"""
Handles the creation of patterns and gradients

Usage documentation at: <https://py-pdf.github.io/fpdf2/Patterns.html>
"""

from abc import ABC
from typing import List, Optional, TYPE_CHECKING, Tuple, Union

from .drawing import DeviceCMYK, DeviceGray, DeviceRGB, convert_to_device_color
from .syntax import Name, PDFArray, PDFObject

if TYPE_CHECKING:
    from .fpdf import FPDF


class Pattern(PDFObject):
    """
    Represents a PDF Pattern object.

    Currently, this class supports only "shading patterns" (pattern_type 2),
    using either a linear or radial gradient. Tiling patterns (pattern_type 1)
    are not yet implemented.
    """

    def __init__(self, shading: Union["LinearGradient", "RadialGradient"]):
        super().__init__()
        self.type = Name("Pattern")
        # 1 for a tiling pattern or type 2 for a shading pattern:
        self.pattern_type = 2
        self._shading = shading

    @property
    def shading(self):
        return f"{self._shading.get_shading_object().id} 0 R"


class Type2Function(PDFObject):
    """Transition between 2 colors"""

    def __init__(self, color_1, color_2):
        super().__init__()
        # 0: Sampled function; 2: Exponential interpolation function; 3: Stitching function; 4: PostScript calculator function
        self.function_type = 2
        self.domain = "[0 1]"
        self.c0 = f'[{" ".join(f"{c:.2f}" for c in color_1.colors)}]'
        self.c1 = f'[{" ".join(f"{c:.2f}" for c in color_2.colors)}]'
        self.n = 1


class Type3Function(PDFObject):
    """When multiple colors are used, a type 3 function is necessary to stitch type 2 functions together
    and define the bounds between each color transition"""

    def __init__(self, functions, bounds):
        super().__init__()
        # 0: Sampled function; 2: Exponential interpolation function; 3: Stitching function; 4: PostScript calculator function
        self.function_type = 3
        self.domain = "[0 1]"
        self._functions = functions
        self.bounds = f"[{' '.join(f'{bound:.2f}' for bound in bounds)}]"
        self.encode = f"[{' '.join('0 1' for _ in functions)}]"
        self.n = 1

    @property
    def functions(self):
        return f"[{' '.join(f'{f.id} 0 R' for f in self._functions)}]"


class Shading(PDFObject):
    def __init__(
        self,
        shading_type: int,  # 2 for axial shading, 3 for radial shading
        background: Optional[Union[DeviceRGB, DeviceGray, DeviceCMYK]],
        color_space: str,
        coords: List[int],
        function: Union[Type2Function, Type3Function],
        extend_before: bool,
        extend_after: bool,
    ):
        super().__init__()
        self.shading_type = shading_type
        self.background = (
            f'[{" ".join(f"{c:.2f}" for c in background.colors)}]'
            if background
            else None
        )
        self.color_space = Name(color_space)
        self.coords = coords
        self.function = f"{function.id} 0 R"
        self.extend = f'[{"true" if extend_before else "false"} {"true" if extend_after else "false"}]'


class Gradient(ABC):
    def __init__(self, colors, background, extend_before, extend_after, bounds):
        self.color_space, self.colors = self._convert_colors(colors)
        self.background = None
        if background:
            self.background = (
                convert_to_device_color(background)
                if isinstance(background, (str, DeviceGray, DeviceRGB, DeviceCMYK))
                else convert_to_device_color(*background)
            )
        if self.background and self.background.__class__.__name__ != self.color_space:
            raise ValueError(
                "The background color must be of the same color space as the gradient"
            )
        self.extend_before = extend_before
        self.extend_after = extend_after
        self.bounds = (
            bounds
            if bounds
            else [(i + 1) / (len(self.colors) - 1) for i in range(len(self.colors) - 2)]
        )
        if len(self.bounds) != len(self.colors) - 2:
            raise ValueError(
                "Bounds array length must be two less than the number of colors"
            )
        self.functions = self._generate_functions()
        self.pattern = Pattern(self)
        self._shading_object = None
        self.coords = None
        self.shading_type = 0

    @classmethod
    def _convert_colors(cls, colors) -> Tuple[str, List]:
        color_list = []
        if len(colors) < 2:
            raise ValueError("A gradient must have at least two colors")
        color_spaces = set()
        for color in colors:
            current_color = (
                convert_to_device_color(color)
                if isinstance(color, (str, DeviceGray, DeviceRGB, DeviceCMYK))
                else convert_to_device_color(*color)
            )
            color_list.append(current_color)
            color_spaces.add(type(current_color).__name__)
        if len(color_spaces) == 1:
            return color_spaces.pop(), color_list
        if "DeviceCMYK" in color_spaces:
            raise ValueError("Can't mix CMYK with other color spaces.")
        # mix of DeviceGray and DeviceRGB
        converted = []
        for color in color_list:
            if isinstance(color, DeviceGray):
                converted.append(DeviceRGB(color.g, color.g, color.g))
            else:
                converted.append(color)
        return "DeviceRGB", converted

    def _generate_functions(self):
        if len(self.colors) < 2:
            raise ValueError("A gradient must have at least two colors")
        if len(self.colors) == 2:
            return [Type2Function(self.colors[0], self.colors[1])]
        number_of_colors = len(self.colors)
        functions = []
        for i in range(number_of_colors - 1):
            functions.append(Type2Function(self.colors[i], self.colors[i + 1]))
        functions.append(Type3Function(functions[:], self.bounds))
        return functions

    def get_shading_object(self):
        if not self._shading_object:
            self._shading_object = Shading(
                shading_type=self.shading_type,
                background=self.background,
                color_space=self.color_space,
                coords=PDFArray(self.coords),
                function=self.functions[-1],
                extend_before=self.extend_before,
                extend_after=self.extend_after,
            )
        return self._shading_object

    def get_pattern(self):
        return self.pattern


class LinearGradient(Gradient):
    def __init__(
        self,
        fpdf: "FPDF",
        from_x: int,
        from_y: int,
        to_x: int,
        to_y: int,
        colors: List,
        background=None,
        extend_before: bool = False,
        extend_after: bool = False,
        bounds: List[int] = None,
    ):
        """
        A shading pattern that creates a linear (axial) gradient in a PDF.

        The gradient is defined by two points: (from_x, from_y) and (to_x, to_y),
        along which the specified colors are interpolated. Optionally, you can set
        a background color, extend the gradient beyond its start or end, and
        specify custom color stop positions via `bounds`.

        Args:
            fpdf (FPDF): The FPDF instance used for PDF generation.
            from_x (int or float): The x-coordinate of the starting point of the gradient,
                in user space units.
            from_y (int or float): The y-coordinate of the starting point of the gradient,
                in user space units.
            to_x (int or float): The x-coordinate of the ending point of the gradient,
                in user space units.
            to_y (int or float): The y-coordinate of the ending point of the gradient,
                in user space units.
            colors (List[str or Tuple[int, int, int]]): A list of colors along which the gradient
                will be interpolated. Colors may be given as hex strings (e.g., "#FF0000") or
                (R, G, B) tuples.
            background (str or Tuple[int, int, int], optional): A background color to use
                if the gradient does not fully cover the region it is applied to.
                Defaults to None (no background).
            extend_before (bool, optional): Whether to extend the first color beyond the
                starting point (from_x, from_y). Defaults to False.
            extend_after (bool, optional): Whether to extend the last color beyond the
                ending point (to_x, to_y). Defaults to False.
            bounds (List[float], optional): An optional list of floats in the range (0, 1)
                that represent gradient stops for color transitions. The number of bounds
                should be two less than the number of colors (for multi-color gradients).
                Defaults to None, which evenly distributes color stops.
        """
        super().__init__(colors, background, extend_before, extend_after, bounds)
        coords = [from_x, fpdf.h - from_y, to_x, fpdf.h - to_y]
        self.coords = [f"{fpdf.k * c:.2f}" for c in coords]
        self.shading_type = 2


class RadialGradient(Gradient):
    def __init__(
        self,
        fpdf: "FPDF",
        start_circle_x: int,
        start_circle_y: int,
        start_circle_radius: int,
        end_circle_x: int,
        end_circle_y: int,
        end_circle_radius: int,
        colors: List,
        background=None,
        extend_before: bool = False,
        extend_after: bool = False,
        bounds: List[int] = None,
    ):
        """
        A shading pattern that creates a radial (or circular/elliptical) gradient in a PDF.

        The gradient is defined by two circles (start and end). Colors are blended from the
        start circle to the end circle, forming a radial gradient. You can optionally set a
        background color, extend the gradient beyond its circles, and provide custom color
        stop positions via `bounds`.

        Args:
            fpdf (FPDF): The FPDF instance used for PDF generation.
            start_circle_x (int or float): The x-coordinate of the inner circle's center,
                in user space units.
            start_circle_y (int or float): The y-coordinate of the inner circle's center,
                in user space units.
            start_circle_radius (int or float): The radius of the inner circle, in user space units.
            end_circle_x (int or float): The x-coordinate of the outer circle's center,
                in user space units.
            end_circle_y (int or float): The y-coordinate of the outer circle's center,
                in user space units.
            end_circle_radius (int or float): The radius of the outer circle, in user space units.
            colors (List[str or Tuple[int, int, int]]): A list of colors along which the gradient
                will be interpolated. Colors may be given as hex strings (e.g., "#FF0000") or
                (R, G, B) tuples.
            background (str or Tuple[int, int, int], optional): A background color to display
                if the gradient does not fully cover the region it's applied to. Defaults to None
                (no background).
            extend_before (bool, optional): Whether to extend the gradient beyond the start circle.
                Defaults to False.
            extend_after (bool, optional): Whether to extend the gradient beyond the end circle.
                Defaults to False.
            bounds (List[float], optional): An optional list of floats in the range (0, 1) that
                represent gradient stops for color transitions. The number of bounds should be one
                less than the number of colors (for multi-color gradients). Defaults to None,
                which evenly distributes color stops.
        """
        super().__init__(colors, background, extend_before, extend_after, bounds)
        coords = [
            start_circle_x,
            fpdf.h - start_circle_y,
            start_circle_radius,
            end_circle_x,
            fpdf.h - end_circle_y,
            end_circle_radius,
        ]
        self.coords = [f"{fpdf.k * c:.2f}" for c in coords]
        self.shading_type = 3