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

package nfs4server_test

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"math/big"
	"net"
	"testing"
	"time"

	"sourcedock.dev/petrbalvin/nfs/internal/nfs4"
	"sourcedock.dev/petrbalvin/nfs/internal/nfs4server"
	"sourcedock.dev/petrbalvin/nfs/internal/nfsclient"
	"sourcedock.dev/petrbalvin/nfs/internal/nfsfs"
	"sourcedock.dev/petrbalvin/nfs/internal/server"
)

// benchCert mints one self signed certificate for the TLS tests.
func benchCert(t *testing.T) tls.Certificate {
	t.Helper()
	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		t.Fatalf("key: %v", err)
	}
	tmpl := x509.Certificate{
		SerialNumber: big.NewInt(1),
		Subject:      pkix.Name{CommonName: "nfs-test"},
		NotBefore:    time.Now().Add(-time.Hour),
		NotAfter:     time.Now().Add(time.Hour),
		KeyUsage:     x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
		DNSNames:     []string{"localhost"},
	}
	der, err := x509.CreateCertificate(rand.Reader, &tmpl, &tmpl, &key.PublicKey, key)
	if err != nil {
		t.Fatalf("certificate: %v", err)
	}
	return tls.Certificate{Certificate: [][]byte{der}, PrivateKey: key}
}

// serveTLS starts the handler behind a loopback listener with the given
// certificate and returns the address.
func serveTLS(t *testing.T, cert tls.Certificate) string {
	t.Helper()
	root := t.TempDir()
	backend, err := nfsfs.NewLocal(root)
	if err != nil {
		t.Fatalf("NewLocal: %v", err)
	}
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("Listen: %v", err)
	}
	t.Cleanup(func() { _ = ln.Close() })
	handler := &nfs4server.Handler{FS: backend,
		TLSConfig: &tls.Config{Certificates: []tls.Certificate{cert}}}
	go func() { _ = (&server.Server{Handle: handler.HandleConn}).Serve(t.Context(), ln) }()
	return ln.Addr().String()
}

// TestWireTLSSession drives a full session over an in place TLS upgrade:
// the probe answers the STARTTLS token, the handshake runs, and a
// compound rides the encrypted connection.
func TestWireTLSSession(t *testing.T) {
	addr := serveTLS(t, benchCert(t))
	cl, err := nfsclient.Dial(addr)
	if err != nil {
		t.Fatalf("Dial: %v", err)
	}
	defer cl.Close()
	if err := cl.EnableTLS(&tls.Config{InsecureSkipVerify: true, ServerName: "localhost"}); err != nil {
		t.Fatalf("EnableTLS: %v", err)
	}
	if err := cl.Establish("tls-test"); err != nil {
		t.Fatalf("Establish: %v", err)
	}
	res, _, err := cl.Compound("tls-getattr", [][]byte{
		nfs4.AppendPutRootfh(nil),
		nfs4.AppendGetattr(nil, nfs4.OfBits(nfs4.AttrType)),
	})
	if err != nil {
		t.Fatalf("Compound: %v", err)
	}
	if res.Status != nfs4.ErrOK {
		t.Fatalf("getattr status %d over TLS", res.Status)
	}
}

// TestWirePlaintextRefusedUnderTLS covers the RFC 9289 policy: a client
// that skips STARTTLS and runs procedures in plaintext is refused with
// auth too weak, while the NULL procedure still answers.
func TestWirePlaintextRefusedUnderTLS(t *testing.T) {
	addr := serveTLS(t, benchCert(t))
	cl, err := nfsclient.Dial(addr)
	if err != nil {
		t.Fatalf("Dial: %v", err)
	}
	defer cl.Close()
	if err := cl.Null(); err != nil {
		t.Fatalf("the plaintext NULL no longer answers: %v", err)
	}
	if err := cl.Establish("plaintext-test"); err == nil {
		t.Fatal("a plaintext session was accepted under a TLS certificate")
	}
}