import sys
from functools import lru_cache
from random import randint
from time import time
from typing import Any, Dict, Iterable, List, Optional, Type, Union

from . import errors
from .color import Color, ColorParseError, ColorSystem, blend_rgb
from .terminal_theme import DEFAULT_TERMINAL_THEME, TerminalTheme

# Style instances and style definitions are often interchangable
StyleType = Union[str, "Style"]


class _Bit:
    """A descriptor to get/set a style attribute bit."""

    __slots__ = ["bit"]

    def __init__(self, bit_no: int) -> None:
        self.bit = 1 << bit_no

    def __get__(self, obj: "Style", objtype: Type["Style"]) -> Optional[bool]:
        if obj._set_attributes & self.bit:
            return obj._attributes & self.bit != 0
        return None


class Style:
    """A terminal style.

    A terminal style consists of a color (`color`), a backround color (`bgcolor`), and a number of attributes, such
    as bold, italic etc. The attributes have 3 states: they can either be on
    (``True``), off (``False``), or not set (``None``).
    
    Args:
        color (Union[Color, str], optional): Color of terminal text. Defaults to None.
        bgcolor (Union[Color, str], optional): Color of terminal background. Defaults to None.
        bold (bool, optional): Enable bold text. Defaults to None.
        dim (bool, optional): Enable dim text. Defaults to None.
        italic (bool, optional): Enable italic text. Defaults to None.
        underline (bool, optional): Enable underlined text. Defaults to None.
        blink (bool, optional): Enabled blinking text. Defaults to None.
        blink2 (bool, optional): Enable fast blinking text. Defaults to None.
        reverse (bool, optional): Enabled reverse text. Defaults to None.
        conceal (bool, optional): Enable concealed text. Defaults to None.
        strike (bool, optional): Enable strikethrough text. Defaults to None.
        underline2 (bool, optional): Enable doubly underlined text. Defaults to None.
        frame (bool, optional): Enable framed text. Defaults to None.
        encircle (bool, optional): Enable encircled text. Defaults to None.
        overline (bool, optional): Enable overlined text. Defaults to None.
        link (str, link): Link URL. Defaults to None.
    
    """

    _color: Optional[Color]
    _bgcolor: Optional[Color]
    _attributes: int
    _set_attributes: int

    __slots__ = [
        "_color",
        "_bgcolor",
        "_attributes",
        "_set_attributes",
        "_link",
        "_link_id",
        "_ansi",
        "_style_definition",
    ]

    # maps bits on to SGR parameter
    _style_map = {
        0: "1",
        1: "2",
        2: "3",
        3: "4",
        4: "5",
        5: "6",
        6: "7",
        7: "8",
        8: "9",
        9: "21",
        10: "51",
        11: "52",
        12: "53",
    }

    def __init__(
        self,
        *,
        color: Union[Color, str] = None,
        bgcolor: Union[Color, str] = None,
        bold: bool = None,
        dim: bool = None,
        italic: bool = None,
        underline: bool = None,
        blink: bool = None,
        blink2: bool = None,
        reverse: bool = None,
        conceal: bool = None,
        strike: bool = None,
        underline2: bool = None,
        frame: bool = None,
        encircle: bool = None,
        overline: bool = None,
        link: str = None,
    ):
        self._ansi: Optional[str] = None
        self._style_definition: Optional[str] = None

        def _make_color(color: Union[Color, str]) -> Color:
            return color if isinstance(color, Color) else Color.parse(color)

        self._color = None if color is None else _make_color(color)
        self._bgcolor = None if bgcolor is None else _make_color(bgcolor)
        self._attributes = sum(
            (
                bold and 1 or 0,
                dim and 2 or 0,
                italic and 4 or 0,
                underline and 8 or 0,
                blink and 16 or 0,
                blink2 and 32 or 0,
                reverse and 64 or 0,
                conceal and 128 or 0,
                strike and 256 or 0,
                underline2 and 512 or 0,
                frame and 1024 or 0,
                encircle and 2048 or 0,
                overline and 4096 or 0,
            )
        )
        self._set_attributes = sum(
            (
                bold is not None,
                dim is not None and 2,
                italic is not None and 4,
                underline is not None and 8,
                blink is not None and 16,
                blink2 is not None and 32,
                reverse is not None and 64,
                conceal is not None and 128,
                strike is not None and 256,
                underline2 is not None and 512,
                frame is not None and 1024,
                encircle is not None and 2048,
                overline is not None and 4096,
            )
        )
        self._link = link
        self._link_id = f"{time()}-{randint(0, 999999)}" if link else ""

    bold = _Bit(0)
    dim = _Bit(1)
    italic = _Bit(2)
    underline = _Bit(3)
    blink = _Bit(4)
    blink2 = _Bit(5)
    reverse = _Bit(6)
    conceal = _Bit(7)
    strike = _Bit(8)
    underline2 = _Bit(9)
    frame = _Bit(10)
    encircle = _Bit(11)
    overline = _Bit(12)

    @property
    def link_id(self) -> str:
        """Get a link id, used in ansi code for links."""
        return self._link_id

    def __str__(self) -> str:
        """Re-generate style definition from attributes."""
        if self._style_definition is None:
            attributes: List[str] = []
            append = attributes.append
            bits = self._set_attributes
            if bits & 0b0000000001111:
                if bits & 1:
                    append("bold" if self.bold else "not bold")
                if bits & (1 << 1):
                    append("dim" if self.dim else "not dim")
                if bits & (1 << 2):
                    append("italic" if self.italic else "not italic")
                if bits & (1 << 3):
                    append("underline" if self.underline else "not underline")
            if bits & 0b0000111110000:
                if bits & (1 << 4):
                    append("blink" if self.blink else "not blink")
                if bits & (1 << 5):
                    append("blink2" if self.blink2 else "not blink2")
                if bits & (1 << 6):
                    append("reverse" if self.reverse else "not reverse")
                if bits & (1 << 7):
                    append("conceal" if self.conceal else "not conceal")
                if bits & (1 << 8):
                    append("strike" if self.strike else "not strike")
            if bits & 0b1111000000000:
                if bits & (1 << 9):
                    append("underline2" if self.underline2 else "not underline2")
                if bits & (1 << 10):
                    append("frame" if self.frame else "not frame")
                if bits & (1 << 11):
                    append("encircle" if self.encircle else "not encircle")
                if bits & (1 << 12):
                    append("overline" if self.overline else "not overline")
            if self._color is not None:
                append(self._color.name)
            if self._bgcolor is not None:
                append("on")
                append(self._bgcolor.name)
            if self._link:
                append("link")
                append(self._link)
            self._style_definition = " ".join(attributes) or "none"
        return self._style_definition

    def __bool__(self) -> bool:
        """A Style is false if it has no attributes, colors, or links."""
        return bool(self._set_attributes or self._color or self._bgcolor or self._link)

    def _make_ansi_codes(self, color_system: ColorSystem) -> str:
        """Generate ANSI codes for this style.

        Args:
            color_system (ColorSystem): Color system.

        Returns:
            str: String containing codes.
        """
        if self._ansi is None:
            sgr: List[str] = []
            append = sgr.append
            _style_map = self._style_map
            attributes = self._attributes & self._set_attributes
            if attributes:
                if attributes & 1:
                    append(_style_map[0])
                if attributes & 2:
                    append(_style_map[1])
                if attributes & 4:
                    append(_style_map[2])
                if attributes & 8:
                    append(_style_map[3])
                if attributes & 0b0000111110000:
                    for bit in range(4, 9):
                        if attributes & (1 << bit):
                            append(_style_map[bit])
                if attributes & 0b1111000000000:
                    for bit in range(9, 13):
                        if attributes & (1 << bit):
                            append(_style_map[bit])
            if self._color is not None:
                sgr.extend(self._color.downgrade(color_system).get_ansi_codes())
            if self._bgcolor is not None:
                sgr.extend(
                    self._bgcolor.downgrade(color_system).get_ansi_codes(
                        foreground=False
                    )
                )
            self._ansi = ";".join(sgr)
        return self._ansi

    @classmethod
    @lru_cache(maxsize=1024)
    def normalize(cls, style: str) -> str:
        """Normalize a style definition so that styles with the same effect have the same string
        representation.
        
        Args:
            style (str): A style definition.
        
        Returns:
            str: Normal form of style definition.
        """
        try:
            return str(cls.parse(style))
        except errors.StyleSyntaxError:
            return style.strip().lower()

    @classmethod
    def pick_first(cls, *values: Optional[StyleType]) -> StyleType:
        """Pick first non-None style."""
        for value in values:
            if value is not None:
                return value
        raise ValueError("expected at least one non-None style")

    def __repr__(self) -> str:
        """Render a named style differently from an anonymous style."""
        return f'Style.parse("{self}")'

    def __eq__(self, other: Any) -> bool:
        if not isinstance(other, Style):
            return NotImplemented
        return (
            self._color == other._color
            and self._bgcolor == other._bgcolor
            and self._set_attributes == other._set_attributes
            and self._attributes == other._attributes
            and self._link == other._link
        )

    def __hash__(self) -> int:
        return hash(
            (
                self._color,
                self._bgcolor,
                self._attributes,
                self._set_attributes,
                self._link,
            )
        )

    @property
    def color(self) -> Optional[Color]:
        """The foreground color or None if it is not set."""
        return self._color

    @property
    def bgcolor(self) -> Optional[Color]:
        """The background color or None if it is not set."""
        return self._bgcolor

    @property
    def link(self) -> Optional[str]:
        """Link text, if set."""
        return self._link

    @classmethod
    @lru_cache(maxsize=1024)
    def parse(cls, style_definition: str) -> "Style":
        """Parse a style definition.

        Args:
            style_definition (str): A string containing a style.
        
        Raises:
            errors.StyleSyntaxError: If the style definition syntax is invalid.            
        
        Returns:
            `Style`: A Style instance.
        """
        if style_definition.strip() == "none":
            return cls()

        style_attributes = {
            "dim": "dim",
            "d": "dim",
            "bold": "bold",
            "b": "bold",
            "italic": "italic",
            "i": "italic",
            "underline": "underline",
            "u": "underline",
            "blink": "blink",
            "blink2": "blink2",
            "reverse": "reverse",
            "r": "reverse",
            "conceal": "conceal",
            "c": "conceal",
            "strike": "strike",
            "s": "strike",
            "underline2": "underline2",
            "uu": "underline2",
            "frame": "frame",
            "encircle": "encircle",
            "overline": "overline",
            "o": "overline",
        }
        color: Optional[str] = None
        bgcolor: Optional[str] = None
        attributes: Dict[str, Optional[bool]] = {}
        link: Optional[str] = None

        words = iter(style_definition.split())
        for original_word in words:
            word = original_word.lower()
            if word == "on":
                word = next(words, "")
                if not word:
                    raise errors.StyleSyntaxError("color expected after 'on'")
                try:
                    Color.parse(word) is None
                except ColorParseError as error:
                    raise errors.StyleSyntaxError(
                        f"unable to parse {word} in {style_definition!r}; {error}"
                    ) from None
                bgcolor = word

            elif word == "not":
                word = next(words, "")
                attribute = style_attributes.get(word)
                if attribute is None:
                    raise errors.StyleSyntaxError(
                        f"expected style attribute after 'not', found {original_word!r}"
                    )
                attributes[attribute] = False

            elif word == "link":
                word = next(words, "")
                if not word:
                    raise errors.StyleSyntaxError("URL expected after 'link'")
                link = word

            elif word in style_attributes:
                attributes[style_attributes[word]] = True

            else:
                try:
                    Color.parse(word)
                except ColorParseError as error:
                    raise errors.StyleSyntaxError(
                        f"unable to parse {word!r} in style {style_definition!r}; {error}"
                    ) from None
                color = word
        style = Style(color=color, bgcolor=bgcolor, link=link, **attributes)
        return style

    @lru_cache(maxsize=1024)
    def get_html_style(self, theme: TerminalTheme = None) -> str:
        """Get a CSS style rule."""
        theme = theme or DEFAULT_TERMINAL_THEME
        css: List[str] = []
        append = css.append

        color = self.color
        bgcolor = self.bgcolor
        if self.reverse:
            color, bgcolor = bgcolor, color
        if self.dim:
            foreground_color = (
                theme.foreground_color if color is None else color.get_truecolor(theme)
            )
            color = Color.from_triplet(
                blend_rgb(foreground_color, theme.background_color, 0.5)
            )
        if color is not None:
            theme_color = color.get_truecolor(theme)
            append(f"color: {theme_color.hex}")
        if bgcolor is not None:
            theme_color = bgcolor.get_truecolor(theme, foreground=False)
            append(f"background-color: {theme_color.hex}")
        if self.bold:
            append("font-weight: bold")
        if self.italic:
            append("font-style: italic")
        if self.underline:
            append("text-decoration: underline")
        if self.strike:
            append("text-decoration: line-through")
        if self.overline:
            append("text-decoration: overline")
        return "; ".join(css)

    @classmethod
    def combine(cls, styles: Iterable["Style"]) -> "Style":
        """Combine styles and get result.
        
        Args:
            styles (Iterable[Style]): Styles to combine.
        
        Returns:
            Style: A new style instance.
        """

        return sum(styles, Style())

    @classmethod
    def chain(cls, *styles: "Style") -> "Style":
        """Combine styles from positional argument in to a single style.
        
        Args:
            *styles (Iterable[Style]): Styles to combine.
        
        Returns:
            Style: A new style instance.
        """
        return sum(styles, Style())

    def copy(self) -> "Style":
        """Get a copy of this style.
        
        Returns:
            Style: A new Style instance with identical attributes.
        """
        style = self.__new__(Style)
        style._ansi = self._ansi
        style._style_definition = self._style_definition
        style._color = self._color
        style._bgcolor = self._bgcolor
        style._attributes = self._attributes
        style._set_attributes = self._set_attributes
        style._link = self._link
        style._link_id = f"{time()}-{randint(0, 999999)}" if self._link else ""
        return style

    def render(
        self,
        text: str = "",
        *,
        color_system: Optional[ColorSystem] = ColorSystem.TRUECOLOR,
        legacy_windows: bool = False,
    ) -> str:
        """Render the ANSI codes for the style.
        
        Args:
            text (str, optional): A string to style. Defaults to "".
            color_system (Optional[ColorSystem], optional): Color system to render to. Defaults to ColorSystem.TRUECOLOR.
        
        Returns:
            str: A string containing ANSI style codes.
        """
        if not text or color_system is None:
            return text
        attrs = self._make_ansi_codes(color_system)
        rendered = f"\x1b[{attrs}m{text}\x1b[0m" if attrs else text
        if self._link and not legacy_windows:
            rendered = (
                f"\x1b]8;id={self._link_id};{self._link}\x1b\\{rendered}\x1b]8;;\x1b\\"
            )

        return rendered

    def test(self, text: Optional[str] = None) -> None:
        """Write text with style directly to terminal.

        This method is for testing purposes only.
        
        Args:
            text (Optional[str], optional): Text to style or None for style name.
        
        Returns:
            None:
        """
        text = text or str(self)
        sys.stdout.write(f"{self.render(text)}\n")

    def __add__(self, style: Optional["Style"]) -> "Style":
        if style is None:
            return self
        if not isinstance(style, Style):
            return NotImplemented  # type: ignore
        new_style = self.__new__(Style)
        new_style._ansi = None
        new_style._style_definition = None
        new_style._color = style._color or self._color
        new_style._bgcolor = style._bgcolor or self._bgcolor
        new_style._attributes = (self._attributes & ~style._set_attributes) | (
            style._attributes & style._set_attributes
        )
        new_style._set_attributes = self._set_attributes | style._set_attributes
        new_style._link = style._link or self._link
        new_style._link_id = style._link_id or self._link_id
        return new_style


class StyleStack:
    """A stack of styles."""

    __slots__ = ["_stack"]

    def __init__(self, default_style: "Style") -> None:
        self._stack: List[Style] = [default_style]

    def __repr__(self) -> str:
        return f"<stylestack {self._stack!r}>"

    @property
    def current(self) -> Style:
        """Get the Style at the top of the stack."""
        return self._stack[-1]

    def push(self, style: Style) -> None:
        """Push a new style on to the stack.
        
        Args:
            style (Style): New style to combine with current style.
        """
        self._stack.append(self._stack[-1] + style)

    def pop(self) -> Style:
        """Pop last style and discard.
        
        Returns:
            Style: New current style (also available as stack.current)
        """
        self._stack.pop()
        return self._stack[-1]
