Create main.go

main.go

@@ -0,0 +1,135 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/go-redis/redis/v8"
+)
+
+var (
+	ctx  = context.Background()
+	TTL  = time.Minute * 20
+	conn = redis.NewClient(&redis.Options{
+		Addr:     "localhost:6379",
+		Password: "", // no password set
+		DB:       0,  // use default DB
+	})
+)
+
+func main() {
+	// The user name is the only argument, so we'll grab that here
+	if len(os.Args) != 2 {
+		fmt.Println("Usage: goredchat username")
+		os.Exit(1)
+	}
+	username := os.Args[1]
+
+	defer conn.Close()
+
+	// We make a key and set it with the username as a value and a time to live
+	// this will be the lock on the username and if we can't set it, its a name clash
+
+	userkey := "online." + username
+	val, err := conn.Set(ctx, userkey, username, TTL).Result()
+
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	if val == "" {
+		fmt.Println("User already online")
+		os.Exit(1)
+	}
+
+	valint, err := conn.SAdd(ctx, "users", username).Result()
+
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	if valint == 0 {
+		fmt.Println("User still in online set")
+		os.Exit(1)
+	}
+
+	// A ticker will let us update our presence on the Redis server
+	tickerChan := time.NewTicker(time.Second * 60).C
+
+	// Now we create a channel and go routine that'll subscribe to our published messages
+	// We'll give it its own connection because subscribes like to have their own connection
+	subChan := make(chan string)
+	go func() {
+
+		psc := conn.Subscribe(ctx, "messages")
+		_, err := psc.Receive(ctx)
+		if err != nil {
+			panic(err)
+		}
+		// Go channel which receives messages.
+		ch := psc.Channel()
+		for v := range ch {
+			subChan <- string(v.Payload)
+		}
+	}()
+
+	// Now we'll make a simple channel and go routine that listens for complete lines from the user
+	// When a complete line is entered, it'll be delivered to the channel.
+	sayChan := make(chan string)
+	go func() {
+		prompt := username + ">"
+		bio := bufio.NewReader(os.Stdin)
+		for {
+			fmt.Print(prompt)
+			line, _, err := bio.ReadLine()
+			if err != nil {
+				fmt.Println(err)
+				sayChan <- "/exit"
+				return
+			}
+			sayChan <- string(line)
+		}
+	}()
+
+	conn.Publish(ctx, "messages", username+" has joined")
+
+	chatExit := false
+
+	for !chatExit {
+		select {
+		case msg := <-subChan:
+			fmt.Println(msg)
+		case <-tickerChan:
+			val, err = conn.Set(ctx, userkey, username, TTL).Result()
+			if err != nil || val == "" {
+				fmt.Println("Heartbeat set failed")
+				chatExit = true
+			}
+		case line := <-sayChan:
+			if line == "/exit" {
+				chatExit = true
+			} else if line == "/who" {
+				names, _ := conn.SMembers(ctx, "users").Result()
+
+				for _, name := range names {
+					fmt.Println(name)
+				}
+			} else {
+				conn.Publish(ctx, "messages", username+":"+line)
+			}
+		default:
+			time.Sleep(100 * time.Millisecond)
+		}
+	}
+
+	// We're leaving so let's delete the userkey and remove the username from the online set
+	conn.Del(ctx, userkey)
+	conn.SRem(ctx, "users", username)
+	conn.Publish(ctx, "messages", username+" has left")
+
+}