mprocs-vt100 0.1.1

use crate::term::BufWrite as _;
use unicode_width::UnicodeWidthChar as _;

const MODE_APPLICATION_KEYPAD: u8 = 0b0000_0001;
const MODE_APPLICATION_CURSOR: u8 = 0b0000_0010;
const MODE_HIDE_CURSOR: u8 = 0b0000_0100;
const MODE_ALTERNATE_SCREEN: u8 = 0b0000_1000;
const MODE_BRACKETED_PASTE: u8 = 0b0001_0000;

/// The xterm mouse handling mode currently in use.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum MouseProtocolMode {
  /// Mouse handling is disabled.
  None,

  /// Mouse button events should be reported on button press. Also known as
  /// X10 mouse mode.
  Press,

  /// Mouse button events should be reported on button press and release.
  /// Also known as VT200 mouse mode.
  PressRelease,

  // Highlight,
  /// Mouse button events should be reported on button press and release, as
  /// well as when the mouse moves between cells while a button is held
  /// down.
  ButtonMotion,

  /// Mouse button events should be reported on button press and release,
  /// and mouse motion events should be reported when the mouse moves
  /// between cells regardless of whether a button is held down or not.
  AnyMotion,
  // DecLocator,
}

impl Default for MouseProtocolMode {
  fn default() -> Self {
    Self::None
  }
}

/// The encoding to use for the enabled `MouseProtocolMode`.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum MouseProtocolEncoding {
  /// Default single-printable-byte encoding.
  Default,

  /// UTF-8-based encoding.
  Utf8,

  /// SGR-like encoding.
  Sgr,
  // Urxvt,
}

impl Default for MouseProtocolEncoding {
  fn default() -> Self {
    Self::Default
  }
}

/// Represents the overall terminal state.
#[derive(Clone, Debug)]
pub struct Screen {
  grid: crate::grid::Grid,
  alternate_grid: crate::grid::Grid,

  attrs: crate::attrs::Attrs,
  saved_attrs: crate::attrs::Attrs,

  title: String,
  icon_name: String,

  modes: u8,
  mouse_protocol_mode: MouseProtocolMode,
  mouse_protocol_encoding: MouseProtocolEncoding,

  audible_bell_count: usize,
  visual_bell_count: usize,

  errors: usize,
}

impl Screen {
  pub fn get_selected_text(
    &self,
    low_x: i32,
    low_y: i32,
    high_x: i32,
    high_y: i32,
  ) -> String {
    self.grid().get_selected_text(low_x, low_y, high_x, high_y)
  }

  pub(crate) fn new(size: crate::grid::Size, scrollback_len: usize) -> Self {
    let mut grid = crate::grid::Grid::new(size, scrollback_len);
    grid.allocate_rows();
    Self {
      grid,
      alternate_grid: crate::grid::Grid::new(size, 0),

      attrs: crate::attrs::Attrs::default(),
      saved_attrs: crate::attrs::Attrs::default(),

      title: String::default(),
      icon_name: String::default(),

      modes: 0,
      mouse_protocol_mode: MouseProtocolMode::default(),
      mouse_protocol_encoding: MouseProtocolEncoding::default(),

      audible_bell_count: 0,
      visual_bell_count: 0,

      errors: 0,
    }
  }

  pub(crate) fn set_size(&mut self, rows: u16, cols: u16) {
    self.grid.set_size(crate::grid::Size { rows, cols });
    self
      .alternate_grid
      .set_size(crate::grid::Size { rows, cols });
  }

  /// Returns the current size of the terminal.
  ///
  /// The return value will be (rows, cols).
  #[must_use]
  pub fn size(&self) -> (u16, u16) {
    let size = self.grid().size();
    (size.rows, size.cols)
  }

  /// Returns the current position in the scrollback.
  ///
  /// This position indicates the offset from the top of the screen, and is
  /// `0` when the normal screen is in view.
  #[must_use]
  pub fn scrollback(&self) -> usize {
    self.grid().scrollback()
  }

  pub fn scrollback_len(&self) -> usize {
    self.grid().scrollback_len()
  }

  pub fn set_scrollback(&mut self, rows: usize) {
    self.grid_mut().set_scrollback(rows);
  }

  /// Returns the text contents of the terminal.
  ///
  /// This will not include any formatting information, and will be in plain
  /// text format.
  #[must_use]
  pub fn contents(&self) -> String {
    let mut contents = String::new();
    self.write_contents(&mut contents);
    contents
  }

  fn write_contents(&self, contents: &mut String) {
    self.grid().write_contents(contents);
  }

  /// Returns the text contents of the terminal by row, restricted to the
  /// given subset of columns.
  ///
  /// This will not include any formatting information, and will be in plain
  /// text format.
  ///
  /// Newlines will not be included.
  pub fn rows(
    &self,
    start: u16,
    width: u16,
  ) -> impl Iterator<Item = String> + '_ {
    self.grid().visible_rows().map(move |row| {
      let mut contents = String::new();
      row.write_contents(&mut contents, start, width, false);
      contents
    })
  }

  /// Returns the text contents of the terminal logically between two cells.
  /// This will include the remainder of the starting row after `start_col`,
  /// followed by the entire contents of the rows between `start_row` and
  /// `end_row`, followed by the beginning of the `end_row` up until
  /// `end_col`. This is useful for things like determining the contents of
  /// a clipboard selection.
  #[must_use]
  pub fn contents_between(
    &self,
    start_row: u16,
    start_col: u16,
    end_row: u16,
    end_col: u16,
  ) -> String {
    match start_row.cmp(&end_row) {
      std::cmp::Ordering::Less => {
        let (_, cols) = self.size();
        let mut contents = String::new();
        for (i, row) in self
          .grid()
          .visible_rows()
          .enumerate()
          .skip(usize::from(start_row))
          .take(usize::from(end_row) - usize::from(start_row) + 1)
        {
          if i == usize::from(start_row) {
            row.write_contents(
              &mut contents,
              start_col,
              cols - start_col,
              false,
            );
            if !row.wrapped() {
              contents.push('\n');
            }
          } else if i == usize::from(end_row) {
            row.write_contents(&mut contents, 0, end_col, false);
          } else {
            row.write_contents(&mut contents, 0, cols, false);
            if !row.wrapped() {
              contents.push('\n');
            }
          }
        }
        contents
      }
      std::cmp::Ordering::Equal => {
        if start_col < end_col {
          self
            .rows(start_col, end_col - start_col)
            .nth(usize::from(start_row))
            .unwrap_or_else(String::new)
        } else {
          String::new()
        }
      }
      std::cmp::Ordering::Greater => String::new(),
    }
  }

  /// Return escape codes sufficient to reproduce the entire contents of the
  /// current terminal state. This is a convenience wrapper around
  /// `contents_formatted`, `input_mode_formatted`, and `title_formatted`.
  #[must_use]
  pub fn state_formatted(&self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_contents_formatted(&mut contents);
    self.write_input_mode_formatted(&mut contents);
    self.write_title_formatted(&mut contents);
    contents
  }

  /// Return escape codes sufficient to turn the terminal state of the
  /// screen `prev` into the current terminal state. This is a convenience
  /// wrapper around `contents_diff`, `input_mode_diff`, `title_diff`, and
  /// `bells_diff`.
  #[must_use]
  pub fn state_diff(&self, prev: &Self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_contents_diff(&mut contents, prev);
    self.write_input_mode_diff(&mut contents, prev);
    self.write_title_diff(&mut contents, prev);
    self.write_bells_diff(&mut contents, prev);
    contents
  }

  /// Returns the formatted visible contents of the terminal.
  ///
  /// Formatting information will be included inline as terminal escape
  /// codes. The result will be suitable for feeding directly to a raw
  /// terminal parser, and will result in the same visual output.
  #[must_use]
  pub fn contents_formatted(&self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_contents_formatted(&mut contents);
    contents
  }

  fn write_contents_formatted(&self, contents: &mut Vec<u8>) {
    crate::term::HideCursor::new(self.hide_cursor()).write_buf(contents);
    let prev_attrs = self.grid().write_contents_formatted(contents);
    self.attrs.write_escape_code_diff(contents, &prev_attrs);
  }

  /// Returns the formatted visible contents of the terminal by row,
  /// restricted to the given subset of columns.
  ///
  /// Formatting information will be included inline as terminal escape
  /// codes. The result will be suitable for feeding directly to a raw
  /// terminal parser, and will result in the same visual output.
  ///
  /// You are responsible for positioning the cursor before printing each
  /// row, and the final cursor position after displaying each row is
  /// unspecified.
  // the unwraps in this method shouldn't be reachable
  #[allow(clippy::missing_panics_doc)]
  pub fn rows_formatted(
    &self,
    start: u16,
    width: u16,
  ) -> impl Iterator<Item = Vec<u8>> + '_ {
    let mut wrapping = false;
    self.grid().visible_rows().enumerate().map(move |(i, row)| {
      // number of rows in a grid is stored in a u16 (see Size), so
      // visible_rows can never return enough rows to overflow here
      let i = i.try_into().unwrap();
      let mut contents = vec![];
      row.write_contents_formatted(
        &mut contents,
        start,
        width,
        i,
        wrapping,
        None,
        None,
      );
      if start == 0 && width == self.grid.size().cols {
        wrapping = row.wrapped();
      }
      contents
    })
  }

  /// Returns a terminal byte stream sufficient to turn the visible contents
  /// of the screen described by `prev` into the visible contents of the
  /// screen described by `self`.
  ///
  /// The result of rendering `prev.contents_formatted()` followed by
  /// `self.contents_diff(prev)` should be equivalent to the result of
  /// rendering `self.contents_formatted()`. This is primarily useful when
  /// you already have a terminal parser whose state is described by `prev`,
  /// since the diff will likely require less memory and cause less
  /// flickering than redrawing the entire screen contents.
  #[must_use]
  pub fn contents_diff(&self, prev: &Self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_contents_diff(&mut contents, prev);
    contents
  }

  fn write_contents_diff(&self, contents: &mut Vec<u8>, prev: &Self) {
    if self.hide_cursor() != prev.hide_cursor() {
      crate::term::HideCursor::new(self.hide_cursor()).write_buf(contents);
    }
    let prev_attrs =
      self
        .grid()
        .write_contents_diff(contents, prev.grid(), prev.attrs);
    self.attrs.write_escape_code_diff(contents, &prev_attrs);
  }

  /// Returns a sequence of terminal byte streams sufficient to turn the
  /// visible contents of the subset of each row from `prev` (as described
  /// by `start` and `width`) into the visible contents of the corresponding
  /// row subset in `self`.
  ///
  /// You are responsible for positioning the cursor before printing each
  /// row, and the final cursor position after displaying each row is
  /// unspecified.
  // the unwraps in this method shouldn't be reachable
  #[allow(clippy::missing_panics_doc)]
  pub fn rows_diff<'a>(
    &'a self,
    prev: &'a Self,
    start: u16,
    width: u16,
  ) -> impl Iterator<Item = Vec<u8>> + 'a {
    self
      .grid()
      .visible_rows()
      .zip(prev.grid().visible_rows())
      .enumerate()
      .map(move |(i, (row, prev_row))| {
        // number of rows in a grid is stored in a u16 (see Size), so
        // visible_rows can never return enough rows to overflow here
        let i = i.try_into().unwrap();
        let mut contents = vec![];
        row.write_contents_diff(
          &mut contents,
          prev_row,
          start,
          width,
          i,
          false,
          false,
          crate::grid::Pos { row: i, col: start },
          crate::attrs::Attrs::default(),
        );
        contents
      })
  }

  /// Returns terminal escape sequences sufficient to set the current
  /// terminal's input modes.
  ///
  /// Supported modes are:
  /// * application keypad
  /// * application cursor
  /// * bracketed paste
  /// * xterm mouse support
  #[must_use]
  pub fn input_mode_formatted(&self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_input_mode_formatted(&mut contents);
    contents
  }

  fn write_input_mode_formatted(&self, contents: &mut Vec<u8>) {
    crate::term::ApplicationKeypad::new(self.mode(MODE_APPLICATION_KEYPAD))
      .write_buf(contents);
    crate::term::ApplicationCursor::new(self.mode(MODE_APPLICATION_CURSOR))
      .write_buf(contents);
    crate::term::BracketedPaste::new(self.mode(MODE_BRACKETED_PASTE))
      .write_buf(contents);
    crate::term::MouseProtocolMode::new(
      self.mouse_protocol_mode,
      MouseProtocolMode::None,
    )
    .write_buf(contents);
    crate::term::MouseProtocolEncoding::new(
      self.mouse_protocol_encoding,
      MouseProtocolEncoding::Default,
    )
    .write_buf(contents);
  }

  /// Returns terminal escape sequences sufficient to change the previous
  /// terminal's input modes to the input modes enabled in the current
  /// terminal.
  #[must_use]
  pub fn input_mode_diff(&self, prev: &Self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_input_mode_diff(&mut contents, prev);
    contents
  }

  fn write_input_mode_diff(&self, contents: &mut Vec<u8>, prev: &Self) {
    if self.mode(MODE_APPLICATION_KEYPAD) != prev.mode(MODE_APPLICATION_KEYPAD)
    {
      crate::term::ApplicationKeypad::new(self.mode(MODE_APPLICATION_KEYPAD))
        .write_buf(contents);
    }
    if self.mode(MODE_APPLICATION_CURSOR) != prev.mode(MODE_APPLICATION_CURSOR)
    {
      crate::term::ApplicationCursor::new(self.mode(MODE_APPLICATION_CURSOR))
        .write_buf(contents);
    }
    if self.mode(MODE_BRACKETED_PASTE) != prev.mode(MODE_BRACKETED_PASTE) {
      crate::term::BracketedPaste::new(self.mode(MODE_BRACKETED_PASTE))
        .write_buf(contents);
    }
    crate::term::MouseProtocolMode::new(
      self.mouse_protocol_mode,
      prev.mouse_protocol_mode,
    )
    .write_buf(contents);
    crate::term::MouseProtocolEncoding::new(
      self.mouse_protocol_encoding,
      prev.mouse_protocol_encoding,
    )
    .write_buf(contents);
  }

  /// Returns terminal escape sequences sufficient to set the current
  /// terminal's window title.
  #[must_use]
  pub fn title_formatted(&self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_title_formatted(&mut contents);
    contents
  }

  fn write_title_formatted(&self, contents: &mut Vec<u8>) {
    crate::term::ChangeTitle::new(&self.icon_name, &self.title, "", "")
      .write_buf(contents);
  }

  /// Returns terminal escape sequences sufficient to change the previous
  /// terminal's window title to the window title set in the current
  /// terminal.
  #[must_use]
  pub fn title_diff(&self, prev: &Self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_title_diff(&mut contents, prev);
    contents
  }

  fn write_title_diff(&self, contents: &mut Vec<u8>, prev: &Self) {
    crate::term::ChangeTitle::new(
      &self.icon_name,
      &self.title,
      &prev.icon_name,
      &prev.title,
    )
    .write_buf(contents);
  }

  /// Returns terminal escape sequences sufficient to cause audible and
  /// visual bells to occur if they have been received since the terminal
  /// described by `prev`.
  #[must_use]
  pub fn bells_diff(&self, prev: &Self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_bells_diff(&mut contents, prev);
    contents
  }

  fn write_bells_diff(&self, contents: &mut Vec<u8>, prev: &Self) {
    if self.audible_bell_count != prev.audible_bell_count {
      crate::term::AudibleBell::default().write_buf(contents);
    }
    if self.visual_bell_count != prev.visual_bell_count {
      crate::term::VisualBell::default().write_buf(contents);
    }
  }

  /// Returns terminal escape sequences sufficient to set the current
  /// terminal's drawing attributes.
  ///
  /// Supported drawing attributes are:
  /// * fgcolor
  /// * bgcolor
  /// * bold
  /// * italic
  /// * underline
  /// * inverse
  ///
  /// This is not typically necessary, since `contents_formatted` will leave
  /// the current active drawing attributes in the correct state, but this
  /// can be useful in the case of drawing additional things on top of a
  /// terminal output, since you will need to restore the terminal state
  /// without the terminal contents necessarily being the same.
  #[must_use]
  pub fn attributes_formatted(&self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_attributes_formatted(&mut contents);
    contents
  }

  fn write_attributes_formatted(&self, contents: &mut Vec<u8>) {
    crate::term::ClearAttrs::default().write_buf(contents);
    self
      .attrs
      .write_escape_code_diff(contents, &crate::attrs::Attrs::default());
  }

  /// Returns the current cursor position of the terminal.
  ///
  /// The return value will be (row, col).
  #[must_use]
  pub fn cursor_position(&self) -> (u16, u16) {
    let pos = self.grid().pos();
    (pos.row, pos.col)
  }

  /// Returns terminal escape sequences sufficient to set the current
  /// cursor state of the terminal.
  ///
  /// This is not typically necessary, since `contents_formatted` will leave
  /// the cursor in the correct state, but this can be useful in the case of
  /// drawing additional things on top of a terminal output, since you will
  /// need to restore the terminal state without the terminal contents
  /// necessarily being the same.
  ///
  /// Note that the bytes returned by this function may alter the active
  /// drawing attributes, because it may require redrawing existing cells in
  /// order to position the cursor correctly (for instance, in the case
  /// where the cursor is past the end of a row). Therefore, you should
  /// ensure to reset the active drawing attributes if necessary after
  /// processing this data, for instance by using `attributes_formatted`.
  #[must_use]
  pub fn cursor_state_formatted(&self) -> Vec<u8> {
    let mut contents = vec![];
    self.write_cursor_state_formatted(&mut contents);
    contents
  }

  fn write_cursor_state_formatted(&self, contents: &mut Vec<u8>) {
    crate::term::HideCursor::new(self.hide_cursor()).write_buf(contents);
    self
      .grid()
      .write_cursor_position_formatted(contents, None, None);

    // we don't just call write_attributes_formatted here, because that
    // would still be confusing - consider the case where the user sets
    // their own unrelated drawing attributes (on a different parser
    // instance) and then calls cursor_state_formatted. just documenting
    // it and letting the user handle it on their own is more
    // straightforward.
  }

  /// Returns the `Cell` object at the given location in the terminal, if it
  /// exists.
  #[must_use]
  pub fn cell(&self, row: u16, col: u16) -> Option<&crate::cell::Cell> {
    self.grid().visible_cell(crate::grid::Pos { row, col })
  }

  /// Returns whether the text in row `row` should wrap to the next line.
  #[must_use]
  pub fn row_wrapped(&self, row: u16) -> bool {
    self
      .grid()
      .visible_row(row)
      .map_or(false, crate::row::Row::wrapped)
  }

  /// Returns the terminal's window title.
  #[must_use]
  pub fn title(&self) -> &str {
    &self.title
  }

  /// Returns the terminal's icon name.
  #[must_use]
  pub fn icon_name(&self) -> &str {
    &self.icon_name
  }

  /// Returns a value which changes every time an audible bell is received.
  ///
  /// Typically you would store this number after each call to `process`,
  /// and trigger an audible bell whenever it changes.
  ///
  /// You shouldn't rely on the exact value returned here, since the exact
  /// value will not be maintained by `contents_formatted` or
  /// `contents_diff`.
  #[must_use]
  pub fn audible_bell_count(&self) -> usize {
    self.audible_bell_count
  }

  /// Returns a value which changes every time an visual bell is received.
  ///
  /// Typically you would store this number after each call to `process`,
  /// and trigger an visual bell whenever it changes.
  ///
  /// You shouldn't rely on the exact value returned here, since the exact
  /// value will not be maintained by `contents_formatted` or
  /// `contents_diff`.
  #[must_use]
  pub fn visual_bell_count(&self) -> usize {
    self.visual_bell_count
  }

  /// Returns the number of parsing errors seen so far.
  ///
  /// Currently this only tracks invalid UTF-8 and control characters other
  /// than `0x07`-`0x0f`. This can give an idea of whether the input stream
  /// being fed to the parser is reasonable or not.
  #[must_use]
  pub fn errors(&self) -> usize {
    self.errors
  }

  /// Returns whether the alternate screen is currently in use.
  #[must_use]
  pub fn alternate_screen(&self) -> bool {
    self.mode(MODE_ALTERNATE_SCREEN)
  }

  /// Returns whether the terminal should be in application keypad mode.
  #[must_use]
  pub fn application_keypad(&self) -> bool {
    self.mode(MODE_APPLICATION_KEYPAD)
  }

  /// Returns whether the terminal should be in application cursor mode.
  #[must_use]
  pub fn application_cursor(&self) -> bool {
    self.mode(MODE_APPLICATION_CURSOR)
  }

  /// Returns whether the terminal should be in hide cursor mode.
  #[must_use]
  pub fn hide_cursor(&self) -> bool {
    self.mode(MODE_HIDE_CURSOR)
  }

  /// Returns whether the terminal should be in bracketed paste mode.
  #[must_use]
  pub fn bracketed_paste(&self) -> bool {
    self.mode(MODE_BRACKETED_PASTE)
  }

  /// Returns the currently active `MouseProtocolMode`
  #[must_use]
  pub fn mouse_protocol_mode(&self) -> MouseProtocolMode {
    self.mouse_protocol_mode
  }

  /// Returns the currently active `MouseProtocolEncoding`
  #[must_use]
  pub fn mouse_protocol_encoding(&self) -> MouseProtocolEncoding {
    self.mouse_protocol_encoding
  }

  /// Returns the currently active foreground color.
  #[must_use]
  pub fn fgcolor(&self) -> crate::attrs::Color {
    self.attrs.fgcolor
  }

  /// Returns the currently active background color.
  #[must_use]
  pub fn bgcolor(&self) -> crate::attrs::Color {
    self.attrs.bgcolor
  }

  /// Returns whether newly drawn text should be rendered with the bold text
  /// attribute.
  #[must_use]
  pub fn bold(&self) -> bool {
    self.attrs.bold()
  }

  /// Returns whether newly drawn text should be rendered with the italic
  /// text attribute.
  #[must_use]
  pub fn italic(&self) -> bool {
    self.attrs.italic()
  }

  /// Returns whether newly drawn text should be rendered with the
  /// underlined text attribute.
  #[must_use]
  pub fn underline(&self) -> bool {
    self.attrs.underline()
  }

  /// Returns whether newly drawn text should be rendered with the inverse
  /// text attribute.
  #[must_use]
  pub fn inverse(&self) -> bool {
    self.attrs.inverse()
  }

  fn grid(&self) -> &crate::grid::Grid {
    if self.mode(MODE_ALTERNATE_SCREEN) {
      &self.alternate_grid
    } else {
      &self.grid
    }
  }

  fn grid_mut(&mut self) -> &mut crate::grid::Grid {
    if self.mode(MODE_ALTERNATE_SCREEN) {
      &mut self.alternate_grid
    } else {
      &mut self.grid
    }
  }

  fn enter_alternate_grid(&mut self) {
    self.grid_mut().set_scrollback(0);
    self.set_mode(MODE_ALTERNATE_SCREEN);
    self.alternate_grid.allocate_rows();
  }

  fn exit_alternate_grid(&mut self) {
    self.clear_mode(MODE_ALTERNATE_SCREEN);
  }

  fn save_cursor(&mut self) {
    self.grid_mut().save_cursor();
    self.saved_attrs = self.attrs;
  }

  fn restore_cursor(&mut self) {
    self.grid_mut().restore_cursor();
    self.attrs = self.saved_attrs;
  }

  fn set_mode(&mut self, mode: u8) {
    self.modes |= mode;
  }

  fn clear_mode(&mut self, mode: u8) {
    self.modes &= !mode;
  }

  fn mode(&self, mode: u8) -> bool {
    self.modes & mode != 0
  }

  fn set_mouse_mode(&mut self, mode: MouseProtocolMode) {
    self.mouse_protocol_mode = mode;
  }

  fn clear_mouse_mode(&mut self, mode: MouseProtocolMode) {
    if self.mouse_protocol_mode == mode {
      self.mouse_protocol_mode = MouseProtocolMode::default();
    }
  }

  fn set_mouse_encoding(&mut self, encoding: MouseProtocolEncoding) {
    self.mouse_protocol_encoding = encoding;
  }

  fn clear_mouse_encoding(&mut self, encoding: MouseProtocolEncoding) {
    if self.mouse_protocol_encoding == encoding {
      self.mouse_protocol_encoding = MouseProtocolEncoding::default();
    }
  }
}

impl Screen {
  fn text(&mut self, c: char) {
    let pos = self.grid().pos();
    let size = self.grid().size();
    let attrs = self.attrs;

    let width = c.width();
    if width.is_none() && (u32::from(c)) < 256 {
      // don't even try to draw control characters
      return;
    }
    let width = width
      .unwrap_or(1)
      .try_into()
      // width() can only return 0, 1, or 2
      .unwrap();

    // it doesn't make any sense to wrap if the last column in a row
    // didn't already have contents. don't try to handle the case where a
    // character wraps because there was only one column left in the
    // previous row - literally everything handles this case differently,
    // and this is tmux behavior (and also the simplest). i'm open to
    // reconsidering this behavior, but only with a really good reason
    // (xterm handles this by introducing the concept of triple width
    // cells, which i really don't want to do).
    let mut wrap = false;
    if pos.col > size.cols - width {
      let last_cell = self
        .grid()
        .drawing_cell(crate::grid::Pos {
          row: pos.row,
          col: size.cols - 1,
        })
        // pos.row is valid, since it comes directly from
        // self.grid().pos() which we assume to always have a valid
        // row value. size.cols - 1 is also always a valid column.
        .unwrap();
      if last_cell.has_contents() || last_cell.is_wide_continuation() {
        wrap = true;
      }
    }
    self.grid_mut().col_wrap(width, wrap);
    let pos = self.grid().pos();

    if width == 0 {
      if pos.col > 0 {
        let mut prev_cell = self
          .grid_mut()
          .drawing_cell_mut(crate::grid::Pos {
            row: pos.row,
            col: pos.col - 1,
          })
          // pos.row is valid, since it comes directly from
          // self.grid().pos() which we assume to always have a
          // valid row value. pos.col - 1 is valid because we just
          // checked for pos.col > 0.
          .unwrap();
        if prev_cell.is_wide_continuation() {
          prev_cell = self
            .grid_mut()
            .drawing_cell_mut(crate::grid::Pos {
              row: pos.row,
              col: pos.col - 2,
            })
            // pos.row is valid, since it comes directly from
            // self.grid().pos() which we assume to always have a
            // valid row value. we know pos.col - 2 is valid
            // because the cell at pos.col - 1 is a wide
            // continuation character, which means there must be
            // the first half of the wide character before it.
            .unwrap();
        }
        prev_cell.append(c);
      } else if pos.row > 0 {
        let prev_row = self
          .grid()
          .drawing_row(pos.row - 1)
          // pos.row is valid, since it comes directly from
          // self.grid().pos() which we assume to always have a
          // valid row value. pos.row - 1 is valid because we just
          // checked for pos.row > 0.
          .unwrap();
        if prev_row.wrapped() {
          let mut prev_cell = self
            .grid_mut()
            .drawing_cell_mut(crate::grid::Pos {
              row: pos.row - 1,
              col: size.cols - 1,
            })
            // pos.row is valid, since it comes directly from
            // self.grid().pos() which we assume to always have a
            // valid row value. pos.row - 1 is valid because we
            // just checked for pos.row > 0. col of size.cols - 1
            // is always valid.
            .unwrap();
          if prev_cell.is_wide_continuation() {
            prev_cell = self
              .grid_mut()
              .drawing_cell_mut(crate::grid::Pos {
                row: pos.row - 1,
                col: size.cols - 2,
              })
              // pos.row is valid, since it comes directly from
              // self.grid().pos() which we assume to always
              // have a valid row value. pos.row - 1 is valid
              // because we just checked for pos.row > 0. col of
              // size.cols - 2 is valid because the cell at
              // size.cols - 1 is a wide continuation character,
              // so it must have the first half of the wide
              // character before it.
              .unwrap();
          }
          prev_cell.append(c);
        }
      }
    } else {
      if self
        .grid()
        .drawing_cell(pos)
        // pos.row is valid because we assume self.grid().pos() to
        // always have a valid row value. pos.col is valid because we
        // called col_wrap() immediately before this, which ensures
        // that self.grid().pos().col has a valid value.
        .unwrap()
        .is_wide_continuation()
      {
        let prev_cell = self
          .grid_mut()
          .drawing_cell_mut(crate::grid::Pos {
            row: pos.row,
            col: pos.col - 1,
          })
          // pos.row is valid because we assume self.grid().pos() to
          // always have a valid row value. pos.col is valid because
          // we called col_wrap() immediately before this, which
          // ensures that self.grid().pos().col has a valid value.
          // pos.col - 1 is valid because the cell at pos.col is a
          // wide continuation character, so it must have the first
          // half of the wide character before it.
          .unwrap();
        prev_cell.clear(attrs);
      }

      if self
        .grid()
        .drawing_cell(pos)
        // pos.row is valid because we assume self.grid().pos() to
        // always have a valid row value. pos.col is valid because we
        // called col_wrap() immediately before this, which ensures
        // that self.grid().pos().col has a valid value.
        .unwrap()
        .is_wide()
      {
        if let Some(next_cell) =
          self.grid_mut().drawing_cell_mut(crate::grid::Pos {
            row: pos.row,
            col: pos.col + 1,
          })
        {
          next_cell.set(' ', attrs);
        }
      }

      let cell = self
        .grid_mut()
        .drawing_cell_mut(pos)
        // pos.row is valid because we assume self.grid().pos() to
        // always have a valid row value. pos.col is valid because we
        // called col_wrap() immediately before this, which ensures
        // that self.grid().pos().col has a valid value.
        .unwrap();
      cell.set(c, attrs);
      self.grid_mut().col_inc(1);
      if width > 1 {
        let pos = self.grid().pos();
        if self
          .grid()
          .drawing_cell(pos)
          // pos.row is valid because we assume self.grid().pos() to
          // always have a valid row value. pos.col is valid because
          // we called col_wrap() earlier, which ensures that
          // self.grid().pos().col has a valid value. this is true
          // even though we just called col_inc, because this branch
          // only happens if width > 1, and col_wrap takes width
          // into account.
          .unwrap()
          .is_wide()
        {
          let next_next_pos = crate::grid::Pos {
            row: pos.row,
            col: pos.col + 1,
          };
          let next_next_cell = self
            .grid_mut()
            .drawing_cell_mut(next_next_pos)
            // pos.row is valid because we assume
            // self.grid().pos() to always have a valid row value.
            // pos.col is valid because we called col_wrap()
            // earlier, which ensures that self.grid().pos().col
            // has a valid value. this is true even though we just
            // called col_inc, because this branch only happens if
            // width > 1, and col_wrap takes width into account.
            // pos.col + 1 is valid because the cell at pos.col is
            // wide, and so it must have the second half of the
            // wide character after it.
            .unwrap();
          next_next_cell.clear(attrs);
          if next_next_pos.col == size.cols - 1 {
            self
              .grid_mut()
              .drawing_row_mut(pos.row)
              // we assume self.grid().pos().row is always valid
              .unwrap()
              .wrap(false);
          }
        }
        let next_cell = self
          .grid_mut()
          .drawing_cell_mut(pos)
          // pos.row is valid because we assume self.grid().pos() to
          // always have a valid row value. pos.col is valid because
          // we called col_wrap() earlier, which ensures that
          // self.grid().pos().col has a valid value. this is true
          // even though we just called col_inc, because this branch
          // only happens if width > 1, and col_wrap takes width
          // into account.
          .unwrap();
        next_cell.clear(crate::attrs::Attrs::default());
        next_cell.set_wide_continuation(true);
        self.grid_mut().col_inc(1);
      }
    }
  }

  // control codes

  fn bel(&mut self) {
    self.audible_bell_count += 1;
  }

  fn bs(&mut self) {
    self.grid_mut().col_dec(1);
  }

  fn tab(&mut self) {
    self.grid_mut().col_tab();
  }

  fn lf(&mut self) {
    self.grid_mut().row_inc_scroll(1);
  }

  fn vt(&mut self) {
    self.lf();
  }

  fn ff(&mut self) {
    self.lf();
  }

  fn cr(&mut self) {
    self.grid_mut().col_set(0);
  }

  // escape codes

  // ESC 7
  fn decsc(&mut self) {
    self.save_cursor();
  }

  // ESC 8
  fn decrc(&mut self) {
    self.restore_cursor();
  }

  // ESC =
  fn deckpam(&mut self) {
    self.set_mode(MODE_APPLICATION_KEYPAD);
  }

  // ESC >
  fn deckpnm(&mut self) {
    self.clear_mode(MODE_APPLICATION_KEYPAD);
  }

  // ESC M
  fn ri(&mut self) {
    self.grid_mut().row_dec_scroll(1);
  }

  // ESC c
  fn ris(&mut self) {
    let title = self.title.clone();
    let icon_name = self.icon_name.clone();
    let audible_bell_count = self.audible_bell_count;
    let visual_bell_count = self.visual_bell_count;
    let errors = self.errors;

    *self = Self::new(self.grid.size(), self.grid.scrollback_len());

    self.title = title;
    self.icon_name = icon_name;
    self.audible_bell_count = audible_bell_count;
    self.visual_bell_count = visual_bell_count;
    self.errors = errors;
  }

  // ESC g
  fn vb(&mut self) {
    self.visual_bell_count += 1;
  }

  // csi codes

  // CSI @
  fn ich(&mut self, count: u16) {
    self.grid_mut().insert_cells(count);
  }

  // CSI A
  fn cuu(&mut self, offset: u16) {
    self.grid_mut().row_dec_clamp(offset);
  }

  // CSI B
  fn cud(&mut self, offset: u16) {
    self.grid_mut().row_inc_clamp(offset);
  }

  // CSI C
  fn cuf(&mut self, offset: u16) {
    self.grid_mut().col_inc_clamp(offset);
  }

  // CSI D
  fn cub(&mut self, offset: u16) {
    self.grid_mut().col_dec(offset);
  }

  // CSI G
  fn cha(&mut self, col: u16) {
    self.grid_mut().col_set(col - 1);
  }

  // CSI H
  fn cup(&mut self, (row, col): (u16, u16)) {
    self.grid_mut().set_pos(crate::grid::Pos {
      row: row - 1,
      col: col - 1,
    });
  }

  // CSI J
  fn ed(&mut self, mode: u16) {
    let attrs = self.attrs;
    match mode {
      0 => self.grid_mut().erase_all_forward(attrs),
      1 => self.grid_mut().erase_all_backward(attrs),
      2 => self.grid_mut().erase_all(attrs),
      n => {
        log::debug!("unhandled ED mode: {}", n);
      }
    }
  }

  // CSI ? J
  fn decsed(&mut self, mode: u16) {
    self.ed(mode);
  }

  // CSI K
  fn el(&mut self, mode: u16) {
    let attrs = self.attrs;
    match mode {
      0 => self.grid_mut().erase_row_forward(attrs),
      1 => self.grid_mut().erase_row_backward(attrs),
      2 => self.grid_mut().erase_row(attrs),
      n => {
        log::debug!("unhandled EL mode: {}", n);
      }
    }
  }

  // CSI ? K
  fn decsel(&mut self, mode: u16) {
    self.el(mode);
  }

  // CSI L
  fn il(&mut self, count: u16) {
    self.grid_mut().insert_lines(count);
  }

  // CSI M
  fn dl(&mut self, count: u16) {
    self.grid_mut().delete_lines(count);
  }

  // CSI P
  fn dch(&mut self, count: u16) {
    self.grid_mut().delete_cells(count);
  }

  // CSI S
  fn su(&mut self, count: u16) {
    self.grid_mut().scroll_up(count);
  }

  // CSI T
  fn sd(&mut self, count: u16) {
    self.grid_mut().scroll_down(count);
  }

  // CSI X
  fn ech(&mut self, count: u16) {
    let attrs = self.attrs;
    self.grid_mut().erase_cells(count, attrs);
  }

  // CSI d
  fn vpa(&mut self, row: u16) {
    self.grid_mut().row_set(row - 1);
  }

  // CSI h
  #[allow(clippy::unused_self)]
  fn sm(&mut self, params: &vte::Params) {
    // nothing, i think?
    if log::log_enabled!(log::Level::Debug) {
      log::debug!("unhandled SM mode: {}", param_str(params));
    }
  }

  // CSI ? h
  fn decset(&mut self, params: &vte::Params) {
    for param in params {
      match param {
        &[1] => self.set_mode(MODE_APPLICATION_CURSOR),
        &[6] => self.grid_mut().set_origin_mode(true),
        &[9] => self.set_mouse_mode(MouseProtocolMode::Press),
        &[25] => self.clear_mode(MODE_HIDE_CURSOR),
        &[47] => self.enter_alternate_grid(),
        &[1000] => {
          self.set_mouse_mode(MouseProtocolMode::PressRelease);
        }
        &[1002] => {
          self.set_mouse_mode(MouseProtocolMode::ButtonMotion);
        }
        &[1003] => self.set_mouse_mode(MouseProtocolMode::AnyMotion),
        &[1005] => {
          self.set_mouse_encoding(MouseProtocolEncoding::Utf8);
        }
        &[1006] => {
          self.set_mouse_encoding(MouseProtocolEncoding::Sgr);
        }
        &[1049] => {
          self.decsc();
          self.alternate_grid.clear();
          self.enter_alternate_grid();
        }
        &[2004] => self.set_mode(MODE_BRACKETED_PASTE),
        ns => {
          if log::log_enabled!(log::Level::Debug) {
            let n = if ns.len() == 1 {
              format!(
                "{}",
                // we just checked that ns.len() == 1, so 0
                // must be valid
                ns[0]
              )
            } else {
              format!("{:?}", ns)
            };
            log::debug!("unhandled DECSET mode: {}", n);
          }
        }
      }
    }
  }

  // CSI l
  #[allow(clippy::unused_self)]
  fn rm(&mut self, params: &vte::Params) {
    // nothing, i think?
    if log::log_enabled!(log::Level::Debug) {
      log::debug!("unhandled RM mode: {}", param_str(params));
    }
  }

  // CSI ? l
  fn decrst(&mut self, params: &vte::Params) {
    for param in params {
      match param {
        &[1] => self.clear_mode(MODE_APPLICATION_CURSOR),
        &[6] => self.grid_mut().set_origin_mode(false),
        &[9] => self.clear_mouse_mode(MouseProtocolMode::Press),
        &[25] => self.set_mode(MODE_HIDE_CURSOR),
        &[47] => {
          self.exit_alternate_grid();
        }
        &[1000] => {
          self.clear_mouse_mode(MouseProtocolMode::PressRelease);
        }
        &[1002] => {
          self.clear_mouse_mode(MouseProtocolMode::ButtonMotion);
        }
        &[1003] => {
          self.clear_mouse_mode(MouseProtocolMode::AnyMotion);
        }
        &[1005] => {
          self.clear_mouse_encoding(MouseProtocolEncoding::Utf8);
        }
        &[1006] => {
          self.clear_mouse_encoding(MouseProtocolEncoding::Sgr);
        }
        &[1049] => {
          self.exit_alternate_grid();
          self.decrc();
        }
        &[2004] => self.clear_mode(MODE_BRACKETED_PASTE),
        ns => {
          if log::log_enabled!(log::Level::Debug) {
            let n = if ns.len() == 1 {
              format!(
                "{}",
                // we just checked that ns.len() == 1, so 0
                // must be valid
                ns[0]
              )
            } else {
              format!("{:?}", ns)
            };
            log::debug!("unhandled DECRST mode: {}", n);
          }
        }
      }
    }
  }

  // CSI m
  fn sgr(&mut self, params: &vte::Params) {
    // XXX really i want to just be able to pass in a default Params
    // instance with a 0 in it, but vte doesn't allow creating new Params
    // instances
    if params.is_empty() {
      self.attrs = crate::attrs::Attrs::default();
      return;
    }

    let mut iter = params.iter();

    macro_rules! next_param {
      () => {
        match iter.next() {
          Some(n) => n,
          _ => return,
        }
      };
    }

    macro_rules! to_u8 {
      ($n:expr) => {
        if let Some(n) = u16_to_u8($n) {
          n
        } else {
          return;
        }
      };
    }

    macro_rules! next_param_u8 {
      () => {
        if let &[n] = next_param!() {
          to_u8!(n)
        } else {
          return;
        }
      };
    }

    loop {
      match next_param!() {
        &[0] => self.attrs = crate::attrs::Attrs::default(),
        &[1] => self.attrs.set_bold(true),
        &[3] => self.attrs.set_italic(true),
        &[4] => self.attrs.set_underline(true),
        &[7] => self.attrs.set_inverse(true),
        &[22] => self.attrs.set_bold(false),
        &[23] => self.attrs.set_italic(false),
        &[24] => self.attrs.set_underline(false),
        &[27] => self.attrs.set_inverse(false),
        &[n] if (30..=37).contains(&n) => {
          self.attrs.fgcolor = crate::attrs::Color::Idx(to_u8!(n) - 30);
        }
        &[38, 2, r, g, b] => {
          self.attrs.fgcolor =
            crate::attrs::Color::Rgb(to_u8!(r), to_u8!(g), to_u8!(b));
        }
        &[38, 5, i] => {
          self.attrs.fgcolor = crate::attrs::Color::Idx(to_u8!(i));
        }
        &[38] => match next_param!() {
          &[2] => {
            let r = next_param_u8!();
            let g = next_param_u8!();
            let b = next_param_u8!();
            self.attrs.fgcolor = crate::attrs::Color::Rgb(r, g, b);
          }
          &[5] => {
            self.attrs.fgcolor = crate::attrs::Color::Idx(next_param_u8!());
          }
          ns => {
            if log::log_enabled!(log::Level::Debug) {
              let n = if ns.len() == 1 {
                format!(
                  "{}",
                  // we just checked that ns.len() == 1, so
                  // 0 must be valid
                  ns[0]
                )
              } else {
                format!("{:?}", ns)
              };
              log::debug!("unhandled SGR mode: 38 {}", n);
            }
            return;
          }
        },
        &[39] => {
          self.attrs.fgcolor = crate::attrs::Color::Default;
        }
        &[n] if (40..=47).contains(&n) => {
          self.attrs.bgcolor = crate::attrs::Color::Idx(to_u8!(n) - 40);
        }
        &[48, 2, r, g, b] => {
          self.attrs.bgcolor =
            crate::attrs::Color::Rgb(to_u8!(r), to_u8!(g), to_u8!(b));
        }
        &[48, 5, i] => {
          self.attrs.bgcolor = crate::attrs::Color::Idx(to_u8!(i));
        }
        &[48] => match next_param!() {
          &[2] => {
            let r = next_param_u8!();
            let g = next_param_u8!();
            let b = next_param_u8!();
            self.attrs.bgcolor = crate::attrs::Color::Rgb(r, g, b);
          }
          &[5] => {
            self.attrs.bgcolor = crate::attrs::Color::Idx(next_param_u8!());
          }
          ns => {
            if log::log_enabled!(log::Level::Debug) {
              let n = if ns.len() == 1 {
                format!(
                  "{}",
                  // we just checked that ns.len() == 1, so
                  // 0 must be valid
                  ns[0]
                )
              } else {
                format!("{:?}", ns)
              };
              log::debug!("unhandled SGR mode: 48 {}", n);
            }
            return;
          }
        },
        &[49] => {
          self.attrs.bgcolor = crate::attrs::Color::Default;
        }
        &[n] if (90..=97).contains(&n) => {
          self.attrs.fgcolor = crate::attrs::Color::Idx(to_u8!(n) - 82);
        }
        &[n] if (100..=107).contains(&n) => {
          self.attrs.bgcolor = crate::attrs::Color::Idx(to_u8!(n) - 92);
        }
        ns => {
          if log::log_enabled!(log::Level::Debug) {
            let n = if ns.len() == 1 {
              format!(
                "{}",
                // we just checked that ns.len() == 1, so 0
                // must be valid
                ns[0]
              )
            } else {
              format!("{:?}", ns)
            };
            log::debug!("unhandled SGR mode: {}", n);
          }
        }
      }
    }
  }

  // CSI r
  fn decstbm(&mut self, (top, bottom): (u16, u16)) {
    self.grid_mut().set_scroll_region(top - 1, bottom - 1);
  }

  // osc codes

  fn osc0(&mut self, s: &[u8]) {
    self.osc1(s);
    self.osc2(s);
  }

  fn osc1(&mut self, s: &[u8]) {
    if let Ok(s) = std::str::from_utf8(s) {
      self.icon_name = s.to_string();
    }
  }

  fn osc2(&mut self, s: &[u8]) {
    if let Ok(s) = std::str::from_utf8(s) {
      self.title = s.to_string();
    }
  }
}

impl vte::Perform for Screen {
  fn print(&mut self, c: char) {
    if c == '\u{fffd}' || ('\u{80}'..'\u{a0}').contains(&c) {
      self.errors = self.errors.saturating_add(1);
    }
    self.text(c);
  }

  fn execute(&mut self, b: u8) {
    match b {
      7 => self.bel(),
      8 => self.bs(),
      9 => self.tab(),
      10 => self.lf(),
      11 => self.vt(),
      12 => self.ff(),
      13 => self.cr(),
      // we don't implement shift in/out alternate character sets, but
      // it shouldn't count as an "error"
      14 | 15 => {}
      _ => {
        self.errors = self.errors.saturating_add(1);
        log::debug!("unhandled control character: {}", b);
      }
    }
  }

  fn esc_dispatch(&mut self, intermediates: &[u8], _ignore: bool, b: u8) {
    match intermediates.get(0) {
      None => match b {
        b'7' => self.decsc(),
        b'8' => self.decrc(),
        b'=' => self.deckpam(),
        b'>' => self.deckpnm(),
        b'M' => self.ri(),
        b'c' => self.ris(),
        b'g' => self.vb(),
        _ => {
          log::debug!("unhandled escape code: ESC {}", b);
        }
      },
      Some(i) => {
        log::debug!("unhandled escape code: ESC {} {}", i, b);
      }
    }
  }

  fn csi_dispatch(
    &mut self,
    params: &vte::Params,
    intermediates: &[u8],
    _ignore: bool,
    c: char,
  ) {
    match intermediates.get(0) {
      None => match c {
        '@' => self.ich(canonicalize_params_1(params, 1)),
        'A' => self.cuu(canonicalize_params_1(params, 1)),
        'B' => self.cud(canonicalize_params_1(params, 1)),
        'C' => self.cuf(canonicalize_params_1(params, 1)),
        'D' => self.cub(canonicalize_params_1(params, 1)),
        'G' => self.cha(canonicalize_params_1(params, 1)),
        'H' => self.cup(canonicalize_params_2(params, 1, 1)),
        'J' => self.ed(canonicalize_params_1(params, 0)),
        'K' => self.el(canonicalize_params_1(params, 0)),
        'L' => self.il(canonicalize_params_1(params, 1)),
        'M' => self.dl(canonicalize_params_1(params, 1)),
        'P' => self.dch(canonicalize_params_1(params, 1)),
        'S' => self.su(canonicalize_params_1(params, 1)),
        'T' => self.sd(canonicalize_params_1(params, 1)),
        'X' => self.ech(canonicalize_params_1(params, 1)),
        'd' => self.vpa(canonicalize_params_1(params, 1)),
        'h' => self.sm(params),
        'l' => self.rm(params),
        'm' => self.sgr(params),
        'r' => {
          self.decstbm(canonicalize_params_decstbm(params, self.grid().size()))
        }
        _ => {
          if log::log_enabled!(log::Level::Debug) {
            log::debug!(
              "unhandled csi sequence: CSI {} {}",
              param_str(params),
              c
            );
          }
        }
      },
      Some(b'?') => match c {
        'J' => self.decsed(canonicalize_params_1(params, 0)),
        'K' => self.decsel(canonicalize_params_1(params, 0)),
        'h' => self.decset(params),
        'l' => self.decrst(params),
        _ => {
          if log::log_enabled!(log::Level::Debug) {
            log::debug!(
              "unhandled csi sequence: CSI ? {} {}",
              param_str(params),
              c
            );
          }
        }
      },
      Some(i) => {
        if log::log_enabled!(log::Level::Debug) {
          log::debug!(
            "unhandled csi sequence: CSI {} {} {}",
            i,
            param_str(params),
            c
          );
        }
      }
    }
  }

  fn osc_dispatch(&mut self, params: &[&[u8]], _bel_terminated: bool) {
    match (params.get(0), params.get(1)) {
      (Some(&b"0"), Some(s)) => self.osc0(s),
      (Some(&b"1"), Some(s)) => self.osc1(s),
      (Some(&b"2"), Some(s)) => self.osc2(s),
      _ => {
        if log::log_enabled!(log::Level::Debug) {
          log::debug!("unhandled osc sequence: OSC {}", osc_param_str(params),);
        }
      }
    }
  }

  fn hook(
    &mut self,
    params: &vte::Params,
    intermediates: &[u8],
    _ignore: bool,
    action: char,
  ) {
    if log::log_enabled!(log::Level::Debug) {
      match intermediates.get(0) {
        None => log::debug!(
          "unhandled dcs sequence: DCS {} {}",
          param_str(params),
          action,
        ),
        Some(i) => log::debug!(
          "unhandled dcs sequence: DCS {} {} {}",
          i,
          param_str(params),
          action,
        ),
      }
    }
  }
}

fn canonicalize_params_1(params: &vte::Params, default: u16) -> u16 {
  let first = params.iter().next().map_or(0, |x| *x.get(0).unwrap_or(&0));
  if first == 0 {
    default
  } else {
    first
  }
}

fn canonicalize_params_2(
  params: &vte::Params,
  default1: u16,
  default2: u16,
) -> (u16, u16) {
  let mut iter = params.iter();
  let first = iter.next().map_or(0, |x| *x.get(0).unwrap_or(&0));
  let first = if first == 0 { default1 } else { first };

  let second = iter.next().map_or(0, |x| *x.get(0).unwrap_or(&0));
  let second = if second == 0 { default2 } else { second };

  (first, second)
}

fn canonicalize_params_decstbm(
  params: &vte::Params,
  size: crate::grid::Size,
) -> (u16, u16) {
  let mut iter = params.iter();
  let top = iter.next().map_or(0, |x| *x.get(0).unwrap_or(&0));
  let top = if top == 0 { 1 } else { top };

  let bottom = iter.next().map_or(0, |x| *x.get(0).unwrap_or(&0));
  let bottom = if bottom == 0 { size.rows } else { bottom };

  (top, bottom)
}

fn u16_to_u8(i: u16) -> Option<u8> {
  if i > u16::from(u8::max_value()) {
    None
  } else {
    // safe because we just ensured that the value fits in a u8
    Some(i.try_into().unwrap())
  }
}

fn param_str(params: &vte::Params) -> String {
  let strs: Vec<_> = params
    .iter()
    .map(|subparams| {
      let subparam_strs: Vec<_> = subparams
        .iter()
        .map(std::string::ToString::to_string)
        .collect();
      subparam_strs.join(" : ")
    })
    .collect();
  strs.join(" ; ")
}

fn osc_param_str(params: &[&[u8]]) -> String {
  let strs: Vec<_> = params
    .iter()
    .map(|b| format!("\"{}\"", std::string::String::from_utf8_lossy(*b)))
    .collect();
  strs.join(" ; ")
}