package yggdrasil

import (
	"bytes"
	"crypto/ed25519"
	"crypto/rand"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/hex"
	"encoding/pem"
	"log"
	"math/big"
	"net"
	"time"
)

type tcptls struct {
	tcp         *tcp
	config      *tls.Config
	forDialer   *TcpUpgrade
	forListener *TcpUpgrade
}

func (t *tcptls) init(tcp *tcp) {
	t.tcp = tcp
	t.forDialer = &TcpUpgrade{
		upgrade: t.upgradeDialer,
		name:    "tls",
	}
	t.forListener = &TcpUpgrade{
		upgrade: t.upgradeListener,
		name:    "tls",
	}

	edpriv := make(ed25519.PrivateKey, ed25519.PrivateKeySize)
	copy(edpriv[:], tcp.link.core.sigPriv[:])

	certBuf := &bytes.Buffer{}

	pubtemp := x509.Certificate{
		SerialNumber: big.NewInt(1),
		Subject: pkix.Name{
			CommonName: hex.EncodeToString(tcp.link.core.sigPub[:]),
		},
		NotBefore:             time.Now(),
		NotAfter:              time.Now().Add(time.Hour * 24 * 365),
		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
	}

	derbytes, err := x509.CreateCertificate(rand.Reader, &pubtemp, &pubtemp, edpriv.Public(), edpriv)
	if err != nil {
		log.Fatalf("Failed to create certificate: %s", err)
	}

	if err := pem.Encode(certBuf, &pem.Block{Type: "CERTIFICATE", Bytes: derbytes}); err != nil {
		panic("failed to encode certificate into PEM")
	}

	cpool := x509.NewCertPool()
	cpool.AppendCertsFromPEM(derbytes)

	t.config = &tls.Config{
		RootCAs: cpool,
		Certificates: []tls.Certificate{
			tls.Certificate{
				Certificate: [][]byte{derbytes},
				PrivateKey:  edpriv,
			},
		},
		InsecureSkipVerify: true,
		MinVersion:         tls.VersionTLS13,
	}
}

func (t *tcptls) upgradeListener(c net.Conn) (net.Conn, error) {
	conn := tls.Server(c, t.config)
	if err := conn.Handshake(); err != nil {
		return c, err
	}
	return conn, nil
}

func (t *tcptls) upgradeDialer(c net.Conn) (net.Conn, error) {
	conn := tls.Client(c, t.config)
	if err := conn.Handshake(); err != nil {
		return c, err
	}
	return conn, nil
}