//! Bindings from keys to command for Emacs and Vi modes
use std::cell::RefCell;
use std::collections::HashMap;
use std::rc::Rc;

use config::Config;
use config::EditMode;
use consts::KeyPress;
use tty::RawReader;
use super::Result;

pub type RepeatCount = usize;

#[derive(Debug, Clone, PartialEq)]
pub enum Cmd {
    Abort, // Miscellaneous Command
    AcceptLine,
    BeginningOfHistory,
    CapitalizeWord,
    ClearScreen,
    Complete,
    DowncaseWord,
    EndOfFile,
    EndOfHistory,
    ForwardSearchHistory,
    HistorySearchBackward,
    HistorySearchForward,
    Insert(RepeatCount, String),
    Interrupt,
    Kill(Movement),
    Move(Movement),
    NextHistory,
    Noop,
    PreviousHistory,
    QuotedInsert,
    Replace(RepeatCount, char),
    ReverseSearchHistory,
    SelfInsert(RepeatCount, char),
    Suspend,
    TransposeChars,
    TransposeWords(RepeatCount),
    Unknown,
    UpcaseWord,
    ViYankTo(Movement),
    Yank(RepeatCount, Anchor),
    YankPop,
}

impl Cmd {
    pub fn should_reset_kill_ring(&self) -> bool {
        match *self {
            Cmd::Kill(Movement::BackwardChar(_)) |
            Cmd::Kill(Movement::ForwardChar(_)) => true,
            Cmd::ClearScreen | Cmd::Kill(_) | Cmd::Noop | Cmd::Suspend | Cmd::Yank(_, _) |
            Cmd::YankPop => false,
            _ => true,
        }
    }

    fn is_repeatable_change(&self) -> bool {
        match *self {
            Cmd::Insert(_, _) => true,
            Cmd::Kill(_) => true,
            Cmd::Replace(_, _) => true,
            Cmd::SelfInsert(_, _) => true,
            Cmd::TransposeChars => false, // TODO Validate
            Cmd::ViYankTo(_) => true,
            Cmd::Yank(_, _) => true,
            _ => false,
        }
    }
    fn is_repeatable(&self) -> bool {
        match *self {
            Cmd::Move(_) => true,
            _ => self.is_repeatable_change(),
        }
    }

    fn redo(&self, new: Option<RepeatCount>) -> Cmd {
        match *self {
            Cmd::Insert(previous, ref text) => {
                Cmd::Insert(repeat_count(previous, new), text.clone())
            }
            Cmd::Kill(ref mvt) => Cmd::Kill(mvt.redo(new)),
            Cmd::Move(ref mvt) => Cmd::Move(mvt.redo(new)),
            Cmd::Replace(previous, c) => Cmd::Replace(repeat_count(previous, new), c),
            Cmd::SelfInsert(previous, c) => Cmd::SelfInsert(repeat_count(previous, new), c),
            //Cmd::TransposeChars => Cmd::TransposeChars,
            Cmd::ViYankTo(ref mvt) => Cmd::ViYankTo(mvt.redo(new)),
            Cmd::Yank(previous, anchor) => Cmd::Yank(repeat_count(previous, new), anchor),
            _ => unreachable!(),
        }
    }
}

fn repeat_count(previous: RepeatCount, new: Option<RepeatCount>) -> RepeatCount {
    match new {
        Some(n) => n,
        None => previous,
    }
}

#[derive(Debug, Clone, PartialEq, Copy)]
pub enum Word {
    // non-blanks characters
    Big,
    // alphanumeric characters
    Emacs,
    // alphanumeric (and '_') characters
    Vi,
}

#[derive(Debug, Clone, PartialEq, Copy)]
pub enum At {
    Start,
    BeforeEnd,
    AfterEnd,
}

#[derive(Debug, Clone, PartialEq, Copy)]
pub enum Anchor {
    After,
    Before,
}

#[derive(Debug, Clone, PartialEq)]
pub enum CharSearch {
    Forward(char),
    // until
    ForwardBefore(char),
    Backward(char),
    // until
    BackwardAfter(char),
}

impl CharSearch {
    fn opposite(&self) -> CharSearch {
        match *self {
            CharSearch::Forward(c) => CharSearch::Backward(c),
            CharSearch::ForwardBefore(c) => CharSearch::BackwardAfter(c),
            CharSearch::Backward(c) => CharSearch::Forward(c),
            CharSearch::BackwardAfter(c) => CharSearch::ForwardBefore(c),
        }
    }
}


#[derive(Debug, Clone, PartialEq)]
pub enum Movement {
    WholeLine, // not really a movement
    BeginningOfLine,
    EndOfLine,
    BackwardWord(RepeatCount, Word), // Backward until start of word
    ForwardWord(RepeatCount, At, Word), // Forward until start/end of word
    ViCharSearch(RepeatCount, CharSearch),
    ViFirstPrint,
    BackwardChar(RepeatCount),
    ForwardChar(RepeatCount),
}

impl Movement {
    fn redo(&self, new: Option<RepeatCount>) -> Movement {
        match *self {
            Movement::WholeLine => Movement::WholeLine,
            Movement::BeginningOfLine => Movement::BeginningOfLine,
            Movement::ViFirstPrint => Movement::ViFirstPrint,
            Movement::EndOfLine => Movement::EndOfLine,
            Movement::BackwardWord(previous, word) => {
                Movement::BackwardWord(repeat_count(previous, new), word)
            }
            Movement::ForwardWord(previous, at, word) => {
                Movement::ForwardWord(repeat_count(previous, new), at, word)
            }
            Movement::ViCharSearch(previous, ref char_search) => {
                Movement::ViCharSearch(repeat_count(previous, new), char_search.clone())
            }
            Movement::BackwardChar(previous) => Movement::BackwardChar(repeat_count(previous, new)),
            Movement::ForwardChar(previous) => Movement::ForwardChar(repeat_count(previous, new)),
        }
    }
}

pub struct EditState {
    mode: EditMode,
    custom_bindings: Rc<RefCell<HashMap<KeyPress, Cmd>>>,
    // Vi Command/Alternate, Insert/Input mode
    insert: bool, // vi only ?
    // numeric arguments: http://web.mit.edu/gnu/doc/html/rlman_1.html#SEC7
    num_args: i16,
    last_cmd: Cmd, // vi only
    consecutive_insert: bool,
    last_char_search: Option<CharSearch>, // vi only
}

impl EditState {
    pub fn new(config: &Config, custom_bindings: Rc<RefCell<HashMap<KeyPress, Cmd>>>) -> EditState {
        EditState {
            mode: config.edit_mode(),
            custom_bindings: custom_bindings,
            insert: true,
            num_args: 0,
            last_cmd: Cmd::Noop,
            consecutive_insert: false,
            last_char_search: None,
        }
    }

    pub fn is_emacs_mode(&self) -> bool {
        self.mode == EditMode::Emacs
    }

    pub fn next_cmd<R: RawReader>(&mut self, rdr: &mut R) -> Result<Cmd> {
        match self.mode {
            EditMode::Emacs => self.emacs(rdr),
            EditMode::Vi if self.insert => self.vi_insert(rdr),
            EditMode::Vi => self.vi_command(rdr),
        }
    }

    // TODO dynamic prompt (arg: ?)
    fn emacs_digit_argument<R: RawReader>(&mut self, rdr: &mut R, digit: char) -> Result<KeyPress> {
        match digit {
            '0'...'9' => {
                self.num_args = digit.to_digit(10).unwrap() as i16;
            }
            '-' => {
                self.num_args = -1;
            }
            _ => unreachable!(),
        }
        loop {
            let key = try!(rdr.next_key());
            match key {
                KeyPress::Char(digit @ '0'...'9') |
                KeyPress::Meta(digit @ '0'...'9') => {
                    if self.num_args == -1 {
                        self.num_args *= digit.to_digit(10).unwrap() as i16;
                    } else {
                        self.num_args = self.num_args
                            .saturating_mul(10)
                            .saturating_add(digit.to_digit(10).unwrap() as i16);
                    }
                }
                _ => return Ok(key),
            };
        }
    }

    fn emacs<R: RawReader>(&mut self, rdr: &mut R) -> Result<Cmd> {
        let mut key = try!(rdr.next_key());
        if let KeyPress::Meta(digit @ '-') = key {
            key = try!(self.emacs_digit_argument(rdr, digit));
        } else if let KeyPress::Meta(digit @ '0'...'9') = key {
            key = try!(self.emacs_digit_argument(rdr, digit));
        }
        let (n, positive) = self.emacs_num_args(); // consume them in all cases
        if let Some(cmd) = self.custom_bindings.borrow().get(&key) {
            debug!(target: "rustyline", "Custom command: {:?}", cmd);
            return Ok(if cmd.is_repeatable() {
                          cmd.redo(Some(n))
                      } else {
                          cmd.clone()
                      });
        }
        let cmd = match key {
            KeyPress::Char(c) => {
                if positive {
                    Cmd::SelfInsert(n, c)
                } else {
                    Cmd::Unknown
                }
            }
            KeyPress::Ctrl('A') => Cmd::Move(Movement::BeginningOfLine),
            KeyPress::Ctrl('B') => {
                if positive {
                    Cmd::Move(Movement::BackwardChar(n))
                } else {
                    Cmd::Move(Movement::ForwardChar(n))
                }
            }
            KeyPress::Ctrl('E') => Cmd::Move(Movement::EndOfLine),
            KeyPress::Ctrl('F') => {
                if positive {
                    Cmd::Move(Movement::ForwardChar(n))
                } else {
                    Cmd::Move(Movement::BackwardChar(n))
                }
            }
            KeyPress::Ctrl('G') |
            KeyPress::Esc => Cmd::Abort,
            KeyPress::Ctrl('H') |
            KeyPress::Backspace => {
                if positive {
                    Cmd::Kill(Movement::BackwardChar(n))
                } else {
                    Cmd::Kill(Movement::ForwardChar(n))
                }
            }
            KeyPress::Tab => Cmd::Complete,
            KeyPress::Ctrl('K') => {
                if positive {
                    Cmd::Kill(Movement::EndOfLine)
                } else {
                    Cmd::Kill(Movement::BeginningOfLine)
                }
            }
            KeyPress::Ctrl('L') => Cmd::ClearScreen,
            KeyPress::Ctrl('N') => Cmd::NextHistory,
            KeyPress::Ctrl('P') => Cmd::PreviousHistory,
            KeyPress::Meta('\x08') |
            KeyPress::Meta('\x7f') => {
                if positive {
                    Cmd::Kill(Movement::BackwardWord(n, Word::Emacs))
                } else {
                    Cmd::Kill(Movement::ForwardWord(n, At::AfterEnd, Word::Emacs))
                }
            }
            KeyPress::Meta('<') => Cmd::BeginningOfHistory,
            KeyPress::Meta('>') => Cmd::EndOfHistory,
            KeyPress::Meta('B') => {
                if positive {
                    Cmd::Move(Movement::BackwardWord(n, Word::Emacs))
                } else {
                    Cmd::Move(Movement::ForwardWord(n, At::AfterEnd, Word::Emacs))
                }
            }
            KeyPress::Meta('C') => Cmd::CapitalizeWord,
            KeyPress::Meta('D') => {
                if positive {
                    Cmd::Kill(Movement::ForwardWord(n, At::AfterEnd, Word::Emacs))
                } else {
                    Cmd::Kill(Movement::BackwardWord(n, Word::Emacs))
                }
            }
            KeyPress::Meta('F') => {
                if positive {
                    Cmd::Move(Movement::ForwardWord(n, At::AfterEnd, Word::Emacs))
                } else {
                    Cmd::Move(Movement::BackwardWord(n, Word::Emacs))
                }
            }
            KeyPress::Meta('L') => Cmd::DowncaseWord,
            KeyPress::Meta('T') => Cmd::TransposeWords(n),
            KeyPress::Meta('U') => Cmd::UpcaseWord,
            KeyPress::Meta('Y') => Cmd::YankPop,
            _ => self.common(key, n, positive),
        };
        debug!(target: "rustyline", "Emacs command: {:?}", cmd);
        Ok(cmd)
    }

    fn vi_arg_digit<R: RawReader>(&mut self, rdr: &mut R, digit: char) -> Result<KeyPress> {
        self.num_args = digit.to_digit(10).unwrap() as i16;
        loop {
            let key = try!(rdr.next_key());
            match key {
                KeyPress::Char(digit @ '0'...'9') => {
                    self.num_args = self.num_args
                        .saturating_mul(10)
                        .saturating_add(digit.to_digit(10).unwrap() as i16);
                }
                _ => return Ok(key),
            };
        }
    }

    fn vi_command<R: RawReader>(&mut self, rdr: &mut R) -> Result<Cmd> {
        let mut key = try!(rdr.next_key());
        if let KeyPress::Char(digit @ '1'...'9') = key {
            key = try!(self.vi_arg_digit(rdr, digit));
        }
        let no_num_args = self.num_args == 0;
        let n = self.vi_num_args(); // consume them in all cases
        if let Some(cmd) = self.custom_bindings.borrow().get(&key) {
            debug!(target: "rustyline", "Custom command: {:?}", cmd);
            return Ok(if cmd.is_repeatable() {
                          if no_num_args {
                              cmd.redo(None)
                          } else {
                              cmd.redo(Some(n))
                          }
                      } else {
                          cmd.clone()
                      });
        }
        let cmd = match key {
            KeyPress::Char('$') |
            KeyPress::End => Cmd::Move(Movement::EndOfLine),
            KeyPress::Char('.') => { // vi-redo
                if no_num_args {
                    self.last_cmd.redo(None)
                } else {
                    self.last_cmd.redo(Some(n))
                }
            },
            // TODO KeyPress::Char('%') => Cmd::???, Move to the corresponding opening/closing bracket
            KeyPress::Char('0') => Cmd::Move(Movement::BeginningOfLine),
            KeyPress::Char('^') => Cmd::Move(Movement::ViFirstPrint),
            KeyPress::Char('a') => {
                // vi-append-mode: Vi enter insert mode after the cursor.
                self.insert = true;
                Cmd::Move(Movement::ForwardChar(n))
            }
            KeyPress::Char('A') => {
                // vi-append-eol: Vi enter insert mode at end of line.
                self.insert = true;
                Cmd::Move(Movement::EndOfLine)
            }
            KeyPress::Char('b') => Cmd::Move(Movement::BackwardWord(n, Word::Vi)), // vi-prev-word
            KeyPress::Char('B') => Cmd::Move(Movement::BackwardWord(n, Word::Big)),
            KeyPress::Char('c') => {
                self.insert = true;
                match try!(self.vi_cmd_motion(rdr, key, n)) {
                    Some(mvt) => Cmd::Kill(mvt),
                    None => Cmd::Unknown,
                }
            }
            KeyPress::Char('C') => {
                self.insert = true;
                Cmd::Kill(Movement::EndOfLine)
            }
            KeyPress::Char('d') => {
                match try!(self.vi_cmd_motion(rdr, key, n)) {
                    Some(mvt) => Cmd::Kill(mvt),
                    None => Cmd::Unknown,
                }
            }
            KeyPress::Char('D') |
            KeyPress::Ctrl('K') => Cmd::Kill(Movement::EndOfLine),
            KeyPress::Char('e') => Cmd::Move(Movement::ForwardWord(n, At::BeforeEnd, Word::Vi)),
            KeyPress::Char('E') => Cmd::Move(Movement::ForwardWord(n, At::BeforeEnd, Word::Big)),
            KeyPress::Char('i') => {
                // vi-insertion-mode
                self.insert = true;
                Cmd::Noop
            }
            KeyPress::Char('I') => {
                // vi-insert-beg
                self.insert = true;
                Cmd::Move(Movement::BeginningOfLine)
            }
            KeyPress::Char(c) if c == 'f' || c == 'F' || c == 't' || c == 'T' => {
                // vi-char-search
                let cs = try!(self.vi_char_search(rdr, c));
                match cs {
                    Some(cs) => Cmd::Move(Movement::ViCharSearch(n, cs)),
                    None => Cmd::Unknown,
                }
            }
            KeyPress::Char(';') => {
                match self.last_char_search {
                    Some(ref cs) => Cmd::Move(Movement::ViCharSearch(n, cs.clone())),
                    None => Cmd::Noop,
                }
            }
            KeyPress::Char(',') => {
                match self.last_char_search {
                    Some(ref cs) => Cmd::Move(Movement::ViCharSearch(n, cs.opposite())),
                    None => Cmd::Noop,
                }
            }
            // TODO KeyPress::Char('G') => Cmd::???, Move to the history line n
            KeyPress::Char('p') => Cmd::Yank(n, Anchor::After), // vi-put
            KeyPress::Char('P') => Cmd::Yank(n, Anchor::Before), // vi-put
            KeyPress::Char('r') => {
                // vi-replace-char: Vi replace character under the cursor with the next character typed.
                let ch = try!(rdr.next_key());
                match ch {
                    KeyPress::Char(c) => Cmd::Replace(n, c),
                    KeyPress::Esc => Cmd::Noop,
                    _ => Cmd::Unknown,
                }
            }
            // TODO KeyPress::Char('R') => Cmd::???, vi-replace-mode: Vi enter replace mode. Replaces characters under the cursor. (overwrite-mode)
            KeyPress::Char('s') => {
                // vi-substitute-char: Vi replace character under the cursor and enter insert mode.
                self.insert = true;
                Cmd::Kill(Movement::ForwardChar(n))
            }
            KeyPress::Char('S') => {
                // vi-substitute-line: Vi substitute entire line.
                self.insert = true;
                Cmd::Kill(Movement::WholeLine)
            }
            // KeyPress::Char('U') => Cmd::???, // revert-line
            KeyPress::Char('w') => Cmd::Move(Movement::ForwardWord(n, At::Start, Word::Vi)), // vi-next-word
            KeyPress::Char('W') => Cmd::Move(Movement::ForwardWord(n, At::Start, Word::Big)), // vi-next-word
            KeyPress::Char('x') => Cmd::Kill(Movement::ForwardChar(n)), // vi-delete: TODO move backward if eol
            KeyPress::Char('X') => Cmd::Kill(Movement::BackwardChar(n)), // vi-rubout
            KeyPress::Char('y') => {
                match try!(self.vi_cmd_motion(rdr, key, n)) {
                    Some(mvt) => Cmd::ViYankTo(mvt),
                    None => Cmd::Unknown,
                }
            }
            // KeyPress::Char('Y') => Cmd::???, // vi-yank-to
            KeyPress::Char('h') |
            KeyPress::Ctrl('H') |
            KeyPress::Backspace => Cmd::Move(Movement::BackwardChar(n)),
            KeyPress::Ctrl('G') => Cmd::Abort,
            KeyPress::Char('l') |
            KeyPress::Char(' ') => Cmd::Move(Movement::ForwardChar(n)),
            KeyPress::Ctrl('L') => Cmd::ClearScreen,
            KeyPress::Char('+') |
            KeyPress::Char('j') | // TODO: move to the start of the line.
            KeyPress::Ctrl('N') => Cmd::NextHistory,
            KeyPress::Char('-') |
            KeyPress::Char('k') | // TODO: move to the start of the line.
            KeyPress::Ctrl('P') => Cmd::PreviousHistory,
            KeyPress::Ctrl('R') => {
                self.insert = true; // TODO Validate
                Cmd::ReverseSearchHistory
            }
            KeyPress::Ctrl('S') => {
                self.insert = true; // TODO Validate
                Cmd::ForwardSearchHistory
            }
            KeyPress::Esc => Cmd::Noop,
            _ => self.common(key, n, true),
        };
        debug!(target: "rustyline", "Vi command: {:?}", cmd);
        if cmd.is_repeatable_change() {
            self.update_last_cmd(cmd.clone());
        }
        Ok(cmd)
    }

    fn vi_insert<R: RawReader>(&mut self, rdr: &mut R) -> Result<Cmd> {
        let key = try!(rdr.next_key());
        if let Some(cmd) = self.custom_bindings.borrow().get(&key) {
            debug!(target: "rustyline", "Custom command: {:?}", cmd);
            return Ok(if cmd.is_repeatable() {
                          cmd.redo(None)
                      } else {
                          cmd.clone()
                      });
        }
        let cmd = match key {
            KeyPress::Char(c) => Cmd::SelfInsert(1, c),
            KeyPress::Ctrl('H') |
            KeyPress::Backspace => Cmd::Kill(Movement::BackwardChar(1)),
            KeyPress::Tab => Cmd::Complete,
            KeyPress::Esc => {
                // vi-movement-mode/vi-command-mode: Vi enter command mode (use alternative key bindings).
                self.insert = false;
                Cmd::Move(Movement::BackwardChar(1))
            }
            _ => self.common(key, 1, true),
        };
        debug!(target: "rustyline", "Vi insert: {:?}", cmd);
        if cmd.is_repeatable_change() {
            self.update_last_cmd(cmd.clone());
        }
        self.consecutive_insert = match cmd {
            Cmd::SelfInsert(_, _) => true,
            _ => false,
        };
        Ok(cmd)
    }

    fn vi_cmd_motion<R: RawReader>(&mut self,
                                   rdr: &mut R,
                                   key: KeyPress,
                                   n: RepeatCount)
                                   -> Result<Option<Movement>> {
        let mut mvt = try!(rdr.next_key());
        if mvt == key {
            return Ok(Some(Movement::WholeLine));
        }
        let mut n = n;
        if let KeyPress::Char(digit @ '1'...'9') = mvt {
            // vi-arg-digit
            mvt = try!(self.vi_arg_digit(rdr, digit));
            n = self.vi_num_args().saturating_mul(n);
        }
        Ok(match mvt {
               KeyPress::Char('$') => Some(Movement::EndOfLine), // vi-change-to-eol: Vi change to end of line.
               KeyPress::Char('0') => Some(Movement::BeginningOfLine), // vi-kill-line-prev: Vi cut from beginning of line to cursor.
               KeyPress::Char('^') => Some(Movement::ViFirstPrint),
               KeyPress::Char('b') => Some(Movement::BackwardWord(n, Word::Vi)),
               KeyPress::Char('B') => Some(Movement::BackwardWord(n, Word::Big)),
               KeyPress::Char('e') => Some(Movement::ForwardWord(n, At::AfterEnd, Word::Vi)),
               KeyPress::Char('E') => Some(Movement::ForwardWord(n, At::AfterEnd, Word::Big)),
               KeyPress::Char(c) if c == 'f' || c == 'F' || c == 't' || c == 'T' => {
            let cs = try!(self.vi_char_search(rdr, c));
            match cs {
                Some(cs) => Some(Movement::ViCharSearch(n, cs)),
                None => None,
            }
        }
               KeyPress::Char(';') => {
                   match self.last_char_search {
                       Some(ref cs) => Some(Movement::ViCharSearch(n, cs.clone())),
                       None => None,
                   }
               }
               KeyPress::Char(',') => {
                   match self.last_char_search {
                       Some(ref cs) => Some(Movement::ViCharSearch(n, cs.opposite())),
                       None => None,
                   }
               }
               KeyPress::Char('h') |
               KeyPress::Ctrl('H') |
               KeyPress::Backspace => Some(Movement::BackwardChar(n)), // vi-delete-prev-char: Vi move to previous character (backspace).
               KeyPress::Char('l') |
               KeyPress::Char(' ') => Some(Movement::ForwardChar(n)),
               KeyPress::Char('w') => {
            // 'cw' is 'ce'
            if key == KeyPress::Char('c') {
                Some(Movement::ForwardWord(n, At::AfterEnd, Word::Vi))
            } else {
                Some(Movement::ForwardWord(n, At::Start, Word::Vi))
            }
        }
               KeyPress::Char('W') => {
            // 'cW' is 'cE'
            if key == KeyPress::Char('c') {
                Some(Movement::ForwardWord(n, At::AfterEnd, Word::Big))
            } else {
                Some(Movement::ForwardWord(n, At::Start, Word::Big))
            }
        }
               _ => None,
           })
    }

    fn vi_char_search<R: RawReader>(&mut self,
                                    rdr: &mut R,
                                    cmd: char)
                                    -> Result<Option<CharSearch>> {
        let ch = try!(rdr.next_key());
        Ok(match ch {
               KeyPress::Char(ch) => {
            let cs = match cmd {
                'f' => CharSearch::Forward(ch),
                't' => CharSearch::ForwardBefore(ch),
                'F' => CharSearch::Backward(ch),
                'T' => CharSearch::BackwardAfter(ch),
                _ => unreachable!(),
            };
            self.last_char_search = Some(cs.clone());
            Some(cs)
        }
               _ => None,
           })
    }

    fn common(&mut self, key: KeyPress, n: RepeatCount, positive: bool) -> Cmd {
        match key {
            KeyPress::Home => Cmd::Move(Movement::BeginningOfLine),
            KeyPress::Left => {
                if positive {
                    Cmd::Move(Movement::BackwardChar(n))
                } else {
                    Cmd::Move(Movement::ForwardChar(n))
                }
            }
            KeyPress::Ctrl('C') => Cmd::Interrupt,
            KeyPress::Ctrl('D') => Cmd::EndOfFile,
            KeyPress::Delete => {
                if positive {
                    Cmd::Kill(Movement::ForwardChar(n))
                } else {
                    Cmd::Kill(Movement::BackwardChar(n))
                }
            }
            KeyPress::End => Cmd::Move(Movement::EndOfLine),
            KeyPress::Right => {
                if positive {
                    Cmd::Move(Movement::ForwardChar(n))
                } else {
                    Cmd::Move(Movement::BackwardChar(n))
                }
            }
            KeyPress::Ctrl('J') |
            KeyPress::Enter => Cmd::AcceptLine,
            KeyPress::Down => Cmd::NextHistory,
            KeyPress::Up => Cmd::PreviousHistory,
            KeyPress::Ctrl('R') => Cmd::ReverseSearchHistory,
            KeyPress::Ctrl('S') => Cmd::ForwardSearchHistory, // most terminals override Ctrl+S to suspend execution
            KeyPress::Ctrl('T') => Cmd::TransposeChars,
            KeyPress::Ctrl('U') => {
                if positive {
                Cmd::Kill(Movement::BeginningOfLine)
                } else {
                Cmd::Kill(Movement::EndOfLine)
                }
            },
            KeyPress::Ctrl('Q') | // most terminals override Ctrl+Q to resume execution
            KeyPress::Ctrl('V') => Cmd::QuotedInsert,
            KeyPress::Ctrl('W') => {
                if positive {
                    Cmd::Kill(Movement::BackwardWord(n, Word::Big))
                } else {
                    Cmd::Kill(Movement::ForwardWord(n, At::AfterEnd, Word::Big))
                }
            }
            KeyPress::Ctrl('Y') => {
                if positive {
                    Cmd::Yank(n, Anchor::Before)
                } else {
                    Cmd::Unknown // TODO Validate
                }
            }
            KeyPress::Ctrl('Z') => Cmd::Suspend,
            KeyPress::UnknownEscSeq => Cmd::Noop,
            _ => Cmd::Unknown,
        }
    }

    fn num_args(&mut self) -> i16 {
        let num_args = match self.num_args {
            0 => 1,
            _ => self.num_args,
        };
        self.num_args = 0;
        num_args
    }

    fn emacs_num_args(&mut self) -> (RepeatCount, bool) {
        let num_args = self.num_args();
        if num_args < 0 {
            if let (n, false) = num_args.overflowing_abs() {
                (n as RepeatCount, false)
            } else {
                (RepeatCount::max_value(), false)
            }
        } else {
            (num_args as RepeatCount, true)
        }
    }

    fn vi_num_args(&mut self) -> RepeatCount {
        let num_args = self.num_args();
        if num_args < 0 {
            unreachable!()
        } else {
            num_args.abs() as RepeatCount
        }
    }

    fn update_last_cmd(&mut self, new: Cmd) {
        // consecutive char inserts are repeatable not only the last one...
        if !self.consecutive_insert {
            self.last_cmd = new;
        } else if let Cmd::SelfInsert(_, c) = new {
            match self.last_cmd {
                Cmd::SelfInsert(_, pc) => {
                    let mut text = String::new();
                    text.push(pc);
                    text.push(c);
                    self.last_cmd = Cmd::Insert(1, text);
                }
                Cmd::Insert(_, ref mut text) => {
                    text.push(c);
                }
                _ => self.last_cmd = new,
            }
        } else {
            self.last_cmd = new;
        }
    }
}