package main

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

	"github.com/wzray/dns/internal/resolv"
	"github.com/wzray/dns/internal/server"
)

func main() {
	addr := flag.String("addr", ":8080", "HTTP listen address")
	logLevel := flag.String("log-level", "info", "Log level: debug, info, warn, error")
	logFormat := flag.String("log-format", "text", "Log format: text or json")
	flag.Parse()

	log := newLogger(*logLevel, *logFormat)

	resolvPath := resolv.DefaultPath
	if err := os.MkdirAll(filepath.Dir(resolvPath), 0o755); err != nil {
		log.Error("prepare resolv directory", "err", err)
		os.Exit(1)
	}

	mgr := resolv.New(resolvPath)
	srv := server.New(mgr, log)

	httpSrv := &http.Server{
		Addr:              *addr,
		Handler:           srv.Handler(),
		ReadHeaderTimeout: 5 * time.Second,
	}

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

	errCh := make(chan error, 1)
	go func() {
		log.Info("starting server", "addr", *addr)
		if err := httpSrv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			errCh <- err
		}
	}()

	select {
	case <-ctx.Done():
		log.Info("shutting down")
	case err := <-errCh:
		log.Error("server error", "err", err)
		os.Exit(1)
	}

	shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if err := httpSrv.Shutdown(shutdownCtx); err != nil {
		log.Error("graceful shutdown failed", "err", err)
		os.Exit(1)
	}
}

func newLogger(level, format string) *slog.Logger {
	var lvl slog.Level
	switch level {
	case "debug":
		lvl = slog.LevelDebug
	case "warn":
		lvl = slog.LevelWarn
	case "error":
		lvl = slog.LevelError
	default:
		lvl = slog.LevelInfo
	}
	opts := &slog.HandlerOptions{Level: lvl}
	var h slog.Handler
	if format == "json" {
		h = slog.NewJSONHandler(os.Stderr, opts)
	} else {
		h = slog.NewTextHandler(os.Stderr, opts)
	}
	return slog.New(h)
}