fix(tui): keep the login screen responsive while connecting

The login screen ignored every key while a connect+login attempt ran, so
against an unreachable server it sat on a static "Connecting…" for 20s or
more, with a hint promising that Esc would quit.

While connecting it now shows a spinner: Enter or r restarts the attempt,
Esc stops it and returns to the form, q or Ctrl-C quits. Ctrl-C quits from
every state of the screen instead of typing a "c" into a field.

A failure that got no verdict (unreachable, timed out) keeps the password,
so Enter or r retries it; only a rejection, Ok(false) or
AuthenticationFailed, clears it. Because a retry can now reuse a password
that came from the CLI, env or keychain, entered_via_form compares the
credentials with the ones the flow started with instead of trusting any
submit, so a retried stored password is never written to the keychain.

A restart of an attempt younger than a second is ignored: each attempt
rescans the shares and opens a listener, and a held Enter would otherwise
start one per key repeat. The attempt result is read before drawing, so a
key is never handled against a phase the screen did not show.

A stopped or restarted attempt is abandoned, not cancelled: the server
actor blocks its own mailbox in connect_timeout, so a stop could not reach
it sooner. Its thread runs out its timeouts and drops the client, which
disconnects. Until then it holds the listener port, so a restarted session
can fall back to an ephemeral port, and should a slow server accept the
abandoned login after its replacement got in, the late login displaces the
new session. Fixing either needs a cancellable connect, or a bind after the
login verdict, in the library.

soulseek-rs/src/ui/login.rs

@@ -6,21 +6,25 @@
 //! ([`run_login_flow`]) drives it against a real terminal and client.
 
 use crate::ui::{
-    GLYPH_CURSOR, accent_style, dimmed_style, error_style, info_style, mask,
-    pane_block, primary_style, title_style, warning_style,
+    GLYPH_CURSOR, accent_style, dimmed_style, error_style, get_spinner_char,
+    info_style, mask, pane_block, primary_style, title_style, warning_style,
 };
 use color_eyre::Result;
 use ratatui::{
     DefaultTerminal, Frame,
-    crossterm::event::{self, Event, KeyCode, KeyEvent, KeyEventKind, poll},
+    crossterm::event::{
+        self, Event, KeyCode, KeyEvent, KeyEventKind, KeyModifiers, poll,
+    },
     layout::{Constraint, Flex, Layout, Rect},
     style::Modifier,
     text::{Line, Span},
     widgets::{Clear, Paragraph},
 };
-use soulseek_rs::{Client, ClientSettings};
+use soulseek_rs::{Client, ClientSettings, SoulseekRs};
 use std::sync::mpsc::{Receiver, channel};
-use std::time::Duration;
+use std::time::{Duration, Instant};
+
+const RESTART_FLOOR: Duration = Duration::from_secs(1);
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum LoginField {
@@ -36,15 +40,17 @@ pub enum LoginPhase {
     Connecting,
     /// The last attempt failed; the message is shown until the next key.
     Failed(String),
+    Rejected(String),
 }
 
 /// What the caller should do after feeding a key to the form.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum LoginAction {
     None,
-    /// Both fields are filled and the user pressed Enter.
+    /// Both fields are filled and the user pressed Enter or r.
     Submit,
-    /// User pressed Esc — abort the whole program.
+    Stop,
+    /// User pressed Esc, q or Ctrl-C — abort the whole program.
     Cancel,
 }
 
@@ -72,9 +78,33 @@ impl LoginForm {
     }
 
     pub fn handle_key(&mut self, key: KeyEvent) -> LoginAction {
+        if key.code == KeyCode::Char('c')
+            && key.modifiers.contains(KeyModifiers::CONTROL)
+        {
+            return LoginAction::Cancel;
+        }
+
         match self.phase {
-            LoginPhase::Connecting => return LoginAction::None,
+            LoginPhase::Connecting => {
+                return match key.code {
+                    KeyCode::Enter | KeyCode::Char('r') => LoginAction::Submit,
+                    KeyCode::Esc => {
+                        self.phase = LoginPhase::Editing;
+                        LoginAction::Stop
+                    }
+                    KeyCode::Char('q') => LoginAction::Cancel,
+                    _ => LoginAction::None,
+                };
+            }
             LoginPhase::Failed(_) => {
+                self.phase = LoginPhase::Editing;
+                return match key.code {
+                    KeyCode::Enter | KeyCode::Char('r') => self.submit(),
+                    KeyCode::Esc => LoginAction::Cancel,
+                    _ => LoginAction::None,
+                };
+            }
+            LoginPhase::Rejected(_) => {
                 // Any key acknowledges the error; the password was wrong (or
                 // the name is taken), so make the user retype it.
                 self.phase = LoginPhase::Editing;
@@ -97,20 +127,7 @@ impl LoginForm {
                 };
                 LoginAction::None
             }
-            KeyCode::Enter => {
-                if !self.username.is_empty() && !self.password.is_empty() {
-                    self.phase = LoginPhase::Connecting;
-                    LoginAction::Submit
-                } else {
-                    // Move to the first empty field instead of submitting.
-                    self.focused = if self.username.is_empty() {
-                        LoginField::Username
-                    } else {
-                        LoginField::Password
-                    };
-                    LoginAction::None
-                }
-            }
+            KeyCode::Enter => self.submit(),
             KeyCode::Backspace => {
                 self.focused_field_mut().pop();
                 LoginAction::None
@@ -123,6 +140,20 @@ impl LoginForm {
         }
     }
 
+    fn submit(&mut self) -> LoginAction {
+        if !self.username.is_empty() && !self.password.is_empty() {
+            self.phase = LoginPhase::Connecting;
+            return LoginAction::Submit;
+        }
+        // Move to the first empty field instead of submitting.
+        self.focused = if self.username.is_empty() {
+            LoginField::Username
+        } else {
+            LoginField::Password
+        };
+        LoginAction::None
+    }
+
     const fn focused_field_mut(&mut self) -> &mut String {
         match self.focused {
             LoginField::Username => &mut self.username,
@@ -142,7 +173,7 @@ pub struct LoginOutcome {
 }
 
 /// Drive the login screen until a login succeeds (`Some`) or the user
-/// cancels with Esc (`None`). When both credentials are already known an
+/// quits (`None`). When both credentials are already known an
 /// attempt starts immediately and the form is only shown on failure.
 pub fn run_login_flow(
     terminal: &mut DefaultTerminal,
@@ -150,27 +181,31 @@ pub fn run_login_flow(
     initial_username: Option<String>,
     initial_password: Option<String>,
 ) -> Result<Option<LoginOutcome>> {
-    let mut form = LoginForm::new(initial_username);
-    let mut entered_via_form = false;
-    let mut attempt: Option<Receiver<Result<Client, String>>> =
-        match initial_password {
-            Some(password) if !form.username.is_empty() => {
-                form.password = password;
-                form.phase = LoginPhase::Connecting;
-                Some(spawn_attempt(make_settings(
-                    form.username.clone(),
-                    form.password.clone(),
-                )))
-            }
-            _ => None,
-        };
+    let start = |form: &LoginForm| {
+        spawn_attempt(make_settings(
+            form.username.clone(),
+            form.password.clone(),
+        ))
+    };
+    let mut form = LoginForm::new(initial_username.clone());
+    let mut attempt = match &initial_password {
+        Some(password) if !form.username.is_empty() => {
+            form.password.clone_from(password);
+            form.phase = LoginPhase::Connecting;
+            Some(start(&form))
+        }
+        _ => None,
+    };
+    let mut started = Instant::now();
 
     loop {
-        terminal.draw(|frame| render(frame, &form))?;
-
         if let Some(rx) = &attempt {
             match rx.try_recv() {
                 Ok(Ok(client)) => {
+                    let entered_via_form = initial_username.as_deref()
+                        != Some(form.username.as_str())
+                        || initial_password.as_deref()
+                            != Some(form.password.as_str());
                     return Ok(Some(LoginOutcome {
                         client,
                         username: form.username,
@@ -178,8 +213,8 @@ pub fn run_login_flow(
                         entered_via_form,
                     }));
                 }
-                Ok(Err(message)) => {
-                    form.phase = LoginPhase::Failed(message);
+                Ok(Err(failure)) => {
+                    form.phase = failure;
                     attempt = None;
                 }
                 Err(std::sync::mpsc::TryRecvError::Empty) => {}
@@ -191,19 +226,24 @@ pub fn run_login_flow(
             }
         }
 
+        let spinner =
+            get_spinner_char(started.elapsed().subsec_millis() as usize / 100);
+        terminal.draw(|frame| render(frame, &form, spinner))?;
+
         if poll(Duration::from_millis(100))?
             && let Event::Key(key) = event::read()?
             && key.kind == KeyEventKind::Press
         {
             match form.handle_key(key) {
                 LoginAction::Cancel => return Ok(None),
+                LoginAction::Submit
+                    if attempt.is_some()
+                        && started.elapsed() < RESTART_FLOOR => {}
                 LoginAction::Submit => {
-                    entered_via_form = true;
-                    attempt = Some(spawn_attempt(make_settings(
-                        form.username.clone(),
-                        form.password.clone(),
-                    )));
+                    attempt = Some(start(&form));
+                    started = Instant::now();
                 }
+                LoginAction::Stop => attempt = None,
                 LoginAction::None => {}
             }
         }
@@ -211,27 +251,35 @@ pub fn run_login_flow(
 }
 
 /// Connect and log in on a background thread so the UI stays responsive.
-fn spawn_attempt(settings: ClientSettings) -> Receiver<Result<Client, String>> {
+fn spawn_attempt(
+    settings: ClientSettings,
+) -> Receiver<Result<Client, LoginPhase>> {
     let (tx, rx) = channel();
     std::thread::spawn(move || {
         let mut client = Client::with_settings(settings);
         let result = client
             .connect()
-            .map_err(|e| format!("Failed to connect: {e}"))
-            .and_then(|()| match client.login() {
-                Ok(true) => Ok(()),
-                Ok(false) => Err(
-                    "Login rejected: wrong password, or the username is taken"
-                        .to_string(),
-                ),
-                Err(e) => Err(format!("Login failed: {e}")),
-            });
+            .map_err(|e| LoginPhase::Failed(format!("Failed to connect: {e}")))
+            .and_then(|()| verdict(client.login()));
         let _ = tx.send(result.map(|()| client));
     });
     rx
 }
 
-fn render(frame: &mut Frame, form: &LoginForm) {
+fn verdict(login: soulseek_rs::Result<bool>) -> Result<(), LoginPhase> {
+    match login {
+        Ok(true) => Ok(()),
+        Ok(false) | Err(SoulseekRs::AuthenticationFailed) => {
+            Err(LoginPhase::Rejected(
+                "Login rejected: wrong password, or the username is taken"
+                    .to_string(),
+            ))
+        }
+        Err(e) => Err(LoginPhase::Failed(format!("Login failed: {e}"))),
+    }
+}
+
+fn render(frame: &mut Frame, form: &LoginForm, spinner: &str) {
     let area = centered(frame.area(), 52, 12);
     frame.render_widget(Clear, area);
 
@@ -290,21 +338,32 @@ fn render(frame: &mut Frame, form: &LoginForm) {
     let status = match &form.phase {
         LoginPhase::Editing => Paragraph::new(""),
         LoginPhase::Connecting => Paragraph::new(Line::from(Span::styled(
-            "Connecting…",
+            format!("{spinner} Connecting…"),
             warning_style(),
         ))),
-        LoginPhase::Failed(message) => Paragraph::new(Line::from(
-            Span::styled(message.clone(), error_style()),
-        ))
-        .wrap(ratatui::widgets::Wrap { trim: true }),
+        LoginPhase::Failed(message) | LoginPhase::Rejected(message) => {
+            Paragraph::new(Line::from(Span::styled(
+                message.clone(),
+                error_style(),
+            )))
+            .wrap(ratatui::widgets::Wrap { trim: true })
+        }
     };
     frame.render_widget(status, rows[3]);
 
+    let keys = match form.phase {
+        LoginPhase::Connecting => {
+            "Enter/r: restart · Esc: stop · q/Ctrl-C: quit"
+        }
+        LoginPhase::Failed(_) => "Enter/r: retry · Esc: quit",
+        LoginPhase::Editing | LoginPhase::Rejected(_) => {
+            "Tab: switch · Enter: log in · Esc: quit"
+        }
+    };
     frame.render_widget(
-        Paragraph::new(
-            "New usernames are registered automatically.\n\
-             Tab: switch · Enter: log in · Esc: quit",
-        )
+        Paragraph::new(format!(
+            "New usernames are registered automatically.\n{keys}"
+        ))
         .style(dimmed_style()),
         rows[5],
     );
@@ -323,7 +382,6 @@ fn centered(area: Rect, width: u16, height: u16) -> Rect {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use ratatui::crossterm::event::KeyModifiers;
 
     fn key(code: KeyCode) -> KeyEvent {
         KeyEvent::new(code, KeyModifiers::NONE)
@@ -335,6 +393,13 @@ mod tests {
         }
     }
 
+    fn connecting() -> LoginForm {
+        let mut form = LoginForm::new(Some("alice".into()));
+        type_str(&mut form, "pw");
+        assert_eq!(form.handle_key(key(KeyCode::Enter)), LoginAction::Submit);
+        form
+    }
+
     #[test]
     fn prefilled_username_focuses_password() {
         let form = LoginForm::new(Some("alice".into()));
@@ -402,11 +467,93 @@ mod tests {
     }
 
     #[test]
-    fn key_after_failure_returns_to_editing_and_clears_password() {
-        let mut form = LoginForm::new(Some("alice".into()));
-        type_str(&mut form, "wrong");
-        form.handle_key(key(KeyCode::Enter));
-        form.phase = LoginPhase::Failed("INVALIDPASS".into());
+    fn ctrl_c_quits_from_every_phase_without_typing() {
+        let ctrl_c = KeyEvent::new(KeyCode::Char('c'), KeyModifiers::CONTROL);
+        for phase in [
+            LoginPhase::Editing,
+            LoginPhase::Connecting,
+            LoginPhase::Failed("unreachable".into()),
+            LoginPhase::Rejected("INVALIDPASS".into()),
+        ] {
+            let mut form = LoginForm::new(None);
+            form.phase = phase.clone();
+            assert_eq!(
+                form.handle_key(ctrl_c),
+                LoginAction::Cancel,
+                "{phase:?}"
+            );
+            assert_eq!(form.username, "", "{phase:?}");
+        }
+    }
+
+    #[test]
+    fn typing_is_ignored_while_connecting() {
+        let mut form = connecting();
+        let action = form.handle_key(key(KeyCode::Char('x')));
+        assert_eq!(action, LoginAction::None);
+        assert_eq!(form.password, "pw");
+        assert_eq!(form.phase, LoginPhase::Connecting);
+    }
+
+    #[test]
+    fn escape_while_connecting_stops_and_keeps_the_credentials() {
+        let mut form = connecting();
+        assert_eq!(form.handle_key(key(KeyCode::Esc)), LoginAction::Stop);
+        assert_eq!(form.phase, LoginPhase::Editing);
+        assert_eq!(form.password, "pw");
+        assert_eq!(form.handle_key(key(KeyCode::Enter)), LoginAction::Submit);
+    }
+
+    #[test]
+    fn enter_or_r_while_connecting_restarts() {
+        for code in [KeyCode::Enter, KeyCode::Char('r')] {
+            let mut form = connecting();
+            assert_eq!(form.handle_key(key(code)), LoginAction::Submit);
+            assert_eq!(form.phase, LoginPhase::Connecting);
+            assert_eq!(form.password, "pw");
+        }
+    }
+
+    #[test]
+    fn q_while_connecting_quits() {
+        let mut form = connecting();
+        assert_eq!(
+            form.handle_key(key(KeyCode::Char('q'))),
+            LoginAction::Cancel
+        );
+    }
+
+    #[test]
+    fn enter_or_r_after_a_failed_connection_retries_with_the_same_password() {
+        for code in [KeyCode::Enter, KeyCode::Char('r')] {
+            let mut form = connecting();
+            form.phase = LoginPhase::Failed("Login failed: timed out".into());
+            assert_eq!(form.handle_key(key(code)), LoginAction::Submit);
+            assert_eq!(form.phase, LoginPhase::Connecting);
+            assert_eq!(form.password, "pw");
+        }
+    }
+
+    #[test]
+    fn other_key_after_a_failed_connection_edits_with_the_password_kept() {
+        let mut form = connecting();
+        form.phase = LoginPhase::Failed("Login failed: timed out".into());
+        assert_eq!(form.handle_key(key(KeyCode::Char('x'))), LoginAction::None);
+        assert_eq!(form.phase, LoginPhase::Editing);
+        assert_eq!(form.password, "pw");
+    }
+
+    #[test]
+    fn escape_after_a_failed_connection_quits() {
+        let mut form = connecting();
+        form.phase = LoginPhase::Failed("Login failed: timed out".into());
+        assert_eq!(form.handle_key(key(KeyCode::Esc)), LoginAction::Cancel);
+    }
+
+    #[test]
+    fn key_after_rejection_returns_to_editing_and_clears_password() {
+        let mut form = connecting();
+        form.phase = LoginPhase::Rejected("INVALIDPASS".into());
         let action = form.handle_key(key(KeyCode::Char('x')));
         assert_eq!(action, LoginAction::None);
         assert_eq!(form.phase, LoginPhase::Editing);
@@ -414,13 +561,14 @@ mod tests {
     }
 
     #[test]
-    fn keys_ignored_while_connecting() {
-        let mut form = LoginForm::new(Some("alice".into()));
-        type_str(&mut form, "pw");
-        form.handle_key(key(KeyCode::Enter));
-        assert_eq!(form.phase, LoginPhase::Connecting);
-        let action = form.handle_key(key(KeyCode::Char('x')));
-        assert_eq!(action, LoginAction::None);
-        assert_eq!(form.password, "pw");
+    fn a_wrong_password_is_rejected_and_an_unanswered_login_failed() {
+        assert_eq!(verdict(Ok(true)), Ok(()));
+        for rejected in [Ok(false), Err(SoulseekRs::AuthenticationFailed)] {
+            assert!(matches!(verdict(rejected), Err(LoginPhase::Rejected(_))));
+        }
+        for failed in [Err(SoulseekRs::Timeout), Err(SoulseekRs::NotConnected)]
+        {
+            assert!(matches!(verdict(failed), Err(LoginPhase::Failed(_))));
+        }
     }
 }