First chat implementation

nats-client/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "nats-client"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+nats = "0.24.0"
+serde = "1.0.162"
+serde_json = "1.0.96"

nats-client/src/main.rs

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+use std::{
+    fmt::{self, Display},
+    io::{self, BufRead},
+};
+
+use nats::Connection;
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize)]
+struct Message {
+    author: String,
+    message: String,
+}
+
+impl Display for Message {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Message from {}: {}", self.author, self.message)
+    }
+}
+
+const SUBJECT_MESSAGES: &str = "here.happens.messaging";
+
+fn main() -> io::Result<()> {
+    let nc = nats::connect("127.0.0.1")?;
+
+    let username = ask_user_name();
+    println!(
+        "Hello {}, please write your message. Use q to quit:",
+        username
+    );
+
+    let my_username = username.clone();
+    let sub = nc.subscribe(SUBJECT_MESSAGES)?.with_handler(move |msg| {
+        // This runs in a separate Thread
+        let message: Message = serde_json::from_str(&String::from_utf8(msg.data).unwrap()).unwrap();
+
+        // Do not show messages from me
+        if message.author != my_username {
+            println!("Received {}", message);
+        }
+        Ok(())
+    });
+
+    let stdin = io::stdin();
+    for line in stdin.lock().lines() {
+        let line = line.unwrap();
+        let line = line.trim();
+        if line.is_empty() {
+            continue;
+        }
+
+        if line == "q" || line == "Q" {
+            break;
+        }
+
+        publish_message(
+            &Message {
+                author: username.clone(),
+                message: line.to_string(),
+            },
+            &nc,
+        )?;
+    }
+    sub.unsubscribe()?;
+    Ok(())
+}
+
+fn publish_message(message: &Message, nc: &Connection) -> io::Result<()> {
+    let json_string_utf8 = serde_json::to_string(message).expect("Cannot serialize message");
+    nc.publish(SUBJECT_MESSAGES, json_string_utf8)?;
+    Ok(())
+}
+
+fn ask_user_name() -> String {
+    println!("Please enter your username: ");
+    let mut input_text = String::new();
+    io::stdin()
+        .read_line(&mut input_text)
+        .expect("Failed reading from stdin");
+    input_text = input_text.trim().to_string();
+    if input_text.is_empty() {
+        println!("Your input was empty. Please try again.");
+        return ask_user_name();
+    }
+    input_text
+}