Add solution for challenge 8 by Cpoing (#288)

Author: Cpoing

challenge-8/submissions/Cpoing/solution-template.go

@@ -0,0 +1,128 @@
+// Package challenge8 contains the solution for Challenge 8: Chat Server with Channels.
+package challenge8
+
+import (
+	"errors"
+	"sync"
+	// Add any other necessary imports
+)
+
+// Client represents a connected chat client
+type Client struct {
+	// TODO: Implement this struct
+	// Hint: username, message channel, mutex, disconnected flag
+	username  string
+	messages  chan string
+	connected bool
+	mutex     sync.RWMutex
+}
+
+// Send sends a message to the client
+func (c *Client) Send(message string) {
+	// TODO: Implement this method
+	// Hint: thread-safe, non-blocking send
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	if !c.connected {
+		return
+	}
+
+	c.messages <- message
+}
+
+// Receive returns the next message for the client (blocking)
+func (c *Client) Receive() string {
+	// TODO: Implement this method
+	// Hint: read from channel, handle closed channel
+	if message, ok := <-c.messages; ok {
+		return message
+	}
+	return ""
+}
+
+// ChatServer manages client connections and message routing
+type ChatServer struct {
+	// TODO: Implement this struct
+	// Hint: clients map, mutex
+	clients map[string]*Client
+	mutex   sync.RWMutex
+}
+
+// NewChatServer creates a new chat server instance
+func NewChatServer() *ChatServer {
+	// TODO: Implement this function
+	return &ChatServer{
+		clients: make(map[string]*Client),
+	}
+}
+
+// Connect adds a new client to the chat server
+func (s *ChatServer) Connect(username string) (*Client, error) {
+	// TODO: Implement this method
+	// Hint: check username, create client, add to map
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	if _, exists := s.clients[username]; exists {
+		return nil, ErrUsernameAlreadyTaken
+	}
+	client := &Client{
+		username:  username,
+		messages:  make(chan string),
+		connected: true,
+	}
+	s.clients[username] = client
+	return client, nil
+
+}
+
+// Disconnect removes a client from the chat server
+func (s *ChatServer) Disconnect(client *Client) {
+	// TODO: Implement this method
+	// Hint: remove from map, close channels
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	delete(s.clients, client.username)
+	client.connected = false
+	close(client.messages)
+}
+
+// Broadcast sends a message to all connected clients
+func (s *ChatServer) Broadcast(sender *Client, message string) {
+	// TODO: Implement this method
+	// Hint: format message, send to all clients
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	for _, client := range s.clients {
+		client.Send(message)
+	}
+}
+
+// PrivateMessage sends a message to a specific client
+func (s *ChatServer) PrivateMessage(sender *Client, recipient string, message string) error {
+	// TODO: Implement this method
+	// Hint: find recipient, check errors, send message
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	if !sender.connected {
+		return ErrClientDisconnected
+	}
+	if client, exists := s.clients[recipient]; !exists {
+		return ErrRecipientNotFound
+	} else if !client.connected {
+		return ErrClientDisconnected
+	} else {
+		client.Send(message)
+		return nil
+	}
+
+}
+
+// Common errors that can be returned by the Chat Server
+var (
+	ErrUsernameAlreadyTaken = errors.New("username already taken")
+	ErrRecipientNotFound    = errors.New("recipient not found")
+	ErrClientDisconnected   = errors.New("client disconnected")
+	// Add more error types as needed
+)