package main

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

	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/updateagent"
)

func main() {
	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelInfo}))
	if err := run(logger); err != nil {
		logger.Error("update agent stopped", "error", err)
		os.Exit(1)
	}
}

func run(logger *slog.Logger) error {
	socket := env("UPDATE_AGENT_SOCKET", "/run/domain-control-update/agent.sock")
	dockerSocket := env("UPDATE_DOCKER_SOCKET", "/var/run/docker.sock")
	image := env("UPDATE_IMAGE_REPOSITORY", "git.j-mahler.de/admin/domain-control-webinterface-prod")
	targetLabel := env("UPDATE_TARGET_LABEL", "de.j-mahler.domain-control.role=app")
	directory := filepath.Dir(socket)
	if err := os.MkdirAll(directory, 0o711); err != nil {
		return err
	}
	if err := os.Chmod(directory, 0o711); err != nil {
		return err
	}
	if err := os.Remove(socket); err != nil && !errors.Is(err, os.ErrNotExist) {
		return err
	}
	listener, err := net.Listen("unix", socket)
	if err != nil {
		return err
	}
	defer listener.Close()
	defer os.Remove(socket)
	// The container runs as uid 0 with gid 10001. Group-only access lets the
	// unprivileged web process connect without exposing the socket to others.
	if err := os.Chmod(socket, 0o660); err != nil {
		return err
	}
	runner := updateagent.NewDockerRunner(dockerSocket, image, targetLabel, logger)
	controller := updateagent.NewController(runner, logger)
	server := &http.Server{
		Handler:           controller.Handler(),
		ReadHeaderTimeout: 3 * time.Second,
		ReadTimeout:       5 * time.Second,
		WriteTimeout:      5 * time.Second,
		IdleTimeout:       15 * time.Second,
		MaxHeaderBytes:    8 << 10,
	}
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	serverErrors := make(chan error, 1)
	go func() {
		logger.Info("update agent ready", "socket", socket)
		serverErrors <- server.Serve(listener)
	}()
	select {
	case err := <-serverErrors:
		if errors.Is(err, http.ErrServerClosed) {
			return nil
		}
		return err
	case <-ctx.Done():
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()
		return server.Shutdown(shutdownCtx)
	}
}

func env(name, fallback string) string {
	if value := strings.TrimSpace(os.Getenv(name)); value != "" {
		return value
	}
	return fallback
}