fn input()

in crates/alacritty_terminal/src/term/mod.rs [910:998]
77 lines of code
13 McCabe index (conditional complexity)

    fn input(&mut self, c: char) {
        trace!("Input: {}", c);

        // Number of cells the char will occupy.
        let width = match c.width() {
            Some(width) => width,
            None => return,
        };

        // Handle zero-width characters.
        if width == 0 {
            // Get previous column.
            let mut column = self.grid.cursor.point.column;
            if !self.grid.cursor.input_needs_wrap {
                column.0 = column.saturating_sub(1);
            }

            // Put zerowidth characters over first fullwidth character cell.
            let line = self.grid.cursor.point.line;
            if self.grid[line][column].flags.contains(ShellFlags::WIDE_CHAR_SPACER) {
                column.0 = column.saturating_sub(1);
            }

            self.grid[line][column].push_zerowidth(c);
            return;
        }

        // Move cursor to next line.
        if self.grid.cursor.input_needs_wrap {
            self.wrapline();
        }

        // If in insert mode, first shift cells to the right.
        let columns = self.columns();
        if self.mode.contains(TermMode::INSERT) && self.grid.cursor.point.column + width < columns {
            let line = self.grid.cursor.point.line;
            let col = self.grid.cursor.point.column;
            let row = &mut self.grid[line][..];

            for col in (col.0..(columns - width)).rev() {
                row.swap(col + width, col);
            }
        }

        if width == 1 {
            self.write_at_cursor(c);
        } else {
            if self.grid.cursor.point.column + 1 >= columns {
                if self.mode.contains(TermMode::LINE_WRAP) {
                    // Insert placeholder before wide char if glyph does not fit in this row.
                    self.grid
                        .cursor
                        .template
                        .flags
                        .insert(ShellFlags::LEADING_WIDE_CHAR_SPACER);
                    self.write_at_cursor(' ');
                    self.grid
                        .cursor
                        .template
                        .flags
                        .remove(ShellFlags::LEADING_WIDE_CHAR_SPACER);
                    self.wrapline();
                } else {
                    // Prevent out of bounds crash when linewrapping is disabled.
                    self.grid.cursor.input_needs_wrap = true;
                    return;
                }
            }

            // Write full width glyph to current cursor cell.
            self.grid.cursor.template.flags.insert(ShellFlags::WIDE_CHAR);
            self.write_at_cursor(c);
            self.grid.cursor.template.flags.remove(ShellFlags::WIDE_CHAR);

            // Write spacer to cell following the wide glyph.
            self.grid.cursor.point.column += 1;
            self.grid.cursor.template.flags.insert(ShellFlags::WIDE_CHAR_SPACER);
            self.write_at_cursor(' ');
            self.grid.cursor.template.flags.remove(ShellFlags::WIDE_CHAR_SPACER);
        }

        if self.grid.cursor.point.column + 1 < columns {
            self.grid.cursor.point.column += 1;
        } else {
            self.grid.cursor.input_needs_wrap = true;
        }

        trace!("Current cursor position: {:?}", self.grid.cursor.point);
    }