# Copyright (c) 2020-2021, Matthew Broadway
# Copyright (c) 2020-2023, Manfred Moitzi
# License: MIT License
from __future__ import annotations

import os
import pathlib
from typing import (
    TYPE_CHECKING,
    Optional,
    Union,
    cast,
    Sequence,
    Callable,
    Iterable,
    NamedTuple,
)
import re
import copy
import logging
import sys

from ezdxf import options
from ezdxf.colors import RGB
from ezdxf.addons import acadctb
from ezdxf.addons.drawing.config import Configuration
from ezdxf.addons.drawing.type_hints import Color
from ezdxf.colors import DXF_DEFAULT_COLORS, int2rgb
from ezdxf.entities import (
    Attrib,
    Insert,
    Face3d,
    Linetype,
    Viewport,
    Layer,
    LayerOverrides,
    Textstyle,
    DXFGraphic,
)
from ezdxf.entities.ltype import CONTINUOUS_PATTERN
from ezdxf.entities.polygon import DXFPolygon
from ezdxf.enums import InsertUnits, Measurement
from ezdxf.filemanagement import find_support_file
from ezdxf.lldxf import const
from ezdxf.lldxf.validator import make_table_key as layer_key
from ezdxf.fonts import fonts
from ezdxf.tools.pattern import scale_pattern, HatchPatternType

if TYPE_CHECKING:
    from ezdxf.document import Drawing
    from ezdxf.sections.table import Table
    from ezdxf.layouts import Layout

__all__ = [
    "Properties",
    "BackendProperties",
    "LayerProperties",
    "LayoutProperties",
    "RenderContext",
    "layer_key",
    "is_valid_color",
    "rgb_to_hex",
    "hex_to_rgb",
    "MODEL_SPACE_BG_COLOR",
    "PAPER_SPACE_BG_COLOR",
    "VIEWPORT_COLOR",
    "OLE2FRAME_COLOR",
    "set_color_alpha",
    "Filling",
]

table_key = layer_key
MODEL_SPACE_BG_COLOR = "#212830"
PAPER_SPACE_BG_COLOR = "#ffffff"
VIEWPORT_COLOR = "#aaaaaa"  # arbitrary choice
OLE2FRAME_COLOR = "#89adba"  # arbitrary choice
logger = logging.getLogger("ezdxf")


def is_dark_color(color: Color, dark: float = 0.2) -> bool:
    return RGB.from_hex(color).luminance <= dark


class Filling:
    SOLID = 0
    PATTERN = 1
    GRADIENT = 2

    def __init__(self) -> None:
        # Solid fill color is stored in Properties.color attribute
        self.type = Filling.SOLID
        # Gradient- or pattern name
        self.name: str = "SOLID"
        # Gradient- or pattern angle
        self.angle: float = 0.0  # in degrees
        self.gradient_color1: Optional[Color] = None
        self.gradient_color2: Optional[Color] = None
        self.gradient_centered: float = 0.0  # todo: what's the meaning?
        self.pattern_scale: float = 1.0
        self.pattern: HatchPatternType = []


class Properties:
    """An implementation agnostic representation of DXF entity properties like
    color and linetype. These properties represent the actual values after
    resolving all DXF specific rules like "by layer", "by block" and so on.
    """

    def __init__(self) -> None:
        # color string format "#RRGGBB" or "#RRGGBBAA"
        # alpha channel AA: 0x00 = transparent; 0xff = opaque
        self.color: str = "#ffffff"
        self.pen = 7  # equals the ACI (1-255), for pen based backends like plotters

        # Linetype rendering is done by the frontend, the backend receives only solid
        # lines.
        self.linetype_name: str = "CONTINUOUS"

        # Simplified DXF linetype definition:
        # all line elements >= 0.0, 0.0 = point
        # all gap elements > 0.0
        # Usage as alternating line - gap sequence: line-gap-line-gap ....
        # (line could be a point 0.0), line-line or gap-gap - makes no sense
        # Examples:
        # DXF: ("DASHED", "Dashed __ __ __ __ __ __ __ __ __ __ __ __ __ _",
        #      [0.6, 0.5, -0.1])
        # first entry 0.6 is the total pattern length = sum(linetype_pattern)
        # linetype_pattern: [0.5, 0.1] = line-gap
        # DXF: ("DASHDOTX2", "Dash dot (2x) ____  .  ____  .  ____  .  ____",
        #      [2.4, 2.0, -0.2, 0.0, -0.2])
        # linetype_pattern: [2.0, 0.2, 0.0, 0.2] = line-gap-point-gap
        # The continuous pattern is an empty tuple ()
        self.linetype_pattern: Sequence[float] = CONTINUOUS_PATTERN
        self.linetype_scale: float = 1.0
        # line weight in mm, todo: default lineweight is 0.25?
        self.lineweight: float = 0.25
        self.is_visible = True

        # The 'layer' attribute stores the resolved layer of an entity:
        # Entities inside a block references get properties from the layer
        # of the INSERT entity, if they reside on the layer '0'.
        # To get the "real" layer of an entity, you have to use `entity.dxf.layer`
        self.layer: str = "0"

        # Font definition object for text entities:
        # Font rendering is done by the frontend, backends receive paths for
        # stroke-fonts (.shx) and filled paths for outline fonts (.ttf).
        self.font: Optional[fonts.FontFace] = None  # use default font

        # Filling properties: Solid, Pattern, Gradient
        # Pattern rendering is done by the frontend, backends receive only solid lines,
        # and the fill color for filled polygons and filled paths is passed as the
        # color attribute in the BackendProperties, gradients are not supported.
        self.filling: Optional[Filling] = None

        self.units = InsertUnits.Unitless

    def __str__(self):
        return (
            f"({self.color}, {self.linetype_name}, {self.lineweight}, "
            f'"{self.layer}")'
        )

    @property
    def rgb(self) -> RGB:
        """Returns color as RGB tuple."""
        return RGB.from_hex(self.color)

    @property
    def luminance(self) -> float:
        """Returns perceived color luminance in range [0, 1] from dark to light."""
        return self.rgb.luminance


class BackendProperties(NamedTuple):
    """The backend receives a condensed version of the entity properties."""

    color: Color = "#000000"
    lineweight: float = 0.25  # in mm
    layer: str = "0"  # maybe useful to group entities (SVG, PDF)
    pen: int = 1  # equals the ACI (1-255), for pen based backends like plotters
    handle: str = ""  # top level entity handle

    @property
    def rgb(self) -> RGB:
        """Returns color as RGB tuple."""
        return RGB.from_hex(self.color)

    @property
    def luminance(self) -> float:
        """Returns perceived color luminance in range [0, 1] from dark to light."""
        return self.rgb.luminance


class LayerProperties(Properties):
    """Modified attribute meaning:

    is_visible: Whether entities belonging to this layer should be drawn
    layer: Stores real layer name (mixed case)

    """

    def __init__(self):
        super().__init__()
        self.has_aci_color_7 = False

    def get_entity_color_from_layer(self, fg: Color) -> Color:
        """Returns the layer color or if layer color is ACI color 7 the
        given layout default foreground color `fg`.
        """
        if self.has_aci_color_7:
            return fg
        else:
            return self.color


DEFAULT_LAYER_PROPERTIES = LayerProperties()


class LayoutProperties:
    # The LAYOUT, BLOCK and BLOCK_RECORD entities do not have
    # explicit graphic properties.
    def __init__(
        self,
        name: str,
        background_color: Color,
        foreground_color: Optional[Color] = None,
        units=InsertUnits.Unitless,
        dark_background: Optional[bool] = None,
    ):
        """
        Args:
            name: tab/display name
            units: enum :class:`ezdxf.enums.InsertUnits`
        """
        self.name = name
        self.units: InsertUnits = units

        self._background_color = ""
        self._default_color = ""
        self._has_dark_background = False
        self.set_colors(background_color, foreground_color)

        if dark_background is not None:
            self._has_dark_background = dark_background

    @property
    def background_color(self) -> Color:
        """Returns the default layout background color."""
        return self._background_color

    @property
    def default_color(self) -> Color:
        """Returns the default layout foreground color."""
        return self._default_color

    @property
    def has_dark_background(self) -> bool:
        """Returns ``True`` if the actual background-color is "dark"."""
        return self._has_dark_background

    @staticmethod
    def modelspace(units=InsertUnits.Unitless) -> LayoutProperties:
        return LayoutProperties(
            "Model",
            MODEL_SPACE_BG_COLOR,
            units=units,
        )

    @staticmethod
    def from_layout(layout: Layout, units: Optional[int] = None) -> LayoutProperties:
        """Setup default layout properties."""
        if layout.name == "Model":
            bg = MODEL_SPACE_BG_COLOR
        else:
            bg = PAPER_SPACE_BG_COLOR
        if units is None:
            units = layout.units
        return LayoutProperties(layout.name, bg, units=units)

    def set_colors(self, bg: Color, fg: Optional[Color] = None) -> None:
        """Setup default layout colors.

        Required color format "#RRGGBB" or including alpha transparency
        "#RRGGBBAA".
        """
        if not is_valid_color(bg):
            raise ValueError(f"Invalid background color: {bg}")
        self._background_color = bg
        if len(bg) == 9:  # including transparency
            bg = bg[:7]
        self._has_dark_background = is_dark_color(bg)
        if fg is not None:
            if not is_valid_color(fg):
                raise ValueError(f"Invalid foreground color: {fg}")
            self._default_color = fg
        else:
            self._default_color = "#ffffff" if self._has_dark_background else "#000000"


LayerPropsOverride = Callable[[Sequence[LayerProperties]], None]


class RenderContext:
    """The render context for the given DXF document. The
    :class:`RenderContext` resolves the properties of DXF entities from the
    context they reside in to actual values like RGB colors, transparency,
    linewidth and so on.

    A given `ctb` file (plot style file) overrides the default properties for
    all layouts, which means the plot style table stored in the layout is
    always ignored.

    Args:
        doc: DXF document
        ctb: path to a plot style table
        export_mode: Whether to render the document as it would look when
            exported (plotted) by a CAD application to a file such as pdf,
            or whether to render the document as it would appear inside a
            CAD application.
    """

    def __init__(
        self,
        doc: Optional[Drawing] = None,
        *,
        ctb: str = "",
        export_mode: bool = False,
    ):
        self._saved_states: list[Properties] = []
        self.line_pattern: dict[str, Sequence[float]] = dict()
        self.current_block_reference_properties: Optional[Properties] = None
        self.export_mode = export_mode
        self.override_ctb = ctb
        self.layers: dict[str, LayerProperties] = dict()
        self.fonts: dict[str, fonts.FontFace] = dict()
        self.units = InsertUnits.Unitless  # modelspace units
        self.linetype_scale: float = 1.0  # overall modelspace linetype scaling
        self.measurement = Measurement.Imperial
        self.pdsize: float = 0
        self.pdmode: int = 0
        self.document_dir: Optional[pathlib.Path] = None
        self._hatch_pattern_cache: dict[str, HatchPatternType] = dict()
        self.current_layout_properties = LayoutProperties.modelspace()
        self.plot_styles = self._load_plot_style_table(self.override_ctb)
        # Order for resolving SHX fonts: 1. "t"=TrueType; 2. "s"=SHX; 3. "l"=LFF
        self.shx_resolve_order = options.get(
            "drawing-addon", "shx_resolve_order", "tsl"
        )
        # callable to override layer properties:
        self._layer_properties_override: Optional[LayerPropsOverride] = None

        if doc:
            self.set_current_layout(doc.modelspace())
            self.line_pattern = _load_line_pattern(doc.linetypes)
            self.linetype_scale = doc.header.get("$LTSCALE", 1.0)
            self.pdsize = doc.header.get("$PDSIZE", 1.0)
            self.pdmode = doc.header.get("$PDMODE", 0)
            if doc.filename is not None:
                self.document_dir = pathlib.Path(
                    doc.filename.replace("\\", os.path.sep)
                ).parent.resolve()
            self._setup_text_styles(doc)
            try:
                self.units = InsertUnits(doc.header.get("$INSUNITS", 0))
            except ValueError:
                self.units = InsertUnits.Unitless
            try:
                self.measurement = Measurement(doc.header.get("$MEASUREMENT", 0))
            except ValueError:
                self.measurement = Measurement.Imperial
            if self.units == InsertUnits.Unitless:
                if self.measurement == Measurement.Metric:
                    self.units = InsertUnits.Meters
                else:
                    self.units = InsertUnits.Inches
        self.current_layout_properties.units = self.units  # default modelspace

    def set_layer_properties_override(self, func: Optional[LayerPropsOverride] = None):
        """The function `func` is called with the current layer properties as
        argument after resetting them, so the function can override the layer
        properties.
        """
        self._layer_properties_override = func

    def _override_layer_properties(self, layers: Sequence[LayerProperties]):
        if self._layer_properties_override:
            self._layer_properties_override(layers)

    def set_current_layout(self, layout: Layout, ctb: str = ""):
        """Set the current layout and update layout specific properties."""
        # the given ctb has the highest priority
        if ctb == "":
            # next is the override ctb
            ctb = self.override_ctb
        if ctb == "":
            # last is the ctb stored in the layout
            ctb = layout.get_plot_style_filename()
        self.current_layout_properties = LayoutProperties.from_layout(layout)
        self.plot_styles = self._load_plot_style_table(ctb)
        self.layers = dict()
        if layout.doc:
            self.layers = self._setup_layers(layout.doc)
            self._override_layer_properties(list(self.layers.values()))

    def copy(self):
        """Returns a shallow copy."""
        return copy.copy(self)

    def update_configuration(self, config: Configuration) -> Configuration:
        """Where the user has not specified a value, populate configuration
        fields based on the dxf header values
        """
        changes = {}
        if config.pdsize is None:
            changes["pdsize"] = self.pdsize
        if config.pdmode is None:
            changes["pdmode"] = self.pdmode
        if config.measurement is None:
            changes["measurement"] = self.measurement
        return config.with_changes(**changes)

    def _setup_layers(self, doc: Drawing) -> dict[str, LayerProperties]:
        layers: dict[str, LayerProperties] = dict()
        for layer in doc.layers:
            layer_properties = self.resolve_layer_properties(cast(Layer, layer))
            layers[layer_key(layer_properties.layer)] = layer_properties
        return layers

    def _setup_text_styles(self, doc: Drawing):
        for text_style in doc.styles:
            self.add_text_style(cast("Textstyle", text_style))

    def _setup_vp_layers(self, vp: Viewport) -> dict[str, LayerProperties]:
        doc = vp.doc
        assert doc is not None
        frozen_layer_names = {layer_key(name) for name in vp.frozen_layers}
        vp_handle = vp.dxf.handle
        layers: dict[str, LayerProperties] = dict()
        for layer in doc.layers:
            layer = cast(Layer, layer)
            overrides = layer.get_vp_overrides()
            if overrides.has_overrides(vp_handle):
                layer = layer.copy()
                self._apply_layer_overrides(vp_handle, layer, overrides)
            layer_properties = self.resolve_layer_properties(layer)
            key = layer_key(layer_properties.layer)
            layers[key] = layer_properties
            if key in frozen_layer_names:
                layer_properties.is_visible = False
        return layers

    @staticmethod
    def _apply_layer_overrides(
        vp_handle: str,
        layer: Layer,
        overrides: LayerOverrides,
    ) -> None:
        layer.color = overrides.get_color(vp_handle)
        rgb_color = overrides.get_rgb(vp_handle)
        if rgb_color is not None:
            layer.rgb = rgb_color
        layer.transparency = overrides.get_transparency(vp_handle)
        layer.dxf.linetype = overrides.get_linetype(vp_handle)
        layer.dxf.lineweight = overrides.get_lineweight(vp_handle)

    def from_viewport(self, vp: Viewport) -> RenderContext:
        if vp.doc is None:
            return self
        vp_ctx = self.copy()
        ctb = vp_ctx.override_ctb
        if ctb == "":
            ctb = vp.dxf.get("plot_style_name")
        if ctb:
            vp_ctx.plot_styles = vp_ctx._load_plot_style_table(ctb)
        layers = vp_ctx._setup_vp_layers(vp)
        vp_ctx.layers = layers
        vp_ctx._override_layer_properties(list(layers.values()))
        return vp_ctx

    def resolve_layer_properties(self, layer: Layer) -> LayerProperties:
        """Resolve layer properties."""
        properties = LayerProperties()
        # Store real layer name (mixed case):
        properties.layer = layer.dxf.name
        properties.pen = layer.dxf.color
        properties.color = self._true_layer_color(layer)

        # set layer transparency
        alpha = transparency_to_alpha(layer.transparency)
        if alpha < 255:
            properties.color = set_color_alpha(properties.color, alpha)

        # Depend layer ACI color from layout background color?
        # True color overrides ACI color and layers with only true color set
        # have default ACI color 7!
        if not layer.has_dxf_attrib("true_color"):
            properties.has_aci_color_7 = layer.dxf.color == 7

        # Normalize linetype names to UPPERCASE:
        properties.linetype_name = str(layer.dxf.linetype).upper()
        properties.linetype_pattern = self.line_pattern.get(
            properties.linetype_name, CONTINUOUS_PATTERN
        )
        properties.lineweight = self._true_layer_lineweight(layer.dxf.lineweight)
        properties.is_visible = layer.is_on() and not layer.is_frozen()
        if self.export_mode:
            properties.is_visible &= bool(layer.dxf.plot)
        return properties

    def add_text_style(self, text_style: Textstyle):
        """Setup text style properties."""
        name = table_key(text_style.dxf.name)
        font_file = text_style.dxf.font
        font_face = None
        if font_file == "":  # Font family stored in XDATA?
            family, italic, bold = text_style.get_extended_font_data()
            if family:
                font_face = fonts.find_best_match(
                    family=family, weight=700 if bold else 400, italic=italic
                )
        else:
            try:
                font_face = fonts.resolve_font_face(
                    font_file, order=self.shx_resolve_order
                )
            except fonts.FontNotFoundError:
                logger.warning("no fonts available, not even fallback fonts")

        if font_face is None:  # fall back to default font
            font_face = fonts.FontFace()
        self.fonts[name] = font_face

    def _true_layer_color(self, layer: Layer) -> Color:
        if layer.dxf.hasattr("true_color"):
            return rgb_to_hex(layer.rgb)  # type: ignore
        else:
            # Don't use layer.dxf.color: color < 0 is layer state off
            aci = layer.color
            # aci: 0=BYBLOCK, 256=BYLAYER, 257=BYOBJECT
            if aci < 1 or aci > 255:
                aci = 7  # default layer color
            return self._aci_to_true_color(aci)

    def _true_layer_lineweight(self, lineweight: int) -> float:
        if lineweight < 0:
            return self.default_lineweight()
        else:
            return float(lineweight) / 100.0

    @staticmethod
    def _load_plot_style_table(filename: str):
        # Each layout can have a different plot style table stored in
        # Layout.dxf.current_style_sheet.
        # HEADER var $STYLESHEET stores the default ctb-file name.
        filename = find_support_file(filename, options.support_dirs)
        try:
            ctb = acadctb.load(filename)
        except IOError:
            ctb = acadctb.new_ctb()

        # Colors in CTB files can be RGB colors but don't have to,
        # therefore initialize color without RGB values by the
        # default AutoCAD palette:
        for aci in range(1, 256):
            entry = ctb[aci]  # type: ignore
            if entry.has_object_color():
                # initialize with default AutoCAD palette
                entry.color = int2rgb(DXF_DEFAULT_COLORS[aci])
        return ctb

    @property
    def inside_block_reference(self) -> bool:
        """Returns ``True`` if current processing state is inside of a block
        reference (INSERT).
        """
        return bool(self.current_block_reference_properties)

    def push_state(self, block_reference: Properties) -> None:
        self._saved_states.append(self.current_block_reference_properties)  # type: ignore
        self.current_block_reference_properties = block_reference

    def pop_state(self) -> None:
        self.current_block_reference_properties = self._saved_states.pop()

    def resolve_all(self, entity: DXFGraphic) -> Properties:
        """Resolve all properties of `entity`."""
        p = Properties()
        p.layer = self.resolve_layer(entity)
        resolved_layer = layer_key(p.layer)
        p.units = self.resolve_units()
        p.color = self.resolve_color(entity, resolved_layer=resolved_layer)
        p.pen = self.resolve_pen(entity, resolved_layer=resolved_layer)
        p.linetype_name, p.linetype_pattern = self.resolve_linetype(
            entity, resolved_layer=resolved_layer
        )
        p.lineweight = self.resolve_lineweight(entity, resolved_layer=resolved_layer)
        p.linetype_scale = self.resolve_linetype_scale(entity)
        p.is_visible = self.resolve_visible(entity, resolved_layer=resolved_layer)
        if entity.is_supported_dxf_attrib("style"):
            p.font = self.resolve_font(entity)
        if isinstance(entity, DXFPolygon):
            p.filling = self.resolve_filling(entity)
        return p

    def resolve_units(self) -> InsertUnits:
        return self.current_layout_properties.units

    def resolve_linetype_scale(self, entity: DXFGraphic) -> float:
        return entity.dxf.ltscale * self.linetype_scale

    def resolve_visible(
        self, entity: DXFGraphic, *, resolved_layer: Optional[str] = None
    ) -> bool:
        """Resolve the visibility state of `entity`. Returns ``True`` if
        `entity` is visible.
        """
        if isinstance(entity, Insert):
            # depends only on the invisible flag, the layer state has no effect!
            return not bool(entity.dxf.invisible)
        elif isinstance(entity, Face3d):
            return any(entity.get_edges_visibility())
        elif isinstance(entity, Viewport):
            # The layer visibility of the VIEWPORT entity does not affect the
            # content of the Viewport. If the layer is off the viewport borders
            # are invisible.
            return entity.is_visible

        entity_layer = resolved_layer or layer_key(self.resolve_layer(entity))
        layer_properties = self.layers.get(entity_layer)
        if layer_properties and not layer_properties.is_visible:
            return False
        elif isinstance(entity, Attrib):
            return not bool(entity.dxf.invisible) and not entity.is_invisible
        else:
            return not bool(entity.dxf.invisible)

    def resolve_layer(self, entity: DXFGraphic) -> str:
        """Resolve the layer of `entity`, this is only relevant for entities
        inside of block references.
        """
        layer = entity.dxf.layer
        if layer == "0" and self.inside_block_reference:
            layer = self.current_block_reference_properties.layer  # type: ignore
        return layer

    def resolve_color(
        self, entity: DXFGraphic, *, resolved_layer: Optional[str] = None
    ) -> Color:
        """Resolve the rgb-color of `entity` as hex color string:
        "#RRGGBB" or "#RRGGBBAA".
        """
        if entity.dxf.hasattr("true_color"):
            # An existing true color value always overrides ACI color!
            # Do not default to BYLAYER or BYBLOCK, this ACI value is ignored!
            aci = 7
        else:
            aci = entity.dxf.color  # defaults to BYLAYER

        entity_layer = resolved_layer or layer_key(self.resolve_layer(entity))
        layer_properties = self.layers.get(entity_layer, DEFAULT_LAYER_PROPERTIES)

        if aci == const.BYLAYER:
            color = layer_properties.get_entity_color_from_layer(
                self.current_layout_properties.default_color
            )
        elif aci == const.BYBLOCK:
            if not self.inside_block_reference:
                color = self.current_layout_properties.default_color
            else:
                color = self.current_block_reference_properties.color  # type: ignore
        else:  # BYOBJECT
            color = self._true_entity_color(entity.rgb, aci)
        alpha = self._entity_alpha_str(
            entity.dxf.get("transparency"), layer_properties.color
        )
        return color[:7] + alpha

    def resolve_pen(
        self, entity: DXFGraphic, *, resolved_layer: Optional[str] = None
    ) -> int:
        """Resolve the aci-color of `entity` as pen number in the range of [1..255]."""
        pen = entity.dxf.color  # defaults to BYLAYER
        entity_layer = resolved_layer or layer_key(self.resolve_layer(entity))
        layer_properties = self.layers.get(entity_layer, DEFAULT_LAYER_PROPERTIES)

        if pen == const.BYLAYER:
            pen = layer_properties.pen
        elif pen == const.BYBLOCK:
            if not self.inside_block_reference:
                pen = 7
            else:
                pen = self.current_block_reference_properties.pen  # type: ignore
        elif pen == const.BYOBJECT:
            pen = 7  # ???
        return pen

    def _entity_alpha_str(
        self, raw_transparency: Optional[int], layer_color: Color
    ) -> str:
        """Returns the alpha value as hex string "xx" or empty string if opaque."""
        # alpha 0 = fully transparent
        # alpha 255 = opaque
        # DXF Transparency 0 = fully transparent
        # DXF Transparency 255 = opaque
        if raw_transparency == const.TRANSPARENCY_BYBLOCK:
            if self.inside_block_reference:
                return self.current_block_reference_properties.color[7:]  # type: ignore
            # else: entity is not in a block
            # There is no default transparency value for layouts, AutoCAD and
            # BricsCAD shows opaque entities!
            return ""
        # No transparency attribute means "by layer"
        elif raw_transparency is None:
            return layer_color[7:]

        alpha = raw_transparency & 0xFF
        if alpha < 255:
            return f"{alpha:02x}"
        return ""

    def resolve_aci_color(self, aci: int, resolved_layer: str) -> Color:
        """Resolve the `aci` color as hex color string: "#RRGGBB" """
        if aci == const.BYLAYER:
            layer = self.layers.get(layer_key(resolved_layer), DEFAULT_LAYER_PROPERTIES)
            color = layer.get_entity_color_from_layer(
                self.current_layout_properties.default_color
            )
        elif aci == const.BYBLOCK:
            if not self.inside_block_reference:
                color = self.current_layout_properties.default_color
            else:
                color = self.current_block_reference_properties.color  # type: ignore
        else:  # BYOBJECT
            color = self._true_entity_color(None, aci)
        return color

    def _true_entity_color(
        self, true_color: Optional[tuple[int, int, int]], aci: int
    ) -> Color:
        """Returns rgb color in hex format: "#RRGGBB".

        `true_color` has higher priority than `aci`.
        """
        if true_color is not None:
            return rgb_to_hex(true_color)
        elif 0 < aci < 256:
            return self._aci_to_true_color(aci)
        else:
            return self.current_layout_properties.default_color  # unknown / invalid

    def _aci_to_true_color(self, aci: int) -> Color:
        """Returns the `aci` value (AutoCAD Color Index) as rgb value in
        hex format: "#RRGGBB".
        """
        if aci == 7:  # black/white
            return self.current_layout_properties.default_color
        else:
            return rgb_to_hex(self.plot_styles[aci].color)

    def resolve_linetype(
        self, entity: DXFGraphic, *, resolved_layer: Optional[str] = None
    ) -> tuple[str, Sequence[float]]:
        """Resolve the linetype of `entity`. Returns a tuple of the linetype
        name as upper-case string and the simplified linetype pattern as tuple
        of floats.
        """
        aci = entity.dxf.color
        # Not sure if plotstyle table overrides actual entity setting?
        if (0 < aci < 256) and self.plot_styles[
            aci
        ].linetype != acadctb.OBJECT_LINETYPE:
            # todo: return special line types - overriding linetypes by
            #  plotstyle table
            pass
        name = entity.dxf.linetype.upper()  # default is 'BYLAYER'
        if name == "BYLAYER":
            entity_layer = resolved_layer or layer_key(self.resolve_layer(entity))
            layer = self.layers.get(entity_layer, DEFAULT_LAYER_PROPERTIES)
            name = layer.linetype_name
            pattern = layer.linetype_pattern

        elif name == "BYBLOCK":
            if self.inside_block_reference:
                name = self.current_block_reference_properties.linetype_name  # type: ignore
                pattern = (
                    self.current_block_reference_properties.linetype_pattern  # type: ignore
                )
            else:
                # There is no default layout linetype
                name = "STANDARD"
                pattern = CONTINUOUS_PATTERN
        else:
            pattern = self.line_pattern.get(name, CONTINUOUS_PATTERN)
        return name, pattern

    def resolve_lineweight(
        self, entity: DXFGraphic, *, resolved_layer: Optional[str] = None
    ) -> float:
        """Resolve the lineweight of `entity` in mm.

        DXF stores the lineweight in mm times 100 (e.g. 0.13mm = 13).
        The smallest line weight is 0 and the biggest line weight is 211.
        The DXF/DWG format is limited to a fixed value table,
        see: :attr:`ezdxf.lldxf.const.VALID_DXF_LINEWEIGHTS`

        CAD applications draw lineweight 0mm as an undefined small value, to
        prevent backends to draw nothing for lineweight 0mm the smallest
        return value is 0.01mm.

        """

        def lineweight():
            aci = entity.dxf.color
            # Not sure if plotstyle table overrides actual entity setting?
            if (0 < aci < 256) and self.plot_styles[
                aci
            ].lineweight != acadctb.OBJECT_LINEWEIGHT:
                # overriding lineweight by plotstyle table
                return self.plot_styles.get_lineweight(aci)
            lineweight = entity.dxf.lineweight  # default is BYLAYER
            if lineweight == const.LINEWEIGHT_BYLAYER:
                entity_layer = resolved_layer or layer_key(self.resolve_layer(entity))
                return self.layers.get(
                    entity_layer, DEFAULT_LAYER_PROPERTIES
                ).lineweight

            elif lineweight == const.LINEWEIGHT_BYBLOCK:
                if self.inside_block_reference:
                    return self.current_block_reference_properties.lineweight
                else:
                    # There is no default layout lineweight
                    return self.default_lineweight()
            elif lineweight == const.LINEWEIGHT_DEFAULT:
                return self.default_lineweight()
            else:
                return float(lineweight) / 100.0

        return max(0.01, lineweight())

    def default_lineweight(self):
        """Returns the default lineweight of the document."""
        # todo: is this value stored anywhere (e.g. HEADER section)?
        return 0.25

    def resolve_font(self, entity: DXFGraphic) -> Optional[fonts.FontFace]:
        """Resolve the text style of `entity` to a font name.
        Returns ``None`` for the default font.
        """
        # todo: extended font data
        style = entity.dxf.get("style", "Standard")
        return self.fonts.get(table_key(style))

    def resolve_filling(self, entity: DXFGraphic) -> Optional[Filling]:
        """Resolve filling properties (SOLID, GRADIENT, PATTERN) of `entity`."""

        def setup_gradient():
            filling.type = Filling.GRADIENT
            filling.name = gradient.name.upper()
            # todo: no idea when to use aci1 and aci2
            filling.gradient_color1 = rgb_to_hex(gradient.color1)
            if gradient.one_color:
                c = round(gradient.tint * 255)  # channel value
                filling.gradient_color2 = rgb_to_hex((c, c, c))
            else:
                filling.gradient_color2 = rgb_to_hex(gradient.color2)

            filling.angle = gradient.rotation
            filling.gradient_centered = gradient.centered

        def setup_pattern():
            filling.type = Filling.PATTERN
            filling.name = polygon.dxf.pattern_name.upper()
            filling.pattern_scale = polygon.dxf.pattern_scale
            filling.angle = polygon.dxf.pattern_angle
            if polygon.dxf.pattern_double:
                # This value is not editable by CAD-App-GUI:
                filling.pattern_scale *= 2  # todo: is this correct?

            filling.pattern = self._hatch_pattern_cache.get(filling.name)
            if filling.pattern:
                return

            pattern = polygon.pattern
            if not pattern:
                return

            # DXF stores the hatch pattern already rotated and scaled,
            # pattern_scale and pattern_rotation are just hints for the CAD
            # application to modify the pattern if required.
            # It's better to revert the scaling and rotation, because in general
            # back-ends do not handle pattern that way, they need a base-pattern
            # and separated scaling and rotation attributes and these
            # base-pattern could be cached by their name.
            #
            # There is no advantage of simplifying the hatch line pattern and
            # this format is required by the PatternAnalyser():
            filling.pattern = scale_pattern(
                pattern.as_list(), 1.0 / filling.pattern_scale, -filling.angle
            )
            self._hatch_pattern_cache[filling.name] = filling.pattern

        if not isinstance(entity, DXFPolygon):
            return None

        polygon = cast(DXFPolygon, entity)
        filling = Filling()
        if polygon.dxf.solid_fill:
            gradient = polygon.gradient
            if gradient is None:
                filling.type = Filling.SOLID
            else:
                if gradient.kind == 0:  # Solid
                    filling.type = Filling.SOLID
                    filling.gradient_color1 = rgb_to_hex(gradient.color1)
                else:
                    setup_gradient()
        else:
            setup_pattern()
        return filling


COLOR_PATTERN = re.compile("#[0-9A-Fa-f]{6,8}")


def is_valid_color(color: Color) -> bool:
    if type(color) is not Color:
        raise TypeError(f"Invalid argument type: {type(color)}.")
    if len(color) in (7, 9):
        return bool(COLOR_PATTERN.fullmatch(color))
    return False


def rgb_to_hex(rgb: Union[tuple[int, int, int], tuple[float, float, float]]) -> Color:
    """Returns color in hex format: "#RRGGBB"."""
    assert all(0 <= x <= 255 for x in rgb), f"invalid RGB color: {rgb}"
    r, g, b = rgb
    return f"#{r:02x}{g:02x}{b:02x}"


def hex_to_rgb(hex_string: Color) -> RGB:
    """Returns hex string color as (r, g, b) tuple."""
    hex_string = hex_string.lstrip("#")
    assert len(hex_string) == 6
    r = int(hex_string[0:2], 16)
    g = int(hex_string[2:4], 16)
    b = int(hex_string[4:6], 16)
    return RGB(r, g, b)


def set_color_alpha(color: Color, alpha: int) -> Color:
    """Returns `color` including the new `alpha` channel in hex format:
    "#RRGGBBAA".

    Args:
        color: may be an RGB or RGBA hex color string
        alpha: the new alpha value (0-255)
    """
    assert color.startswith("#") and len(color) in (
        7,
        9,
    ), f'invalid RGB color: "{color}"'
    assert 0 <= alpha < 256, f"alpha out of range: {alpha}"
    return f"{color[:7]}{alpha:02x}"


def transparency_to_alpha(value: float) -> int:
    # clamp into range [0, 1]
    value = min(max(0.0, value), 1.0)
    return int(round((1.0 - value) * 255))


def _load_line_pattern(linetypes: Table) -> dict[str, Sequence[float]]:
    """Load linetypes defined in a DXF document into  as dictionary,
    key is the upper case linetype name, value is the simplified line pattern,
    see :func:`compile_line_pattern`.
    """
    pattern: dict[str, Sequence[float]] = dict()
    for linetype in linetypes:
        assert isinstance(linetype, Linetype)
        name = linetype.dxf.name.upper()
        pattern[name] = linetype.simplified_line_pattern()
    return pattern


def set_layers_state(
    layers: Sequence[LayerProperties], layer_names: Iterable[str], state=True
):
    """Set layer state of `layers` to on/off.

    Args:
        layers: layer properties
        layer_names: iterable of layer names
        state: `True` turn this `layers` on and others off,
            `False` turn this `layers` off and others on
    """
    unique_layer_names = {layer_key(name) for name in layer_names}
    for layer in layers:
        if layer_key(layer.layer) in unique_layer_names:
            layer.is_visible = state
        else:
            layer.is_visible = not state
