//! Keyboard-shortcut help modal.
//!
//! Renders a static reference card as a centered overlay.
//! Any key (including `Esc`) closes the modal.

use ratatui::Frame;
use ratatui::crossterm::event::{Event, KeyCode, KeyEventKind};
use ratatui::layout::{Alignment, Rect};
use ratatui::widgets::{Block, Borders, Clear, Paragraph};

use crate::tui::state::AppState;

// ---------------------------------------------------------------------------
// Geometry helpers
// ---------------------------------------------------------------------------

/// Dialog dimensions.
const DIALOG_WIDTH: u16 = 36;
const DIALOG_HEIGHT: u16 = 36;

/// Compute a centered [`Rect`] of the given size within `area`.
fn centered_rect(width: u16, height: u16, area: Rect) -> Rect {
    let x = area.x + area.width.saturating_sub(width) / 2;
    let y = area.y + area.height.saturating_sub(height) / 2;
    Rect {
        x,
        y,
        width: width.min(area.width),
        height: height.min(area.height),
    }
}

// ---------------------------------------------------------------------------
// Static help content
// ---------------------------------------------------------------------------

const HELP_TEXT: &str = "\
 Navigation\n\
  \u{2191}/\u{2193} k/j  scroll up/dn\n\
  Spc/PgDn  page down\n\
  \u{21e7}Spc/PgUp  page up\n\
  \u{2190}/\u{2192} h/l  scroll lr\n\
  Home/gg   jump to top\n\
  End/G     jump to bottom\n\
  Tab       cycle panes\n\
  Enter     open/select\n\
  Esc       go back\n\
\n\
 Filter (sessions)\n\
  t / /     open filter\n\
  Enter     apply & close\n\
  Esc       clear input\n\
\n\
 Filter fields\n\
  model:haiku    substring\n\
  project:foo    substring\n\
  id:abc         substring\n\
  agents>0       numeric\n\
  messages<50    numeric (alias: msgs)\n\
  in>5000        input tokens\n\
  out<1000       output tokens\n\
  tokens>50000   total tokens\n\
  date>2026-01   date\n\
\n\
 Search (transcript)\n\
  t / /     open search\n\
  n / N     next/prev match\n\
  Enter     apply & close\n\
  Esc       clear & close\n\
\n\
 Global\n\
  q/Q       quit\n\
  ?         this help\n\
  c         toggle color";

// ---------------------------------------------------------------------------
// Rendering
// ---------------------------------------------------------------------------

/// Render the help overlay as a centered dialog.
pub fn render_help_modal(f: &mut Frame, area: Rect) {
    let dialog_area = centered_rect(DIALOG_WIDTH, DIALOG_HEIGHT, area);

    // Clear the background behind the dialog.
    f.render_widget(Clear, dialog_area);

    let block = Block::default()
        .title(" Keyboard Shortcuts ")
        .borders(Borders::ALL);

    let paragraph = Paragraph::new(HELP_TEXT)
        .block(block)
        .alignment(Alignment::Left);

    f.render_widget(paragraph, dialog_area);
}

// ---------------------------------------------------------------------------
// Event handling
// ---------------------------------------------------------------------------

/// Handle an event while the help modal is visible.
///
/// `Esc` closes the modal; all other keys are also consumed so the modal
/// intercepts all input while open.  Always returns `true`.
pub fn handle_help_modal_event(event: Event, state: &mut AppState) -> bool {
    let Event::Key(key) = event else {
        return true;
    };
    if key.kind != KeyEventKind::Press {
        return true;
    }

    if key.code == KeyCode::Esc {
        state.show_help = false;
    }

    true
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

#[cfg(test)]
mod tests {
    use ratatui::crossterm::event::{KeyEvent, KeyEventState, KeyModifiers};

    use super::*;

    fn press(code: KeyCode) -> Event {
        Event::Key(KeyEvent {
            code,
            modifiers: KeyModifiers::NONE,
            kind: KeyEventKind::Press,
            state: KeyEventState::NONE,
        })
    }

    fn release(code: KeyCode) -> Event {
        Event::Key(KeyEvent {
            code,
            modifiers: KeyModifiers::NONE,
            kind: KeyEventKind::Release,
            state: KeyEventState::NONE,
        })
    }

    /// `Esc` closes the help modal.
    #[test]
    fn esc_closes_help() {
        let mut state = AppState::new();
        state.show_help = true;
        let consumed = handle_help_modal_event(press(KeyCode::Esc), &mut state);
        assert!(consumed);
        assert!(!state.show_help);
    }

    /// Any other key is consumed but leaves the modal open.
    #[test]
    fn other_key_consumed_modal_stays_open() {
        let mut state = AppState::new();
        state.show_help = true;
        let consumed = handle_help_modal_event(press(KeyCode::Char('x')), &mut state);
        assert!(consumed);
        assert!(state.show_help);
    }

    /// Key-release events are consumed (modal intercepts all input).
    #[test]
    fn key_release_consumed() {
        let mut state = AppState::new();
        state.show_help = true;
        let consumed = handle_help_modal_event(release(KeyCode::Esc), &mut state);
        assert!(consumed);
        // Release does NOT close the modal.
        assert!(state.show_help);
    }

    /// Non-key events are consumed.
    #[test]
    fn non_key_event_consumed() {
        let mut state = AppState::new();
        state.show_help = true;
        let consumed = handle_help_modal_event(Event::FocusGained, &mut state);
        assert!(consumed);
    }

    /// `centered_rect` places the dialog in the middle of the area.
    #[test]
    fn centered_rect_centers_correctly() {
        let area = Rect {
            x: 0,
            y: 0,
            width: 80,
            height: 24,
        };
        let r = centered_rect(32, 14, area);
        // x = (80 - 32) / 2 = 24
        assert_eq!(r.x, 24);
        // y = (24 - 14) / 2 = 5
        assert_eq!(r.y, 5);
        assert_eq!(r.width, 32);
        assert_eq!(r.height, 14);
    }
}