//! Reserved keymap: the constants every Alloy TUI navigates by, and the
//! classifier that turns a raw key event into one of them.
//!
//! Per docs/COMPONENT-LIBRARY.md the reserved keys live in exactly one place so
//! apps match against `Action` rather than hardcoding keycodes: `Tab` /
//! `Shift-Tab` move focus, `l` / `h` move between tabs, `Enter` activates,
//! `Esc` cancels, `Ctrl-S` saves, `q` quits, `?` opens help, `/` filters, `:`
//! opens the command line.
//!
//! Tabs get `l` / `h` rather than `Tab` because `Tab` already means focus and
//! that meaning is documented across every view. Two navigation axes need two
//! keys, and the vim pair reads as horizontal movement, which is what a tab bar
//! is.
//!
//! Descended from sysop-tui's `keys.rs`, widened from that crate's six actions
//! to the full reserved set the console's form surfaces need.

use ratatui::crossterm::event::{KeyCode, KeyEvent, KeyModifiers};

/// A reserved key's meaning. `Passthrough` means the key is not reserved and
/// belongs to whatever view currently holds focus.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Action {
    NextFocus,
    PrevFocus,
    NextTab,
    PrevTab,
    Activate,
    Cancel,
    Save,
    Help,
    Quit,
    Filter,
    Command,
    Passthrough,
}

/// Classify a key event against the reserved keymap.
///
/// This is a pure classifier with no notion of mode: it reports what a key
/// *means* in the reserved map, not whether the app should honor it. Two
/// caller obligations follow from that:
///
/// - **Filter to `KeyEventKind::Press` first.** Windows terminals deliver both
///   press and release for every key, so an unfiltered event loop performs
///   each action twice.
/// - **Ignore the character actions while text entry has focus.** `q`, `/`,
///   `:`, `h`, and `l` are literal characters a user types into a field; a view
///   holding an active text input should route keys to the input and consult
///   this classifier only for `Cancel`, `Save`, and the focus movers.
///
///   `h` and `l` make this obligation sharper than it was. The earlier
///   character actions were punctuation and one letter that rarely opens a
///   word; `h` and `l` are ordinary letters that appear in almost any typed
///   value, so a view that forwards raw keys to an input without this check
///   now changes tabs mid-word rather than merely on a stray `q`.
pub fn classify(key: KeyEvent) -> Action {
    let ctrl = key.modifiers.contains(KeyModifiers::CONTROL);
    let shift = key.modifiers.contains(KeyModifiers::SHIFT);

    match key.code {
        KeyCode::Char('s' | 'S') if ctrl => Action::Save,
        KeyCode::BackTab => Action::PrevFocus,
        KeyCode::Tab if shift => Action::PrevFocus,
        KeyCode::Tab => Action::NextFocus,
        KeyCode::Char('l') => Action::NextTab,
        KeyCode::Char('h') => Action::PrevTab,
        KeyCode::Enter => Action::Activate,
        KeyCode::Esc => Action::Cancel,
        KeyCode::Char('?') => Action::Help,
        KeyCode::Char('q') => Action::Quit,
        KeyCode::Char('/') => Action::Filter,
        KeyCode::Char(':') => Action::Command,
        _ => Action::Passthrough,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn key(code: KeyCode, mods: KeyModifiers) -> KeyEvent {
        KeyEvent::new(code, mods)
    }

    #[test]
    fn ctrl_s_saves_but_bare_s_does_not() {
        assert_eq!(
            classify(key(KeyCode::Char('s'), KeyModifiers::CONTROL)),
            Action::Save
        );
        assert_eq!(
            classify(key(KeyCode::Char('s'), KeyModifiers::NONE)),
            Action::Passthrough
        );
    }

    // Terminals disagree on how they report Shift-Tab: some send BackTab with no
    // modifier, others send Tab with SHIFT. Both must reach PrevFocus, or focus
    // navigation silently becomes one-directional on half the terminal emulators
    // in the stack.
    #[test]
    fn both_shift_tab_encodings_move_focus_backward() {
        assert_eq!(
            classify(key(KeyCode::BackTab, KeyModifiers::NONE)),
            Action::PrevFocus
        );
        assert_eq!(
            classify(key(KeyCode::BackTab, KeyModifiers::SHIFT)),
            Action::PrevFocus
        );
        assert_eq!(
            classify(key(KeyCode::Tab, KeyModifiers::SHIFT)),
            Action::PrevFocus
        );
        assert_eq!(
            classify(key(KeyCode::Tab, KeyModifiers::NONE)),
            Action::NextFocus
        );
    }

    #[test]
    fn unreserved_keys_pass_through() {
        assert_eq!(
            classify(key(KeyCode::Char('j'), KeyModifiers::NONE)),
            Action::Passthrough
        );
        assert_eq!(
            classify(key(KeyCode::Down, KeyModifiers::NONE)),
            Action::Passthrough
        );
    }

    #[test]
    fn h_and_l_move_between_tabs() {
        assert_eq!(
            classify(key(KeyCode::Char('l'), KeyModifiers::NONE)),
            Action::NextTab
        );
        assert_eq!(
            classify(key(KeyCode::Char('h'), KeyModifiers::NONE)),
            Action::PrevTab
        );
    }

    // Tabs and focus are two navigation axes and must stay on separate keys.
    // docs/COMPONENT-LIBRARY.md documents Tab as focus movement across every
    // view, so a tab bar claiming Tab would silently redefine it everywhere.
    #[test]
    fn tab_key_still_means_focus_not_tabs() {
        assert_eq!(
            classify(key(KeyCode::Tab, KeyModifiers::NONE)),
            Action::NextFocus
        );
        assert_eq!(
            classify(key(KeyCode::BackTab, KeyModifiers::NONE)),
            Action::PrevFocus
        );
    }

    // j/k stay unreserved so a list cursor keeps them. Only the horizontal half
    // of the vim pair is spoken for.
    #[test]
    fn vertical_vim_keys_are_not_claimed_by_tabs() {
        assert_eq!(
            classify(key(KeyCode::Char('j'), KeyModifiers::NONE)),
            Action::Passthrough
        );
        assert_eq!(
            classify(key(KeyCode::Char('k'), KeyModifiers::NONE)),
            Action::Passthrough
        );
    }
}