Adding upstream version 3.0.36.upstream/3.0.36upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1190 insertions, 0 deletions

diff --git a/src/prompt_toolkit/document.py b/src/prompt_toolkit/document.py
new file mode 100644
index 0000000..1984155
--- /dev/null
+++ b/src/prompt_toolkit/document.py
@@ -0,0 +1,1190 @@
+"""
+The `Document` that implements all the text operations/querying.
+"""
+import bisect
+import re
+import string
+import weakref
+from typing import (
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    NoReturn,
+    Optional,
+    Pattern,
+    Tuple,
+    cast,
+)
+
+from .clipboard import ClipboardData
+from .filters import vi_mode
+from .selection import PasteMode, SelectionState, SelectionType
+
+__all__ = [
+    "Document",
+]
+
+
+# Regex for finding "words" in documents. (We consider a group of alnum
+# characters a word, but also a group of special characters a word, as long as
+# it doesn't contain a space.)
+# (This is a 'word' in Vi.)
+_FIND_WORD_RE = re.compile(r"([a-zA-Z0-9_]+|[^a-zA-Z0-9_\s]+)")
+_FIND_CURRENT_WORD_RE = re.compile(r"^([a-zA-Z0-9_]+|[^a-zA-Z0-9_\s]+)")
+_FIND_CURRENT_WORD_INCLUDE_TRAILING_WHITESPACE_RE = re.compile(
+    r"^(([a-zA-Z0-9_]+|[^a-zA-Z0-9_\s]+)\s*)"
+)
+
+# Regex for finding "WORDS" in documents.
+# (This is a 'WORD in Vi.)
+_FIND_BIG_WORD_RE = re.compile(r"([^\s]+)")
+_FIND_CURRENT_BIG_WORD_RE = re.compile(r"^([^\s]+)")
+_FIND_CURRENT_BIG_WORD_INCLUDE_TRAILING_WHITESPACE_RE = re.compile(r"^([^\s]+\s*)")
+
+# Share the Document._cache between all Document instances.
+# (Document instances are considered immutable. That means that if another
+# `Document` is constructed with the same text, it should have the same
+# `_DocumentCache`.)
+_text_to_document_cache: Dict[str, "_DocumentCache"] = cast(
+    Dict[str, "_DocumentCache"],
+    weakref.WeakValueDictionary(),  # Maps document.text to DocumentCache instance.
+)
+
+
+class _ImmutableLineList(List[str]):
+    """
+    Some protection for our 'lines' list, which is assumed to be immutable in the cache.
+    (Useful for detecting obvious bugs.)
+    """
+
+    def _error(self, *a: object, **kw: object) -> NoReturn:
+        raise NotImplementedError("Attempt to modify an immutable list.")
+
+    __setitem__ = _error  # type: ignore
+    append = _error
+    clear = _error
+    extend = _error
+    insert = _error
+    pop = _error
+    remove = _error
+    reverse = _error
+    sort = _error  # type: ignore
+
+
+class _DocumentCache:
+    def __init__(self) -> None:
+        #: List of lines for the Document text.
+        self.lines: Optional[_ImmutableLineList] = None
+
+        #: List of index positions, pointing to the start of all the lines.
+        self.line_indexes: Optional[List[int]] = None
+
+
+class Document:
+    """
+    This is a immutable class around the text and cursor position, and contains
+    methods for querying this data, e.g. to give the text before the cursor.
+
+    This class is usually instantiated by a :class:`~prompt_toolkit.buffer.Buffer`
+    object, and accessed as the `document` property of that class.
+
+    :param text: string
+    :param cursor_position: int
+    :param selection: :class:`.SelectionState`
+    """
+
+    __slots__ = ("_text", "_cursor_position", "_selection", "_cache")
+
+    def __init__(
+        self,
+        text: str = "",
+        cursor_position: Optional[int] = None,
+        selection: Optional[SelectionState] = None,
+    ) -> None:
+
+        # Check cursor position. It can also be right after the end. (Where we
+        # insert text.)
+        assert cursor_position is None or cursor_position <= len(text), AssertionError(
+            f"cursor_position={cursor_position!r}, len_text={len(text)!r}"
+        )
+
+        # By default, if no cursor position was given, make sure to put the
+        # cursor position is at the end of the document. This is what makes
+        # sense in most places.
+        if cursor_position is None:
+            cursor_position = len(text)
+
+        # Keep these attributes private. A `Document` really has to be
+        # considered to be immutable, because otherwise the caching will break
+        # things. Because of that, we wrap these into read-only properties.
+        self._text = text
+        self._cursor_position = cursor_position
+        self._selection = selection
+
+        # Cache for lines/indexes. (Shared with other Document instances that
+        # contain the same text.
+        try:
+            self._cache = _text_to_document_cache[self.text]
+        except KeyError:
+            self._cache = _DocumentCache()
+            _text_to_document_cache[self.text] = self._cache
+
+        # XX: For some reason, above, we can't use 'WeakValueDictionary.setdefault'.
+        #     This fails in Pypy3. `self._cache` becomes None, because that's what
+        #     'setdefault' returns.
+        # self._cache = _text_to_document_cache.setdefault(self.text, _DocumentCache())
+        # assert self._cache
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.text!r}, {self.cursor_position!r})"
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, Document):
+            return False
+
+        return (
+            self.text == other.text
+            and self.cursor_position == other.cursor_position
+            and self.selection == other.selection
+        )
+
+    @property
+    def text(self) -> str:
+        "The document text."
+        return self._text
+
+    @property
+    def cursor_position(self) -> int:
+        "The document cursor position."
+        return self._cursor_position
+
+    @property
+    def selection(self) -> Optional[SelectionState]:
+        ":class:`.SelectionState` object."
+        return self._selection
+
+    @property
+    def current_char(self) -> str:
+        """Return character under cursor or an empty string."""
+        return self._get_char_relative_to_cursor(0) or ""
+
+    @property
+    def char_before_cursor(self) -> str:
+        """Return character before the cursor or an empty string."""
+        return self._get_char_relative_to_cursor(-1) or ""
+
+    @property
+    def text_before_cursor(self) -> str:
+        return self.text[: self.cursor_position :]
+
+    @property
+    def text_after_cursor(self) -> str:
+        return self.text[self.cursor_position :]
+
+    @property
+    def current_line_before_cursor(self) -> str:
+        """Text from the start of the line until the cursor."""
+        _, _, text = self.text_before_cursor.rpartition("\n")
+        return text
+
+    @property
+    def current_line_after_cursor(self) -> str:
+        """Text from the cursor until the end of the line."""
+        text, _, _ = self.text_after_cursor.partition("\n")
+        return text
+
+    @property
+    def lines(self) -> List[str]:
+        """
+        Array of all the lines.
+        """
+        # Cache, because this one is reused very often.
+        if self._cache.lines is None:
+            self._cache.lines = _ImmutableLineList(self.text.split("\n"))
+
+        return self._cache.lines
+
+    @property
+    def _line_start_indexes(self) -> List[int]:
+        """
+        Array pointing to the start indexes of all the lines.
+        """
+        # Cache, because this is often reused. (If it is used, it's often used
+        # many times. And this has to be fast for editing big documents!)
+        if self._cache.line_indexes is None:
+            # Create list of line lengths.
+            line_lengths = map(len, self.lines)
+
+            # Calculate cumulative sums.
+            indexes = [0]
+            append = indexes.append
+            pos = 0
+
+            for line_length in line_lengths:
+                pos += line_length + 1
+                append(pos)
+
+            # Remove the last item. (This is not a new line.)
+            if len(indexes) > 1:
+                indexes.pop()
+
+            self._cache.line_indexes = indexes
+
+        return self._cache.line_indexes
+
+    @property
+    def lines_from_current(self) -> List[str]:
+        """
+        Array of the lines starting from the current line, until the last line.
+        """
+        return self.lines[self.cursor_position_row :]
+
+    @property
+    def line_count(self) -> int:
+        r"""Return the number of lines in this document. If the document ends
+        with a trailing \n, that counts as the beginning of a new line."""
+        return len(self.lines)
+
+    @property
+    def current_line(self) -> str:
+        """Return the text on the line where the cursor is. (when the input
+        consists of just one line, it equals `text`."""
+        return self.current_line_before_cursor + self.current_line_after_cursor
+
+    @property
+    def leading_whitespace_in_current_line(self) -> str:
+        """The leading whitespace in the left margin of the current line."""
+        current_line = self.current_line
+        length = len(current_line) - len(current_line.lstrip())
+        return current_line[:length]
+
+    def _get_char_relative_to_cursor(self, offset: int = 0) -> str:
+        """
+        Return character relative to cursor position, or empty string
+        """
+        try:
+            return self.text[self.cursor_position + offset]
+        except IndexError:
+            return ""
+
+    @property
+    def on_first_line(self) -> bool:
+        """
+        True when we are at the first line.
+        """
+        return self.cursor_position_row == 0
+
+    @property
+    def on_last_line(self) -> bool:
+        """
+        True when we are at the last line.
+        """
+        return self.cursor_position_row == self.line_count - 1
+
+    @property
+    def cursor_position_row(self) -> int:
+        """
+        Current row. (0-based.)
+        """
+        row, _ = self._find_line_start_index(self.cursor_position)
+        return row
+
+    @property
+    def cursor_position_col(self) -> int:
+        """
+        Current column. (0-based.)
+        """
+        # (Don't use self.text_before_cursor to calculate this. Creating
+        # substrings and doing rsplit is too expensive for getting the cursor
+        # position.)
+        _, line_start_index = self._find_line_start_index(self.cursor_position)
+        return self.cursor_position - line_start_index
+
+    def _find_line_start_index(self, index: int) -> Tuple[int, int]:
+        """
+        For the index of a character at a certain line, calculate the index of
+        the first character on that line.
+
+        Return (row, index) tuple.
+        """
+        indexes = self._line_start_indexes
+
+        pos = bisect.bisect_right(indexes, index) - 1
+        return pos, indexes[pos]
+
+    def translate_index_to_position(self, index: int) -> Tuple[int, int]:
+        """
+        Given an index for the text, return the corresponding (row, col) tuple.
+        (0-based. Returns (0, 0) for index=0.)
+        """
+        # Find start of this line.
+        row, row_index = self._find_line_start_index(index)
+        col = index - row_index
+
+        return row, col
+
+    def translate_row_col_to_index(self, row: int, col: int) -> int:
+        """
+        Given a (row, col) tuple, return the corresponding index.
+        (Row and col params are 0-based.)
+
+        Negative row/col values are turned into zero.
+        """
+        try:
+            result = self._line_start_indexes[row]
+            line = self.lines[row]
+        except IndexError:
+            if row < 0:
+                result = self._line_start_indexes[0]
+                line = self.lines[0]
+            else:
+                result = self._line_start_indexes[-1]
+                line = self.lines[-1]
+
+        result += max(0, min(col, len(line)))
+
+        # Keep in range. (len(self.text) is included, because the cursor can be
+        # right after the end of the text as well.)
+        result = max(0, min(result, len(self.text)))
+        return result
+
+    @property
+    def is_cursor_at_the_end(self) -> bool:
+        """True when the cursor is at the end of the text."""
+        return self.cursor_position == len(self.text)
+
+    @property
+    def is_cursor_at_the_end_of_line(self) -> bool:
+        """True when the cursor is at the end of this line."""
+        return self.current_char in ("\n", "")
+
+    def has_match_at_current_position(self, sub: str) -> bool:
+        """
+        `True` when this substring is found at the cursor position.
+        """
+        return self.text.find(sub, self.cursor_position) == self.cursor_position
+
+    def find(
+        self,
+        sub: str,
+        in_current_line: bool = False,
+        include_current_position: bool = False,
+        ignore_case: bool = False,
+        count: int = 1,
+    ) -> Optional[int]:
+        """
+        Find `text` after the cursor, return position relative to the cursor
+        position. Return `None` if nothing was found.
+
+        :param count: Find the n-th occurrence.
+        """
+        assert isinstance(ignore_case, bool)
+
+        if in_current_line:
+            text = self.current_line_after_cursor
+        else:
+            text = self.text_after_cursor
+
+        if not include_current_position:
+            if len(text) == 0:
+                return None  # (Otherwise, we always get a match for the empty string.)
+            else:
+                text = text[1:]
+
+        flags = re.IGNORECASE if ignore_case else 0
+        iterator = re.finditer(re.escape(sub), text, flags)
+
+        try:
+            for i, match in enumerate(iterator):
+                if i + 1 == count:
+                    if include_current_position:
+                        return match.start(0)
+                    else:
+                        return match.start(0) + 1
+        except StopIteration:
+            pass
+        return None
+
+    def find_all(self, sub: str, ignore_case: bool = False) -> List[int]:
+        """
+        Find all occurrences of the substring. Return a list of absolute
+        positions in the document.
+        """
+        flags = re.IGNORECASE if ignore_case else 0
+        return [a.start() for a in re.finditer(re.escape(sub), self.text, flags)]
+
+    def find_backwards(
+        self,
+        sub: str,
+        in_current_line: bool = False,
+        ignore_case: bool = False,
+        count: int = 1,
+    ) -> Optional[int]:
+        """
+        Find `text` before the cursor, return position relative to the cursor
+        position. Return `None` if nothing was found.
+
+        :param count: Find the n-th occurrence.
+        """
+        if in_current_line:
+            before_cursor = self.current_line_before_cursor[::-1]
+        else:
+            before_cursor = self.text_before_cursor[::-1]
+
+        flags = re.IGNORECASE if ignore_case else 0
+        iterator = re.finditer(re.escape(sub[::-1]), before_cursor, flags)
+
+        try:
+            for i, match in enumerate(iterator):
+                if i + 1 == count:
+                    return -match.start(0) - len(sub)
+        except StopIteration:
+            pass
+        return None
+
+    def get_word_before_cursor(
+        self, WORD: bool = False, pattern: Optional[Pattern[str]] = None
+    ) -> str:
+        """
+        Give the word before the cursor.
+        If we have whitespace before the cursor this returns an empty string.
+
+        :param pattern: (None or compiled regex). When given, use this regex
+            pattern.
+        """
+        if self._is_word_before_cursor_complete(WORD=WORD, pattern=pattern):
+            # Space before the cursor or no text before cursor.
+            return ""
+
+        text_before_cursor = self.text_before_cursor
+        start = self.find_start_of_previous_word(WORD=WORD, pattern=pattern) or 0
+
+        return text_before_cursor[len(text_before_cursor) + start :]
+
+    def _is_word_before_cursor_complete(
+        self, WORD: bool = False, pattern: Optional[Pattern[str]] = None
+    ) -> bool:
+        if pattern:
+            return self.find_start_of_previous_word(WORD=WORD, pattern=pattern) is None
+        else:
+            return (
+                self.text_before_cursor == "" or self.text_before_cursor[-1:].isspace()
+            )
+
+    def find_start_of_previous_word(
+        self, count: int = 1, WORD: bool = False, pattern: Optional[Pattern[str]] = None
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the start
+        of the previous word. Return `None` if nothing was found.
+
+        :param pattern: (None or compiled regex). When given, use this regex
+            pattern.
+        """
+        assert not (WORD and pattern)
+
+        # Reverse the text before the cursor, in order to do an efficient
+        # backwards search.
+        text_before_cursor = self.text_before_cursor[::-1]
+
+        if pattern:
+            regex = pattern
+        elif WORD:
+            regex = _FIND_BIG_WORD_RE
+        else:
+            regex = _FIND_WORD_RE
+
+        iterator = regex.finditer(text_before_cursor)
+
+        try:
+            for i, match in enumerate(iterator):
+                if i + 1 == count:
+                    return -match.end(0)
+        except StopIteration:
+            pass
+        return None
+
+    def find_boundaries_of_current_word(
+        self,
+        WORD: bool = False,
+        include_leading_whitespace: bool = False,
+        include_trailing_whitespace: bool = False,
+    ) -> Tuple[int, int]:
+        """
+        Return the relative boundaries (startpos, endpos) of the current word under the
+        cursor. (This is at the current line, because line boundaries obviously
+        don't belong to any word.)
+        If not on a word, this returns (0,0)
+        """
+        text_before_cursor = self.current_line_before_cursor[::-1]
+        text_after_cursor = self.current_line_after_cursor
+
+        def get_regex(include_whitespace: bool) -> Pattern[str]:
+            return {
+                (False, False): _FIND_CURRENT_WORD_RE,
+                (False, True): _FIND_CURRENT_WORD_INCLUDE_TRAILING_WHITESPACE_RE,
+                (True, False): _FIND_CURRENT_BIG_WORD_RE,
+                (True, True): _FIND_CURRENT_BIG_WORD_INCLUDE_TRAILING_WHITESPACE_RE,
+            }[(WORD, include_whitespace)]
+
+        match_before = get_regex(include_leading_whitespace).search(text_before_cursor)
+        match_after = get_regex(include_trailing_whitespace).search(text_after_cursor)
+
+        # When there is a match before and after, and we're not looking for
+        # WORDs, make sure that both the part before and after the cursor are
+        # either in the [a-zA-Z_] alphabet or not. Otherwise, drop the part
+        # before the cursor.
+        if not WORD and match_before and match_after:
+            c1 = self.text[self.cursor_position - 1]
+            c2 = self.text[self.cursor_position]
+            alphabet = string.ascii_letters + "0123456789_"
+
+            if (c1 in alphabet) != (c2 in alphabet):
+                match_before = None
+
+        return (
+            -match_before.end(1) if match_before else 0,
+            match_after.end(1) if match_after else 0,
+        )
+
+    def get_word_under_cursor(self, WORD: bool = False) -> str:
+        """
+        Return the word, currently below the cursor.
+        This returns an empty string when the cursor is on a whitespace region.
+        """
+        start, end = self.find_boundaries_of_current_word(WORD=WORD)
+        return self.text[self.cursor_position + start : self.cursor_position + end]
+
+    def find_next_word_beginning(
+        self, count: int = 1, WORD: bool = False
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the start
+        of the next word. Return `None` if nothing was found.
+        """
+        if count < 0:
+            return self.find_previous_word_beginning(count=-count, WORD=WORD)
+
+        regex = _FIND_BIG_WORD_RE if WORD else _FIND_WORD_RE
+        iterator = regex.finditer(self.text_after_cursor)
+
+        try:
+            for i, match in enumerate(iterator):
+                # Take first match, unless it's the word on which we're right now.
+                if i == 0 and match.start(1) == 0:
+                    count += 1
+
+                if i + 1 == count:
+                    return match.start(1)
+        except StopIteration:
+            pass
+        return None
+
+    def find_next_word_ending(
+        self, include_current_position: bool = False, count: int = 1, WORD: bool = False
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the end
+        of the next word. Return `None` if nothing was found.
+        """
+        if count < 0:
+            return self.find_previous_word_ending(count=-count, WORD=WORD)
+
+        if include_current_position:
+            text = self.text_after_cursor
+        else:
+            text = self.text_after_cursor[1:]
+
+        regex = _FIND_BIG_WORD_RE if WORD else _FIND_WORD_RE
+        iterable = regex.finditer(text)
+
+        try:
+            for i, match in enumerate(iterable):
+                if i + 1 == count:
+                    value = match.end(1)
+
+                    if include_current_position:
+                        return value
+                    else:
+                        return value + 1
+
+        except StopIteration:
+            pass
+        return None
+
+    def find_previous_word_beginning(
+        self, count: int = 1, WORD: bool = False
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the start
+        of the previous word. Return `None` if nothing was found.
+        """
+        if count < 0:
+            return self.find_next_word_beginning(count=-count, WORD=WORD)
+
+        regex = _FIND_BIG_WORD_RE if WORD else _FIND_WORD_RE
+        iterator = regex.finditer(self.text_before_cursor[::-1])
+
+        try:
+            for i, match in enumerate(iterator):
+                if i + 1 == count:
+                    return -match.end(1)
+        except StopIteration:
+            pass
+        return None
+
+    def find_previous_word_ending(
+        self, count: int = 1, WORD: bool = False
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the end
+        of the previous word. Return `None` if nothing was found.
+        """
+        if count < 0:
+            return self.find_next_word_ending(count=-count, WORD=WORD)
+
+        text_before_cursor = self.text_after_cursor[:1] + self.text_before_cursor[::-1]
+
+        regex = _FIND_BIG_WORD_RE if WORD else _FIND_WORD_RE
+        iterator = regex.finditer(text_before_cursor)
+
+        try:
+            for i, match in enumerate(iterator):
+                # Take first match, unless it's the word on which we're right now.
+                if i == 0 and match.start(1) == 0:
+                    count += 1
+
+                if i + 1 == count:
+                    return -match.start(1) + 1
+        except StopIteration:
+            pass
+        return None
+
+    def find_next_matching_line(
+        self, match_func: Callable[[str], bool], count: int = 1
+    ) -> Optional[int]:
+        """
+        Look downwards for empty lines.
+        Return the line index, relative to the current line.
+        """
+        result = None
+
+        for index, line in enumerate(self.lines[self.cursor_position_row + 1 :]):
+            if match_func(line):
+                result = 1 + index
+                count -= 1
+
+            if count == 0:
+                break
+
+        return result
+
+    def find_previous_matching_line(
+        self, match_func: Callable[[str], bool], count: int = 1
+    ) -> Optional[int]:
+        """
+        Look upwards for empty lines.
+        Return the line index, relative to the current line.
+        """
+        result = None
+
+        for index, line in enumerate(self.lines[: self.cursor_position_row][::-1]):
+            if match_func(line):
+                result = -1 - index
+                count -= 1
+
+            if count == 0:
+                break
+
+        return result
+
+    def get_cursor_left_position(self, count: int = 1) -> int:
+        """
+        Relative position for cursor left.
+        """
+        if count < 0:
+            return self.get_cursor_right_position(-count)
+
+        return -min(self.cursor_position_col, count)
+
+    def get_cursor_right_position(self, count: int = 1) -> int:
+        """
+        Relative position for cursor_right.
+        """
+        if count < 0:
+            return self.get_cursor_left_position(-count)
+
+        return min(count, len(self.current_line_after_cursor))
+
+    def get_cursor_up_position(
+        self, count: int = 1, preferred_column: Optional[int] = None
+    ) -> int:
+        """
+        Return the relative cursor position (character index) where we would be if the
+        user pressed the arrow-up button.
+
+        :param preferred_column: When given, go to this column instead of
+                                 staying at the current column.
+        """
+        assert count >= 1
+        column = (
+            self.cursor_position_col if preferred_column is None else preferred_column
+        )
+
+        return (
+            self.translate_row_col_to_index(
+                max(0, self.cursor_position_row - count), column
+            )
+            - self.cursor_position
+        )
+
+    def get_cursor_down_position(
+        self, count: int = 1, preferred_column: Optional[int] = None
+    ) -> int:
+        """
+        Return the relative cursor position (character index) where we would be if the
+        user pressed the arrow-down button.
+
+        :param preferred_column: When given, go to this column instead of
+                                 staying at the current column.
+        """
+        assert count >= 1
+        column = (
+            self.cursor_position_col if preferred_column is None else preferred_column
+        )
+
+        return (
+            self.translate_row_col_to_index(self.cursor_position_row + count, column)
+            - self.cursor_position
+        )
+
+    def find_enclosing_bracket_right(
+        self, left_ch: str, right_ch: str, end_pos: Optional[int] = None
+    ) -> Optional[int]:
+        """
+        Find the right bracket enclosing current position. Return the relative
+        position to the cursor position.
+
+        When `end_pos` is given, don't look past the position.
+        """
+        if self.current_char == right_ch:
+            return 0
+
+        if end_pos is None:
+            end_pos = len(self.text)
+        else:
+            end_pos = min(len(self.text), end_pos)
+
+        stack = 1
+
+        # Look forward.
+        for i in range(self.cursor_position + 1, end_pos):
+            c = self.text[i]
+
+            if c == left_ch:
+                stack += 1
+            elif c == right_ch:
+                stack -= 1
+
+            if stack == 0:
+                return i - self.cursor_position
+
+        return None
+
+    def find_enclosing_bracket_left(
+        self, left_ch: str, right_ch: str, start_pos: Optional[int] = None
+    ) -> Optional[int]:
+        """
+        Find the left bracket enclosing current position. Return the relative
+        position to the cursor position.
+
+        When `start_pos` is given, don't look past the position.
+        """
+        if self.current_char == left_ch:
+            return 0
+
+        if start_pos is None:
+            start_pos = 0
+        else:
+            start_pos = max(0, start_pos)
+
+        stack = 1
+
+        # Look backward.
+        for i in range(self.cursor_position - 1, start_pos - 1, -1):
+            c = self.text[i]
+
+            if c == right_ch:
+                stack += 1
+            elif c == left_ch:
+                stack -= 1
+
+            if stack == 0:
+                return i - self.cursor_position
+
+        return None
+
+    def find_matching_bracket_position(
+        self, start_pos: Optional[int] = None, end_pos: Optional[int] = None
+    ) -> int:
+        """
+        Return relative cursor position of matching [, (, { or < bracket.
+
+        When `start_pos` or `end_pos` are given. Don't look past the positions.
+        """
+
+        # Look for a match.
+        for pair in "()", "[]", "{}", "<>":
+            A = pair[0]
+            B = pair[1]
+            if self.current_char == A:
+                return self.find_enclosing_bracket_right(A, B, end_pos=end_pos) or 0
+            elif self.current_char == B:
+                return self.find_enclosing_bracket_left(A, B, start_pos=start_pos) or 0
+
+        return 0
+
+    def get_start_of_document_position(self) -> int:
+        """Relative position for the start of the document."""
+        return -self.cursor_position
+
+    def get_end_of_document_position(self) -> int:
+        """Relative position for the end of the document."""
+        return len(self.text) - self.cursor_position
+
+    def get_start_of_line_position(self, after_whitespace: bool = False) -> int:
+        """Relative position for the start of this line."""
+        if after_whitespace:
+            current_line = self.current_line
+            return (
+                len(current_line)
+                - len(current_line.lstrip())
+                - self.cursor_position_col
+            )
+        else:
+            return -len(self.current_line_before_cursor)
+
+    def get_end_of_line_position(self) -> int:
+        """Relative position for the end of this line."""
+        return len(self.current_line_after_cursor)
+
+    def last_non_blank_of_current_line_position(self) -> int:
+        """
+        Relative position for the last non blank character of this line.
+        """
+        return len(self.current_line.rstrip()) - self.cursor_position_col - 1
+
+    def get_column_cursor_position(self, column: int) -> int:
+        """
+        Return the relative cursor position for this column at the current
+        line. (It will stay between the boundaries of the line in case of a
+        larger number.)
+        """
+        line_length = len(self.current_line)
+        current_column = self.cursor_position_col
+        column = max(0, min(line_length, column))
+
+        return column - current_column
+
+    def selection_range(
+        self,
+    ) -> Tuple[
+        int, int
+    ]:  # XXX: shouldn't this return `None` if there is no selection???
+        """
+        Return (from, to) tuple of the selection.
+        start and end position are included.
+
+        This doesn't take the selection type into account. Use
+        `selection_ranges` instead.
+        """
+        if self.selection:
+            from_, to = sorted(
+                [self.cursor_position, self.selection.original_cursor_position]
+            )
+        else:
+            from_, to = self.cursor_position, self.cursor_position
+
+        return from_, to
+
+    def selection_ranges(self) -> Iterable[Tuple[int, int]]:
+        """
+        Return a list of `(from, to)` tuples for the selection or none if
+        nothing was selected. The upper boundary is not included.
+
+        This will yield several (from, to) tuples in case of a BLOCK selection.
+        This will return zero ranges, like (8,8) for empty lines in a block
+        selection.
+        """
+        if self.selection:
+            from_, to = sorted(
+                [self.cursor_position, self.selection.original_cursor_position]
+            )
+
+            if self.selection.type == SelectionType.BLOCK:
+                from_line, from_column = self.translate_index_to_position(from_)
+                to_line, to_column = self.translate_index_to_position(to)
+                from_column, to_column = sorted([from_column, to_column])
+                lines = self.lines
+
+                if vi_mode():
+                    to_column += 1
+
+                for l in range(from_line, to_line + 1):
+                    line_length = len(lines[l])
+
+                    if from_column <= line_length:
+                        yield (
+                            self.translate_row_col_to_index(l, from_column),
+                            self.translate_row_col_to_index(
+                                l, min(line_length, to_column)
+                            ),
+                        )
+            else:
+                # In case of a LINES selection, go to the start/end of the lines.
+                if self.selection.type == SelectionType.LINES:
+                    from_ = max(0, self.text.rfind("\n", 0, from_) + 1)
+
+                    if self.text.find("\n", to) >= 0:
+                        to = self.text.find("\n", to)
+                    else:
+                        to = len(self.text) - 1
+
+                # In Vi mode, the upper boundary is always included. For Emacs,
+                # that's not the case.
+                if vi_mode():
+                    to += 1
+
+                yield from_, to
+
+    def selection_range_at_line(self, row: int) -> Optional[Tuple[int, int]]:
+        """
+        If the selection spans a portion of the given line, return a (from, to) tuple.
+
+        The returned upper boundary is not included in the selection, so
+        `(0, 0)` is an empty selection.  `(0, 1)`, is a one character selection.
+
+        Returns None if the selection doesn't cover this line at all.
+        """
+        if self.selection:
+            line = self.lines[row]
+
+            row_start = self.translate_row_col_to_index(row, 0)
+            row_end = self.translate_row_col_to_index(row, len(line))
+
+            from_, to = sorted(
+                [self.cursor_position, self.selection.original_cursor_position]
+            )
+
+            # Take the intersection of the current line and the selection.
+            intersection_start = max(row_start, from_)
+            intersection_end = min(row_end, to)
+
+            if intersection_start <= intersection_end:
+                if self.selection.type == SelectionType.LINES:
+                    intersection_start = row_start
+                    intersection_end = row_end
+
+                elif self.selection.type == SelectionType.BLOCK:
+                    _, col1 = self.translate_index_to_position(from_)
+                    _, col2 = self.translate_index_to_position(to)
+                    col1, col2 = sorted([col1, col2])
+
+                    if col1 > len(line):
+                        return None  # Block selection doesn't cross this line.
+
+                    intersection_start = self.translate_row_col_to_index(row, col1)
+                    intersection_end = self.translate_row_col_to_index(row, col2)
+
+                _, from_column = self.translate_index_to_position(intersection_start)
+                _, to_column = self.translate_index_to_position(intersection_end)
+
+                # In Vi mode, the upper boundary is always included. For Emacs
+                # mode, that's not the case.
+                if vi_mode():
+                    to_column += 1
+
+                return from_column, to_column
+        return None
+
+    def cut_selection(self) -> Tuple["Document", ClipboardData]:
+        """
+        Return a (:class:`.Document`, :class:`.ClipboardData`) tuple, where the
+        document represents the new document when the selection is cut, and the
+        clipboard data, represents whatever has to be put on the clipboard.
+        """
+        if self.selection:
+            cut_parts = []
+            remaining_parts = []
+            new_cursor_position = self.cursor_position
+
+            last_to = 0
+            for from_, to in self.selection_ranges():
+                if last_to == 0:
+                    new_cursor_position = from_
+
+                remaining_parts.append(self.text[last_to:from_])
+                cut_parts.append(self.text[from_:to])
+                last_to = to
+
+            remaining_parts.append(self.text[last_to:])
+
+            cut_text = "\n".join(cut_parts)
+            remaining_text = "".join(remaining_parts)
+
+            # In case of a LINES selection, don't include the trailing newline.
+            if self.selection.type == SelectionType.LINES and cut_text.endswith("\n"):
+                cut_text = cut_text[:-1]
+
+            return (
+                Document(text=remaining_text, cursor_position=new_cursor_position),
+                ClipboardData(cut_text, self.selection.type),
+            )
+        else:
+            return self, ClipboardData("")
+
+    def paste_clipboard_data(
+        self,
+        data: ClipboardData,
+        paste_mode: PasteMode = PasteMode.EMACS,
+        count: int = 1,
+    ) -> "Document":
+        """
+        Return a new :class:`.Document` instance which contains the result if
+        we would paste this data at the current cursor position.
+
+        :param paste_mode: Where to paste. (Before/after/emacs.)
+        :param count: When >1, Paste multiple times.
+        """
+        before = paste_mode == PasteMode.VI_BEFORE
+        after = paste_mode == PasteMode.VI_AFTER
+
+        if data.type == SelectionType.CHARACTERS:
+            if after:
+                new_text = (
+                    self.text[: self.cursor_position + 1]
+                    + data.text * count
+                    + self.text[self.cursor_position + 1 :]
+                )
+            else:
+                new_text = (
+                    self.text_before_cursor + data.text * count + self.text_after_cursor
+                )
+
+            new_cursor_position = self.cursor_position + len(data.text) * count
+            if before:
+                new_cursor_position -= 1
+
+        elif data.type == SelectionType.LINES:
+            l = self.cursor_position_row
+            if before:
+                lines = self.lines[:l] + [data.text] * count + self.lines[l:]
+                new_text = "\n".join(lines)
+                new_cursor_position = len("".join(self.lines[:l])) + l
+            else:
+                lines = self.lines[: l + 1] + [data.text] * count + self.lines[l + 1 :]
+                new_cursor_position = len("".join(self.lines[: l + 1])) + l + 1
+                new_text = "\n".join(lines)
+
+        elif data.type == SelectionType.BLOCK:
+            lines = self.lines[:]
+            start_line = self.cursor_position_row
+            start_column = self.cursor_position_col + (0 if before else 1)
+
+            for i, line in enumerate(data.text.split("\n")):
+                index = i + start_line
+                if index >= len(lines):
+                    lines.append("")
+
+                lines[index] = lines[index].ljust(start_column)
+                lines[index] = (
+                    lines[index][:start_column]
+                    + line * count
+                    + lines[index][start_column:]
+                )
+
+            new_text = "\n".join(lines)
+            new_cursor_position = self.cursor_position + (0 if before else 1)
+
+        return Document(text=new_text, cursor_position=new_cursor_position)
+
+    def empty_line_count_at_the_end(self) -> int:
+        """
+        Return number of empty lines at the end of the document.
+        """
+        count = 0
+        for line in self.lines[::-1]:
+            if not line or line.isspace():
+                count += 1
+            else:
+                break
+
+        return count
+
+    def start_of_paragraph(self, count: int = 1, before: bool = False) -> int:
+        """
+        Return the start of the current paragraph. (Relative cursor position.)
+        """
+
+        def match_func(text: str) -> bool:
+            return not text or text.isspace()
+
+        line_index = self.find_previous_matching_line(
+            match_func=match_func, count=count
+        )
+
+        if line_index:
+            add = 0 if before else 1
+            return min(0, self.get_cursor_up_position(count=-line_index) + add)
+        else:
+            return -self.cursor_position
+
+    def end_of_paragraph(self, count: int = 1, after: bool = False) -> int:
+        """
+        Return the end of the current paragraph. (Relative cursor position.)
+        """
+
+        def match_func(text: str) -> bool:
+            return not text or text.isspace()
+
+        line_index = self.find_next_matching_line(match_func=match_func, count=count)
+
+        if line_index:
+            add = 0 if after else 1
+            return max(0, self.get_cursor_down_position(count=line_index) - add)
+        else:
+            return len(self.text_after_cursor)
+
+    # Modifiers.
+
+    def insert_after(self, text: str) -> "Document":
+        """
+        Create a new document, with this text inserted after the buffer.
+        It keeps selection ranges and cursor position in sync.
+        """
+        return Document(
+            text=self.text + text,
+            cursor_position=self.cursor_position,
+            selection=self.selection,
+        )
+
+    def insert_before(self, text: str) -> "Document":
+        """
+        Create a new document, with this text inserted before the buffer.
+        It keeps selection ranges and cursor position in sync.
+        """
+        selection_state = self.selection
+
+        if selection_state:
+            selection_state = SelectionState(
+                original_cursor_position=selection_state.original_cursor_position
+                + len(text),
+                type=selection_state.type,
+            )
+
+        return Document(
+            text=text + self.text,
+            cursor_position=self.cursor_position + len(text),
+            selection=selection_state,
+        )