"""
Content is a container for text, with spans marked up with color / style.
It is equivalent to Rich's Text object, with support for more of Textual features.

Unlike Rich Text, Content is *immutable* so you can't modify it in place, and most methods will return a new Content instance.
This is more like the builtin str, and allows Textual to make some significant optimizations.

"""

from __future__ import annotations

import re
from functools import cached_property, total_ordering
from operator import itemgetter
from typing import Callable, Iterable, NamedTuple, Sequence, Union

import rich.repr
from rich._wrap import divide_line
from rich.cells import set_cell_size
from rich.console import Console
from rich.segment import Segment
from rich.style import Style as RichStyle
from rich.terminal_theme import TerminalTheme
from rich.text import Text
from typing_extensions import Final, TypeAlias

from textual._cells import cell_len
from textual._context import active_app
from textual._loop import loop_last
from textual.cache import FIFOCache
from textual.color import Color
from textual.css.types import TextAlign, TextOverflow
from textual.selection import Selection
from textual.strip import Strip
from textual.style import Style
from textual.visual import RenderOptions, RulesMap, Visual

__all__ = ["ContentType", "Content", "Span"]

ContentType: TypeAlias = Union["Content", str]
"""Type alias used where content and a str are interchangeable in a function."""

ContentText: TypeAlias = Union["Content", Text, str]
"""A type that may be used to construct Text."""

ANSI_DEFAULT = Style(
    background=Color(0, 0, 0, 0, ansi=-1),
    foreground=Color(0, 0, 0, 0, ansi=-1),
)
"""A Style for ansi default background and foreground."""

TRANSPARENT_STYLE = Style()
"""A null style."""

_re_whitespace = re.compile(r"\s+$")
_STRIP_CONTROL_CODES: Final = [
    7,  # Bell
    8,  # Backspace
    11,  # Vertical tab
    12,  # Form feed
    13,  # Carriage return
]
_CONTROL_STRIP_TRANSLATE: Final = {
    _codepoint: None for _codepoint in _STRIP_CONTROL_CODES
}


def _strip_control_codes(
    text: str, _translate_table: dict[int, None] = _CONTROL_STRIP_TRANSLATE
) -> str:
    """Remove control codes from text.

    Args:
        text (str): A string possibly contain control codes.

    Returns:
        str: String with control codes removed.
    """
    return text.translate(_translate_table)


@rich.repr.auto
class Span(NamedTuple):
    """A style applied to a range of character offsets."""

    start: int
    end: int
    style: Style | str

    def __rich_repr__(self) -> rich.repr.Result:
        yield self.start
        yield self.end
        yield "style", self.style

    def extend(self, cells: int) -> "Span":
        """Extend the span by the given number of cells.

        Args:
            cells (int): Additional space to add to end of span.

        Returns:
            Span: A span.
        """
        if cells:
            start, end, style = self
            return Span(start, end + cells, style)
        return self

    def _shift(self, distance: int) -> "Span":
        """Shift a span a given distance.

        Note that the start offset is clamped to 0.
        The end offset is not clamped, as it is assumed this has already been checked by the caller.

        Args:
            distance: Number of characters to move.

        Returns:
            New Span.
        """
        if distance < 0:
            start, end, style = self
            return Span(
                offset if (offset := start + distance) > 0 else 0, end + distance, style
            )
        else:
            start, end, style = self
            return Span(start + distance, end + distance, style)


@rich.repr.auto
@total_ordering
class Content(Visual):
    """Text content with marked up spans.

    This object can be considered immutable, although it might update its internal state
    in a way that is consistent with immutability.

    """

    __slots__ = ["_text", "_spans", "_cell_length"]

    _NORMALIZE_TEXT_ALIGN = {"start": "left", "end": "right", "justify": "full"}

    def __init__(
        self,
        text: str = "",
        spans: list[Span] | None = None,
        cell_length: int | None = None,
        strip_control_codes: bool = True,
    ) -> None:
        """
        Initialize a Content object.

        Args:
            text: text content.
            spans: Optional list of spans.
            cell_length: Cell length of text if known, otherwise `None`.
            strip_control_codes: Strip control codes that may break output?
        """

        self._text: str = (
            _strip_control_codes(text) if strip_control_codes and text else text
        )
        self._spans: list[Span] = [] if spans is None else spans
        self._cell_length = cell_length
        self._optimal_width_cache: int | None = None
        self._minimal_width_cache: int | None = None
        self._height_cache: tuple[tuple[int, str, bool] | None, int] = (None, 0)
        self._divide_cache: (
            FIFOCache[Sequence[int], list[tuple[Span, int, int]]] | None
        ) = None
        self._split_cache: FIFOCache[tuple[str, bool, bool], list[Content]] | None = (
            None
        )
        # If there are 1 or 0 spans, it can't be simplified further
        self._simplified = len(self._spans) <= 1

    def __str__(self) -> str:
        return self._text

    @property
    def _is_regular(self) -> bool:
        """Check if the line is regular (spans.end > span.start for all spans).

        This is a debugging aid, and unlikely to be useful in your app.

        Returns:
            `True` if the content is regular, `False` if it is not (and broken).
        """
        for span in self.spans:
            if span.end <= span.start:
                return False
        return True

    @cached_property
    def markup(self) -> str:
        """Get content markup to render this Text.

        Returns:
            str: A string potentially creating markup tags.
        """
        from textual.markup import escape

        output: list[str] = []

        plain = self.plain
        markup_spans = [
            (0, False, None),
            *((span.start, False, span.style) for span in self._spans),
            *((span.end, True, span.style) for span in self._spans),
            (len(plain), True, None),
        ]
        markup_spans.sort(key=itemgetter(0, 1))
        position = 0
        append = output.append
        for offset, closing, style in markup_spans:
            if offset > position:
                append(escape(plain[position:offset]))
                position = offset
            if style:
                append(f"[/{style}]" if closing else f"[{style}]")
        markup = "".join(output)
        return markup

    @classmethod
    def empty(cls) -> Content:
        """Get an empty (blank) content"""
        return EMPTY_CONTENT

    @classmethod
    def from_text(
        cls, markup_content_or_text: ContentText, markup: bool = True
    ) -> Content:
        """Construct content from Text or str. If the argument is already Content, then
        return it unmodified.

        This method exists to make (Rich) Text and Content interchangeable. While Content
        is preferred, we don't want to make it harder than necessary for apps to use Text.

        Args:
            markup_content_or_text: Value to create Content from.
            markup: If `True`, then str values will be parsed as markup, otherwise they will
                be considered literals.

        Raises:
            TypeError: If the supplied argument is not a valid type.

        Returns:
            A new Content instance.
        """
        if isinstance(markup_content_or_text, Content):
            return markup_content_or_text
        elif isinstance(markup_content_or_text, str):
            if markup:
                return cls.from_markup(markup_content_or_text)
            else:
                return cls(markup_content_or_text)
        elif isinstance(markup_content_or_text, Text):
            return cls.from_rich_text(markup_content_or_text)
        else:
            raise TypeError(
                "This method expects a str, a Text instance, or a Content instance"
            )

    @classmethod
    def from_markup(cls, markup: str | Content, **variables: object) -> Content:
        """Create content from markup, optionally combined with template variables.

        If `markup` is already a Content instance, it will be returned unmodified.

        See the guide on [Content](../guide/content.md#content-class) for more details.


        Example:
            ```python
            content = Content.from_markup("Hello, [b]$name[/b]!", name="Will")
            ```

        Args:
            markup: Content markup, or Content.
            **variables: Optional template variables used

        Returns:
            New Content instance.
        """
        _rich_traceback_omit = True
        if isinstance(markup, Content):
            if variables:
                raise ValueError("A literal string is require to substitute variables.")
            return markup
        markup = _strip_control_codes(markup)
        if "[" not in markup and not variables:
            return Content(markup)
        from textual.markup import to_content

        content = to_content(markup, template_variables=variables or None)
        return content

    @classmethod
    def from_rich_text(
        cls, text: str | Text, console: Console | None = None
    ) -> Content:
        """Create equivalent Visual Content for str or Text.

        Args:
            text: String or Rich Text.
            console: A Console object to use if parsing Rich Console markup, or `None` to
                use app default.

        Returns:
            New Content.
        """
        if isinstance(text, str):
            text = Text.from_markup(text)

        ansi_theme: TerminalTheme | None = None

        if console is not None:
            get_style = console.get_style
        else:
            try:
                app = active_app.get()
            except LookupError:
                get_style = RichStyle.parse
            else:
                get_style = app.console.get_style

        if text._spans:
            try:
                ansi_theme = active_app.get().ansi_theme
            except LookupError:
                ansi_theme = None
            spans = [
                Span(
                    start,
                    end,
                    (
                        Style.from_rich_style(get_style(style), ansi_theme)
                        if isinstance(style, str)
                        else Style.from_rich_style(style, ansi_theme)
                    ),
                )
                for start, end, style in text._spans
            ]
        else:
            spans = []

        content = cls(text.plain, spans)
        if text.style:
            try:
                ansi_theme = active_app.get().ansi_theme
            except LookupError:
                ansi_theme = None
            content = content.stylize_before(
                text.style
                if isinstance(text.style, str)
                else Style.from_rich_style(text.style, ansi_theme)
            )
        return content

    @classmethod
    def styled(
        cls,
        text: str,
        style: Style | str = "",
        cell_length: int | None = None,
        strip_control_codes: bool = True,
    ) -> Content:
        """Create a Content instance from text and an optional style.

        Args:
            text: String content.
            style: Desired style.
            cell_length: Cell length of text if known, otherwise `None`.
            strip_control_codes: Strip control codes that may break output.

        Returns:
            New Content instance.
        """
        if not text:
            return EMPTY_CONTENT
        new_content = cls(
            text,
            [Span(0, len(text), style)] if style else None,
            cell_length,
            strip_control_codes=strip_control_codes,
        )
        return new_content

    @classmethod
    def blank(cls, width: int, style: Style | str | None = None) -> Content:
        """Get a Content instance consisting of spaces.

        Args:
            width: Width of blank content (number of spaces).
            style: Style of blank.

        Returns:
            Content instance.
        """
        if not width:
            return EMPTY_CONTENT
        blank = cls(
            " " * width,
            [Span(0, width, style)] if style else None,
            cell_length=width,
        )
        return blank

    @classmethod
    def assemble(
        cls,
        *parts: str | Content | tuple[str, str | Style],
        end: str = "",
        strip_control_codes: bool = True,
    ) -> Content:
        """Construct new content from string, content, or tuples of (TEXT, STYLE).

        This is an efficient way of constructing Content composed of smaller pieces of
        text and / or other Content objects.

        Example:
            ```python
            content = Content.assemble(
                Content.from_markup("[b]assemble[/b]: "),  # Other content
                "pieces of text or content into a",  # Simple string of text
                ("a single Content instance", "underline"),  # A tuple of text and a style
            )
            ```

        Args:
            *parts: Parts to join to gether. A *part* may be a simple string, another Content
            instance, or tuple containing text and a style.
            end: Optional end to the Content.
            strip_control_codes: Strip control codes that may break output.
        """
        text: list[str] = []
        spans: list[Span] = []
        _Span = Span
        text_append = text.append

        position: int = 0
        for part in parts:
            if isinstance(part, str):
                text_append(part)
                position += len(part)
            elif isinstance(part, tuple):
                part_text, part_style = part
                text_append(part_text)
                if part_style:
                    spans.append(
                        _Span(position, position + len(part_text), part_style),
                    )
                position += len(part_text)
            elif isinstance(part, Content):
                text_append(part.plain)
                if part.spans:
                    spans.extend(
                        [
                            _Span(start + position, end + position, style)
                            for start, end, style in part.spans
                        ]
                    )
                position += len(part.plain)
        if end:
            text_append(end)
        assembled_content = cls(
            "".join(text), spans, strip_control_codes=strip_control_codes
        )
        return assembled_content

    def simplify(self) -> Content:
        """Simplify spans by joining contiguous spans together.

        This may produce faster renders if you have concatenated a large number of small pieces
        of content with repeating styles.

        Note that this modifies the Content instance in-place, which might appear
        to violate the immutability constraints, but it will not change the rendered output,
        nor its hash.

        Returns:
            Self.
        """
        if not (spans := self._spans) or self._simplified:
            return self
        last_span = Span(-1, -1, "")
        new_spans: list[Span] = []
        changed: bool = False
        for span in spans:
            if span.start == last_span.end and span.style == last_span.style:
                last_span = new_spans[-1] = Span(last_span.start, span.end, span.style)
                changed = True
            else:
                new_spans.append(span)
                last_span = span
        if changed:
            self._spans[:] = new_spans
        self._simplified = True
        return self

    def add_spans(self, spans: Sequence[Span]) -> Content:
        """Adds spans to this Content instance.

        Args:
            spans: A sequence of spans.

        Returns:
            A Content instance.
        """
        if spans:
            return Content(
                self.plain,
                [*self._spans, *spans],
                self._cell_length,
                strip_control_codes=False,
            )
        return self

    def __eq__(self, other: object) -> bool:
        """Compares text only, so that markup doesn't effect sorting."""
        if isinstance(other, str):
            return self.plain == other
        elif isinstance(other, Content):
            return self.plain == other.plain
        return NotImplemented

    def __lt__(self, other: object) -> bool:
        if isinstance(other, str):
            return self.plain < other
        if isinstance(other, Content):
            return self.plain < other.plain
        return NotImplemented

    def is_same(self, content: Content) -> bool:
        """Compare to another Content object.

        Two Content objects are the same if their text *and* spans match.
        Note that if you use the `==` operator to compare Content instances, it will only consider
        the plain text portion of the content (and not the spans).

        Args:
            content: Content instance.

        Returns:
            `True` if this is identical to `content`, otherwise `False`.
        """
        if self is content:
            return True
        if self.plain != content.plain:
            return False
        return self.spans == content.spans

    def get_optimal_width(self, rules: RulesMap, container_width: int) -> int:
        """Get optimal width of the Visual to display its content.

        The exact definition of "optimal width" is dependant on the Visual, but
        will typically be wide enough to display output without cropping or wrapping,
        and without superfluous space.

        Args:
            rules: A mapping of style rules, such as the Widgets `styles` object.

        Returns:
            A width in cells.

        """
        if self._optimal_width_cache is None:
            self._optimal_width_cache = width = max(
                cell_len(line) for line in self.plain.split("\n")
            )
        else:
            width = self._optimal_width_cache
        return width + rules.get("line_pad", 0) * 2

    def get_minimal_width(self, rules: RulesMap) -> int:
        """Minimal width is the largest single word."""
        if not self.plain.strip():
            return 0
        if self._minimal_width_cache is None:
            self._minimal_width_cache = width = max(
                cell_len(word)
                for line in self.plain.splitlines()
                for word in line.split()
                if word.strip()
            )
        else:
            width = self._minimal_width_cache
        return width + rules.get("line_pad", 0) * 2

    def get_height(self, rules: RulesMap, width: int) -> int:
        """Get the height of the Visual if rendered at the given width.

        Args:
            rules: A mapping of style rules, such as the Widgets `styles` object.
            width: Width of visual in cells.

        Returns:
            A height in lines.
        """
        get_rule = rules.get
        line_pad = get_rule("line_pad", 0) * 2
        overflow = get_rule("text_overflow", "fold")
        no_wrap = get_rule("text_wrap", "wrap") == "nowrap"
        cache_key = (width + line_pad, overflow, no_wrap)
        if self._height_cache[0] == cache_key:
            height = self._height_cache[1]
        else:
            lines = self.without_spans._wrap_and_format(
                width - line_pad, overflow=overflow, no_wrap=no_wrap
            )
            height = len(lines)
            self._height_cache = (cache_key, height)
        return height

    def _wrap_and_format(
        self,
        width: int,
        align: TextAlign = "left",
        overflow: TextOverflow = "fold",
        no_wrap: bool = False,
        line_pad: int = 0,
        tab_size: int = 8,
        selection: Selection | None = None,
        selection_style: Style | None = None,
        post_style: Style | None = None,
        get_style: Callable[[str | Style], Style] = Style.parse,
    ) -> list[_FormattedLine]:
        """Wraps the text and applies formatting.

        Args:
            width: Desired width.
            align: Text alignment.
            overflow: Overflow method.
            no_wrap: Disabled wrapping.
            tab_size: Cell with of tabs.
            selection: Selection information or `None` if no selection.
            selection_style: Selection style, or `None` if no selection.

        Returns:
            List of formatted lines.
        """
        output_lines: list[_FormattedLine] = []

        if selection is not None:
            get_span = selection.get_span
        else:

            def get_span(y: int) -> tuple[int, int] | None:
                return None

        for y, line in enumerate(self.split(allow_blank=True)):
            if post_style is not None:
                line = line.stylize(post_style)

            if selection_style is not None and (span := get_span(y)) is not None:
                start, end = span
                if end == -1:
                    end = len(line.plain)
                line = line.stylize(selection_style, start, end)

            line = line.expand_tabs(tab_size)

            if no_wrap:
                if overflow == "fold":
                    cuts = list(range(0, line.cell_length, width))[1:]
                    new_lines = [
                        _FormattedLine(get_style, line, width, y=y, align=align)
                        for line in line.divide(cuts)
                    ]
                else:
                    line = line.truncate(width, ellipsis=overflow == "ellipsis")
                    content_line = _FormattedLine(
                        get_style, line, width, y=y, align=align
                    )
                    new_lines = [content_line]
            else:
                content_line = _FormattedLine(get_style, line, width, y=y, align=align)
                offsets = divide_line(
                    line.plain, width - line_pad * 2, fold=overflow == "fold"
                )
                divided_lines = content_line.content.divide(offsets)
                ellipsis = overflow == "ellipsis"
                divided_lines = [
                    (
                        line.truncate(width, ellipsis=ellipsis)
                        if last
                        else line.rstrip().truncate(width, ellipsis=ellipsis)
                    )
                    for last, line in loop_last(divided_lines)
                ]

                new_lines = [
                    _FormattedLine(
                        get_style,
                        content.rstrip_end(width).pad(line_pad, line_pad),
                        width,
                        offset,
                        y,
                        align=align,
                    )
                    for content, offset in zip(divided_lines, [0, *offsets])
                ]
                new_lines[-1].line_end = True

            output_lines.extend(new_lines)

        return output_lines

    def render_strips(
        self, width: int, height: int | None, style: Style, options: RenderOptions
    ) -> list[Strip]:
        """Render the Visual into an iterable of strips. Part of the Visual protocol.

        Args:
            width: Width of desired render.
            height: Height of desired render or `None` for any height.
            style: The base style to render on top of.
            options: Additional render options.

        Returns:
            An list of Strips.
        """

        if not width:
            return []

        get_rule = options.rules.get
        lines = self._wrap_and_format(
            width,
            align=get_rule("text_align", "left"),
            overflow=get_rule("text_overflow", "fold"),
            no_wrap=get_rule("text_wrap", "wrap") == "nowrap",
            line_pad=get_rule("line_pad", 0),
            tab_size=8,
            selection=options.selection,
            selection_style=options.selection_style,
            post_style=options.post_style,
            get_style=options.get_style,
        )

        if height is not None:
            lines = lines[:height]

        strip_lines = [Strip(*line.to_strip(style)) for line in lines]
        return strip_lines

    def __len__(self) -> int:
        return len(self.plain)

    def __bool__(self) -> bool:
        return self._text != ""

    def __hash__(self) -> int:
        return hash(self._text)

    def __rich_repr__(self) -> rich.repr.Result:
        try:
            yield self._text
            yield "spans", self._spans, []
        except AttributeError:
            pass

    @property
    def spans(self) -> Sequence[Span]:
        """A sequence of spans used to markup regions of the content.

        !!! warning
            Never attempt to mutate the spans, as this would certainly break the output--possibly
            in quite subtle ways!

        """
        return self._spans

    @property
    def cell_length(self) -> int:
        """The cell length of the content."""
        # Calculated on demand
        if self._cell_length is None:
            self._cell_length = cell_len(self.plain)
        return self._cell_length

    @property
    def plain(self) -> str:
        """Get the text as a single string."""
        return self._text

    @property
    def without_spans(self) -> Content:
        """The content with no spans"""
        if self._spans:
            return Content(self.plain, [], self._cell_length, strip_control_codes=False)
        return self

    @property
    def first_line(self) -> Content:
        """The first line of the content."""
        if "\n" not in self.plain:
            return self
        return self[: self.plain.index("\n")]

    def __getitem__(self, slice: int | slice) -> Content:
        def get_text_at(offset: int) -> "Content":
            _Span = Span
            content = Content(
                self.plain[offset],
                spans=[
                    _Span(0, 1, style)
                    for start, end, style in self._spans
                    if end > offset >= start
                ],
                strip_control_codes=False,
            )
            return content

        if isinstance(slice, int):
            return get_text_at(slice)
        else:
            start, stop, step = slice.indices(len(self.plain))
            if step == 1:
                if start == 0:
                    if stop >= len(self.plain):
                        return self
                    text = self.plain[:stop]
                    sliced_content = Content(
                        text,
                        self._trim_spans(text, self._spans),
                        strip_control_codes=False,
                    )
                else:
                    text = self.plain[start:stop]
                    spans = [
                        span._shift(-start)
                        for span in self._spans
                        if span.end - start > 0
                    ]
                    sliced_content = Content(
                        text, self._trim_spans(text, spans), strip_control_codes=False
                    )
                return sliced_content

            else:
                # This would be a bit of work to implement efficiently
                # For now, its not required
                raise TypeError("slices with step!=1 are not supported")

    def __add__(self, other: Content | str) -> Content:
        if isinstance(other, str):
            return Content(self._text + other, self._spans, strip_control_codes=False)
        if isinstance(other, Content):
            offset = len(self.plain)
            content = Content(
                self.plain + other.plain,
                (
                    self._spans
                    + [
                        Span(start + offset, end + offset, style)
                        for start, end, style in other._spans
                    ]
                ),
                (
                    None
                    if self._cell_length is not None
                    else (self.cell_length + other.cell_length)
                ),
            )
            return content
        return NotImplemented

    def __radd__(self, other: str) -> Content:
        if not isinstance(other, str):
            return NotImplemented
        return Content(other) + self

    @classmethod
    def _trim_spans(cls, text: str, spans: list[Span]) -> list[Span]:
        """Remove or modify any spans that are over the end of the text."""
        max_offset = len(text)
        _Span = Span
        spans = [
            (
                span
                if span.end < max_offset
                else _Span(span.start, min(max_offset, span.end), span.style)
            )
            for span in spans
            if span.start < max_offset
        ]
        return spans

    def append(self, content: Content | str) -> Content:
        """Append text or content to this content.

        Note this is a little inefficient, if you have many strings to append, consider [`join`][textual.content.Content.join].

        Args:
            content: A content instance, or a string.

        Returns:
            New content.
        """
        if isinstance(content, str):
            return Content(
                f"{self.plain}{content}",
                self._spans,
                (
                    None
                    if self._cell_length is None
                    else self._cell_length + cell_len(content)
                ),
                strip_control_codes=False,
            )
        return EMPTY_CONTENT.join([self, content])

    def append_text(self, text: str, style: Style | str = "") -> Content:
        """Append text give as a string, with an optional style.

        Args:
            text: Text to append.
            style: Optional style for new text.

        Returns:
            New content.
        """
        return self.append(Content.styled(text, style))

    def join(self, lines: Iterable[Content | str]) -> Content:
        """Join an iterable of content or strings.

        This works much like the join method on `str` objects.
        Self is the separator (which maybe empty) placed between each string or Content.

        Args:
            lines: An iterable of other Content instances or or strings.

        Returns:
            A single Content instance, containing all of the lines.

        """
        text: list[str] = []
        spans: list[Span] = []

        def iter_content() -> Iterable[Content]:
            """Iterate the lines, optionally inserting the separator."""
            if self.plain:
                for last, line in loop_last(lines):
                    yield (
                        line
                        if isinstance(line, Content)
                        else Content(line, strip_control_codes=False)
                    )
                    if not last:
                        yield self
            else:
                for line in lines:
                    yield (
                        line
                        if isinstance(line, Content)
                        else Content(line, strip_control_codes=False)
                    )

        extend_text = text.extend
        extend_spans = spans.extend
        offset = 0
        _Span = Span

        total_cell_length: int | None = self._cell_length

        for content in iter_content():
            if not content:
                continue
            extend_text(content._text)
            extend_spans(
                _Span(offset + start, offset + end, style)
                for start, end, style in content._spans
                if style
            )
            offset += len(content._text)
            if total_cell_length is not None:
                total_cell_length = (
                    None
                    if content._cell_length is None
                    else total_cell_length + content._cell_length
                )

        return Content("".join(text), spans, total_cell_length)

    def wrap(
        self, width: int, *, align: TextAlign = "left", overflow: TextOverflow = "fold"
    ) -> list[Content]:
        """Wrap text so that it fits within the given dimensions.

        Note that Textual will automatically wrap Content in widgets.
        This method is only required if you need some additional processing to lines.

        Args:
            width: Maximum width of the line (in cells).
            align: Alignment of lines.
            overflow: Overflow of lines (what happens when the text doesn't fit).

        Returns:
            A list of Content objects, one per line.
        """
        lines = self._wrap_and_format(width, align, overflow)
        content_lines = [line.content for line in lines]
        return content_lines

    def fold(self, width: int) -> list[Content]:
        """Fold this line into a list of lines which have a cell length no less than 2 and no greater than `width`.

        Folded lines may be 1 less than the width if it contains double width characters (which may
        not be subdivided).

        Note that this method will not do any word wrapping. For that, see [wrap()][textual.content.Content.wrap].

        Args:
            width: Desired maximum width (in cells)

        Returns:
            List of content instances.
        """
        if not self:
            return [self]
        text = self.plain
        lines: list[Content] = []
        position = 0
        width = max(width, 2)
        while True:
            snip = text[position : position + width]
            if not snip:
                break
            snip_cell_length = cell_len(snip)
            if snip_cell_length < width:
                # last snip
                lines.append(self[position : position + width])
                break
            if snip_cell_length == width:
                # Cell length is exactly width
                lines.append(self[position : position + width])
                position += len(snip)
                continue
            # TODO: Can this be more efficient?
            extra_cells = snip_cell_length - width
            if start_snip := extra_cells // 2:
                snip_cell_length -= cell_len(snip[-start_snip:])
                snip = snip[: len(snip) - start_snip]
            while snip_cell_length > width:
                snip_cell_length -= cell_len(snip[-1])
                snip = snip[:-1]
            lines.append(self[position : position + len(snip)])
            position += len(snip)

        return lines

    def get_style_at_offset(self, offset: int) -> Style:
        """Get the style of a character at give offset.

        Args:
            offset (int): Offset into text (negative indexing supported)

        Returns:
            Style: A Style instance.
        """
        # TODO: This is a little inefficient, it is only used by full justify
        if offset < 0:
            offset = len(self) + offset

        style = Style()
        for start, end, span_style in self._spans:
            if end > offset >= start:
                style += span_style
        return style

    def truncate(
        self,
        max_width: int,
        *,
        ellipsis=False,
        pad: bool = False,
    ) -> Content:
        """Truncate the content at a given cell width.

        Args:
            max_width: The maximum width in cells.
            ellipsis: Insert an ellipsis when cropped.
            pad: Pad the content if less than `max_width`.

        Returns:
            New Content.
        """

        length = self.cell_length
        if length == max_width:
            return self

        text = self.plain
        spans = self._spans
        if pad and length < max_width:
            spaces = max_width - length
            text = f"{self.plain}{' ' * spaces}"
            return Content(text, spans, max_width, strip_control_codes=False)
        elif length > max_width:
            if ellipsis and max_width:
                text = set_cell_size(self.plain, max_width - 1) + "…"
            else:
                text = set_cell_size(self.plain, max_width)
            spans = self._trim_spans(text, self._spans)
            return Content(text, spans, max_width, strip_control_codes=False)
        else:
            return self

    def pad_left(self, count: int, character: str = " ") -> Content:
        """Pad the left with a given character.

        Args:
            count (int): Number of characters to pad.
            character (str, optional): Character to pad with. Defaults to " ".
        """
        assert len(character) == 1, "Character must be a string of length 1"
        if count:
            text = f"{character * count}{self.plain}"
            _Span = Span
            spans = [
                _Span(start + count, end + count, style)
                for start, end, style in self._spans
            ]
            content = Content(
                text,
                spans,
                None if self._cell_length is None else self._cell_length + count,
                strip_control_codes=False,
            )
            return content

        return self

    def extend_right(self, count: int, character: str = " ") -> Content:
        """Add repeating characters (typically spaces) to the content with the style(s) of the last character.

        Args:
            count: Number of spaces.
            character: Character to add with.

        Returns:
            A Content instance.
        """
        if count:
            plain = self.plain
            plain_len = len(plain)
            return Content(
                f"{plain}{character * count}",
                [
                    (span.extend(count) if span.end == plain_len else span)
                    for span in self._spans
                ],
                None if self._cell_length is None else self._cell_length + count,
                strip_control_codes=False,
            )
        return self

    def pad_right(self, count: int, character: str = " ") -> Content:
        """Pad the right with a given character.

        Args:
            count (int): Number of characters to pad.
            character (str, optional): Character to pad with. Defaults to " ".
        """
        assert len(character) == 1, "Character must be a string of length 1"
        if count:
            return Content(
                f"{self.plain}{character * count}",
                self._spans,
                None if self._cell_length is None else self._cell_length + count,
                strip_control_codes=False,
            )
        return self

    def pad(self, left: int, right: int, character: str = " ") -> Content:
        """Pad both the left and right edges with a given number of characters.

        Args:
            left (int): Number of characters to pad on the left.
            right (int): Number of characters to pad on the right.
            character (str, optional): Character to pad with. Defaults to " ".
        """
        assert len(character) == 1, "Character must be a string of length 1"
        if left or right:
            text = f"{character * left}{self.plain}{character * right}"
            _Span = Span
            if left:
                spans = [
                    _Span(start + left, end + left, style)
                    for start, end, style in self._spans
                ]
            else:
                spans = self._spans
            content = Content(
                text,
                spans,
                None if self._cell_length is None else self._cell_length + left + right,
                strip_control_codes=False,
            )
            return content

        return self

    def center(self, width: int, ellipsis: bool = False) -> Content:
        """Align a line to the center.

        Args:
            width: Desired width of output.
            ellipsis: Insert ellipsis if content is truncated.

        Returns:
            New line Content.
        """
        content = self.rstrip().truncate(width, ellipsis=ellipsis)
        left = (width - content.cell_length) // 2
        right = width - left
        content = content.pad(left, right)
        return content

    def right(self, width: int, ellipsis: bool = False) -> Content:
        """Align a line to the right.

        Args:
            width: Desired width of output.
            ellipsis: Insert ellipsis if content is truncated.

        Returns:
            New line Content.
        """
        content = self.rstrip().truncate(width, ellipsis=ellipsis)
        content = content.pad_left(width - content.cell_length)
        return content

    def right_crop(self, amount: int = 1) -> Content:
        """Remove a number of characters from the end of the text.

        Args:
            amount: Number of characters to crop.

        Returns:
            New Content

        """
        max_offset = len(self.plain) - amount
        _Span = Span
        spans = [
            (
                span
                if span.end < max_offset
                else _Span(span.start, min(max_offset, span.end), span.style)
            )
            for span in self._spans
            if span.start < max_offset
        ]
        text = self.plain[:-amount]
        length = None if self._cell_length is None else self._cell_length - amount
        return Content(text, spans, length, strip_control_codes=False)

    def stylize(
        self, style: Style | str, start: int = 0, end: int | None = None
    ) -> Content:
        """Apply a style to the text, or a portion of the text.

        Args:
            style (Union[str, Style]): Style instance or style definition to apply.
            start (int): Start offset (negative indexing is supported). Defaults to 0.
            end (Optional[int], optional): End offset (negative indexing is supported), or None for end of text. Defaults to None.
        """
        if not style:
            return self
        length = len(self)
        if start < 0:
            start = length + start
        if end is None:
            end = length
        if end < 0:
            end = length + end
        if start >= length or end <= start:
            # Span not in text or not valid
            return self
        return Content(
            self.plain,
            self._spans + [Span(start, length if length < end else end, style)],
            self._cell_length,
            strip_control_codes=False,
        )

    def stylize_before(
        self,
        style: Style | str,
        start: int = 0,
        end: int | None = None,
    ) -> Content:
        """Apply a style to the text, or a portion of the text.

        Styles applies with this method will be applied *before* other styles already present.

        Args:
            style (Union[str, Style]): Style instance or style definition to apply.
            start (int): Start offset (negative indexing is supported). Defaults to 0.
            end (Optional[int], optional): End offset (negative indexing is supported), or None for end of text. Defaults to None.
        """
        if not style:
            return self
        length = len(self)
        if start < 0:
            start = length + start
        if end is None:
            end = length
        if end < 0:
            end = length + end
        if start >= length or end <= start:
            # Span not in text or not valid
            return self
        return Content(
            self.plain,
            [Span(start, length if length < end else end, style), *self._spans],
            self._cell_length,
            strip_control_codes=False,
        )

    def render(
        self,
        base_style: Style = Style.null(),
        end: str = "\n",
        parse_style: Callable[[str | Style], Style] | None = None,
    ) -> Iterable[tuple[str, Style]]:
        """Render Content in to an iterable of strings and styles.

        This is typically called by Textual when displaying Content, but may be used if you want to do more advanced
        processing of the output.

        Args:
            base_style: The style used as a base. This will typically be the style of the widget underneath the content.
            end: Text to end the output, such as a new line.
            parse_style: Method to parse a style. Use `App.parse_style` to apply CSS variables in styles.

        Returns:
            An iterable of string and styles, which make up the content.

        """
        if not self._spans:
            yield (self._text, base_style)
            if end:
                yield end, base_style
            return

        get_style: Callable[[str | Style], Style]
        if parse_style is None:

            def _get_style(style: str | Style) -> Style:
                """The default get_style method."""
                if isinstance(style, Style):
                    return style
                try:
                    visual_style = Style.parse(style)
                except Exception:
                    visual_style = Style.null()
                return visual_style

            get_style = _get_style

        else:
            get_style = parse_style

        enumerated_spans = list(enumerate(self._spans, 1))
        style_map = {
            index: (
                get_style(span.style) if isinstance(span.style, str) else span.style
            )
            for index, span in enumerated_spans
        }
        style_map[0] = base_style
        text = self.plain

        spans = [
            (0, False, 0),
            *((span.start, False, index) for index, span in enumerated_spans),
            *((span.end, True, index) for index, span in enumerated_spans),
            (len(text), True, 0),
        ]
        spans.sort(key=itemgetter(0, 1))

        stack: list[int] = []
        stack_append = stack.append
        stack_pop = stack.remove

        style_cache: dict[tuple[int, ...], Style] = {}
        style_cache_get = style_cache.get
        combine = Style.combine

        def get_current_style() -> Style:
            """Construct current style from stack."""
            cache_key = tuple(stack)
            cached_style = style_cache_get(cache_key)
            if cached_style is not None:
                return cached_style
            styles = [style_map[_style_id] for _style_id in cache_key]
            current_style = combine(styles)
            style_cache[cache_key] = current_style
            return current_style

        for (offset, leaving, style_id), (next_offset, _, _) in zip(spans, spans[1:]):
            if leaving:
                stack_pop(style_id)
            else:
                stack_append(style_id)
            if next_offset > offset:
                yield text[offset:next_offset], get_current_style()
        if end:
            yield end, base_style

    def render_segments(
        self, base_style: Style = Style.null(), end: str = ""
    ) -> list[Segment]:
        """Render the Content in to a list of segments.

        Args:
            base_style: Base style for render (style under the content). Defaults to Style.null().
            end: Character to end the segments with. Defaults to "".

        Returns:
            A list of segments.
        """
        _Segment = Segment
        segments = [
            _Segment(text, (style.rich_style if style else None))
            for text, style in self.render(base_style, end)
        ]
        return segments

    def __rich__(self):
        """Allow Content to be rendered with rich.print."""
        from rich.segment import Segments

        return Segments(self.render_segments(Style(), "\n"))

    def _divide_spans(self, offsets: tuple[int, ...]) -> list[tuple[Span, int, int]]:
        """Divide content from a list of offset to cut.

        Args:
            offsets: A tuple of indices in to the text.

        Returns:
            A list of tuples containing Spans and their line offsets.
        """
        if self._divide_cache is None:
            self._divide_cache = FIFOCache(4)
        if (cached_result := self._divide_cache.get(offsets)) is not None:
            return cached_result

        line_ranges = list(zip(offsets, offsets[1:]))
        text_length = len(self.plain)
        line_count = len(line_ranges)
        span_ranges: list[tuple[Span, int, int]] = []
        for span in self._spans:
            span_start, span_end, _style = span
            if span_start >= text_length:
                continue
            span_end = min(text_length, span_end)
            lower_bound = 0
            upper_bound = line_count
            start_line_no = (lower_bound + upper_bound) // 2

            while True:
                line_start, line_end = line_ranges[start_line_no]
                if span_start < line_start:
                    upper_bound = start_line_no - 1
                elif span_start > line_end:
                    lower_bound = start_line_no + 1
                else:
                    break
                start_line_no = (lower_bound + upper_bound) // 2

            if span_end < line_end:
                end_line_no = start_line_no
            else:
                end_line_no = lower_bound = start_line_no
                upper_bound = line_count

                while True:
                    line_start, line_end = line_ranges[end_line_no]
                    if span_end < line_start:
                        upper_bound = end_line_no - 1
                    elif span_end > line_end:
                        lower_bound = end_line_no + 1
                    else:
                        break
                    end_line_no = (lower_bound + upper_bound) // 2

            span_ranges.append((span, start_line_no, end_line_no + 1))
        self._divide_cache[offsets] = span_ranges
        return span_ranges

    def divide(self, offsets: Sequence[int]) -> list[Content]:
        """Divide the content at the given offsets.

        This will cut the content in to pieces, and return those pieces. Note that the number of pieces
        return will be one greater than the number of cuts.

        Args:
            offsets: Sequence of offsets (in characters) of where to apply the cuts.

        Returns:
            List of Content instances which combined would be equal to the whole.
        """
        if not offsets:
            return [self]

        offsets = sorted(offsets)
        text = self.plain
        divide_offsets = tuple([0, *offsets, len(text)])
        line_ranges = list(zip(divide_offsets, divide_offsets[1:]))
        line_text = [text[start:end] for start, end in line_ranges]
        new_lines = [Content(line, None) for line in line_text]

        if not self._spans:
            return new_lines

        _line_appends = [line._spans.append for line in new_lines]
        _Span = Span

        for (
            (span_start, span_end, style),
            start_line,
            end_line,
        ) in self._divide_spans(divide_offsets):
            for line_no in range(start_line, end_line):
                line_start, line_end = line_ranges[line_no]
                new_start = max(0, span_start - line_start)
                new_end = min(span_end - line_start, line_end - line_start)
                if new_end > new_start:
                    _line_appends[line_no](_Span(new_start, new_end, style))

        return new_lines

    def split(
        self,
        separator: str = "\n",
        *,
        include_separator: bool = False,
        allow_blank: bool = False,
    ) -> list[Content]:
        """Split rich text into lines, preserving styles.

        Args:
            separator (str, optional): String to split on. Defaults to "\\\\n".
            include_separator (bool, optional): Include the separator in the lines. Defaults to False.
            allow_blank (bool, optional): Return a blank line if the text ends with a separator. Defaults to False.

        Returns:
            List[Content]: A list of Content, one per line of the original.
        """
        assert separator, "separator must not be empty"
        text = self.plain
        if separator not in text:
            return [self]

        cache_key = (separator, include_separator, allow_blank)
        if self._split_cache is None:
            self._split_cache = FIFOCache(4)
        if (cached_result := self._split_cache.get(cache_key)) is not None:
            return cached_result.copy()

        if include_separator:
            lines = self.divide(
                [match.end() for match in re.finditer(re.escape(separator), text)],
            )
        else:

            def flatten_spans() -> Iterable[int]:
                for match in re.finditer(re.escape(separator), text):
                    yield from match.span()

            lines = [
                line
                for line in self.divide(list(flatten_spans()))
                if line.plain != separator
            ]

        if not allow_blank and text.endswith(separator):
            lines.pop()

        self._split_cache[cache_key] = lines
        return lines

    def rstrip(self, chars: str | None = None) -> Content:
        """Strip characters from end of text."""
        text = self.plain.rstrip(chars)
        return Content(text, self._trim_spans(text, self._spans))

    def rstrip_end(self, size: int) -> Content:
        """Remove whitespace beyond a certain width at the end of the text.

        Args:
            size (int): The desired size of the text.
        """
        text_length = len(self)
        if text_length > size:
            excess = text_length - size
            whitespace_match = _re_whitespace.search(self.plain)
            if whitespace_match is not None:
                whitespace_count = len(whitespace_match.group(0))
                return self.right_crop(min(whitespace_count, excess))
        return self

    def extend_style(self, spaces: int) -> Content:
        """Extend the Text given number of spaces where the spaces have the same style as the last character.

        Args:
            spaces (int): Number of spaces to add to the Text.

        Returns:
            New content with additional spaces at the end.
        """
        if spaces <= 0:
            return self
        spans = self._spans
        new_spaces = " " * spaces
        if spans:
            end_offset = len(self)
            spans = [
                span.extend(spaces) if span.end >= end_offset else span
                for span in spans
            ]
            return Content(self._text + new_spaces, spans, self.cell_length + spaces)
        return Content(self._text + new_spaces, self._spans, self._cell_length)

    def expand_tabs(self, tab_size: int = 8) -> Content:
        """Converts tabs to spaces.

        Args:
            tab_size (int, optional): Size of tabs. Defaults to 8.

        """
        if "\t" not in self.plain:
            return self

        if not self._spans:
            return Content(self.plain.expandtabs(tab_size))

        new_text: list[Content] = []
        append = new_text.append

        for line in self.split("\n", include_separator=True):
            if "\t" not in line.plain:
                append(line)
            else:
                cell_position = 0
                parts = line.split("\t", include_separator=True)
                for part in parts:
                    if part.plain.endswith("\t"):
                        part = Content(
                            part._text[:-1] + " ", part._spans, part._cell_length
                        )
                        cell_position += part.cell_length
                        tab_remainder = cell_position % tab_size
                        if tab_remainder:
                            spaces = tab_size - tab_remainder
                            part = part.extend_style(spaces)
                            cell_position += spaces
                    else:
                        cell_position += part.cell_length
                    append(part)

        content = EMPTY_CONTENT.join(new_text)
        return content

    def highlight_regex(
        self,
        highlight_regex: re.Pattern[str] | str,
        *,
        style: Style | str,
        maximum_highlights: int | None = None,
    ) -> Content:
        """Apply a style to text that matches a regular expression.

        Args:
            highlight_regex: Regular expression as a string, or compiled.
            style: Style to apply.
            maximum_highlights: Maximum number of matches to highlight, or `None` for no maximum.

        Returns:
            new content.
        """
        spans: list[Span] = self._spans.copy()
        append_span = spans.append
        _Span = Span
        plain = self.plain
        if isinstance(highlight_regex, str):
            re_highlight = re.compile(highlight_regex)
        else:
            re_highlight = highlight_regex
        count = 0
        for match in re_highlight.finditer(plain):
            start, end = match.span()
            if end > start:
                append_span(_Span(start, end, style))
            if (
                maximum_highlights is not None
                and (count := count + 1) >= maximum_highlights
            ):
                break
        return Content(self._text, spans, cell_length=self._cell_length)


class _FormattedLine:
    """A line of content with additional formatting information.

    This class is used internally within Content, and you are unlikely to need it an an app.
    """

    def __init__(
        self,
        get_style: Callable[[str | Style], Style],
        content: Content,
        width: int,
        x: int = 0,
        y: int = 0,
        align: TextAlign = "left",
        line_end: bool = False,
        link_style: Style | None = None,
    ) -> None:
        self.get_style = get_style
        self.content = content
        self.width = width
        self.x = x
        self.y = y
        self.align = align
        self.line_end = line_end
        self.link_style = link_style

    @property
    def plain(self) -> str:
        return self.content.plain

    def to_strip(self, style: Style) -> tuple[list[Segment], int]:
        _Segment = Segment
        align = self.align
        width = self.width
        pad_left = pad_right = 0
        content = self.content
        x = self.x
        y = self.y
        get_style = self.get_style

        if align in ("start", "left") or (align == "justify" and self.line_end):
            pass

        elif align == "center":
            excess_space = width - self.content.cell_length
            pad_left = excess_space // 2
            pad_right = excess_space - pad_left

        elif align in ("end", "right"):
            pad_left = width - self.content.cell_length

        elif align == "justify":
            words = content.split(" ", include_separator=False)
            words_size = sum(cell_len(word.plain.rstrip(" ")) for word in words)
            num_spaces = len(words) - 1
            spaces = [1] * num_spaces
            index = 0
            if spaces:
                while words_size + num_spaces < width:
                    spaces[len(spaces) - index - 1] += 1
                    num_spaces += 1
                    index = (index + 1) % len(spaces)

            segments: list[Segment] = []
            add_segment = segments.append
            x = self.x
            for index, word in enumerate(words):
                for text, text_style in word.render(
                    style, end="", parse_style=get_style
                ):
                    add_segment(
                        _Segment(
                            text, (style + text_style).rich_style_with_offset(x, y)
                        )
                    )
                    x += len(text) + 1
                if index < len(spaces) and (pad := spaces[index]):
                    add_segment(_Segment(" " * pad, (style + text_style).rich_style))

            return segments, width

        segments = (
            [Segment(" " * pad_left, style.background_style.rich_style)]
            if pad_left
            else []
        )
        add_segment = segments.append
        for text, text_style in content.render(style, end="", parse_style=get_style):
            add_segment(
                _Segment(text, (style + text_style).rich_style_with_offset(x, y))
            )
            x += len(text)

        if pad_right:
            segments.append(
                _Segment(" " * pad_right, style.background_style.rich_style)
            )

        return (segments, content.cell_length + pad_left + pad_right)

    def _apply_link_style(
        self, link_style: RichStyle, segments: list[Segment]
    ) -> list[Segment]:
        _Segment = Segment
        segments = [
            _Segment(
                text,
                (
                    style
                    if style._meta is None
                    else (style + link_style if "@click" in style.meta else style)
                ),
                control,
            )
            for text, style, control in segments
            if style is not None
        ]
        return segments


EMPTY_CONTENT: Final = Content("")
