// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>

package main

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

	buildinfo "git.ipng.ch/ipng/vpp-maglev/cmd"
)

func main() {
	if err := run(); err != nil {
		slog.Error("startup-fatal", "err", err)
		os.Exit(1)
	}
}

func run() error {
	// All env vars are prefixed with MAGLEV_FRONTEND_ so a single
	// /etc/default/vpp-maglev (or a Docker env file) can be shared
	// with maglevd without its MAGLEV_LOG_LEVEL / MAGLEV_GRPC_ADDR /
	// etc. leaking into this process's config.
	printVersion := flag.Bool("version", false, "print version and exit")
	servers := stringFlag("server", "", "MAGLEV_FRONTEND_SERVERS", "comma-separated maglevd gRPC addresses (required)")
	listen := stringFlag("listen", ":8080", "MAGLEV_FRONTEND_LISTEN", "HTTP listen address")
	logLevel := stringFlag("log-level", "info", "MAGLEV_FRONTEND_LOG_LEVEL", "log verbosity (debug|info|warn|error)")
	flag.Parse()

	if *printVersion {
		fmt.Printf("maglevd-frontend %s (commit %s, built %s)\n",
			buildinfo.Version(), buildinfo.Commit(), buildinfo.Date())
		return nil
	}

	var level slog.Level
	if err := level.UnmarshalText([]byte(*logLevel)); err != nil {
		return fmt.Errorf("invalid log level %q: %w", *logLevel, err)
	}
	slog.SetDefault(slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: level})))
	slog.Info("starting",
		"version", buildinfo.Version(),
		"commit", buildinfo.Commit(),
		"date", buildinfo.Date())

	addrs := parseServers(*servers)
	if len(addrs) == 0 {
		return errors.New("at least one -server address is required")
	}

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	broker := NewBroker()

	clients := make([]*maglevClient, 0, len(addrs))
	for _, addr := range addrs {
		c, err := newMaglevClient(addr, broker)
		if err != nil {
			return fmt.Errorf("connect %s: %w", addr, err)
		}
		clients = append(clients, c)
		c.Start(ctx)
		slog.Info("maglevd-configured", "name", c.name, "address", c.address)
	}

	admin := adminCreds{
		User:     os.Getenv("MAGLEV_FRONTEND_USER"),
		Password: os.Getenv("MAGLEV_FRONTEND_PASSWORD"),
	}
	admin.Enabled = admin.User != "" && admin.Password != ""
	if admin.Enabled {
		slog.Info("admin-enabled", "user", admin.User)
	} else {
		slog.Info("admin-disabled",
			"reason", "MAGLEV_FRONTEND_USER and MAGLEV_FRONTEND_PASSWORD must both be set and non-empty")
	}

	mux := http.NewServeMux()
	registerHandlers(mux, clients, broker, admin)

	srv := &http.Server{
		Addr:              *listen,
		Handler:           mux,
		ReadHeaderTimeout: 10 * time.Second,
	}

	// Ignore SIGHUP so a controlling-terminal disconnect (or any
	// stray process-group SIGHUP) doesn't kill the daemon — the
	// default Go handler terminates the process with "Hangup",
	// which is the wrong behaviour for a long-running network
	// service. SIGTERM / SIGINT remain the clean-shutdown signals.
	signal.Ignore(syscall.SIGHUP)
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGTERM, syscall.SIGINT)

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

	select {
	case sig := <-sigCh:
		slog.Info("shutdown", "signal", sig)
	case err := <-errCh:
		cancel()
		return err
	}

	cancel()
	shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer shutdownCancel()
	_ = srv.Shutdown(shutdownCtx)
	for _, c := range clients {
		c.Close()
	}
	return nil
}

func parseServers(s string) []string {
	var out []string
	for _, part := range strings.Split(s, ",") {
		if p := strings.TrimSpace(part); p != "" {
			out = append(out, p)
		}
	}
	return out
}

func stringFlag(name, defaultVal, envKey, usage string) *string {
	val := defaultVal
	if v := os.Getenv(envKey); v != "" {
		val = v
	}
	return flag.String(name, val, fmt.Sprintf("%s (env: %s)", usage, envKey))
}