Loop TUI until successful auth

src/main.rs

@@ -4,16 +4,7 @@ mod tui;
 use std::io;
 
 fn main() -> io::Result<()> {
-    let (username, password) = tui::run()?;
-
-    match auth::authenticate(&username, &password) {
-        Ok(()) => {
-            println!("authentication successful");
-        }
-        Err(_) => {
-            println!("authentication failed");
-        }
-    }
-
+    let username = tui::run(|u, p| auth::authenticate(u, p).is_ok())?;
+    println!("authenticated as {username}");
     Ok(())
 }

src/tui.rs

@@ -14,7 +14,10 @@ use std::io;
 
 /// Runs the TUI and returns the entered username and password.
 /// This module owns all terminal state.
-pub fn run() -> io::Result<(String, String)> {
+pub fn run<F>(auth_fn: F) -> io::Result<String>
+where
+    F: Fn(&str, &str) -> bool,
+{
     enable_raw_mode()?;
     let mut stdout = io::stdout();
     execute!(stdout, EnterAlternateScreen)?;
@@ -22,6 +25,8 @@ pub fn run() -> io::Result<(String, String)> {
     let backend = CrosstermBackend::new(stdout);
     let mut terminal = Terminal::new(backend)?;
 
+    let mut error_msg: Option<&str> = None;
+
     let mut username = String::new();
     let mut password = String::new();
     let mut focus = 0;
@@ -30,7 +35,11 @@ pub fn run() -> io::Result<(String, String)> {
         terminal.draw(|f| {
             let chunks = Layout::default()
                 .direction(Direction::Vertical)
-                .constraints([Constraint::Length(3), Constraint::Length(3)])
+                .constraints([
+                    Constraint::Length(3),
+                    Constraint::Length(3),
+                    Constraint::Length(2),
+                ])
                 .split(f.area());
 
             let user = Paragraph::new(username.as_str())
@@ -51,8 +60,11 @@ pub fn run() -> io::Result<(String, String)> {
                     Style::default()
                 });
 
+            let error = Paragraph::new(error_msg.unwrap_or("")).style(Style::new().fg(Color::Red));
+
             f.render_widget(user, chunks[0]);
             f.render_widget(pass, chunks[1]);
+            f.render_widget(error, chunks[2]);
         })?;
 
         if let Event::Key(key) = event::read()? {
@@ -61,7 +73,11 @@ pub fn run() -> io::Result<(String, String)> {
                 KeyCode::Tab => focus = (focus + 1) % 2,
                 KeyCode::Enter => {
                     if !username.is_empty() && !password.is_empty() {
-                        break;
+                        if auth_fn(&username, &password) {
+                            break;
+                        }
+                        password.clear();
+                        error_msg = Some("Authentication failed");
                     }
                 }
 
@@ -87,5 +103,5 @@ pub fn run() -> io::Result<(String, String)> {
     disable_raw_mode()?;
     execute!(terminal.backend_mut(), LeaveAlternateScreen)?;
 
-    Ok((username, password))
+    Ok(username)
 }