From 2172b7410566e6a082f6dab82cb1bef61a149f89 Mon Sep 17 00:00:00 2001
From: Richard <snugger-lotion0w@icloud.com>
Date: Sun, 24 Sep 2023 16:01:57 +0200
Subject: [PATCH] Chat

---
 chat.go | 210 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 main.go |   4 +-
 2 files changed, 213 insertions(+), 1 deletion(-)
 create mode 100644 chat.go

diff --git a/chat.go b/chat.go
new file mode 100644
index 0000000..b16ff07
--- /dev/null
+++ b/chat.go
@@ -0,0 +1,210 @@
+package main
+
+import (
+"net"
+"os"
+"fmt"
+"strings"
+"bufio"
+"regexp"
+)
+
+type ChatMessage struct {
+	from uint
+	mtype uint
+	data string
+}
+
+type ChatServer struct {
+	port uint16
+	numSessions uint
+	q chan ChatMessage
+	clients map[uint]*ChatSession
+}
+
+func NewChatServer(port uint16) *ChatServer {
+	return &ChatServer{
+		port,
+		0,
+		make(chan ChatMessage),
+		make(map[uint]*ChatSession),
+	}
+}
+
+type ChatSession struct{
+	sessionId uint
+	username string
+	q chan string
+	backend chan ChatMessage
+	con net.Conn
+	isOnline bool
+}
+
+func NewChatSession(sessionId uint, con net.Conn, backend chan ChatMessage) *ChatSession {
+	return &ChatSession{
+		sessionId,
+		"",
+		make(chan string),
+		backend,
+		con,
+		false,
+	}
+}
+
+func (s *ChatServer) broadcaster(){
+	
+	for m := range s.q {
+		client, ok := s.clients[m.from]
+		if ok != true { continue }
+		switch m.mtype {
+			case 1: s.handleJoin(m, client)
+			case 2: s.handleMsg(m, client)
+			case 3: s.handleLeave(m, client)
+		}
+	}
+}
+
+func (s *ChatServer) chatNames(except uint) string {
+	first := true
+	result := ""
+	for key, session := range s.clients {
+		if key == except {
+		  continue
+		}
+    if first {
+			first = false
+    } else {
+			result += ", "
+    }
+		result += session.username
+  }
+	if first {
+		result = "empty space"
+	}
+	return result
+}
+func (s *ChatServer) handleJoin(m ChatMessage, c *ChatSession) {
+	msg := fmt.Sprintf("* You see %s floating around here\n", s.chatNames(m.from))
+	c.q <- msg
+	msg = fmt.Sprintf("* %s just docked!\n", c.username)
+	fmt.Printf(msg)
+	for key, session := range s.clients {
+		if key == m.from || session.isOnline == false {
+		  continue
+		}
+    session.q <- msg
+  }
+}
+
+func (s *ChatServer) handleMsg(m ChatMessage, c *ChatSession) {
+	msg := fmt.Sprintf("[%s] %s\n", c.username, m.data)
+	fmt.Printf(msg)
+	for key, session := range s.clients {
+		if key == m.from || session.isOnline == false{
+		  continue
+		}
+    session.q <- msg
+  }
+}
+
+func (s *ChatServer) handleLeave(m ChatMessage, c *ChatSession) {
+	msg := fmt.Sprintf("* %s just fired up his hyperdrive!\n", c.username)
+	delete(s.clients, c.sessionId)
+	fmt.Println(msg)
+	for key, session := range s.clients {
+		if key == m.from || session.isOnline == false {
+		  continue
+		}
+    session.q <- msg
+  }
+}
+
+func (s *ChatServer) Run() {
+	go s.broadcaster()
+	addr := fmt.Sprintf("0.0.0.0:%d", s.port)
+	server, err := net.Listen("tcp", addr)
+    if err != nil {
+      fmt.Println("Error listening:", err.Error())
+        os.Exit(1)
+    }
+    defer server.Close()
+    fmt.Println("ChatServer waiting for client...")
+    for {
+      connection, err := server.Accept()
+      if err != nil {
+        fmt.Println("Error accepting: ", err.Error())
+        os.Exit(1)
+      }
+      fmt.Println("client connected")
+      s.processClient(connection)
+		}
+		close(s.q)
+}
+
+func (s *ChatServer) processClient(con net.Conn) {
+	sessionId := s.numSessions
+	s.numSessions += 1
+	session := NewChatSession( sessionId, con, s.q)
+	s.clients[sessionId] = session
+	go session.chatReceiver()
+	go session.chatSender()
+}
+
+func chatUsernameValid(username string) bool {
+	var invalidUsername = regexp.MustCompile(`[^0-9a-zA-Z]`)
+	
+	if len(username) < 1 {
+		return false
+	}
+	return ! invalidUsername.MatchString(username)
+}
+func (s *ChatSession) logon(r *bufio.Reader) error {
+	fmt.Fprintf(s.con, "Howdy! welcome to station 42!\n")
+	username, err := r.ReadString('\n')
+	if err != nil { return err }
+	username = strings.TrimSpace(username)
+	if ! chatUsernameValid(username) {
+		return fmt.Errorf("Invalid username %s", username)
+	}
+	s.isOnline = true
+	s.username = username
+	m := ChatMessage{s.sessionId, 1, username}
+	s.backend <- m
+	return nil
+}
+
+func (s *ChatSession) chat(r *bufio.Reader) error {
+	msg, err := r.ReadString('\n')
+	if err != nil { return err }
+	msg = strings.TrimSpace(msg)
+	m := ChatMessage{s.sessionId, 2, msg}
+	s.backend <- m
+	return nil
+}
+
+func (s *ChatSession) close() {
+	fmt.Printf("close %d\n", s.sessionId)
+	if s.isOnline {
+  	m := ChatMessage{s.sessionId, 3, s.username}
+	  s.backend <- m
+	}
+	s.isOnline = false
+	close(s.q)
+  s.con.Close()
+}
+
+func (s *ChatSession) chatReceiver() {
+	defer s.close()
+	r := bufio.NewReader(s.con)
+	err := s.logon(r)
+	for err == nil {
+		err = s.chat(r)
+	}
+}
+
+func (s *ChatSession) chatSender() {
+	for m := range s.q {
+		s.con.Write([]byte(m))
+	}
+}
+
diff --git a/main.go b/main.go
index b507018..30dc7bf 100644
--- a/main.go
+++ b/main.go
@@ -12,7 +12,7 @@ type Server interface {
 	
 func main() {
 	var challenge int
-	flag.IntVar(&challenge, "challenge",2, "Challenge number")
+	flag.IntVar(&challenge, "challenge",3, "Challenge number")
 	flag.Parse()
 	
 	var port uint16 
@@ -25,6 +25,8 @@ func main() {
 	  	server = NewPrimeServer(port);
 		case 2:
 	  	server = NewMeansServer(port);
+		case 3:
+	  	server = NewChatServer(port);
 		default:
 			fmt.Printf("Unknown challenge\n")
 			os.Exit(1)