Initial commit

go.mod

@@ -0,0 +1,8 @@
+module github.com/ivanfetch/chat-server
+
+go 1.20
+
+require (
+	github.com/sirupsen/logrus v1.9.2 // indirect
+	golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 // indirect
+)

go.sum

@@ -0,0 +1,11 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sirupsen/logrus v1.9.2 h1:oxx1eChJGI6Uks2ZC4W1zpLlVgqB8ner4EuQwV4Ik1Y=
+github.com/sirupsen/logrus v1.9.2/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 h1:0A+M6Uqn+Eje4kHMK80dtF3JCXC4ykBgQG4Fe06QRhQ=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

main.go

@@ -0,0 +1,150 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"net"
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+)
+
+type message struct {
+	sender, text string
+}
+
+// String formats the message sender and text.
+func (m message) String() string {
+	return fmt.Sprintf("%s: %s\n", m.sender, m.text)
+}
+
+var debugLog *log.Logger = log.New()
+
+// startConnectionAndMessageManager runs a goroutine that tracks connections to the chat
+// server, and processes messages sent by clients.
+func startConnectionAndMessageManager(addConnCh, removeConnCh chan net.Conn, addMessageCh chan message) {
+	var connections []net.Conn
+	// TODO: Add context to respond to signals and cleanup connections?
+	go func() {
+		debugLog.Println("starting connection manager")
+		for {
+			select {
+			case newConn := <-addConnCh:
+				debugLog.Printf("adding connection from %s", newConn.RemoteAddr())
+				connections = append(connections, newConn)
+			case removeConn := <-removeConnCh:
+				debugLog.Printf("removing connection %s", removeConn.RemoteAddr())
+				newConnections := make([]net.Conn, len(connections)-1)
+				newI := 0
+				for _, conn := range connections {
+					if conn != removeConn {
+						newConnections[newI] = conn
+						newI++
+					}
+				}
+				connections = newConnections
+			case newMessage := <-addMessageCh:
+				debugLog.Printf("processing new message from %s: %s", newMessage.sender, newMessage.text)
+				go broadcast(newMessage, connections, removeConnCh)
+			default:
+				// do nothing
+			}
+		}
+	}()
+}
+
+// processInput scans a chat connection for text and hands chat commands or
+// messages.
+func processInput(con net.Conn, addMessageCh chan message, removeConnCh chan net.Conn) {
+	log.Println("saying hello to our connection")
+	fmt.Fprintln(con, `Well hello there!
+
+Anything you type to me will be displayed in the output of this chat-server.
+`)
+	scanner := bufio.NewScanner(con)
+	for scanner.Scan() {
+		line := scanner.Text()
+		debugLog.Printf("received from %s: %s", con.RemoteAddr(), line)
+		if strings.HasPrefix(line, "/") {
+			exiting := processCommands(line, con)
+			if exiting {
+				con.Close()
+				removeConnCh <- con
+				return
+			}
+			continue
+		}
+		addMessageCh <- message{
+			text:   line,
+			sender: con.RemoteAddr().String(),
+		}
+	}
+	err := scanner.Err()
+	if err != nil {
+		debugLog.Println("while reading from %s: %v", con.RemoteAddr(), err)
+	}
+}
+
+func broadcast(msg message, allConnections []net.Conn, removeConnCh chan net.Conn) {
+	debugLog.Printf("broadcasting to %d connections: %s", len(allConnections), msg)
+	for _, con := range allConnections {
+		if con.RemoteAddr().String() == msg.sender {
+			_, err := fmt.Fprintf(con, "> %s\n", msg.text)
+			if err != nil {
+				debugLog.Printf("error writing to %v: %v", con, err)
+				removeConnCh <- con
+			}
+			continue
+		}
+		_, err := fmt.Fprintf(con, msg.String())
+		if err != nil {
+			debugLog.Printf("error writing to %v: %v", con, err)
+			removeConnCh <- con
+		}
+	}
+}
+
+func processCommands(input string, con net.Conn) (clientIsLeaving bool) {
+	fields := strings.Fields(input)
+	switch strings.ToLower(fields[0][1:]) { // first word minus its first character(/)
+	case "quit", "exit", "leave":
+		fmt.Fprintf(con, "You're leaving? Ok - have a nice day. :)\n")
+		debugLog.Printf("client %s has signed off", con.RemoteAddr())
+		return true
+	case "help":
+		fmt.Fprintf(con, `Available commands are:
+/quit|leave|exit - Sign off and disconnect from chat.
+/nick|nickname - Set your nickname, to be displayed with your messages.
+`)
+	default:
+		fmt.Fprintf(con, "%q is an invalid command, please use /help for a list of commands.\n", fields[0])
+	}
+	return false
+}
+
+func main() {
+	debugLog.SetFormatter(&log.TextFormatter{
+		PadLevelText: true,
+	})
+
+	const listenAddress = ":8080"
+	l, err := net.Listen("tcp", listenAddress)
+	if err != nil {
+		debugLog.Fatalf("cannot listen: %v", err)
+	}
+	debugLog.Printf("listening for connections on %s", listenAddress)
+	addConnCh := make(chan net.Conn)
+	removeConnCh := make(chan net.Conn)
+	addMessageCh := make(chan message)
+	startConnectionAndMessageManager(addConnCh, removeConnCh, addMessageCh)
+	debugLog.Println("waiting for new connections")
+	for {
+		con, err := l.Accept()
+		if err != nil {
+			debugLog.Printf("while accepting a connection: %v", err)
+			continue
+		}
+		addConnCh <- con
+		go processInput(con, addMessageCh, removeConnCh)
+	}
+}