# pylint: disable=function-redefined
from __future__ import unicode_literals
from prompt_toolkit.application.current import get_app
from prompt_toolkit.buffer import indent, unindent, reshape_text
from prompt_toolkit.clipboard import ClipboardData
from prompt_toolkit.document import Document
from prompt_toolkit.filters import Condition, has_arg, Always, is_read_only, is_searching
from prompt_toolkit.filters.app import vi_navigation_mode, vi_insert_mode, vi_insert_multiple_mode, vi_replace_mode, vi_selection_mode, vi_waiting_for_text_object_mode, vi_digraph_mode, vi_mode, in_paste_mode, is_multiline, vi_search_direction_reversed, vi_recording_macro
from prompt_toolkit.input.vt100_parser import Vt100Parser
from prompt_toolkit.key_binding.digraphs import DIGRAPHS
from prompt_toolkit.key_binding.vi_state import CharacterFind, InputMode
from prompt_toolkit.keys import Keys
from prompt_toolkit.search import SearchDirection
from prompt_toolkit.selection import SelectionType, SelectionState, PasteMode

from .named_commands import get_by_name
from ..key_bindings import KeyBindings, ConditionalKeyBindings, KeyBindingsBase

from six.moves import range
import codecs
import six
import string

try:
    from itertools import accumulate
except ImportError:  # < Python 3.2
    def accumulate(iterable):
        " Super simple 'accumulate' implementation. "
        total = 0
        for item in iterable:
            total += item
            yield total

__all__ = [
    'load_vi_bindings',
    'load_vi_search_bindings',
]

if six.PY2:
    ascii_lowercase = string.ascii_lowercase.decode('ascii')
else:
    ascii_lowercase = string.ascii_lowercase

vi_register_names = ascii_lowercase + '0123456789'


class TextObjectType(object):
    EXCLUSIVE = 'EXCLUSIVE'
    INCLUSIVE = 'INCLUSIVE'
    LINEWISE = 'LINEWISE'
    BLOCK = 'BLOCK'


class TextObject(object):
    """
    Return struct for functions wrapped in ``text_object``.
    Both `start` and `end` are relative to the current cursor position.
    """
    def __init__(self, start, end=0, type=TextObjectType.EXCLUSIVE):
        self.start = start
        self.end = end
        self.type = type

    @property
    def selection_type(self):
        if self.type == TextObjectType.LINEWISE:
            return SelectionType.LINES
        if self.type == TextObjectType.BLOCK:
            return SelectionType.BLOCK
        else:
            return SelectionType.CHARACTERS

    def sorted(self):
        """
        Return a (start, end) tuple where start <= end.
        """
        if self.start < self.end:
            return self.start, self.end
        else:
            return self.end, self.start

    def operator_range(self, document):
        """
        Return a (start, end) tuple with start <= end that indicates the range
        operators should operate on.
        `buffer` is used to get start and end of line positions.

        This should return something that can be used in a slice, so the `end`
        position is *not* included.
        """
        start, end = self.sorted()
        doc = document

        if (self.type == TextObjectType.EXCLUSIVE and
                doc.translate_index_to_position(end + doc.cursor_position)[1] == 0):
            # If the motion is exclusive and the end of motion is on the first
            # column, the end position becomes end of previous line.
            end -= 1
        if self.type == TextObjectType.INCLUSIVE:
            end += 1
        if self.type == TextObjectType.LINEWISE:
            # Select whole lines
            row, col = doc.translate_index_to_position(start + doc.cursor_position)
            start = doc.translate_row_col_to_index(row, 0) - doc.cursor_position
            row, col = doc.translate_index_to_position(end + doc.cursor_position)
            end = doc.translate_row_col_to_index(row, len(doc.lines[row])) - doc.cursor_position
        return start, end

    def get_line_numbers(self, buffer):
        """
        Return a (start_line, end_line) pair.
        """
        # Get absolute cursor positions from the text object.
        from_, to = self.operator_range(buffer.document)
        from_ += buffer.cursor_position
        to += buffer.cursor_position

        # Take the start of the lines.
        from_, _ = buffer.document.translate_index_to_position(from_)
        to, _ = buffer.document.translate_index_to_position(to)

        return from_, to

    def cut(self, buffer):
        """
        Turn text object into `ClipboardData` instance.
        """
        from_, to = self.operator_range(buffer.document)

        from_ += buffer.cursor_position
        to += buffer.cursor_position

        # For Vi mode, the SelectionState does include the upper position,
        # while `self.operator_range` does not. So, go one to the left, unless
        # we're in the line mode, then we don't want to risk going to the
        # previous line, and missing one line in the selection.
        if self.type != TextObjectType.LINEWISE:
            to -= 1

        document = Document(buffer.text, to, SelectionState(
            original_cursor_position=from_, type=self.selection_type))

        new_document, clipboard_data = document.cut_selection()
        return new_document, clipboard_data


def create_text_object_decorator(key_bindings):
    """
    Create a decorator that can be used to register Vi text object implementations.
    """
    assert isinstance(key_bindings, KeyBindingsBase)

    def text_object_decorator(*keys, **kw):
        """
        Register a text object function.

        Usage::

            @text_object('w', filter=..., no_move_handler=False)
            def handler(event):
                # Return a text object for this key.
                return TextObject(...)

        :param no_move_handler: Disable the move handler in navigation mode.
            (It's still active in selection mode.)
        """
        filter = kw.pop('filter', Always())
        no_move_handler = kw.pop('no_move_handler', False)
        no_selection_handler = kw.pop('no_selection_handler', False)
        eager = kw.pop('eager', False)
        assert not kw

        def decorator(text_object_func):
            assert callable(text_object_func)

            @key_bindings.add(*keys, filter=vi_waiting_for_text_object_mode & filter, eager=eager)
            def _(event):
                # Arguments are multiplied.
                vi_state = event.app.vi_state
                event._arg = (vi_state.operator_arg or 1) * (event.arg or 1)

                # Call the text object handler.
                text_obj = text_object_func(event)
                if text_obj is not None:
                    assert isinstance(text_obj, TextObject)

                    # Call the operator function with the text object.
                    vi_state.operator_func(event, text_obj)

                # Clear operator.
                event.app.vi_state.operator_func = None
                event.app.vi_state.operator_arg = None

            # Register a move operation. (Doesn't need an operator.)
            if not no_move_handler:
                @key_bindings.add(*keys, filter=~vi_waiting_for_text_object_mode & filter & vi_navigation_mode, eager=eager)
                def _(event):
                    " Move handler for navigation mode. "
                    text_object = text_object_func(event)
                    event.current_buffer.cursor_position += text_object.start

            # Register a move selection operation.
            if not no_selection_handler:
                @key_bindings.add(*keys, filter=~vi_waiting_for_text_object_mode & filter & vi_selection_mode, eager=eager)
                def _(event):
                    " Move handler for selection mode. "
                    text_object = text_object_func(event)
                    buff = event.current_buffer

                    # When the text object has both a start and end position, like 'i(' or 'iw',
                    # Turn this into a selection, otherwise the cursor.
                    if text_object.end:
                        # Take selection positions from text object.
                        start, end = text_object.operator_range(buff.document)
                        start += buff.cursor_position
                        end += buff.cursor_position

                        buff.selection_state.original_cursor_position = start
                        buff.cursor_position = end

                        # Take selection type from text object.
                        if text_object.type == TextObjectType.LINEWISE:
                            buff.selection_state.type = SelectionType.LINES
                        else:
                            buff.selection_state.type = SelectionType.CHARACTERS
                    else:
                        event.current_buffer.cursor_position += text_object.start

            # Make it possible to chain @text_object decorators.
            return text_object_func

        return decorator
    return text_object_decorator


def create_operator_decorator(key_bindings):
    """
    Create a decorator that can be used for registering Vi operators.
    """
    assert isinstance(key_bindings, KeyBindingsBase)

    def operator_decorator(*keys, **kw):
        """
        Register a Vi operator.

        Usage::

            @operator('d', filter=...)
            def handler(event, text_object):
                # Do something with the text object here.
        """
        filter = kw.pop('filter', Always())
        eager = kw.pop('eager', False)
        assert not kw

        def decorator(operator_func):
            @key_bindings.add(*keys, filter=~vi_waiting_for_text_object_mode & filter & vi_navigation_mode, eager=eager)
            def _(event):
                """
                Handle operator in navigation mode.
                """
                # When this key binding is matched, only set the operator
                # function in the ViState. We should execute it after a text
                # object has been received.
                event.app.vi_state.operator_func = operator_func
                event.app.vi_state.operator_arg = event.arg

            @key_bindings.add(*keys, filter=~vi_waiting_for_text_object_mode & filter & vi_selection_mode, eager=eager)
            def _(event):
                """
                Handle operator in selection mode.
                """
                buff = event.current_buffer
                selection_state = buff.selection_state

                # Create text object from selection.
                if selection_state.type == SelectionType.LINES:
                    text_obj_type = TextObjectType.LINEWISE
                elif selection_state.type == SelectionType.BLOCK:
                    text_obj_type = TextObjectType.BLOCK
                else:
                    text_obj_type = TextObjectType.INCLUSIVE

                text_object = TextObject(
                    selection_state.original_cursor_position - buff.cursor_position,
                    type=text_obj_type)

                # Execute operator.
                operator_func(event, text_object)

                # Quit selection mode.
                buff.selection_state = None

            return operator_func
        return decorator
    return operator_decorator


def load_vi_bindings():
    """
    Vi extensions.

    # Overview of Readline Vi commands:
    # http://www.catonmat.net/download/bash-vi-editing-mode-cheat-sheet.pdf
    """
    # Note: Some key bindings have the "~IsReadOnly()" filter added. This
    #       prevents the handler to be executed when the focus is on a
    #       read-only buffer.
    #       This is however only required for those that change the ViState to
    #       INSERT mode. The `Buffer` class itself throws the
    #       `EditReadOnlyBuffer` exception for any text operations which is
    #       handled correctly. There is no need to add "~IsReadOnly" to all key
    #       bindings that do text manipulation.

    key_bindings = KeyBindings()
    handle = key_bindings.add

    # (Note: Always take the navigation bindings in read-only mode, even when
    #  ViState says different.)

    vi_transform_functions = [
        # Rot 13 transformation
        (('g', '?'), Always(), lambda string: codecs.encode(string, 'rot_13')),

        # To lowercase
        (('g', 'u'), Always(), lambda string: string.lower()),

        # To uppercase.
        (('g', 'U'), Always(), lambda string: string.upper()),

        # Swap case.
        (('g', '~'), Always(), lambda string: string.swapcase()),
        (('~', ), Condition(lambda: get_app().vi_state.tilde_operator), lambda string: string.swapcase()),
    ]

    # Insert a character literally (quoted insert).
    handle('c-v', filter=vi_insert_mode)(get_by_name('quoted-insert'))

    @handle('escape')
    def _(event):
        """
        Escape goes to vi navigation mode.
        """
        buffer = event.current_buffer
        vi_state = event.app.vi_state

        if vi_state.input_mode in (InputMode.INSERT, InputMode.REPLACE):
            buffer.cursor_position += buffer.document.get_cursor_left_position()

        vi_state.input_mode = InputMode.NAVIGATION

        if bool(buffer.selection_state):
            buffer.exit_selection()

    @handle('k', filter=vi_selection_mode)
    def _(event):
        """
        Arrow up in selection mode.
        """
        event.current_buffer.cursor_up(count=event.arg)

    @handle('j', filter=vi_selection_mode)
    def _(event):
        """
        Arrow down in selection mode.
        """
        event.current_buffer.cursor_down(count=event.arg)

    @handle('up', filter=vi_navigation_mode)
    @handle('c-p', filter=vi_navigation_mode)
    def _(event):
        """
        Arrow up and ControlP in navigation mode go up.
        """
        event.current_buffer.auto_up(count=event.arg)

    @handle('k', filter=vi_navigation_mode)
    def _(event):
        """
        Go up, but if we enter a new history entry, move to the start of the
        line.
        """
        event.current_buffer.auto_up(
            count=event.arg, go_to_start_of_line_if_history_changes=True)

    @handle('down', filter=vi_navigation_mode)
    @handle('c-n', filter=vi_navigation_mode)
    def _(event):
        """
        Arrow down and Control-N in navigation mode.
        """
        event.current_buffer.auto_down(count=event.arg)

    @handle('j', filter=vi_navigation_mode)
    def _(event):
        """
        Go down, but if we enter a new history entry, go to the start of the line.
        """
        event.current_buffer.auto_down(
            count=event.arg, go_to_start_of_line_if_history_changes=True)

    @handle('backspace', filter=vi_navigation_mode)
    def _(event):
        """
        In navigation-mode, move cursor.
        """
        event.current_buffer.cursor_position += \
            event.current_buffer.document.get_cursor_left_position(count=event.arg)

    @handle('c-n', filter=vi_insert_mode)
    def _(event):
        b = event.current_buffer

        if b.complete_state:
            b.complete_next()
        else:
            b.start_completion(select_first=True)

    @handle('c-p', filter=vi_insert_mode)
    def _(event):
        """
        Control-P: To previous completion.
        """
        b = event.current_buffer

        if b.complete_state:
            b.complete_previous()
        else:
            b.start_completion(select_last=True)

    @handle('c-g', filter=vi_insert_mode)
    @handle('c-y', filter=vi_insert_mode)
    def _(event):
        """
        Accept current completion.
        """
        event.current_buffer.complete_state = None

    @handle('c-e', filter=vi_insert_mode)
    def _(event):
        """
        Cancel completion. Go back to originally typed text.
        """
        event.current_buffer.cancel_completion()

    @Condition
    def is_returnable():
        return get_app().current_buffer.is_returnable

    # In navigation mode, pressing enter will always return the input.
    handle('enter', filter=vi_navigation_mode & is_returnable)(
        get_by_name('accept-line'))

    # In insert mode, also accept input when enter is pressed, and the buffer
    # has been marked as single line.
    handle('enter', filter=is_returnable & ~is_multiline)(
        get_by_name('accept-line'))

    @handle('enter', filter=~is_returnable & vi_navigation_mode)
    def _(event):
        " Go to the beginning of next line. "
        b = event.current_buffer
        b.cursor_down(count=event.arg)
        b.cursor_position += b.document.get_start_of_line_position(after_whitespace=True)

    # ** In navigation mode **

    # List of navigation commands: http://hea-www.harvard.edu/~fine/Tech/vi.html

    @handle('insert', filter=vi_navigation_mode)
    def _(event):
        " Pressing the Insert key. "
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('a', filter=vi_navigation_mode & ~is_read_only)
            # ~IsReadOnly, because we want to stay in navigation mode for
            # read-only buffers.
    def _(event):
        event.current_buffer.cursor_position += event.current_buffer.document.get_cursor_right_position()
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('A', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        event.current_buffer.cursor_position += event.current_buffer.document.get_end_of_line_position()
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('C', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        """
        # Change to end of line.
        # Same as 'c$' (which is implemented elsewhere.)
        """
        buffer = event.current_buffer

        deleted = buffer.delete(count=buffer.document.get_end_of_line_position())
        event.app.clipboard.set_text(deleted)
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('c', 'c', filter=vi_navigation_mode & ~is_read_only)
    @handle('S', filter=vi_navigation_mode & ~is_read_only)
    def _(event):  # TODO: implement 'arg'
        """
        Change current line
        """
        buffer = event.current_buffer

        # We copy the whole line.
        data = ClipboardData(buffer.document.current_line, SelectionType.LINES)
        event.app.clipboard.set_data(data)

        # But we delete after the whitespace
        buffer.cursor_position += buffer.document.get_start_of_line_position(after_whitespace=True)
        buffer.delete(count=buffer.document.get_end_of_line_position())
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('D', filter=vi_navigation_mode)
    def _(event):
        buffer = event.current_buffer
        deleted = buffer.delete(count=buffer.document.get_end_of_line_position())
        event.app.clipboard.set_text(deleted)

    @handle('d', 'd', filter=vi_navigation_mode)
    def _(event):
        """
        Delete line. (Or the following 'n' lines.)
        """
        buffer = event.current_buffer

        # Split string in before/deleted/after text.
        lines = buffer.document.lines

        before = '\n'.join(lines[:buffer.document.cursor_position_row])
        deleted = '\n'.join(lines[buffer.document.cursor_position_row:
                                  buffer.document.cursor_position_row + event.arg])
        after = '\n'.join(lines[buffer.document.cursor_position_row + event.arg:])

        # Set new text.
        if before and after:
            before = before + '\n'

        # Set text and cursor position.
        buffer.document = Document(
            text=before + after,
            # Cursor At the start of the first 'after' line, after the leading whitespace.
            cursor_position = len(before) + len(after) - len(after.lstrip(' ')))

        # Set clipboard data
        event.app.clipboard.set_data(ClipboardData(deleted, SelectionType.LINES))

    @handle('x', filter=vi_selection_mode)
    def _(event):
        """
        Cut selection.
        ('x' is not an operator.)
        """
        clipboard_data = event.current_buffer.cut_selection()
        event.app.clipboard.set_data(clipboard_data)

    @handle('i', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('I', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        event.app.vi_state.input_mode = InputMode.INSERT
        event.current_buffer.cursor_position += \
            event.current_buffer.document.get_start_of_line_position(after_whitespace=True)

    @Condition
    def in_block_selection():
        buff = get_app().current_buffer
        return buff.selection_state and buff.selection_state.type == SelectionType.BLOCK

    @handle('I', filter=in_block_selection & ~is_read_only)
    def go_to_block_selection(event, after=False):
        " Insert in block selection mode. "
        buff = event.current_buffer

        # Store all cursor positions.
        positions = []

        if after:
            def get_pos(from_to):
                return from_to[1]
        else:
            def get_pos(from_to):
                return from_to[0]

        for i, from_to in enumerate(buff.document.selection_ranges()):
            positions.append(get_pos(from_to))
            if i == 0:
                buff.cursor_position = get_pos(from_to)

        buff.multiple_cursor_positions = positions

        # Go to 'INSERT_MULTIPLE' mode.
        event.app.vi_state.input_mode = InputMode.INSERT_MULTIPLE
        buff.exit_selection()

    @handle('A', filter=in_block_selection & ~is_read_only)
    def _(event):
        go_to_block_selection(event, after=True)

    @handle('J', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        " Join lines. "
        for i in range(event.arg):
            event.current_buffer.join_next_line()

    @handle('g', 'J', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        " Join lines without space. "
        for i in range(event.arg):
            event.current_buffer.join_next_line(separator='')

    @handle('J', filter=vi_selection_mode & ~is_read_only)
    def _(event):
        " Join selected lines. "
        event.current_buffer.join_selected_lines()

    @handle('g', 'J', filter=vi_selection_mode & ~is_read_only)
    def _(event):
        " Join selected lines without space. "
        event.current_buffer.join_selected_lines(separator='')

    @handle('p', filter=vi_navigation_mode)
    def _(event):
        """
        Paste after
        """
        event.current_buffer.paste_clipboard_data(
            event.app.clipboard.get_data(),
            count=event.arg,
            paste_mode=PasteMode.VI_AFTER)

    @handle('P', filter=vi_navigation_mode)
    def _(event):
        """
        Paste before
        """
        event.current_buffer.paste_clipboard_data(
            event.app.clipboard.get_data(),
            count=event.arg,
            paste_mode=PasteMode.VI_BEFORE)

    @handle('"', Keys.Any, 'p', filter=vi_navigation_mode)
    def _(event):
        " Paste from named register. "
        c = event.key_sequence[1].data
        if c in vi_register_names:
            data = event.app.vi_state.named_registers.get(c)
            if data:
                event.current_buffer.paste_clipboard_data(
                    data, count=event.arg, paste_mode=PasteMode.VI_AFTER)

    @handle('"', Keys.Any, 'P', filter=vi_navigation_mode)
    def _(event):
        " Paste (before) from named register. "
        c = event.key_sequence[1].data
        if c in vi_register_names:
            data = event.app.vi_state.named_registers.get(c)
            if data:
                event.current_buffer.paste_clipboard_data(
                    data, count=event.arg, paste_mode=PasteMode.VI_BEFORE)

    @handle('r', Keys.Any, filter=vi_navigation_mode)
    def _(event):
        """
        Replace single character under cursor
        """
        event.current_buffer.insert_text(event.data * event.arg, overwrite=True)
        event.current_buffer.cursor_position -= 1

    @handle('R', filter=vi_navigation_mode)
    def _(event):
        """
        Go to 'replace'-mode.
        """
        event.app.vi_state.input_mode = InputMode.REPLACE

    @handle('s', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        """
        Substitute with new text
        (Delete character(s) and go to insert mode.)
        """
        text = event.current_buffer.delete(count=event.arg)
        event.app.clipboard.set_text(text)
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('u', filter=vi_navigation_mode, save_before=(lambda e: False))
    def _(event):
        for i in range(event.arg):
            event.current_buffer.undo()

    @handle('V', filter=vi_navigation_mode)
    def _(event):
        """
        Start lines selection.
        """
        event.current_buffer.start_selection(selection_type=SelectionType.LINES)

    @handle('c-v', filter=vi_navigation_mode)
    def _(event):
        " Enter block selection mode. "
        event.current_buffer.start_selection(selection_type=SelectionType.BLOCK)

    @handle('V', filter=vi_selection_mode)
    def _(event):
        """
        Exit line selection mode, or go from non line selection mode to line
        selection mode.
        """
        selection_state = event.current_buffer.selection_state

        if selection_state.type != SelectionType.LINES:
            selection_state.type = SelectionType.LINES
        else:
            event.current_buffer.exit_selection()

    @handle('v', filter=vi_navigation_mode)
    def _(event):
        " Enter character selection mode. "
        event.current_buffer.start_selection(selection_type=SelectionType.CHARACTERS)

    @handle('v', filter=vi_selection_mode)
    def _(event):
        """
        Exit character selection mode, or go from non-character-selection mode
        to character selection mode.
        """
        selection_state = event.current_buffer.selection_state

        if selection_state.type != SelectionType.CHARACTERS:
            selection_state.type = SelectionType.CHARACTERS
        else:
            event.current_buffer.exit_selection()

    @handle('c-v', filter=vi_selection_mode)
    def _(event):
        """
        Exit block selection mode, or go from non block selection mode to block
        selection mode.
        """
        selection_state = event.current_buffer.selection_state

        if selection_state.type != SelectionType.BLOCK:
            selection_state.type = SelectionType.BLOCK
        else:
            event.current_buffer.exit_selection()

    @handle('a', 'w', filter=vi_selection_mode)
    @handle('a', 'W', filter=vi_selection_mode)
    def _(event):
        """
        Switch from visual linewise mode to visual characterwise mode.
        """
        buffer = event.current_buffer

        if buffer.selection_state and buffer.selection_state.type == SelectionType.LINES:
            buffer.selection_state.type = SelectionType.CHARACTERS

    @handle('x', filter=vi_navigation_mode)
    def _(event):
        """
        Delete character.
        """
        buff = event.current_buffer
        count = min(event.arg, len(buff.document.current_line_after_cursor))
        if count:
            text = event.current_buffer.delete(count=count)
            event.app.clipboard.set_text(text)

    @handle('X', filter=vi_navigation_mode)
    def _(event):
        buff = event.current_buffer
        count = min(event.arg, len(buff.document.current_line_before_cursor))
        if count:
            text = event.current_buffer.delete_before_cursor(count=count)
            event.app.clipboard.set_text(text)

    @handle('y', 'y', filter=vi_navigation_mode)
    @handle('Y', filter=vi_navigation_mode)
    def _(event):
        """
        Yank the whole line.
        """
        text = '\n'.join(event.current_buffer.document.lines_from_current[:event.arg])
        event.app.clipboard.set_data(ClipboardData(text, SelectionType.LINES))

    @handle('+', filter=vi_navigation_mode)
    def _(event):
        """
        Move to first non whitespace of next line
        """
        buffer = event.current_buffer
        buffer.cursor_position += buffer.document.get_cursor_down_position(count=event.arg)
        buffer.cursor_position += buffer.document.get_start_of_line_position(after_whitespace=True)

    @handle('-', filter=vi_navigation_mode)
    def _(event):
        """
        Move to first non whitespace of previous line
        """
        buffer = event.current_buffer
        buffer.cursor_position += buffer.document.get_cursor_up_position(count=event.arg)
        buffer.cursor_position += buffer.document.get_start_of_line_position(after_whitespace=True)

    @handle('>', '>', filter=vi_navigation_mode)
    def _(event):
        """
        Indent lines.
        """
        buffer = event.current_buffer
        current_row = buffer.document.cursor_position_row
        indent(buffer, current_row, current_row + event.arg)

    @handle('<', '<', filter=vi_navigation_mode)
    def _(event):
        """
        Unindent lines.
        """
        current_row = event.current_buffer.document.cursor_position_row
        unindent(event.current_buffer, current_row, current_row + event.arg)

    @handle('O', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        """
        Open line above and enter insertion mode
        """
        event.current_buffer.insert_line_above(
                copy_margin=not in_paste_mode())
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('o', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        """
        Open line below and enter insertion mode
        """
        event.current_buffer.insert_line_below(
                copy_margin=not in_paste_mode())
        event.app.vi_state.input_mode = InputMode.INSERT

    @handle('~', filter=vi_navigation_mode)
    def _(event):
        """
        Reverse case of current character and move cursor forward.
        """
        buffer = event.current_buffer
        c = buffer.document.current_char

        if c is not None and c != '\n':
            buffer.insert_text(c.swapcase(), overwrite=True)

    @handle('g', 'u', 'u', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        " Lowercase current line. "
        buff = event.current_buffer
        buff.transform_current_line(lambda s: s.lower())

    @handle('g', 'U', 'U', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        " Uppercase current line. "
        buff = event.current_buffer
        buff.transform_current_line(lambda s: s.upper())

    @handle('g', '~', '~', filter=vi_navigation_mode & ~is_read_only)
    def _(event):
        " Swap case of the current line. "
        buff = event.current_buffer
        buff.transform_current_line(lambda s: s.swapcase())

    @handle('#', filter=vi_navigation_mode)
    def _(event):
        """
        Go to previous occurrence of this word.
        """
        b = event.current_buffer
        search_state = event.app.current_search_state

        search_state.text = b.document.get_word_under_cursor()
        search_state.direction = SearchDirection.BACKWARD

        b.apply_search(search_state, count=event.arg,
                       include_current_position=False)

    @handle('*', filter=vi_navigation_mode)
    def _(event):
        """
        Go to next occurrence of this word.
        """
        b = event.current_buffer
        search_state = event.app.current_search_state

        search_state.text = b.document.get_word_under_cursor()
        search_state.direction = SearchDirection.FORWARD

        b.apply_search(search_state, count=event.arg,
                       include_current_position=False)

    @handle('(', filter=vi_navigation_mode)
    def _(event):
        # TODO: go to begin of sentence.
        # XXX: should become text_object.
        pass

    @handle(')', filter=vi_navigation_mode)
    def _(event):
        # TODO: go to end of sentence.
        # XXX: should become text_object.
        pass

    operator = create_operator_decorator(key_bindings)
    text_object = create_text_object_decorator(key_bindings)

    @text_object(Keys.Any, filter=vi_waiting_for_text_object_mode)
    def _(event):
        """
        Unknown key binding while waiting for a text object.
        """
        event.app.output.bell()

    #
    # *** Operators ***
    #

    def create_delete_and_change_operators(delete_only, with_register=False):
        """
        Delete and change operators.

        :param delete_only: Create an operator that deletes, but doesn't go to insert mode.
        :param with_register: Copy the deleted text to this named register instead of the clipboard.
        """
        if with_register:
            handler_keys = ('"', Keys.Any, 'cd'[delete_only])
        else:
            handler_keys = 'cd'[delete_only]

        @operator(*handler_keys, filter=~is_read_only)
        def delete_or_change_operator(event, text_object):
            clipboard_data = None
            buff = event.current_buffer

            if text_object:
                new_document, clipboard_data = text_object.cut(buff)
                buff.document = new_document

            # Set deleted/changed text to clipboard or named register.
            if clipboard_data and clipboard_data.text:
                if with_register:
                    reg_name = event.key_sequence[1].data
                    if reg_name in vi_register_names:
                        event.app.vi_state.named_registers[reg_name] = clipboard_data
                else:
                    event.app.clipboard.set_data(clipboard_data)

            # Only go back to insert mode in case of 'change'.
            if not delete_only:
                event.app.vi_state.input_mode = InputMode.INSERT

    create_delete_and_change_operators(False, False)
    create_delete_and_change_operators(False, True)
    create_delete_and_change_operators(True, False)
    create_delete_and_change_operators(True, True)

    def create_transform_handler(filter, transform_func, *a):
        @operator(*a, filter=filter & ~is_read_only)
        def _(event, text_object):
            """
            Apply transformation (uppercase, lowercase, rot13, swap case).
            """
            buff = event.current_buffer
            start, end = text_object.operator_range(buff.document)

            if start < end:
                # Transform.
                buff.transform_region(
                    buff.cursor_position + start,
                    buff.cursor_position + end,
                    transform_func)

                # Move cursor
                buff.cursor_position += (text_object.end or text_object.start)

    for k, f, func in vi_transform_functions:
        create_transform_handler(f, func, *k)

    @operator('y')
    def yank_handler(event, text_object):
        """
        Yank operator. (Copy text.)
        """
        _, clipboard_data = text_object.cut(event.current_buffer)
        if clipboard_data.text:
            event.app.clipboard.set_data(clipboard_data)

    @operator('"', Keys.Any, 'y')
    def _(event, text_object):
        " Yank selection to named register. "
        c = event.key_sequence[1].data
        if c in vi_register_names:
            _, clipboard_data = text_object.cut(event.current_buffer)
            event.app.vi_state.named_registers[c] = clipboard_data

    @operator('>')
    def _(event, text_object):
        """
        Indent.
        """
        buff = event.current_buffer
        from_, to = text_object.get_line_numbers(buff)
        indent(buff, from_, to + 1, count=event.arg)

    @operator('<')
    def _(event, text_object):
        """
        Unindent.
        """
        buff = event.current_buffer
        from_, to = text_object.get_line_numbers(buff)
        unindent(buff, from_, to + 1, count=event.arg)

    @operator('g', 'q')
    def _(event, text_object):
        """
        Reshape text.
        """
        buff = event.current_buffer
        from_, to = text_object.get_line_numbers(buff)
        reshape_text(buff, from_, to)

    #
    # *** Text objects ***
    #

    @text_object('b')
    def _(event):
        """ Move one word or token left. """
        return TextObject(event.current_buffer.document.find_start_of_previous_word(count=event.arg) or 0)

    @text_object('B')
    def _(event):
        """ Move one non-blank word left """
        return TextObject(event.current_buffer.document.find_start_of_previous_word(count=event.arg, WORD=True) or 0)

    @text_object('$')
    def key_dollar(event):
        """ 'c$', 'd$' and '$':  Delete/change/move until end of line. """
        return TextObject(event.current_buffer.document.get_end_of_line_position())

    @text_object('w')
    def _(event):
        """ 'word' forward. 'cw', 'dw', 'w': Delete/change/move one word.  """
        return TextObject(event.current_buffer.document.find_next_word_beginning(count=event.arg) or
                            event.current_buffer.document.get_end_of_document_position())

    @text_object('W')
    def _(event):
        """ 'WORD' forward. 'cW', 'dW', 'W': Delete/change/move one WORD.  """
        return TextObject(event.current_buffer.document.find_next_word_beginning(count=event.arg, WORD=True) or
                            event.current_buffer.document.get_end_of_document_position())

    @text_object('e')
    def _(event):
        """ End of 'word': 'ce', 'de', 'e' """
        end = event.current_buffer.document.find_next_word_ending(count=event.arg)
        return TextObject(end - 1 if end else 0, type=TextObjectType.INCLUSIVE)

    @text_object('E')
    def _(event):
        """ End of 'WORD': 'cE', 'dE', 'E' """
        end = event.current_buffer.document.find_next_word_ending(count=event.arg, WORD=True)
        return TextObject(end - 1 if end else 0, type=TextObjectType.INCLUSIVE)

    @text_object('i', 'w', no_move_handler=True)
    def _(event):
        """ Inner 'word': ciw and diw """
        start, end = event.current_buffer.document.find_boundaries_of_current_word()
        return TextObject(start, end)

    @text_object('a', 'w', no_move_handler=True)
    def _(event):
        """ A 'word': caw and daw """
        start, end = event.current_buffer.document.find_boundaries_of_current_word(include_trailing_whitespace=True)
        return TextObject(start, end)

    @text_object('i', 'W', no_move_handler=True)
    def _(event):
        """ Inner 'WORD': ciW and diW """
        start, end = event.current_buffer.document.find_boundaries_of_current_word(WORD=True)
        return TextObject(start, end)

    @text_object('a', 'W', no_move_handler=True)
    def _(event):
        """ A 'WORD': caw and daw """
        start, end = event.current_buffer.document.find_boundaries_of_current_word(WORD=True, include_trailing_whitespace=True)
        return TextObject(start, end)

    @text_object('a', 'p', no_move_handler=True)
    def _(event):
        """
        Auto paragraph.
        """
        start = event.current_buffer.document.start_of_paragraph()
        end = event.current_buffer.document.end_of_paragraph(count=event.arg)
        return TextObject(start, end)

    @text_object('^')
    def key_circumflex(event):
        """ 'c^', 'd^' and '^': Soft start of line, after whitespace. """
        return TextObject(event.current_buffer.document.get_start_of_line_position(after_whitespace=True))

    @text_object('0')
    def key_zero(event):
        """
        'c0', 'd0': Hard start of line, before whitespace.
        (The move '0' key is implemented elsewhere, because a '0' could also change the `arg`.)
        """
        return TextObject(event.current_buffer.document.get_start_of_line_position(after_whitespace=False))

    def create_ci_ca_handles(ci_start, ci_end, inner, key=None):
                # TODO: 'dat', 'dit', (tags (like xml)
        """
        Delete/Change string between this start and stop character. But keep these characters.
        This implements all the ci", ci<, ci{, ci(, di", di<, ca", ca<, ... combinations.
        """
        def handler(event):
            if ci_start == ci_end:
                # Quotes
                start = event.current_buffer.document.find_backwards(ci_start, in_current_line=False)
                end = event.current_buffer.document.find(ci_end, in_current_line=False)
            else:
                # Brackets
                start = event.current_buffer.document.find_enclosing_bracket_left(ci_start, ci_end)
                end = event.current_buffer.document.find_enclosing_bracket_right(ci_start, ci_end)

            if start is not None and end is not None:
                offset = 0 if inner else 1
                return TextObject(start + 1 - offset, end + offset)
            else:
                # Nothing found.
                return TextObject(0)

        if key is None:
            text_object('ai'[inner], ci_start, no_move_handler=True)(handler)
            text_object('ai'[inner], ci_end, no_move_handler=True)(handler)
        else:
            text_object('ai'[inner], key, no_move_handler=True)(handler)

    for inner in (False, True):
        for ci_start, ci_end in [('"', '"'), ("'", "'"), ("`", "`"),
                                 ('[', ']'), ('<', '>'), ('{', '}'), ('(', ')')]:
            create_ci_ca_handles(ci_start, ci_end, inner)

        create_ci_ca_handles('(', ')', inner, 'b')  # 'dab', 'dib'
        create_ci_ca_handles('{', '}', inner, 'B')  # 'daB', 'diB'

    @text_object('{')
    def _(event):
        """
        Move to previous blank-line separated section.
        Implements '{', 'c{', 'd{', 'y{'
        """
        index = event.current_buffer.document.start_of_paragraph(
            count=event.arg, before=True)
        return TextObject(index)

    @text_object('}')
    def _(event):
        """
        Move to next blank-line separated section.
        Implements '}', 'c}', 'd}', 'y}'
        """
        index = event.current_buffer.document.end_of_paragraph(count=event.arg, after=True)
        return TextObject(index)

    @text_object('f', Keys.Any)
    def _(event):
        """
        Go to next occurrence of character. Typing 'fx' will move the
        cursor to the next occurrence of character. 'x'.
        """
        event.app.vi_state.last_character_find = CharacterFind(event.data, False)
        match = event.current_buffer.document.find(
            event.data, in_current_line=True, count=event.arg)
        if match:
            return TextObject(match, type=TextObjectType.INCLUSIVE)
        else:
            return TextObject(0)

    @text_object('F', Keys.Any)
    def _(event):
        """
        Go to previous occurrence of character. Typing 'Fx' will move the
        cursor to the previous occurrence of character. 'x'.
        """
        event.app.vi_state.last_character_find = CharacterFind(event.data, True)
        return TextObject(event.current_buffer.document.find_backwards(
            event.data, in_current_line=True, count=event.arg) or 0)

    @text_object('t', Keys.Any)
    def _(event):
        """
        Move right to the next occurrence of c, then one char backward.
        """
        event.app.vi_state.last_character_find = CharacterFind(event.data, False)
        match = event.current_buffer.document.find(
            event.data, in_current_line=True, count=event.arg)
        if match:
            return TextObject(match - 1, type=TextObjectType.INCLUSIVE)
        else:
            return TextObject(0)

    @text_object('T', Keys.Any)
    def _(event):
        """
        Move left to the previous occurrence of c, then one char forward.
        """
        event.app.vi_state.last_character_find = CharacterFind(event.data, True)
        match = event.current_buffer.document.find_backwards(
            event.data, in_current_line=True, count=event.arg)
        return TextObject(match + 1 if match else 0)

    def repeat(reverse):
        """
        Create ',' and ';' commands.
        """
        @text_object(',' if reverse else ';')
        def _(event):
            # Repeat the last 'f'/'F'/'t'/'T' command.
            pos = 0
            vi_state = event.app.vi_state

            type = TextObjectType.EXCLUSIVE

            if vi_state.last_character_find:
                char = vi_state.last_character_find.character
                backwards = vi_state.last_character_find.backwards

                if reverse:
                    backwards = not backwards

                if backwards:
                    pos = event.current_buffer.document.find_backwards(char, in_current_line=True, count=event.arg)
                else:
                    pos = event.current_buffer.document.find(char, in_current_line=True, count=event.arg)
                    type = TextObjectType.INCLUSIVE
            if pos:
                return TextObject(pos, type=type)
            else:
                return TextObject(0)
    repeat(True)
    repeat(False)

    @text_object('h')
    @text_object('left')
    def _(event):
        """ Implements 'ch', 'dh', 'h': Cursor left. """
        return TextObject(event.current_buffer.document.get_cursor_left_position(count=event.arg))

    @text_object('j', no_move_handler=True, no_selection_handler=True)
            # Note: We also need `no_selection_handler`, because we in
            #       selection mode, we prefer the other 'j' binding that keeps
            #       `buffer.preferred_column`.
    def _(event):
        """ Implements 'cj', 'dj', 'j', ... Cursor up. """
        return TextObject(event.current_buffer.document.get_cursor_down_position(count=event.arg),
                          type=TextObjectType.LINEWISE)

    @text_object('k', no_move_handler=True, no_selection_handler=True)
    def _(event):
        """ Implements 'ck', 'dk', 'k', ... Cursor up. """
        return TextObject(event.current_buffer.document.get_cursor_up_position(count=event.arg),
                          type=TextObjectType.LINEWISE)

    @text_object('l')
    @text_object(' ')
    @text_object('right')
    def _(event):
        """ Implements 'cl', 'dl', 'l', 'c ', 'd ', ' '. Cursor right. """
        return TextObject(event.current_buffer.document.get_cursor_right_position(count=event.arg))

    @text_object('H')
    def _(event):
        """
        Moves to the start of the visible region. (Below the scroll offset.)
        Implements 'cH', 'dH', 'H'.
        """
        w = event.app.layout.current_window
        b = event.current_buffer

        if w and w.render_info:
            # When we find a Window that has BufferControl showing this window,
            # move to the start of the visible area.
            pos = (b.document.translate_row_col_to_index(
                       w.render_info.first_visible_line(after_scroll_offset=True), 0) -
                   b.cursor_position)

        else:
            # Otherwise, move to the start of the input.
            pos = -len(b.document.text_before_cursor)
        return TextObject(pos, type=TextObjectType.LINEWISE)

    @text_object('M')
    def _(event):
        """
        Moves cursor to the vertical center of the visible region.
        Implements 'cM', 'dM', 'M'.
        """
        w = event.app.layout.current_window
        b = event.current_buffer

        if w and w.render_info:
            # When we find a Window that has BufferControl showing this window,
            # move to the center of the visible area.
            pos = (b.document.translate_row_col_to_index(
                       w.render_info.center_visible_line(), 0) -
                   b.cursor_position)

        else:
            # Otherwise, move to the start of the input.
            pos = -len(b.document.text_before_cursor)
        return TextObject(pos, type=TextObjectType.LINEWISE)

    @text_object('L')
    def _(event):
        """
        Moves to the end of the visible region. (Above the scroll offset.)
        """
        w = event.app.layout.current_window
        b = event.current_buffer

        if w and w.render_info:
            # When we find a Window that has BufferControl showing this window,
            # move to the end of the visible area.
            pos = (b.document.translate_row_col_to_index(
                       w.render_info.last_visible_line(before_scroll_offset=True), 0) -
                   b.cursor_position)

        else:
            # Otherwise, move to the end of the input.
            pos = len(b.document.text_after_cursor)
        return TextObject(pos, type=TextObjectType.LINEWISE)

    @text_object('n', no_move_handler=True)
    def _(event):
        " Search next. "
        buff = event.current_buffer
        search_state = event.app.current_search_state

        cursor_position = buff.get_search_position(
            search_state, include_current_position=False, count=event.arg)
        return TextObject(cursor_position - buff.cursor_position)

    @handle('n', filter=vi_navigation_mode)
    def _(event):
        " Search next in navigation mode. (This goes through the history.) "
        search_state = event.app.current_search_state

        event.current_buffer.apply_search(
            search_state, include_current_position=False, count=event.arg)

    @text_object('N', no_move_handler=True)
    def _(event):
        " Search previous. "
        buff = event.current_buffer
        search_state = event.app.current_search_state

        cursor_position = buff.get_search_position(
            ~search_state, include_current_position=False, count=event.arg)
        return TextObject(cursor_position - buff.cursor_position)

    @handle('N', filter=vi_navigation_mode)
    def _(event):
        " Search previous in navigation mode. (This goes through the history.) "
        search_state = event.app.current_search_state

        event.current_buffer.apply_search(
            ~search_state, include_current_position=False, count=event.arg)

    @handle('z', '+', filter=vi_navigation_mode|vi_selection_mode)
    @handle('z', 't', filter=vi_navigation_mode|vi_selection_mode)
    @handle('z', 'enter', filter=vi_navigation_mode|vi_selection_mode)
    def _(event):
        """
        Scrolls the window to makes the current line the first line in the visible region.
        """
        b = event.current_buffer
        event.app.layout.current_window.vertical_scroll = b.document.cursor_position_row

    @handle('z', '-', filter=vi_navigation_mode|vi_selection_mode)
    @handle('z', 'b', filter=vi_navigation_mode|vi_selection_mode)
    def _(event):
        """
        Scrolls the window to makes the current line the last line in the visible region.
        """
        # We can safely set the scroll offset to zero; the Window will make
        # sure that it scrolls at least enough to make the cursor visible
        # again.
        event.app.layout.current_window.vertical_scroll = 0

    @handle('z', 'z', filter=vi_navigation_mode|vi_selection_mode)
    def _(event):
        """
        Center Window vertically around cursor.
        """
        w = event.app.layout.current_window
        b = event.current_buffer

        if w and w.render_info:
            info = w.render_info

            # Calculate the offset that we need in order to position the row
            # containing the cursor in the center.
            scroll_height = info.window_height // 2

            y = max(0, b.document.cursor_position_row - 1)
            height = 0
            while y > 0:
                line_height = info.get_height_for_line(y)

                if height + line_height < scroll_height:
                    height += line_height
                    y -= 1
                else:
                    break

            w.vertical_scroll = y

    @text_object('%')
    def _(event):
        """
        Implements 'c%', 'd%', '%, 'y%' (Move to corresponding bracket.)
        If an 'arg' has been given, go this this % position in the file.
        """
        buffer = event.current_buffer

        if event._arg:
            # If 'arg' has been given, the meaning of % is to go to the 'x%'
            # row in the file.
            if 0 < event.arg <= 100:
                absolute_index = buffer.document.translate_row_col_to_index(
                    int((event.arg * buffer.document.line_count - 1) / 100), 0)
                return TextObject(absolute_index - buffer.document.cursor_position, type=TextObjectType.LINEWISE)
            else:
                return TextObject(0)  # Do nothing.

        else:
            # Move to the corresponding opening/closing bracket (()'s, []'s and {}'s).
            match = buffer.document.find_matching_bracket_position()
            if match:
                return TextObject(match, type=TextObjectType.INCLUSIVE)
            else:
                return TextObject(0)

    @text_object('|')
    def _(event):
        # Move to the n-th column (you may specify the argument n by typing
        # it on number keys, for example, 20|).
        return TextObject(event.current_buffer.document.get_column_cursor_position(event.arg - 1))

    @text_object('g', 'g')
    def _(event):
        """
        Implements 'gg', 'cgg', 'ygg'
        """
        d = event.current_buffer.document

        if event._arg:
            # Move to the given line.
            return TextObject(d.translate_row_col_to_index(event.arg - 1, 0) - d.cursor_position, type=TextObjectType.LINEWISE)
        else:
            # Move to the top of the input.
            return TextObject(d.get_start_of_document_position(), type=TextObjectType.LINEWISE)

    @text_object('g', '_')
    def _(event):
        """
        Go to last non-blank of line.
        'g_', 'cg_', 'yg_', etc..
        """
        return TextObject(
            event.current_buffer.document.last_non_blank_of_current_line_position(), type=TextObjectType.INCLUSIVE)

    @text_object('g', 'e')
    def _(event):
        """
        Go to last character of previous word.
        'ge', 'cge', 'yge', etc..
        """
        prev_end = event.current_buffer.document.find_previous_word_ending(count=event.arg)
        return TextObject(prev_end - 1 if prev_end is not None else 0, type=TextObjectType.INCLUSIVE)

    @text_object('g', 'E')
    def _(event):
        """
        Go to last character of previous WORD.
        'gE', 'cgE', 'ygE', etc..
        """
        prev_end = event.current_buffer.document.find_previous_word_ending(count=event.arg, WORD=True)
        return TextObject(prev_end - 1 if prev_end is not None else 0, type=TextObjectType.INCLUSIVE)

    @text_object('g', 'm')
    def _(event):
        """
        Like g0, but half a screenwidth to the right. (Or as much as possible.)
        """
        w = event.app.layout.current_window
        buff = event.current_buffer

        if w and w.render_info:
            width = w.render_info.window_width
            start = buff.document.get_start_of_line_position(after_whitespace=False)
            start += int(min(width / 2, len(buff.document.current_line)))

            return TextObject(start, type=TextObjectType.INCLUSIVE)
        return TextObject(0)

    @text_object('G')
    def _(event):
        """
        Go to the end of the document. (If no arg has been given.)
        """
        buf = event.current_buffer
        return TextObject(buf.document.translate_row_col_to_index(buf.document.line_count - 1, 0) -
                          buf.cursor_position, type=TextObjectType.LINEWISE)

    #
    # *** Other ***
    #

    @handle('G', filter=has_arg)
    def _(event):
        """
        If an argument is given, move to this line in the  history. (for
        example, 15G)
        """
        event.current_buffer.go_to_history(event.arg - 1)

    for n in '123456789':
        @handle(n, filter=vi_navigation_mode|vi_selection_mode|vi_waiting_for_text_object_mode)
        def _(event):
            """
            Always handle numberics in navigation mode as arg.
            """
            event.append_to_arg_count(event.data)

    @handle('0', filter=(vi_navigation_mode|vi_selection_mode|vi_waiting_for_text_object_mode) & has_arg)
    def _(event):
        " Zero when an argument was already give. "
        event.append_to_arg_count(event.data)

    @handle(Keys.Any, filter=vi_replace_mode)
    def _(event):
        """
        Insert data at cursor position.
        """
        event.current_buffer.insert_text(event.data, overwrite=True)

    @handle(Keys.Any, filter=vi_insert_multiple_mode,
            save_before=(lambda e: not e.is_repeat))
    def _(event):
        """
        Insert data at multiple cursor positions at once.
        (Usually a result of pressing 'I' or 'A' in block-selection mode.)
        """
        buff = event.current_buffer
        original_text = buff.text

        # Construct new text.
        text = []
        p = 0

        for p2 in buff.multiple_cursor_positions:
            text.append(original_text[p:p2])
            text.append(event.data)
            p = p2

        text.append(original_text[p:])

        # Shift all cursor positions.
        new_cursor_positions = [
            pos + i + 1 for i, pos in enumerate(buff.multiple_cursor_positions)]

        # Set result.
        buff.text = ''.join(text)
        buff.multiple_cursor_positions = new_cursor_positions
        buff.cursor_position += 1

    @handle('backspace', filter=vi_insert_multiple_mode)
    def _(event):
        " Backspace, using multiple cursors. "
        buff = event.current_buffer
        original_text = buff.text

        # Construct new text.
        deleted_something = False
        text = []
        p = 0

        for p2 in buff.multiple_cursor_positions:
            if p2 > 0 and original_text[p2 - 1] != '\n':  # Don't delete across lines.
                text.append(original_text[p:p2 - 1])
                deleted_something = True
            else:
                text.append(original_text[p:p2])
            p = p2

        text.append(original_text[p:])

        if deleted_something:
            # Shift all cursor positions.
            lengths = [len(part) for part in text[:-1]]
            new_cursor_positions = list(accumulate(lengths))

            # Set result.
            buff.text = ''.join(text)
            buff.multiple_cursor_positions = new_cursor_positions
            buff.cursor_position -= 1
        else:
            event.app.output.bell()

    @handle('delete', filter=vi_insert_multiple_mode)
    def _(event):
        " Delete, using multiple cursors. "
        buff = event.current_buffer
        original_text = buff.text

        # Construct new text.
        deleted_something = False
        text = []
        new_cursor_positions = []
        p = 0

        for p2 in buff.multiple_cursor_positions:
            text.append(original_text[p:p2])
            if p2 >= len(original_text) or original_text[p2] == '\n':
                # Don't delete across lines.
                p = p2
            else:
                p = p2 + 1
                deleted_something = True

        text.append(original_text[p:])

        if deleted_something:
            # Shift all cursor positions.
            lengths = [len(part) for part in text[:-1]]
            new_cursor_positions = list(accumulate(lengths))

            # Set result.
            buff.text = ''.join(text)
            buff.multiple_cursor_positions = new_cursor_positions
        else:
            event.app.output.bell()

    @handle('left', filter=vi_insert_multiple_mode)
    def _(event):
        """
        Move all cursors to the left.
        (But keep all cursors on the same line.)
        """
        buff = event.current_buffer
        new_positions = []

        for p in buff.multiple_cursor_positions:
            if buff.document.translate_index_to_position(p)[1] > 0:
                p -= 1
            new_positions.append(p)

        buff.multiple_cursor_positions = new_positions

        if buff.document.cursor_position_col > 0:
            buff.cursor_position -= 1

    @handle('right', filter=vi_insert_multiple_mode)
    def _(event):
        """
        Move all cursors to the right.
        (But keep all cursors on the same line.)
        """
        buff = event.current_buffer
        new_positions = []

        for p in buff.multiple_cursor_positions:
            row, column = buff.document.translate_index_to_position(p)
            if column < len(buff.document.lines[row]):
                p += 1
            new_positions.append(p)

        buff.multiple_cursor_positions = new_positions

        if not buff.document.is_cursor_at_the_end_of_line:
            buff.cursor_position += 1

    @handle('up', filter=vi_insert_multiple_mode)
    @handle('down', filter=vi_insert_multiple_mode)
    def _(event):
        " Ignore all up/down key presses when in multiple cursor mode. "

    @handle('c-x', 'c-l', filter=vi_insert_mode)
    def _(event):
        """
        Pressing the ControlX - ControlL sequence in Vi mode does line
        completion based on the other lines in the document and the history.
        """
        event.current_buffer.start_history_lines_completion()

    @handle('c-x', 'c-f', filter=vi_insert_mode)
    def _(event):
        """
        Complete file names.
        """
        # TODO
        pass

    @handle('c-k', filter=vi_insert_mode|vi_replace_mode)
    def _(event):
        " Go into digraph mode. "
        event.app.vi_state.waiting_for_digraph = True

    @Condition
    def digraph_symbol_1_given():
        return get_app().vi_state.digraph_symbol1 is not None

    @handle(Keys.Any, filter=vi_digraph_mode & ~digraph_symbol_1_given)
    def _(event):
        event.app.vi_state.digraph_symbol1 = event.data

    @handle(Keys.Any, filter=vi_digraph_mode & digraph_symbol_1_given)
    def _(event):
        " Insert digraph. "
        try:
            # Lookup.
            code = (event.app.vi_state.digraph_symbol1, event.data)
            if code not in DIGRAPHS:
                code = code[::-1]  # Try reversing.
            symbol = DIGRAPHS[code]
        except KeyError:
            # Unknown digraph.
            event.app.output.bell()
        else:
            # Insert digraph.
            overwrite = event.app.vi_state.input_mode == InputMode.REPLACE
            event.current_buffer.insert_text(
                six.unichr(symbol), overwrite=overwrite)
            event.app.vi_state.waiting_for_digraph = False
        finally:
            event.app.vi_state.waiting_for_digraph = False
            event.app.vi_state.digraph_symbol1 = None

    @handle('c-o', filter=vi_insert_mode | vi_replace_mode)
    def _(event):
        " Go into normal mode for one single action. "
        event.app.vi_state.temporary_navigation_mode = True

    @handle('q', Keys.Any, filter=vi_navigation_mode & ~vi_recording_macro)
    def _(event):
        " Start recording macro. "
        c = event.key_sequence[1].data
        if c in vi_register_names:
            vi_state = event.app.vi_state

            vi_state.recording_register = c
            vi_state.current_recording = ''

    @handle('q', filter=vi_navigation_mode & vi_recording_macro)
    def _(event):
        " Stop recording macro. "
        vi_state = event.app.vi_state

        # Store and stop recording.
        vi_state.named_registers[vi_state.recording_register] = ClipboardData(vi_state.current_recording)
        vi_state.recording_register = None
        vi_state.current_recording = ''

    @handle('@', Keys.Any, filter=vi_navigation_mode, record_in_macro=False)
    def _(event):
        """
        Execute macro.

        Notice that we pass `record_in_macro=False`. This ensures that the `@x`
        keys don't appear in the recording itself. This function inserts the
        body of the called macro back into the KeyProcessor, so these keys will
        be added later on to the macro of their handlers have
        `record_in_macro=True`.
        """
        # Retrieve macro.
        c = event.key_sequence[1].data
        try:
            macro = event.app.vi_state.named_registers[c]
        except KeyError:
            return

        # Expand macro (which is a string in the register), in individual keys.
        # Use vt100 parser for this.
        keys = []

        parser = Vt100Parser(keys.append)
        parser.feed(macro.text)
        parser.flush()

        # Now feed keys back to the input processor.
        for _ in range(event.arg):
            event.app.key_processor.feed_multiple(keys, first=True)

    return ConditionalKeyBindings(key_bindings, vi_mode)


def load_vi_search_bindings():
    key_bindings = KeyBindings()
    handle = key_bindings.add
    from . import search

    @Condition
    def search_buffer_is_empty():
        " Returns True when the search buffer is empty. "
        return get_app().current_buffer.text == ''

    # Vi-style forward search.
    handle('/', filter=(vi_navigation_mode|vi_selection_mode)&~vi_search_direction_reversed) \
        (search.start_forward_incremental_search)
    handle('?', filter=(vi_navigation_mode|vi_selection_mode)&vi_search_direction_reversed) \
        (search.start_forward_incremental_search)
    handle('c-s')(search.start_forward_incremental_search)

    # Vi-style backward search.
    handle('?', filter=(vi_navigation_mode|vi_selection_mode)&~vi_search_direction_reversed) \
        (search.start_reverse_incremental_search)
    handle('/', filter=(vi_navigation_mode|vi_selection_mode)&vi_search_direction_reversed) \
        (search.start_reverse_incremental_search)
    handle('c-r')(search.start_reverse_incremental_search)

    # Apply the search. (At the / or ? prompt.)
    handle('enter', filter=is_searching)(search.accept_search)

    handle('c-r', filter=is_searching)(search.reverse_incremental_search)
    handle('c-s', filter=is_searching)(search.forward_incremental_search)

    handle('c-c')(search.abort_search)
    handle('c-g')(search.abort_search)
    handle('backspace', filter=search_buffer_is_empty)(search.abort_search)

    # Handle escape. This should accept the search, just like readline.
    # `abort_search` would be a meaningful alternative.
    handle('escape')(search.accept_search)

    return ConditionalKeyBindings(key_bindings, vi_mode)
