg, database, cipher, updater, softwareUpdates, logger, requestRestart)
	if err != nil {
		return err
	}

	appCtx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	updater.Start(appCtx)
	defer func() {
		stop()
		waitCtx, cancel := context.WithTimeout(context.Background(), cfg.ShutdownTimeout)
		defer cancel()
		if err := updater.Wait(waitCtx); err != nil {
			logger.Warn("waiting for updater shutdown", "error", err)
		}
	}()
	softwareUpdates.Start(appCtx)
	go pruneStore(appCtx, database, logger)
	httpServer := &http.Server{
		Addr:              cfg.Address,
		Handler:           serverUI.Handler(),
		ReadHeaderTimeout: 5 * time.Second,
		ReadTimeout:       15 * time.Second,
		WriteTimeout:      30 * time.Second,
		IdleTimeout:       60 * time.Second,
		MaxHeaderBytes:    16 << 10,
	}
	serverErrors := make(chan error, 1)
	go func() {
		logger.Info("starting server", "address", cfg.Address, "mode", cfg.Mode)
		serverErrors <- httpServer.ListenAndServe()
	}()
	select {
	case err := <-serverErrors:
		if !errors.Is(err, http.ErrServerClosed) {
			return err
		}
		return nil
	case <-restartRequested:
		logger.Info("container restart requested")
		stop()
		shutdownCtx, cancel := context.WithTimeout(context.Background(), cfg.ShutdownTimeout)
		defer cancel()
		return httpServer.Shutdown(shutdownCtx)
	case <-appCtx.Done():
		logger.Info("shutdown requested")
		shutdownCtx, cancel := context.WithTimeout(context.Background(), cfg.ShutdownTimeout)
		defer cancel()
		return httpServer.Shutdown(shutdownCtx)
	}
}

func pruneStore(ctx context.Context, database *store.Store, logger *slog.Logger) {
	ticker := time.NewTicker(24 * time.Hour)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			pruneCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
			err := database.Prune(pruneCtx)
			cancel()
			if err != nil && !errors.Is(err, context.Canceled) {
				logger.Warn("prune old local data", "error", err)
			}
		}
	}
}

func healthcheck() int {
	url := strings.TrimSpace(os.Getenv("APP_HEALTHCHECK_URL"))
	if url == "" {
		url = "http://127.0.0.1:8080/healthz"
	}
	client := &http.Client{Timeout: 3 * time.Second}
	response, err := client.Get(url)
	if err != nil {
		return 1
	}
	defer response.Body.Close()
	if response.StatusCode != http.StatusOK {
		return 1
	}
	return 0
}