use crate::*;

pub struct KeyMatcher {
    valid: bool,
    key:   Option<KeyCode>,
    mods:  KeyModifiers,
}

impl KeyMatcher {
    pub fn new (token: impl AsRef<str>) -> Self {
        let token = token.as_ref();
        if token.len() < 2 {
            Self { valid: false, key: None, mods: KeyModifiers::NONE }
        } else if token.chars().next() != Some('@') {
            Self { valid: false, key: None, mods: KeyModifiers::NONE }
        } else {
            Self { valid: true, key: None, mods: KeyModifiers::NONE }.next(&token[1..])
        }
    }
    pub fn build (self) -> Option<Event> {
        if self.valid && self.key.is_some() {
            Some(Event::Key(KeyEvent::new(self.key.unwrap(), self.mods)))
        } else {
            None
        }
    }
    fn next (mut self, token: &str) -> Self {
        let mut tokens = token.split('-').peekable();
        while let Some(token) = tokens.next() {
            if tokens.peek().is_some() {
                match token {
                    "ctrl"  | "Ctrl"  | "c" | "C" => self.mods |= KeyModifiers::CONTROL,
                    "alt"   | "Alt"   | "m" | "M" => self.mods |= KeyModifiers::ALT,
                    "shift" | "Shift" | "s" | "S" => {
                        self.mods |= KeyModifiers::SHIFT;
                        // + TODO normalize character case, BackTab, etc.
                    },
                    _ => panic!("unknown modifier {token}"),
                }
            } else {
                self.key = if token.len() == 1 {
                    Some(KeyCode::Char(token.chars().next().unwrap()))
                } else {
                    Some(Self::named_key(token).unwrap_or_else(||panic!("unknown character {token}")))
                }
            }
        }
        self
    }
    fn named_key (token: &str) -> Option<KeyCode> {
        use KeyCode::*;
        Some(match token {
            "up"                => Up,
            "down"              => Down,
            "left"              => Left,
            "right"             => Right,
            "esc"    | "escape" => Esc,
            "enter"  | "return" => Enter,
            "delete" | "del"    => Delete,
            "tab"               => Tab,
            "space"             => Char(' '),
            "comma"             => Char(','),
            "period"            => Char('.'),
            "plus"              => Char('+'),
            "minus" | "dash"    => Char('-'),
            "equal" | "equals"  => Char('='),
            "underscore"        => Char('_'),
            "backtick"          => Char('`'),
            "lt"                => Char('<'),
            "gt"                => Char('>'),
            "openbracket"       => Char('['),
            "closebracket"      => Char(']'),
            "pgup" | "pageup"   => PageUp,
            "pgdn" | "pagedown" => PageDown, 
            "f1"                => F(1),
            "f2"                => F(2),
            "f3"                => F(3),
            "f4"                => F(4),
            "f5"                => F(5),
            "f6"                => F(6),
            "f7"                => F(7),
            "f8"                => F(8),
            "f9"                => F(9),
            "f10"               => F(10),
            "f11"               => F(11),
            "f12"               => F(12),
            _ => return None,
        })
    }
}