Adaptive auto-continue input lock overlay

docs/plans/2026-02-26-adaptive-auto-continue-input-lock-overlay.md

@@ -0,0 +1,93 @@
+# Adaptive Auto-Continue Input Lock Overlay
+
+## Context
+
+In adaptive mode, when a drill completes with no milestone popups to show, the app auto-continues to the next drill immediately (`finish_drill` → `start_drill()` with no intermediate screen). The existing 800ms input lock (`POST_DRILL_INPUT_LOCK_MS`) is only armed when there IS an intermediate screen (DrillResult or milestone popup). This means trailing keystrokes from the previous drill can bleed into the next drill as unintended inputs.
+
+The fix: arm the same 800ms lock during adaptive auto-continue, block drill input while it's active, and show a small countdown popup overlay on the drill screen so the user knows why their input is temporarily ignored.
+
+## Changes
+
+### 1. Arm the lock on adaptive auto-continue
+
+**`src/app.rs` — `finish_drill()`**
+
+Currently the auto-continue path does not arm the lock:
+```rust
+if self.drill_mode == DrillMode::Adaptive && self.milestone_queue.is_empty() {
+    self.start_drill();
+}
+```
+
+Add `arm_post_drill_input_lock()` after `start_drill()`. It must come after because `start_drill()` calls `clear_post_drill_input_lock()` as its first action (to clear stale locks from manual continues). Re-arming immediately after means the 800ms window starts from when the new drill begins:
+```rust
+if self.drill_mode == DrillMode::Adaptive && self.milestone_queue.is_empty() {
+    self.start_drill();
+    self.arm_post_drill_input_lock();
+}
+```
+
+**Event ordering safety**: The event loop in `run_app()` is single-threaded: `draw` → `events.next()` → `handle_key` → loop. `finish_drill()` runs inside a `handle_key()` call, so both `start_drill()` and `arm_post_drill_input_lock()` complete within the same event iteration. Any buffered key events are processed in subsequent loop iterations, where the lock is already active.
+
+### 2. Allow Ctrl+C through the lock and add Drill screen to lock guard
+
+**`src/main.rs` — `handle_key()`**
+
+Move the Ctrl+C quit handler ABOVE the input lock guard so it always works, even during lockout. Then add `AppScreen::Drill` to the lock guard:
+
+```rust
+// Ctrl+C always quits, even during input lock
+if key.modifiers.contains(KeyModifiers::CONTROL) && key.code == KeyCode::Char('c') {
+    app.should_quit = true;
+    return;
+}
+
+// Briefly block all input right after a drill completes to avoid accidental
+// popup dismissal or continuation from trailing keystrokes.
+if app.post_drill_input_lock_remaining_ms().is_some()
+    && (!app.milestone_queue.is_empty()
+        || app.screen == AppScreen::DrillResult
+        || app.screen == AppScreen::Drill)
+{
+    return;
+}
+```
+
+This is a behavior change for the existing DrillResult/milestone lock too: previously Ctrl+C was blocked during the 800ms window, now it passes through. All other keys remain blocked. The 800ms window is short enough that blocking everything else is not disruptive.
+
+### 3. Render lock overlay on the drill screen
+
+**`src/main.rs` — end of `render_drill()`**
+
+After all existing drill UI is rendered, if the lock is active, draw a small centered popup overlay on top of the typing area:
+
+- Check `app.post_drill_input_lock_remaining_ms()` — if `None`, skip overlay entirely
+- **Size**: 3 rows tall (top border + message + bottom border), width = message length + 4 (border + padding), centered within the full `area` rect
+- **Clear** the overlay rect with `ratatui::widgets::Clear`
+- **Block**: `Block::bordered()` with `colors.accent()` border style and `colors.bg()` background — same pattern as `render_milestone_overlay`
+- **Message**: `"Keys re-enabled in {ms}ms"` as a `Paragraph` with `colors.text_pending()` style — matches the milestone overlay footer color
+- Render inside the block's `inner()` area
+
+This overlay is intentionally small (single bordered line) since the drill content should remain visible behind it and it only appears for ≤800ms.
+
+**Countdown repainting**: The event loop (`run_app()`) uses `EventHandler::new(Duration::from_millis(100))` which sends `AppEvent::Tick` every 100ms when idle. Each tick triggers `terminal.draw()`, which re-renders the drill screen. `post_drill_input_lock_remaining_ms()` recomputes the remaining time from `Instant::now()` on each call, so the countdown value updates every ~100ms without any additional machinery.
+
+### 4. Tests
+
+**`src/app.rs`** — add to the existing `#[cfg(test)] mod tests`:
+
+1. **`adaptive_auto_continue_arms_input_lock`**: Create `App`, verify it starts in adaptive mode with a drill. Simulate completing the drill by calling `finish_drill()` (set up drill state as complete first). Assert `post_drill_input_lock_remaining_ms().is_some()` and `screen == AppScreen::Drill` after auto-continue.
+
+2. **`adaptive_auto_continue_lock_not_armed_with_milestones`**: Same setup but push a milestone into `milestone_queue` before calling `finish_drill()`. Assert `screen == AppScreen::DrillResult` (not auto-continued) and lock is armed via the existing milestone path.
+
+## Files to modify
+
+- `src/app.rs` — 1-line addition in `finish_drill()` auto-continue path; 2 tests
+- `src/main.rs` — extend input lock guard condition in `handle_key()`; add overlay rendering at end of `render_drill()`
+
+## Verification
+
+1. `cargo test` — all existing and new tests pass
+2. Manual: start adaptive drill, complete it. Verify small popup appears briefly over the next drill, countdown decrements every ~100ms, then disappears and typing works normally
+3. Manual: complete adaptive drill that triggers a milestone popup. Verify milestone popup still works as before (no double-lock or interference)
+4. Manual: complete Code or Passage drill. Verify DrillResult screen lockout still works as before

src/app.rs

@@ -1089,6 +1089,7 @@ impl App {
             // Adaptive mode auto-continues unless milestone popups must be shown first.
             if self.drill_mode == DrillMode::Adaptive && self.milestone_queue.is_empty() {
                 self.start_drill();
+                self.arm_post_drill_input_lock();
             } else {
                 self.screen = AppScreen::DrillResult;
             }
@@ -2303,4 +2304,62 @@ mod tests {
             app.adaptive_word_history.len()
         );
     }
+
+    /// Helper: make the current drill look "completed" so finish_drill() processes it.
+    fn complete_current_drill(app: &mut App) {
+        if let Some(ref mut drill) = app.drill {
+            let now = Instant::now();
+            drill.started_at = Some(now - Duration::from_millis(500));
+            drill.finished_at = Some(now);
+            drill.cursor = drill.target.len();
+            // Fill input so DrillResult::from_drill doesn't panic on length mismatches
+            drill.input = vec![crate::session::input::CharStatus::Correct; drill.target.len()];
+        }
+    }
+
+    #[test]
+    fn adaptive_auto_continue_arms_input_lock() {
+        let mut app = App::new();
+        assert_eq!(app.drill_mode, DrillMode::Adaptive);
+        assert_eq!(app.screen, AppScreen::Drill);
+        assert!(app.drill.is_some());
+
+        // Make sure no milestones are queued
+        app.milestone_queue.clear();
+
+        complete_current_drill(&mut app);
+        app.finish_drill();
+
+        // Auto-continue should have started a new drill and armed the lock
+        assert_eq!(app.screen, AppScreen::Drill);
+        assert!(
+            app.post_drill_input_lock_remaining_ms().is_some(),
+            "Input lock should be armed after adaptive auto-continue"
+        );
+    }
+
+    #[test]
+    fn adaptive_does_not_auto_continue_with_milestones() {
+        let mut app = App::new();
+        assert_eq!(app.drill_mode, DrillMode::Adaptive);
+
+        // Push a milestone before finishing the drill
+        app.milestone_queue.push_back(KeyMilestonePopup {
+            kind: MilestoneKind::Unlock,
+            keys: vec!['a'],
+            finger_info: vec![('a', "left pinky".to_string())],
+            message: "Test milestone",
+        });
+
+        complete_current_drill(&mut app);
+        app.finish_drill();
+
+        // Should go to DrillResult (not auto-continue) since milestones are queued
+        assert_eq!(app.screen, AppScreen::DrillResult);
+        // Lock IS armed via the existing milestone path
+        assert!(
+            app.post_drill_input_lock_remaining_ms().is_some(),
+            "Input lock should be armed for milestone path"
+        );
+    }
 }

src/main.rs

@@ -267,16 +267,19 @@ fn handle_key(app: &mut App, key: KeyEvent) {
         return;
     }
 
-    // Briefly block all input right after a drill completes to avoid accidental
-    // popup dismissal or continuation from trailing keystrokes.
-    if app.post_drill_input_lock_remaining_ms().is_some()
-        && (!app.milestone_queue.is_empty() || app.screen == AppScreen::DrillResult)
-    {
+    // Ctrl+C always quits, even during input lock.
+    if key.modifiers.contains(KeyModifiers::CONTROL) && key.code == KeyCode::Char('c') {
+        app.should_quit = true;
         return;
     }
 
-    if key.modifiers.contains(KeyModifiers::CONTROL) && key.code == KeyCode::Char('c') {
-        app.should_quit = true;
+    // Briefly block all input right after a drill completes to avoid accidental
+    // popup dismissal or continuation from trailing keystrokes.
+    if app.post_drill_input_lock_remaining_ms().is_some()
+        && (!app.milestone_queue.is_empty()
+            || app.screen == AppScreen::DrillResult
+            || app.screen == AppScreen::Drill)
+    {
         return;
     }
 
@@ -1316,6 +1319,27 @@ fn render_drill(frame: &mut ratatui::Frame, app: &App) {
             Style::default().fg(colors.text_pending()),
         )));
         frame.render_widget(footer, app_layout.footer);
+
+        // Show a brief countdown overlay while the post-drill input lock is active.
+        if let Some(ms) = app.post_drill_input_lock_remaining_ms() {
+            let msg = format!("Keys re-enabled in {}ms", ms);
+            let width = msg.len() as u16 + 4; // border + padding
+            let height = 3;
+            let x = area.x + area.width.saturating_sub(width) / 2;
+            let y = area.y + area.height.saturating_sub(height) / 2;
+            let overlay_area = Rect::new(x, y, width.min(area.width), height.min(area.height));
+
+            frame.render_widget(ratatui::widgets::Clear, overlay_area);
+            let block = Block::bordered()
+                .border_style(Style::default().fg(colors.accent()))
+                .style(Style::default().bg(colors.bg()));
+            let inner = block.inner(overlay_area);
+            frame.render_widget(block, overlay_area);
+            frame.render_widget(
+                Paragraph::new(msg).style(Style::default().fg(colors.text_pending())),
+                inner,
+            );
+        }
     }
 }
 
@@ -2312,6 +2336,41 @@ mod review_tests {
             "ni should be confirmed (samples >= 20, streak >= required)"
         );
     }
+
+    #[test]
+    fn drill_screen_input_lock_blocks_normal_keys() {
+        let mut app = test_app();
+        app.screen = AppScreen::Drill;
+        app.drill = Some(crate::session::drill::DrillState::new("abc"));
+        app.post_drill_input_lock_until =
+            Some(Instant::now() + std::time::Duration::from_millis(500));
+
+        let before_cursor = app.drill.as_ref().unwrap().cursor;
+        handle_key(
+            &mut app,
+            KeyEvent::new(KeyCode::Char('a'), KeyModifiers::NONE),
+        );
+        let after_cursor = app.drill.as_ref().unwrap().cursor;
+
+        assert_eq!(before_cursor, after_cursor, "Key should be blocked during input lock on Drill screen");
+        assert_eq!(app.screen, AppScreen::Drill);
+    }
+
+    #[test]
+    fn ctrl_c_passes_through_input_lock() {
+        let mut app = test_app();
+        app.screen = AppScreen::Drill;
+        app.drill = Some(crate::session::drill::DrillState::new("abc"));
+        app.post_drill_input_lock_until =
+            Some(Instant::now() + std::time::Duration::from_millis(500));
+
+        handle_key(
+            &mut app,
+            KeyEvent::new(KeyCode::Char('c'), KeyModifiers::CONTROL),
+        );
+
+        assert!(app.should_quit, "Ctrl+C should set should_quit even during input lock");
+    }
 }
 
 fn render_result(frame: &mut ratatui::Frame, app: &App) {