// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

//go:build linux || freebsd

// Command nuntius runs the contact form backend server.
//
// Configuration is loaded from a TOML file (default: /etc/nuntius/config.toml).
// The TOML file may reference environment variables for secrets using
// ${VAR_NAME} or $VAR_NAME syntax.
package main

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"log/slog"
	"net"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"syscall"
	"time"

	"sourcedock.dev/petrbalvin/nuntius/internal/config"
	"sourcedock.dev/petrbalvin/nuntius/internal/handler"
	"sourcedock.dev/petrbalvin/nuntius/internal/version"
)

func main() {
	showVersion := flag.Bool("version", false, "Print version and exit")
	checkConfig := flag.Bool("check-config", false, "Validate the configuration file and exit without listening")
	flag.Parse()
	if *showVersion {
		fmt.Printf("%s %s\n", version.Name, version.Version())
		return
	}

	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelInfo}))
	slog.SetDefault(logger)

	cfgPath := config.ConfigPath()

	if *checkConfig {
		if _, err := config.Load(cfgPath); err != nil {
			fmt.Fprintf(os.Stderr, "nuntius: configuration %s is invalid: %v\n", cfgPath, err)
			os.Exit(1)
		}
		fmt.Printf("configuration OK: %s\n", cfgPath)
		return
	}

	cfg, err := config.Load(cfgPath)
	if err != nil {
		logger.Error("config load failed", "path", cfgPath, "err", err)
		os.Exit(1)
	}

	h := handler.New(cfg)

	mux := http.NewServeMux()
	h.Register(mux)

	srv := &http.Server{
		// The bind host and every timeout are configuration: an omitted
		// key resolves to the value this release has always used, so the
		// zero-config behaviour is unchanged.
		Addr:              net.JoinHostPort(cfg.Server.Bind, strconv.Itoa(cfg.Server.Port)),
		Handler:           withRequestLog(mux, logger, cfg.Server.TrustProxyHeaders),
		ReadHeaderTimeout: cfg.Server.ReadHeaderTimeout(),
		ReadTimeout:       cfg.Server.ReadTimeout(),
		WriteTimeout:      cfg.Server.WriteTimeout(),
		IdleTimeout:       cfg.Server.IdleTimeout(),
	}

	logger.Info("nuntius starting",
		"version", version.Name+" "+version.Version(),
		"addr", srv.Addr,
		"config", cfgPath,
		"forms", len(cfg.Forms),
	)
	for _, f := range cfg.Forms {
		logger.Info("form registered",
			"name", f.Name,
			"path", f.Path,
			"to", f.To,
			"smtp", f.SMTP.Host,
		)
	}

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

	go func() {
		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			logger.Error("server error", "err", err)
			os.Exit(1)
		}
	}()

	<-ctx.Done()
	logger.Info("shutdown signal received")

	shutdownCtx, cancel := context.WithTimeout(context.Background(), cfg.Server.ShutdownTimeout())
	defer cancel()
	if err := srv.Shutdown(shutdownCtx); err != nil {
		logger.Error("shutdown error", "err", err)
		h.PersistState()
		os.Exit(1)
	}
	h.PersistState()
	h.Close()
	logger.Info("nuntius stopped cleanly")
}

// withRequestLog logs each HTTP request method, path, status, and duration.
// The logged IP follows the same trust rules as rate limiting: proxy
// headers only when cfg says a trusted proxy is in front.
func withRequestLog(next http.Handler, logger *slog.Logger, trustProxy bool) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		rw := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
		next.ServeHTTP(rw, r)
		logger.Info("request",
			"method", r.Method,
			"path", r.URL.Path,
			"status", rw.status,
			"duration_ms", time.Since(start).Milliseconds(),
			"ip", handler.ClientIP(r, trustProxy),
		)
	})
}

type statusRecorder struct {
	http.ResponseWriter
	status int
}

func (r *statusRecorder) WriteHeader(code int) {
	r.status = code
	r.ResponseWriter.WriteHeader(code)
}