//! The one binding table.
//!
//! Every app key lives here, once: the which-key popup renders this table, the
//! footer hint summarises it, and `ui::run_act` dispatches it. A binding that
//! is not in the table cannot be pressed, and one that is in it is documented
//! for free — which is what stops the keymap drifting apart again.
//!
//! # The rule the whole model rests on
//!
//! **Unprefixed keys belong to the embedded `claude`. Always.** There is no
//! focus model, no ctrl-↑/ctrl-↓ dance and no "is this key mine?" question:
//! `q`, `j` and Esc reach Claude Code because nothing else can claim them.
//! Everything cloak owns sits behind [`Prefix`], tmux-style. Two exceptions,
//! both of which a real terminal also keeps for itself rather than forwarding:
//! the **wheel** and **shift**+PgUp/PgDn.
//!
//! Esc is the one key with a rule of its own, and it is a rule about
//! reachability, not about modes: *Esc closes the topmost overlay; with nothing
//! open it goes to the child.* Claude Code uses Esc to interrupt and Esc-Esc to
//! rewind, so eating it unconditionally would break both. View state (a filter
//! set, the lane the feed shows) is deliberately **not** escapable — it is a
//! setting, not a mode, and resetting it on a stray Esc would be a surprise
//! rather than a rescue.

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

/// Something a key does. `Copy`, so dispatch can match on it after the table
/// borrow ends.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum Act {
    /// Session picker overlay (also the home of the turn tree and `b`ranching).
    Sessions,
    /// Stream picker overlay: the main chain, every subagent, every nested
    /// server-tool call. Picking one points the feed at that lane.
    Streams,
    /// Model picker → spawn a brand-new `claude --session-id …`.
    NewSession,
    /// Attach the pane to the most recent past session (`claude -c`).
    Continue,
    /// Entry-kind filter strip.
    Filter,
    /// Incremental search over the displayed lane.
    Search,
    /// Jump the feed to the next / previous user prompt. Repeatable: the menu
    /// stays open so `]]]` walks.
    NextPrompt,
    PrevPrompt,
    /// Pane fullscreen. Esc still reaches the child there — it is nothing *but*
    /// the pane, so nothing is covering it.
    ZoomPane,
    /// Hide the pane, feed takes the screen. This *does* cover the pane, so Esc
    /// leaves it.
    ZoomFeed,
    /// Back to the live main chain of the pane's session, tailing it. Undoes
    /// every kind of pinning at once — a picked session, a picked lane, and a
    /// scroll position parked by a search or a prompt jump.
    FollowLive,
    Reload,
    Quit,
}

impl Act {
    /// Whether the popup marks this entry as leading somewhere — an overlay
    /// that takes over input. Purely cosmetic (`▸`).
    pub fn opens(self) -> bool {
        matches!(
            self,
            Act::Sessions | Act::Streams | Act::NewSession | Act::Filter | Act::Search
        )
    }

    /// Repeatable actions keep the menu up, so the key can be pressed again
    /// without re-pressing the prefix. Everything else closes it.
    pub fn sticky(self) -> bool {
        matches!(self, Act::NextPrompt | Act::PrevPrompt)
    }
}

#[derive(Debug)]
pub struct Bind {
    pub key: char,
    pub label: &'static str,
    pub act: Act,
}

/// A menu level. There is one today (`ROOT`); the type exists because the
/// popup renders *a* level and `EmbedUi::menu` holds the open one, not because
/// nesting is planned. A submenu earns its place when a group of keys is both
/// large and rarely used, and no group is either right now.
#[derive(Debug)]
pub struct Menu {
    pub title: &'static str,
    pub binds: &'static [Bind],
}

impl Menu {
    pub fn find(&self, c: char) -> Option<&Bind> {
        self.binds.iter().find(|b| b.key == c)
    }
}

/// The root menu, in reading order. The popup lays it out in columns.
pub static ROOT: Menu = Menu {
    title: "",
    binds: &[
        Bind { key: 's', label: "sessions", act: Act::Sessions },
        Bind { key: 'a', label: "streams", act: Act::Streams },
        Bind { key: 'n', label: "new", act: Act::NewSession },
        Bind { key: 'c', label: "continue", act: Act::Continue },
        Bind { key: 'f', label: "filter", act: Act::Filter },
        Bind { key: '/', label: "search", act: Act::Search },
        Bind { key: ']', label: "next prompt", act: Act::NextPrompt },
        Bind { key: '[', label: "prev prompt", act: Act::PrevPrompt },
        Bind { key: '.', label: "follow live", act: Act::FollowLive },
        Bind { key: 'z', label: "zoom pane", act: Act::ZoomPane },
        Bind { key: 'Z', label: "zoom feed", act: Act::ZoomFeed },
        Bind { key: 'r', label: "reload", act: Act::Reload },
        Bind { key: 'q', label: "quit", act: Act::Quit },
    ],
};

// ---------------------------------------------------------------------------
// The prefix
// ---------------------------------------------------------------------------

/// The one key that opens the menu. Configurable because the *only* hard
/// requirement is that the embedded Claude Code does not want it, and that is
/// a property of the child's version, not of ours — so it must be changeable
/// without a rebuild. `CT_PREFIX=ctrl-b`, `CT_PREFIX=ctrl-]`, `CT_PREFIX=f1`.
///
/// Default `ctrl-space`. Terminals disagree about what ctrl-space *is* on the
/// wire (NUL, ctrl-`@`, or a real ctrl-modified space), so that one spelling
/// matches all three — see `matches`. `CT_DEBUG_KEYS=1` shows what actually
/// arrives when a terminal delivers none of them.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Prefix {
    code: KeyCode,
    mods: KeyModifiers,
    /// True for the ctrl-space default, which needs the three-way match.
    ctrl_space: bool,
    pub label: String,
}

impl Default for Prefix {
    fn default() -> Self {
        Self::parse("ctrl-space").expect("the default prefix parses")
    }
}

impl Prefix {
    /// Read `CT_PREFIX`, falling back to the default on an unset or
    /// unparseable value (a typo must not leave the app with no menu key).
    pub fn from_env() -> Self {
        std::env::var("CT_PREFIX")
            .ok()
            .and_then(|s| Self::parse(&s))
            .unwrap_or_default()
    }

    pub fn parse(spec: &str) -> Option<Self> {
        let spec = spec.trim();
        let mut mods = KeyModifiers::NONE;
        let mut rest = spec;
        loop {
            let lower = rest.to_ascii_lowercase();
            let (m, tail) = if let Some(t) = lower.strip_prefix("ctrl-") {
                (KeyModifiers::CONTROL, t.len())
            } else if let Some(t) = lower.strip_prefix("shift-") {
                (KeyModifiers::SHIFT, t.len())
            } else if let Some(t) = lower.strip_prefix("alt-") {
                (KeyModifiers::ALT, t.len())
            } else {
                break;
            };
            mods |= m;
            rest = &rest[rest.len() - tail..];
        }
        let low = rest.to_ascii_lowercase();
        let code = match low.as_str() {
            "space" => KeyCode::Char(' '),
            "tab" => KeyCode::Tab,
            "esc" => KeyCode::Esc,
            f if f.starts_with('f') && f[1..].parse::<u8>().is_ok() => {
                KeyCode::F(f[1..].parse().ok()?)
            }
            _ => {
                let mut it = rest.chars();
                let c = it.next()?;
                if it.next().is_some() {
                    return None;
                }
                KeyCode::Char(c.to_ascii_lowercase())
            }
        };
        let ctrl_space = code == KeyCode::Char(' ') && mods.contains(KeyModifiers::CONTROL);
        Some(Self {
            code,
            mods,
            ctrl_space,
            label: pretty(mods, code),
        })
    }

    /// Does this event open the menu?
    ///
    /// ctrl-space is three events depending on the terminal: `Char(' ')` with
    /// CONTROL, `Char('@')` with CONTROL (the NUL byte decoded as its caret
    /// spelling), and a bare `Null`. All three mean the same keypress, so all
    /// three count.
    pub fn matches(&self, k: &KeyEvent) -> bool {
        if self.ctrl_space {
            let ctrl = k.modifiers.contains(KeyModifiers::CONTROL);
            return k.code == KeyCode::Null
                || (ctrl && matches!(k.code, KeyCode::Char(' ') | KeyCode::Char('@')));
        }
        // Compare only the modifiers the spec named: terminals add SHIFT of
        // their own accord for capitals and for some ctrl combinations.
        let want = self.mods & (KeyModifiers::CONTROL | KeyModifiers::ALT);
        let got = k.modifiers & (KeyModifiers::CONTROL | KeyModifiers::ALT);
        let code = match k.code {
            KeyCode::Char(c) => KeyCode::Char(c.to_ascii_lowercase()),
            other => other,
        };
        code == self.code && got == want
    }
}

fn pretty(mods: KeyModifiers, code: KeyCode) -> String {
    let mut s = String::new();
    if mods.contains(KeyModifiers::CONTROL) {
        s.push('^');
    }
    if mods.contains(KeyModifiers::ALT) {
        s.push_str("alt-");
    }
    match code {
        KeyCode::Char(' ') => s.push_str("space"),
        KeyCode::Char(c) => s.push(c),
        KeyCode::Tab => s.push_str("tab"),
        KeyCode::Esc => s.push_str("esc"),
        KeyCode::F(n) => s.push_str(&format!("F{n}")),
        other => s.push_str(&format!("{other:?}")),
    }
    s
}

#[cfg(test)]
mod tests {
    use super::*;
    use ratatui::crossterm::event::KeyEventKind;

    fn ev(code: KeyCode, mods: KeyModifiers) -> KeyEvent {
        KeyEvent {
            code,
            modifiers: mods,
            kind: KeyEventKind::Press,
            state: ratatui::crossterm::event::KeyEventState::NONE,
        }
    }

    /// The default has to survive all three ways a terminal spells ctrl-space,
    /// because we cannot know which one the user's terminal picks.
    #[test]
    fn ctrl_space_matches_every_spelling_terminals_use() {
        let p = Prefix::default();
        assert!(p.matches(&ev(KeyCode::Char(' '), KeyModifiers::CONTROL)));
        assert!(p.matches(&ev(KeyCode::Char('@'), KeyModifiers::CONTROL)));
        assert!(p.matches(&ev(KeyCode::Null, KeyModifiers::NONE)));
        assert!(!p.matches(&ev(KeyCode::Char(' '), KeyModifiers::NONE)), "plain space is the child's");
        assert_eq!(p.label, "^space");
    }

    #[test]
    fn prefix_specs_parse_and_reject() {
        let p = Prefix::parse("ctrl-b").unwrap();
        assert!(p.matches(&ev(KeyCode::Char('b'), KeyModifiers::CONTROL)));
        assert!(!p.matches(&ev(KeyCode::Char('b'), KeyModifiers::NONE)));
        assert_eq!(p.label, "^b");
        assert!(Prefix::parse("f1").unwrap().matches(&ev(KeyCode::F(1), KeyModifiers::NONE)));
        assert!(Prefix::parse("ctrl-]").unwrap().matches(&ev(KeyCode::Char(']'), KeyModifiers::CONTROL)));
        assert!(Prefix::parse("").is_none());
        assert!(Prefix::parse("ctrl-nope").is_none());
    }

    /// Every key in the table is unique per menu, or one of them is dead.
    #[test]
    fn no_menu_binds_a_key_twice() {
        fn check(m: &Menu) {
            let mut seen = Vec::new();
            for b in m.binds {
                assert!(!seen.contains(&b.key), "{} binds {:?} twice", m.title, b.key);
                seen.push(b.key);
            }
        }
        check(&ROOT);
    }
}