4 files changed, 321 insertions, 0 deletions
diff --git a/internal/network/ip.go b/internal/network/ip.go
new file mode 100644
index 0000000..0c6451e
--- /dev/null
+++ b/internal/network/ip.go
@@ -0,0 +1,33 @@
+package network
+
+import (
+	"fmt"
+	"log/slog"
+	"math/rand"
+	"net"
+)
+
+func GetOutboundIP() net.IP {
+	conn, err := net.Dial("udp", "8.8.8.8:80")
+	if err != nil {
+		slog.Error("err", err)
+	}
+	defer conn.Close()
+
+	localAddr := conn.LocalAddr().(*net.UDPAddr)
+
+	return localAddr.IP
+}
+
+func GetRandomAvailablePort() (int, error) {
+	for i := 0; i < 100; i += 1 {
+		port := rand.Intn(65535-1024) + 1024
+		addr := fmt.Sprintf(":%d", port)
+		ln, err := net.Listen("tcp", addr)
+		if err == nil {
+			defer ln.Close()
+			return port, nil
+		}
+	}
+	return 0, fmt.Errorf("failed to find an available port after multiple attempts")
+}
diff --git a/internal/network/network.go b/internal/network/network.go
new file mode 100644
index 0000000..8283993
--- /dev/null
+++ b/internal/network/network.go
@@ -0,0 +1,213 @@
+package network
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	"go.uber.org/zap"
+)
+
+var logger *zap.Logger
+
+// PeerInfo represents a peer's ID and IP.
+type PeerInfo struct {
+	ID   string `json:"id"`
+	IP   string `json:"ip"`
+	Port int    `json:"port"`
+}
+
+// Message represents a structured message.
+type Message struct {
+	Type      string   `json:"type"`
+	Payload   []byte   `json:"payload"`
+	Source    PeerInfo `json:"source"`
+	Target    PeerInfo `json:"target"`
+	Timestamp int64    `json:"timestamp"`
+}
+
+type NetworkCallback func(msg Message)
+
+// TCPNetwork represents a full-duplex TCP peer.
+type TCPNetwork struct {
+	localPeer   PeerInfo
+	connections map[string]net.Conn
+	listener    net.Listener
+	callbacks   map[string]NetworkCallback
+	callbacksMu sync.RWMutex
+	isConnected bool
+	retryDelay  time.Duration
+	sync.Mutex
+}
+
+// initializes a TCP peer
+func NewTCPNetwork(localID, localIP string, localPort int) *TCPNetwork {
+	n := &TCPNetwork{
+		localPeer:   PeerInfo{ID: localID, IP: localIP, Port: localPort},
+		connections: make(map[string]net.Conn),
+		callbacks:   make(map[string]NetworkCallback),
+		isConnected: false,
+		retryDelay:  2 * time.Second,
+	}
+
+	go n.startServer()
+
+	logger, _ = zap.NewProduction()
+
+	return n
+}
+
+// Add a new peer connection to the local peer
+func (n *TCPNetwork) AddPeer(remoteID string, remoteIP string, remotePort int) {
+	go n.retryConnect(remoteID, remoteIP, remotePort)
+}
+
+// startServer starts a TCP server to accept connections.
+func (n *TCPNetwork) startServer() {
+	address := fmt.Sprintf("%s:%d", n.localPeer.IP, n.localPeer.Port)
+	listener, err := net.Listen("tcp", address)
+	if err != nil {
+		logger.Sugar().Errorf("failed to start server: %v", err)
+	}
+	n.listener = listener
+	logger.Sugar().Infof("server started on %s\n", address)
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			logger.Sugar().Errorf("failed to accept connection: %v\n", err)
+			continue
+		}
+
+		remoteAddr := conn.RemoteAddr().String()
+		n.Lock()
+		n.connections[remoteAddr] = conn
+		n.Unlock()
+		n.isConnected = true
+		n.retryDelay = 2 * time.Second
+
+		logger.Sugar().Infof("connected to remote peer %s\n", remoteAddr)
+		go n.listenForMessages(conn)
+	}
+}
+
+// retryConnect attempts to connect to a remote peer.
+func (n *TCPNetwork) retryConnect(remoteID, remoteIP string, remotePort int) {
+	for {
+		n.Lock()
+		_, exists := n.connections[remoteID]
+		n.Unlock()
+
+		if exists {
+			time.Sleep(5 * time.Second)
+			continue
+		}
+
+		address := fmt.Sprintf("%s:%d", remoteIP, remotePort)
+		conn, err := net.Dial("tcp", address)
+
+		if err != nil {
+			logger.Sugar().Errorf("failed to connect to %s: %v. Retrying in %v...", remoteID, err, n.retryDelay)
+			time.Sleep(n.retryDelay)
+			if n.retryDelay < 30*time.Second {
+				n.retryDelay *= 2
+			}
+			continue
+		}
+
+		n.Lock()
+		n.connections[remoteID] = conn
+		n.Unlock()
+		logger.Sugar().Infof("successfully connected to peer %s!", remoteID)
+
+		go n.listenForMessages(conn)
+	}
+}
+
+// Send sends a message to a specified remote peer.
+func (n *TCPNetwork) Send(remoteID, messageType string, payload []byte) error {
+	n.Lock()
+	conn, exists := n.connections[remoteID]
+	n.Unlock()
+
+	if !exists {
+		return fmt.Errorf("not connected to peer %s", remoteID)
+	}
+
+	msg := Message{
+		Type:      messageType,
+		Payload:   payload,
+		Source:    n.localPeer,
+		Target:    PeerInfo{ID: remoteID},
+		Timestamp: time.Now().Unix(),
+	}
+
+	data, err := json.Marshal(msg)
+	if err != nil {
+		return fmt.Errorf("failed to marshal message: %v", err)
+	}
+
+	_, err = conn.Write(append(data, '\n'))
+	if err != nil {
+		logger.Sugar().Errorf("failed to send message to %s: %v. Reconnecting...", remoteID, err)
+		n.Lock()
+		delete(n.connections, remoteID)
+		n.Unlock()
+		go n.retryConnect(remoteID, "", 0)
+		return fmt.Errorf("failed to send message: %v", err)
+	}
+
+	return nil
+}
+
+// RegisterHandler registers a callback for a message type.
+func (n *TCPNetwork) RegisterHandler(messageType string, callback NetworkCallback) {
+	n.callbacksMu.Lock()
+	n.callbacks[messageType] = callback
+	n.callbacksMu.Unlock()
+}
+
+// listenForMessages listens for incoming messages.
+func (n *TCPNetwork) listenForMessages(conn net.Conn) {
+	reader := bufio.NewReader(conn)
+
+	for {
+		data, err := reader.ReadBytes('\n')
+		if err != nil {
+			logger.Debug("connection lost. Reconnecting...")
+			n.Lock()
+			for id, c := range n.connections {
+				if c == conn {
+					delete(n.connections, id)
+					go n.retryConnect(id, "", 0)
+					break
+				}
+			}
+			n.Unlock()
+			return
+		}
+
+		var message Message
+		if err := json.Unmarshal(data, &message); err != nil {
+			logger.Sugar().Errorf("failed to unmarshal message: %v\n", err)
+			continue
+		}
+
+		n.callbacksMu.RLock()
+		callback, exists := n.callbacks[message.Type]
+		n.callbacksMu.RUnlock()
+
+		if exists {
+			go callback(message)
+		}
+	}
+}
+
+func (n *TCPNetwork) IsConnected() bool {
+	n.Lock()
+	defer n.Unlock()
+	return n.isConnected
+}
diff --git a/internal/network/network_test.go b/internal/network/network_test.go
new file mode 100644
index 0000000..9dbc416
--- /dev/null
+++ b/internal/network/network_test.go
@@ -0,0 +1,52 @@
+package network
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// TestPeerToPeerCommunication tests if two peers can communicate.
+func TestPeerToPeerCommunication(t *testing.T) {
+	// Create a mock of the first peer (peer-1)
+	peer1IP := "127.0.0.1"
+	peer1Port := 9001
+	peer1 := NewTCPNetwork("peer-1", peer1IP, peer1Port)
+
+	// Create a mock of the second peer (peer-2)
+	peer2IP := "127.0.0.1"
+	peer2Port := 9002
+	peer2 := NewTCPNetwork("peer-2", peer2IP, peer2Port)
+
+	// Register a message handler on peer-2 to receive the message from peer-1
+	peer2.RegisterHandler("chat", func(msg Message) {
+		assert.Equal(t, "peer-1", msg.Source.ID)
+		assert.Equal(t, "Hey from peer-1!", string(msg.Payload))
+	})
+
+	// Start the first peer and add the second peer
+	go peer1.AddPeer("peer-2", peer2IP, peer2Port)
+	go peer2.AddPeer("peer-1", peer1IP, peer1Port)
+
+	// Wait for the connections to be established
+	// You might need a little more time based on network delay and retry logic
+	time.Sleep(5 * time.Second)
+
+	// Send a message from peer-1 to peer-2
+	err := peer1.Send("peer-2", "chat", []byte("Hey from peer-1!"))
+	assert.NoError(t, err)
+
+	// Allow some time for the message to be received and handled
+	time.Sleep(2 * time.Second)
+}
+
+// TestSendFailure tests if sending a message fails when no connection exists.
+func TestSendFailure(t *testing.T) {
+	peer1 := NewTCPNetwork("peer-1", "127.0.0.1", 9001)
+	_ = NewTCPNetwork("peer-2", "127.0.0.1", 9002)
+
+	// Attempt to send a message without establishing a connection first
+	err := peer1.Send("peer-2", "chat", []byte("Message without connection"))
+	assert.Error(t, err, "Expected error when sending to a non-connected peer")
+}
diff --git a/internal/network/session.go b/internal/network/session.go
new file mode 100644
index 0000000..a4f60aa
--- /dev/null
+++ b/internal/network/session.go
@@ -0,0 +1,23 @@
+package network
+
+import (
+	"math/rand"
+)
+
+var adjectives = []string{
+	"adamant", "adept", "adventurous", "arcadian", "auspicious",
+	"awesome", "blossoming", "brave", "charming", "chatty",
+	"circular", "considerate", "cubic", "curious", "delighted",
+}
+
+var nouns = []string{
+	"aardvark", "accordion", "apple", "apricot", "bee",
+	"brachiosaur", "cactus", "capsicum", "clarinet", "cowbell",
+	"crab", "cuckoo", "cymbal", "diplodocus", "donkey",
+}
+
+func NewSession() string {
+	noun := nouns[rand.Intn(len(nouns))]
+	adjective := adjectives[rand.Intn(len(adjectives))]
+	return noun + "-" + adjective
+}