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

// Command nfsd serves NFS over TCP. It is the server binary of the nfs
// project: it exports one local directory tree over NFSv4.2 as described
// in docs/ARCHITECTURE.md.
package main

import (
	"context"
	"crypto/tls"
	"flag"
	"fmt"
	"log"
	"net"
	"os"
	"os/signal"
	"runtime/debug"
	"syscall"

	"sourcedock.dev/petrbalvin/nfs/internal/nfs4server"
	"sourcedock.dev/petrbalvin/nfs/internal/nfsfs"
	"sourcedock.dev/petrbalvin/nfs/internal/server"
)

func main() {
	log.SetFlags(0)
	flags := flag.CommandLine
	addr := flags.String("addr", ":2049", "TCP address to listen on")
	export := flags.String("export", "", "directory to serve")
	readOnly := flags.Bool("ro", false, "serve the export read only: every mutation answers NFS4ERR_ROFS")
	rootSquash := flags.Bool("root-squash", false, "map a client claiming uid 0 onto nobody (65534), so root acts as the anonymous identity")
	tlsCert := flags.String("tls-cert", "", "certificate chain in PEM for RPC-with-TLS; requires -tls-key")
	tlsKey := flags.String("tls-key", "", "private key in PEM for RPC-with-TLS; requires -tls-cert")
	logOps := flags.Bool("log-ops", false, "log every operation with its status and duration to stderr")
	maxConns := flags.Int("max-connections", 0, "cap on live connections; a connection above the cap closes at once; 0 means no cap")
	stateDir := flags.String("state-dir", "", "directory for persisted client state: handles and opens survive a restart, and a grace window follows it")
	configPath := flags.String("config", "", "configuration file in TOML; never read unless named, the flags override it")
	version := flags.Bool("version", false, "print the version and exit")
	flags.Parse(os.Args[1:])

	// The configuration file is the base, the flags override it: only
	// the flags present on the command line keep their value, everything
	// else yields to the file.
	if *configPath != "" {
		cfg, err := loadConfig(*configPath)
		if err != nil {
			log.Fatalf("nfsd: %v", err)
		}
		given := make(map[string]bool)
		flags.Visit(func(f *flag.Flag) { given[f.Name] = true })
		applyConfig(cfg, flags, func(name string) bool { return given[name] })
	}

	if *version {
		fmt.Println(buildVersion())
		return
	}

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

	if *export == "" {
		log.Fatalf("nfsd: no export given: pass -export DIR")
	}
	backend, err := nfsfs.NewLocal(*export)
	if err != nil {
		log.Fatalf("nfsd: %v", err)
	}
	var fs nfsfs.FS = backend
	if *readOnly {
		fs = nfsfs.ReadOnly(backend)
	}
	if *stateDir != "" {
		if err := os.MkdirAll(*stateDir, 0o700); err != nil {
			log.Fatalf("nfsd: %v", err)
		}
		// The handle map is the backend half of the recovery state: load
		// what a previous life wrote, then keep writing as handles are
		// minted, so a restart resolves what it served before.
		if err := backend.LoadPersistedHandles(*stateDir); err != nil {
			log.Fatalf("nfsd: %v", err)
		}
		backend.SetPersistPath(*stateDir)
	}
	var tlsCfg *tls.Config
	if *tlsCert != "" || *tlsKey != "" {
		if *tlsCert == "" || *tlsKey == "" {
			log.Fatalf("nfsd: -tls-cert and -tls-key go together")
		}
		cert, err := tls.LoadX509KeyPair(*tlsCert, *tlsKey)
		if err != nil {
			log.Fatalf("nfsd: %v", err)
		}
		tlsCfg = &tls.Config{Certificates: []tls.Certificate{cert}}
	}

	ln, err := net.Listen("tcp", *addr)
	if err != nil {
		log.Fatalf("nfsd: %v", err)
	}
	log.Printf("nfsd: serving %s on %s", *export, ln.Addr())
	// The listener is the moment the service can answer: a Type=notify
	// unit learns it here.
	notifyReadyOrLog()

	srv := &server.Server{
		Handle: (&nfs4server.Handler{
			FS:         fs,
			TLSConfig:  tlsCfg,
			LogOps:     *logOps,
			StateDir:   *stateDir,
			RootSquash: *rootSquash,
		}).HandleConn,
		MaxConns: *maxConns,
	}
	if err := srv.Serve(ctx, ln); err != nil {
		log.Fatalf("nfsd: %v", err)
	}
}

// buildVersion reports the module version the toolchain recorded at build
// time. A build made at a tag reports the tag; a build outside version
// control reports devel.
func buildVersion() string {
	v := "devel"
	if bi, ok := debug.ReadBuildInfo(); ok && bi.Main.Version != "(devel)" {
		v = bi.Main.Version
	}
	return v
}