package libp2ptls

import (
	"context"
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/rsa"
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"math/big"
	mrand "math/rand"
	"net"
	"time"

	"github.com/onsi/gomega/gbytes"

	cs "github.com/libp2p/go-conn-security"
	ci "github.com/libp2p/go-libp2p-crypto"
	peer "github.com/libp2p/go-libp2p-peer"
	. "github.com/onsi/ginkgo"
	. "github.com/onsi/gomega"
)

type transform struct {
	name      string
	apply     func(*Identity)
	remoteErr string // the error that the side validating the chain gets
}

var _ = Describe("Transport", func() {
	var (
		serverKey, clientKey ci.PrivKey
		serverID, clientID   peer.ID
	)

	createPeer := func() (peer.ID, ci.PrivKey) {
		var priv ci.PrivKey
		if mrand.Int()%2 == 0 {
			fmt.Fprintf(GinkgoWriter, " using an ECDSA key: ")
			var err error
			priv, _, err = ci.GenerateECDSAKeyPair(rand.Reader)
			Expect(err).ToNot(HaveOccurred())
		} else {
			fmt.Fprintf(GinkgoWriter, " using an RSA key: ")
			var err error
			priv, _, err = ci.GenerateRSAKeyPair(1024, rand.Reader)
			Expect(err).ToNot(HaveOccurred())
		}
		id, err := peer.IDFromPrivateKey(priv)
		Expect(err).ToNot(HaveOccurred())
		fmt.Fprintln(GinkgoWriter, id.Pretty())
		return id, priv
	}

	connect := func() (net.Conn, net.Conn) {
		ln, err := net.Listen("tcp", "localhost:0")
		Expect(err).ToNot(HaveOccurred())
		defer ln.Close()
		serverConnChan := make(chan net.Conn)
		go func() {
			defer GinkgoRecover()
			conn, err := ln.Accept()
			Expect(err).ToNot(HaveOccurred())
			serverConnChan <- conn
		}()
		conn, err := net.Dial("tcp", ln.Addr().String())
		Expect(err).ToNot(HaveOccurred())
		return conn, <-serverConnChan
	}

	BeforeEach(func() {
		fmt.Fprintf(GinkgoWriter, "Initializing a server")
		serverID, serverKey = createPeer()
		fmt.Fprintf(GinkgoWriter, "Initializing a client")
		clientID, clientKey = createPeer()
	})

	It("handshakes", func() {
		clientTransport, err := New(clientKey)
		Expect(err).ToNot(HaveOccurred())
		serverTransport, err := New(serverKey)
		Expect(err).ToNot(HaveOccurred())

		clientInsecureConn, serverInsecureConn := connect()

		serverConnChan := make(chan cs.Conn)
		go func() {
			defer GinkgoRecover()
			serverConn, err := serverTransport.SecureInbound(context.Background(), serverInsecureConn)
			Expect(err).ToNot(HaveOccurred())
			serverConnChan <- serverConn
		}()
		clientConn, err := clientTransport.SecureOutbound(context.Background(), clientInsecureConn, serverID)
		Expect(err).ToNot(HaveOccurred())
		var serverConn cs.Conn
		Eventually(serverConnChan).Should(Receive(&serverConn))
		defer clientConn.Close()
		defer serverConn.Close()
		Expect(clientConn.LocalPeer()).To(Equal(clientID))
		Expect(serverConn.LocalPeer()).To(Equal(serverID))
		Expect(clientConn.LocalPrivateKey()).To(Equal(clientKey))
		Expect(serverConn.LocalPrivateKey()).To(Equal(serverKey))
		Expect(clientConn.RemotePeer()).To(Equal(serverID))
		Expect(serverConn.RemotePeer()).To(Equal(clientID))
		Expect(clientConn.RemotePublicKey()).To(Equal(serverKey.GetPublic()))
		Expect(serverConn.RemotePublicKey()).To(Equal(clientKey.GetPublic()))
		// exchange some data
		_, err = serverConn.Write([]byte("foobar"))
		Expect(err).ToNot(HaveOccurred())
		b := make([]byte, 6)
		_, err = clientConn.Read(b)
		Expect(err).ToNot(HaveOccurred())
		Expect(string(b)).To(Equal("foobar"))
	})

	It("fails when the context of the outgoing connection is canceled", func() {
		clientTransport, err := New(clientKey)
		Expect(err).ToNot(HaveOccurred())
		serverTransport, err := New(serverKey)
		Expect(err).ToNot(HaveOccurred())

		clientInsecureConn, serverInsecureConn := connect()

		go func() {
			defer GinkgoRecover()
			_, err := serverTransport.SecureInbound(context.Background(), serverInsecureConn)
			Expect(err).To(HaveOccurred())
		}()
		ctx, cancel := context.WithCancel(context.Background())
		cancel()
		_, err = clientTransport.SecureOutbound(ctx, clientInsecureConn, serverID)
		Expect(err).To(MatchError(context.Canceled))
	})

	It("fails when the context of the incoming connection is canceled", func() {
		clientTransport, err := New(clientKey)
		Expect(err).ToNot(HaveOccurred())
		serverTransport, err := New(serverKey)
		Expect(err).ToNot(HaveOccurred())

		clientInsecureConn, serverInsecureConn := connect()

		go func() {
			defer GinkgoRecover()
			ctx, cancel := context.WithCancel(context.Background())
			cancel()
			_, err := serverTransport.SecureInbound(ctx, serverInsecureConn)
			Expect(err).To(MatchError(context.Canceled))
		}()
		_, err = clientTransport.SecureOutbound(context.Background(), clientInsecureConn, serverID)
		Expect(err).To(HaveOccurred())
	})

	It("fails if the peer ID doesn't match", func() {
		fmt.Fprintf(GinkgoWriter, "Creating another peer")
		thirdPartyID, _ := createPeer()

		serverTransport, err := New(serverKey)
		Expect(err).ToNot(HaveOccurred())
		clientTransport, err := New(clientKey)
		Expect(err).ToNot(HaveOccurred())

		clientInsecureConn, serverInsecureConn := connect()

		done := make(chan struct{})
		go func() {
			defer GinkgoRecover()
			_, err := serverTransport.SecureInbound(context.Background(), serverInsecureConn)
			Expect(err).To(HaveOccurred())
			Expect(err.Error()).To(ContainSubstring("tls: bad certificate"))
			close(done)
		}()
		// dial, but expect the wrong peer ID
		_, err = clientTransport.SecureOutbound(context.Background(), clientInsecureConn, thirdPartyID)
		Expect(err).To(MatchError("peer IDs don't match"))
		Eventually(done).Should(BeClosed())
	})

	Context("invalid certificates", func() {
		invalidateCertChain := func(identity *Identity) {
			switch identity.config.Certificates[0].PrivateKey.(type) {
			case *rsa.PrivateKey:
				key, err := rsa.GenerateKey(rand.Reader, 1024)
				Expect(err).ToNot(HaveOccurred())
				identity.config.Certificates[0].PrivateKey = key
			case *ecdsa.PrivateKey:
				key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
				Expect(err).ToNot(HaveOccurred())
				identity.config.Certificates[0].PrivateKey = key
			default:
				Fail("unexpected private key type")
			}
		}

		twoCerts := func(identity *Identity) {
			tmpl := &x509.Certificate{SerialNumber: big.NewInt(1)}
			key1, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
			Expect(err).ToNot(HaveOccurred())
			key2, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
			Expect(err).ToNot(HaveOccurred())
			cert1DER, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, key1.Public(), key1)
			Expect(err).ToNot(HaveOccurred())
			cert1, err := x509.ParseCertificate(cert1DER)
			Expect(err).ToNot(HaveOccurred())
			cert2DER, err := x509.CreateCertificate(rand.Reader, tmpl, cert1, key2.Public(), key2)
			Expect(err).ToNot(HaveOccurred())
			identity.config.Certificates = []tls.Certificate{{
				Certificate: [][]byte{cert2DER, cert1DER},
				PrivateKey:  key2,
			}}
		}

		expiredCert := func(identity *Identity) {
			tmpl := &x509.Certificate{
				SerialNumber: big.NewInt(1),
				NotBefore:    time.Now().Add(-time.Hour),
				NotAfter:     time.Now().Add(-time.Minute),
			}
			key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
			Expect(err).ToNot(HaveOccurred())
			cert, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, key.Public(), key)
			Expect(err).ToNot(HaveOccurred())
			identity.config.Certificates = []tls.Certificate{{
				Certificate: [][]byte{cert},
				PrivateKey:  key,
			}}
		}

		transforms := []transform{
			{
				name:      "private key used in the TLS handshake doesn't match the public key in the cert",
				apply:     invalidateCertChain,
				remoteErr: "tls: invalid certificate signature",
			},
			{
				name:      "certificate chain contains 2 certs",
				apply:     twoCerts,
				remoteErr: "expected one certificates in the chain",
			},
			{
				name:      "cert is expired",
				apply:     expiredCert,
				remoteErr: "certificate verification failed: x509: certificate has expired or is not yet valid",
			},
		}

		for i := range transforms {
			t := transforms[i]

			It(fmt.Sprintf("fails if the client presents an invalid cert: %s", t.name), func() {
				serverTransport, err := New(serverKey)
				Expect(err).ToNot(HaveOccurred())
				clientTransport, err := New(clientKey)
				Expect(err).ToNot(HaveOccurred())
				t.apply(clientTransport.identity)

				clientInsecureConn, serverInsecureConn := connect()

				done := make(chan struct{})
				go func() {
					defer GinkgoRecover()
					_, err := serverTransport.SecureInbound(context.Background(), serverInsecureConn)
					Expect(err).To(MatchError(t.remoteErr))
					close(done)
				}()

				conn, err := clientTransport.SecureOutbound(context.Background(), clientInsecureConn, serverID)
				Expect(err).ToNot(HaveOccurred())
				_, err = gbytes.TimeoutReader(conn, time.Second).Read([]byte{0})
				Expect(err).To(Or(
					// if the certificate's public key doesn't match the private key used for signing
					MatchError("remote error: tls: error decrypting message"),
					// all other errors
					MatchError("remote error: tls: bad certificate"),
				))
				Eventually(done).Should(BeClosed())
			})

			It(fmt.Sprintf("fails if the server presents an invalid cert: %s", t.name), func() {
				serverTransport, err := New(serverKey)
				Expect(err).ToNot(HaveOccurred())
				t.apply(serverTransport.identity)
				clientTransport, err := New(clientKey)
				Expect(err).ToNot(HaveOccurred())

				clientInsecureConn, serverInsecureConn := connect()

				done := make(chan struct{})
				go func() {
					defer GinkgoRecover()
					_, err := serverTransport.SecureInbound(context.Background(), serverInsecureConn)
					Expect(err).To(HaveOccurred())
					Expect(err.Error()).To(ContainSubstring("remote error: tls:"))
					close(done)
				}()

				_, err = clientTransport.SecureOutbound(context.Background(), clientInsecureConn, serverID)
				Expect(err).To(MatchError(t.remoteErr))
				Eventually(done).Should(BeClosed())
			})
		}
	})
})