Split tui/mod.rs up into multiple files. (#3)

The mod.rs file was too large, split it up.

Reviewed-on: #3
Co-authored-by: Drew Galbraith <drew@tiramisu.one>
Co-committed-by: Drew Galbraith <drew@tiramisu.one>

src/tui/input.rs

@@ -0,0 +1,509 @@
+//! Keyboard input handling: vim modes, chords, and command execution.
+
+use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
+
+use super::{AppState, Mode};
+use crate::core::types::Role;
+
+/// Internal control flow signal returned by [`handle_key`].
+pub(super) enum LoopControl {
+    /// The user pressed Enter with non-empty input; send this message to the core.
+    SendMessage(String),
+    /// The user pressed Ctrl+C or Ctrl+D; exit the event loop.
+    Quit,
+    /// The user ran `:clear`; wipe the conversation.
+    ClearHistory,
+}
+
+/// Map a key event to a [`LoopControl`] signal, mutating `state` as a side-effect.
+///
+/// Ctrl+C / Ctrl+D quit from any mode. All other keys are dispatched to the
+/// handler for the current [`Mode`].
+pub(super) fn handle_key(key: Option<KeyEvent>, state: &mut AppState) -> Option<LoopControl> {
+    let key = key?;
+    // Clear any transient status error on the next keypress.
+    state.status_error = None;
+    // Ctrl+C quits from any mode.
+    if key.modifiers.contains(KeyModifiers::CONTROL) && key.code == KeyCode::Char('c') {
+        return Some(LoopControl::Quit);
+    }
+    // Ctrl+D quits only from Insert/Command mode. In Normal mode it scrolls.
+    if key.modifiers.contains(KeyModifiers::CONTROL)
+        && key.code == KeyCode::Char('d')
+        && !matches!(state.mode, Mode::Normal)
+    {
+        return Some(LoopControl::Quit);
+    }
+    match &state.mode {
+        Mode::Normal => handle_normal_key(key, state),
+        Mode::Insert => handle_insert_key(key, state),
+        Mode::Command => handle_command_key(key, state),
+    }
+}
+
+enum ChordResult {
+    /// The chord was fully matched; the returned closure applies the effect.
+    Executed,
+    /// The keys so far are a valid prefix of at least one chord.
+    Prefix,
+    /// The keys don't match any chord or prefix.
+    NoMatch,
+}
+
+/// Check `keys` against known multi-key chords in Normal mode.
+///
+/// Currently only `gg` (scroll to top) is defined. Returns the match status
+/// without mutating state -- the caller applies effects for `Executed`.
+fn resolve_chord(keys: &[char]) -> ChordResult {
+    match keys {
+        [.., 'g', 'g'] => ChordResult::Executed,
+        [.., 'g'] => ChordResult::Prefix,
+        _ => ChordResult::NoMatch,
+    }
+}
+
+/// Handle a keypress in Normal mode.
+///
+/// | Key | Effect                                    |
+/// |-----|-------------------------------------------|
+/// | `i` | Switch to Insert mode                     |
+/// | `:` | Switch to Command mode (empty buffer)     |
+/// | `j` | Scroll down one line                      |
+/// | `k` | Scroll up one line                        |
+/// | `G` | Scroll to bottom                          |
+/// | `g` | Begin chord; `gg` scrolls to top          |
+/// | Ctrl+d | Scroll down half a page                |
+/// | Ctrl+u | Scroll up half a page                  |
+fn handle_normal_key(key: KeyEvent, state: &mut AppState) -> Option<LoopControl> {
+    let is_ctrl = key.modifiers.contains(KeyModifiers::CONTROL);
+    match key.code {
+        KeyCode::Char('d') if is_ctrl => {
+            let half = (state.viewport_height / 2).max(1);
+            state.scroll = state.scroll.saturating_add(half);
+            state.pending_keys.clear();
+        }
+        KeyCode::Char('u') if is_ctrl => {
+            let half = (state.viewport_height / 2).max(1);
+            state.scroll = state.scroll.saturating_sub(half);
+            state.pending_keys.clear();
+        }
+        KeyCode::Char('i') if !is_ctrl && state.pending_keys.is_empty() => {
+            state.mode = Mode::Insert;
+        }
+        KeyCode::Char(':') if !is_ctrl && state.pending_keys.is_empty() => {
+            state.command_buffer.clear();
+            state.mode = Mode::Command;
+        }
+        KeyCode::Char('j') if !is_ctrl && state.pending_keys.is_empty() => {
+            state.scroll = state.scroll.saturating_add(1);
+        }
+        KeyCode::Char('k') if !is_ctrl && state.pending_keys.is_empty() => {
+            state.scroll = state.scroll.saturating_sub(1);
+        }
+        KeyCode::Char('G') if !is_ctrl && state.pending_keys.is_empty() => {
+            state.scroll = u16::MAX;
+        }
+        KeyCode::Char(c) => {
+            state.pending_keys.push(c);
+            match resolve_chord(&state.pending_keys) {
+                ChordResult::Executed => {
+                    // Apply the chord effect. Currently only `gg`.
+                    state.scroll = 0;
+                    state.pending_keys.clear();
+                }
+                ChordResult::NoMatch => {
+                    state.pending_keys.clear();
+                }
+                ChordResult::Prefix => {} // wait for more keys
+            }
+        }
+        _ => {
+            state.pending_keys.clear();
+        }
+    }
+    None
+}
+
+/// Handle a keypress in Insert mode (the default text-entry mode).
+///
+/// | Key              | Effect                                          |
+/// |------------------|-------------------------------------------------|
+/// | Esc              | Switch to Normal mode                           |
+/// | Printable char   | Append to input buffer                          |
+/// | Backspace        | Pop last char from input buffer                  |
+/// | Enter (non-empty)| Take input, push User message, return `SendMessage` |
+/// | Enter (empty)    | No-op                                           |
+fn handle_insert_key(key: KeyEvent, state: &mut AppState) -> Option<LoopControl> {
+    match key.code {
+        KeyCode::Esc => {
+            state.mode = Mode::Normal;
+            None
+        }
+        KeyCode::Char(c) if !key.modifiers.contains(KeyModifiers::CONTROL) => {
+            state.input.push(c);
+            None
+        }
+        KeyCode::Backspace => {
+            state.input.pop();
+            None
+        }
+        KeyCode::Enter => {
+            let msg = std::mem::take(&mut state.input);
+            if msg.is_empty() {
+                None
+            } else {
+                state.messages.push((Role::User, msg.clone()));
+                Some(LoopControl::SendMessage(msg))
+            }
+        }
+        _ => None,
+    }
+}
+
+/// Execute a parsed command string and return the appropriate control signal.
+///
+/// | Command       | Effect                                          |
+/// |---------------|-------------------------------------------------|
+/// | `quit` / `q`  | Return `LoopControl::Quit`                      |
+/// | `clear`       | Clear messages and scroll, return `ClearHistory` |
+/// | anything else | Set `status_error` on state                     |
+fn execute_command(buf: &str, state: &mut AppState) -> Option<LoopControl> {
+    match buf.trim() {
+        "quit" | "q" => Some(LoopControl::Quit),
+        "clear" => {
+            state.messages.clear();
+            state.scroll = 0;
+            Some(LoopControl::ClearHistory)
+        }
+        other => {
+            state.status_error = Some(format!("Unknown command: {other}"));
+            None
+        }
+    }
+}
+
+/// Handle a keypress in Command mode (ex-style `:` command entry).
+///
+/// | Key       | Effect                                              |
+/// |-----------|-----------------------------------------------------|
+/// | Esc       | Abandon command, return to Normal                   |
+/// | Enter     | Accept command (execution deferred to 2.3), Normal  |
+/// | Backspace | Pop from buffer; if empty, return to Normal         |
+/// | Char(c)   | Append to command buffer                            |
+fn handle_command_key(key: KeyEvent, state: &mut AppState) -> Option<LoopControl> {
+    match key.code {
+        KeyCode::Esc => {
+            state.mode = Mode::Normal;
+        }
+        KeyCode::Enter => {
+            state.mode = Mode::Normal;
+            return execute_command(&state.command_buffer.clone(), state);
+        }
+        KeyCode::Backspace => {
+            state.command_buffer.pop();
+        }
+        KeyCode::Char(c) => {
+            state.command_buffer.push(c);
+        }
+        _ => {}
+    }
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn make_key(code: KeyCode) -> Option<KeyEvent> {
+        Some(KeyEvent::new(code, KeyModifiers::empty()))
+    }
+
+    fn ctrl_key(c: char) -> Option<KeyEvent> {
+        Some(KeyEvent::new(KeyCode::Char(c), KeyModifiers::CONTROL))
+    }
+
+    // --- handle_key tests ---
+
+    #[test]
+    fn handle_key_printable_appends() {
+        let mut state = AppState::new();
+        handle_key(make_key(KeyCode::Char('h')), &mut state);
+        assert_eq!(state.input, "h");
+    }
+
+    #[test]
+    fn handle_key_backspace_pops() {
+        let mut state = AppState::new();
+        state.input = "ab".to_string();
+        handle_key(make_key(KeyCode::Backspace), &mut state);
+        assert_eq!(state.input, "a");
+    }
+
+    #[test]
+    fn handle_key_backspace_empty_noop() {
+        let mut state = AppState::new();
+        handle_key(make_key(KeyCode::Backspace), &mut state);
+        assert_eq!(state.input, "");
+    }
+
+    #[test]
+    fn handle_key_enter_empty_noop() {
+        let mut state = AppState::new();
+        let result = handle_key(make_key(KeyCode::Enter), &mut state);
+        assert!(result.is_none());
+        assert!(state.messages.is_empty());
+    }
+
+    #[test]
+    fn handle_key_enter_sends_and_clears() {
+        let mut state = AppState::new();
+        state.input = "hello".to_string();
+        let result = handle_key(make_key(KeyCode::Enter), &mut state);
+        assert!(state.input.is_empty());
+        assert_eq!(state.messages.len(), 1);
+        assert!(matches!(result, Some(LoopControl::SendMessage(ref m)) if m == "hello"));
+    }
+
+    #[test]
+    fn handle_key_ctrl_c_quits() {
+        let mut state = AppState::new();
+        let result = handle_key(ctrl_key('c'), &mut state);
+        assert!(matches!(result, Some(LoopControl::Quit)));
+    }
+
+    #[test]
+    fn insert_ctrl_char_is_noop() {
+        let mut state = AppState::new();
+        handle_key(ctrl_key('a'), &mut state);
+        assert_eq!(state.input, "", "Ctrl+A should not insert 'a'");
+    }
+
+    // --- mode tests ---
+
+    #[test]
+    fn mode_starts_insert() {
+        assert_eq!(AppState::new().mode, Mode::Insert);
+    }
+
+    #[test]
+    fn insert_esc_enters_normal() {
+        let mut state = AppState::new();
+        handle_key(make_key(KeyCode::Esc), &mut state);
+        assert_eq!(state.mode, Mode::Normal);
+    }
+
+    #[test]
+    fn normal_i_enters_insert() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        handle_key(make_key(KeyCode::Char('i')), &mut state);
+        assert_eq!(state.mode, Mode::Insert);
+    }
+
+    #[test]
+    fn normal_colon_enters_command() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        handle_key(make_key(KeyCode::Char(':')), &mut state);
+        assert_eq!(state.mode, Mode::Command);
+    }
+
+    #[test]
+    fn command_esc_enters_normal() {
+        let mut state = AppState::new();
+        state.mode = Mode::Command;
+        state.command_buffer = "q".to_string();
+        handle_key(make_key(KeyCode::Esc), &mut state);
+        assert_eq!(state.mode, Mode::Normal);
+    }
+
+    #[test]
+    fn command_enter_enters_normal() {
+        let mut state = AppState::new();
+        state.mode = Mode::Command;
+        handle_key(make_key(KeyCode::Enter), &mut state);
+        assert_eq!(state.mode, Mode::Normal);
+    }
+
+    #[test]
+    fn command_chars_append_to_buffer() {
+        let mut state = AppState::new();
+        state.mode = Mode::Command;
+        handle_key(make_key(KeyCode::Char('q')), &mut state);
+        assert_eq!(state.mode, Mode::Command);
+        assert_eq!(state.command_buffer, "q");
+    }
+
+    #[test]
+    fn command_backspace_empty_stays_in_command() {
+        let mut state = AppState::new();
+        state.mode = Mode::Command;
+        state.command_buffer = "ab".to_string();
+        handle_key(make_key(KeyCode::Backspace), &mut state);
+        assert_eq!(state.command_buffer, "a");
+        handle_key(make_key(KeyCode::Backspace), &mut state);
+        assert_eq!(state.command_buffer, "");
+        handle_key(make_key(KeyCode::Backspace), &mut state);
+        assert_eq!(state.command_buffer, "");
+        handle_key(make_key(KeyCode::Backspace), &mut state);
+        assert_eq!(state.command_buffer, "");
+    }
+
+    #[test]
+    fn normal_j_increments_scroll() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        handle_key(make_key(KeyCode::Char('j')), &mut state);
+        assert_eq!(state.scroll, 1);
+    }
+
+    #[test]
+    fn normal_k_decrements_scroll() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        state.scroll = 5;
+        handle_key(make_key(KeyCode::Char('k')), &mut state);
+        assert_eq!(state.scroll, 4);
+    }
+
+    #[test]
+    fn normal_k_clamps_at_zero() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        handle_key(make_key(KeyCode::Char('k')), &mut state);
+        assert_eq!(state.scroll, 0);
+    }
+
+    #[test]
+    fn normal_big_g_scrolls_bottom() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        handle_key(make_key(KeyCode::Char('G')), &mut state);
+        assert_eq!(state.scroll, u16::MAX);
+    }
+
+    #[test]
+    fn normal_gg_scrolls_top() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        state.scroll = 50;
+        handle_key(make_key(KeyCode::Char('g')), &mut state);
+        assert_eq!(state.pending_keys, vec!['g']); // prefix, waiting
+        handle_key(make_key(KeyCode::Char('g')), &mut state);
+        assert_eq!(state.scroll, 0);
+        assert!(state.pending_keys.is_empty());
+    }
+
+    #[test]
+    fn normal_g_then_other_clears_pending() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        state.scroll = 50;
+        handle_key(make_key(KeyCode::Char('g')), &mut state);
+        handle_key(make_key(KeyCode::Char('x')), &mut state);
+        assert!(state.pending_keys.is_empty());
+        assert_eq!(state.scroll, 50); // unchanged
+    }
+
+    #[test]
+    fn ctrl_c_quits_from_any_mode() {
+        for mode in [Mode::Normal, Mode::Insert, Mode::Command] {
+            let mut state = AppState::new();
+            state.mode = mode;
+            let result = handle_key(ctrl_key('c'), &mut state);
+            assert!(matches!(result, Some(LoopControl::Quit)));
+        }
+    }
+
+    #[test]
+    fn ctrl_d_quits_from_insert() {
+        let mut state = AppState::new();
+        let result = handle_key(ctrl_key('d'), &mut state);
+        assert!(matches!(result, Some(LoopControl::Quit)));
+    }
+
+    #[test]
+    fn ctrl_d_scrolls_in_normal() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        state.viewport_height = 20;
+        let result = handle_key(ctrl_key('d'), &mut state);
+        assert!(result.is_none());
+        assert_eq!(state.scroll, 10);
+    }
+
+    #[test]
+    fn ctrl_u_scrolls_up_in_normal() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        state.viewport_height = 20;
+        state.scroll = 15;
+        let result = handle_key(ctrl_key('u'), &mut state);
+        assert!(result.is_none());
+        assert_eq!(state.scroll, 5);
+    }
+
+    #[test]
+    fn ctrl_u_clamps_at_zero() {
+        let mut state = AppState::new();
+        state.mode = Mode::Normal;
+        state.viewport_height = 20;
+        state.scroll = 3;
+        handle_key(ctrl_key('u'), &mut state);
+        assert_eq!(state.scroll, 0);
+    }
+
+    // --- execute_command tests ---
+
+    #[test]
+    fn command_quit_returns_quit() {
+        let mut state = AppState::new();
+        let result = execute_command("quit", &mut state);
+        assert!(matches!(result, Some(LoopControl::Quit)));
+    }
+
+    #[test]
+    fn command_q_returns_quit() {
+        let mut state = AppState::new();
+        let result = execute_command("q", &mut state);
+        assert!(matches!(result, Some(LoopControl::Quit)));
+    }
+
+    #[test]
+    fn command_clear_empties_messages() {
+        let mut state = AppState::new();
+        state.messages.push((Role::User, "hi".to_string()));
+        state.messages.push((Role::Assistant, "hello".to_string()));
+        state.scroll = 10;
+        let result = execute_command("clear", &mut state);
+        assert!(matches!(result, Some(LoopControl::ClearHistory)));
+        assert!(state.messages.is_empty());
+        assert_eq!(state.scroll, 0);
+    }
+
+    #[test]
+    fn command_unknown_sets_status_error() {
+        let mut state = AppState::new();
+        let result = execute_command("foo", &mut state);
+        assert!(result.is_none());
+        assert_eq!(state.status_error.as_deref(), Some("Unknown command: foo"));
+    }
+
+    #[test]
+    fn status_error_cleared_on_next_keypress() {
+        let mut state = AppState::new();
+        state.status_error = Some("some error".to_string());
+        handle_key(make_key(KeyCode::Char('h')), &mut state);
+        assert!(state.status_error.is_none());
+    }
+
+    #[test]
+    fn command_enter_executes_quit() {
+        let mut state = AppState::new();
+        state.mode = Mode::Command;
+        state.command_buffer = "q".to_string();
+        let result = handle_key(make_key(KeyCode::Enter), &mut state);
+        assert!(matches!(result, Some(LoopControl::Quit)));
+        assert_eq!(state.mode, Mode::Normal);
+    }
+}