1 files changed, 215 insertions, 0 deletions
diff --git a/internal/client/gateway/gateway.go b/internal/client/gateway/gateway.go
new file mode 100644
index 0000000..2798950
--- /dev/null
+++ b/internal/client/gateway/gateway.go
@@ -0,0 +1,215 @@
+package gateway
+
+import (
+	"context"
+	"crypto/ed25519"
+	"crypto/tls"
+	"crypto/x509"
+	_ "embed"
+	"errors"
+	"io"
+	"log"
+	"net"
+	"os"
+	"sync"
+	"time"
+
+	tea "github.com/charmbracelet/bubbletea"
+
+	"github.com/kyren223/eko/internal/packet"
+	"github.com/kyren223/eko/pkg/assert"
+)
+
+//go:embed server.crt
+var certPEM []byte
+
+var (
+	tlsConfig *tls.Config
+
+	asyncResponses []chan packet.Payload
+	responsesMu    sync.Mutex
+
+	connection net.Conn
+	connMu     sync.Mutex
+)
+
+func init() {
+	certPool := x509.NewCertPool()
+	if !certPool.AppendCertsFromPEM(certPEM) {
+		log.Fatalln("failed to append server certificate")
+	}
+
+	tlsConfig = &tls.Config{
+		RootCAs:    certPool,
+		ServerName: "localhost",
+	}
+}
+
+func Connect(ctx context.Context, program *tea.Program, privKey ed25519.PrivateKey) {
+	conn, err := tls.Dial("tcp4", ":7223", tlsConfig)
+	if err != nil {
+		assert.NoError(err, "TODO handle error")
+	}
+	log.Println("established connection with server")
+
+	if err := handleAuth(ctx, conn, privKey); err != nil {
+		assert.NoError(err, "TODO handle error")
+	}
+	log.Println("successfully authenticated with server")
+
+	framer := packet.NewFramer(ctx)
+
+	go func() {
+		connection = conn
+		handleConnection(ctx, conn, framer)
+		close(framer.Out)
+		conn.Close()
+		connection = nil
+	}()
+
+	go handlePacketStream(framer, program)
+}
+
+func handleAuth(ctx context.Context, conn net.Conn, privKey ed25519.PrivateKey) error {
+	const nonceSize = 32
+	challengeRequest := make([]byte, 1+nonceSize)
+
+	err := conn.SetDeadline(time.Now().Add(10 * time.Second))
+	assert.NoError(err, "setting deadline should not error")
+	defer func() {
+		err := conn.SetDeadline(time.Time{})
+		assert.NoError(err, "unsetting deadline should not error")
+	}()
+	bytesRead := 0
+	for bytesRead < 1+nonceSize {
+		n, err := conn.Read(challengeRequest[bytesRead:])
+		if err != nil {
+			return err
+		}
+		bytesRead += n
+	}
+
+	assert.Assert(challengeRequest[0] == packet.VERSION, "client should always have the same version as the server")
+
+	challengeResponse := make([]byte, 1+ed25519.PublicKeySize+ed25519.SignatureSize)
+	challengeResponse[0] = packet.VERSION
+	copy(challengeResponse[1:1+ed25519.PublicKeySize], privKey.Public().(ed25519.PublicKey))
+	signedNonce := ed25519.Sign(privKey, challengeRequest[1:])
+	n := copy(challengeResponse[1+ed25519.PublicKeySize:], signedNonce)
+	assert.Assert(n == ed25519.SignatureSize, "copy should've copied the entire signature exactly")
+
+	_, err = conn.Write(challengeResponse)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func handleConnection(ctx context.Context, conn net.Conn, framer packet.PacketFramer) {
+	buffer := make([]byte, 512)
+	for {
+		err := conn.SetReadDeadline(time.Now().Add(time.Second))
+		assert.NoError(err, "setting a read deadline should not error")
+		n, err := conn.Read(buffer)
+		deadlineExceeded := errors.Is(err, os.ErrDeadlineExceeded)
+		if err != nil && !deadlineExceeded {
+			if !errors.Is(err, io.EOF) {
+				log.Println("read error:", err)
+			}
+			break
+		}
+
+		if ctx.Err() != nil {
+			log.Println("context error:", ctx.Err())
+			break
+		}
+
+		err = framer.Push(ctx, buffer[:n])
+		if ctx.Err() != nil {
+			log.Println("context error:", ctx.Err())
+			break
+		}
+		assert.NoError(err, "packets from server should always be correct")
+	}
+}
+
+func handlePacketStream(framer packet.PacketFramer, program *tea.Program) {
+	for {
+		pkt, ok := <-framer.Out
+		if !ok {
+			break
+		}
+
+		payload, err := pkt.DecodedPayload()
+		assert.NoError(err, "server should always provide a decodeable packet")
+
+		if pkt.Type().IsPush() {
+			log.Println("received streamed packet:", payload)
+			program.Send(payload)
+			continue
+		}
+
+		responsesMu.Lock()
+		assert.Assert(len(asyncResponses) != 0, "there must always be at least 1 response waiting")
+		responseChan := asyncResponses[0]
+		copy(asyncResponses, asyncResponses[1:])
+		asyncResponses = asyncResponses[:len(asyncResponses)-1]
+		responsesMu.Unlock()
+
+		go func() {
+			responseChan <- payload
+		}()
+	}
+}
+
+func conn() net.Conn {
+	return connection
+}
+
+func Send(request packet.Payload) <-chan packet.Payload {
+	responseChan := make(chan packet.Payload)
+	go func() {
+		pkt := packet.NewPacket(packet.NewMsgPackEncoder(request))
+
+		conn := conn()
+		if conn == nil {
+			log.Println("request send error:", "connection is closed")
+			close(responseChan)
+			return
+		}
+
+		connMu.Lock()
+		errDeadline := conn.SetWriteDeadline(time.Now().Add(5 * time.Second))
+		assert.NoError(errDeadline, "setting a write deadline should not error")
+		_, err := pkt.Into(conn)
+		errDeadline = conn.SetWriteDeadline(time.Time{})
+		assert.NoError(errDeadline, "setting a write deadline should not error")
+		connMu.Unlock()
+		if err != nil {
+			log.Println("request send error:", err)
+			close(responseChan)
+			return
+		}
+
+		responsesMu.Lock()
+		asyncResponses = append(asyncResponses, responseChan)
+		responsesMu.Unlock()
+
+		time.Sleep(5 * time.Second)
+		responsesMu.Lock()
+		index := -1
+		for i, ch := range asyncResponses {
+			if ch == responseChan {
+				index = i
+			}
+		}
+		if index != -1 {
+			copy(asyncResponses[index:], asyncResponses[index+1:])
+			asyncResponses = asyncResponses[:len(asyncResponses)-1]
+			close(responseChan)
+		}
+		responsesMu.Unlock()
+	}()
+	return responseChan
+}