use std::str::FromStr;

use syntect::highlighting::Color as SynColor;

use super::*;

/// How a fill or stroke should be painted.
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub enum Paint {
    /// A solid color.
    Solid(Color),
}

impl<T> From<T> for Paint
where
    T: Into<Color>,
{
    fn from(t: T) -> Self {
        Self::Solid(t.into())
    }
}

impl Debug for Paint {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        match self {
            Self::Solid(color) => color.fmt(f),
        }
    }
}

/// A color in a dynamic format.
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub enum Color {
    /// An 8-bit RGBA color.
    Rgba(RgbaColor),
    /// An 8-bit CMYK color.
    Cmyk(CmykColor),
}

impl Color {
    pub const BLACK: Self = Self::Rgba(RgbaColor::new(0x00, 0x00, 0x00, 0xFF));
    pub const GRAY: Self = Self::Rgba(RgbaColor::new(0xAA, 0xAA, 0xAA, 0xFF));
    pub const SILVER: Self = Self::Rgba(RgbaColor::new(0xDD, 0xDD, 0xDD, 0xFF));
    pub const WHITE: Self = Self::Rgba(RgbaColor::new(0xFF, 0xFF, 0xFF, 0xFF));
    pub const NAVY: Self = Self::Rgba(RgbaColor::new(0x00, 0x1f, 0x3f, 0xFF));
    pub const BLUE: Self = Self::Rgba(RgbaColor::new(0x00, 0x74, 0xD9, 0xFF));
    pub const AQUA: Self = Self::Rgba(RgbaColor::new(0x7F, 0xDB, 0xFF, 0xFF));
    pub const TEAL: Self = Self::Rgba(RgbaColor::new(0x39, 0xCC, 0xCC, 0xFF));
    pub const EASTERN: Self = Self::Rgba(RgbaColor::new(0x23, 0x9D, 0xAD, 0xFF));
    pub const PURPLE: Self = Self::Rgba(RgbaColor::new(0xB1, 0x0D, 0xC9, 0xFF));
    pub const FUCHSIA: Self = Self::Rgba(RgbaColor::new(0xF0, 0x12, 0xBE, 0xFF));
    pub const MAROON: Self = Self::Rgba(RgbaColor::new(0x85, 0x14, 0x4b, 0xFF));
    pub const RED: Self = Self::Rgba(RgbaColor::new(0xFF, 0x41, 0x36, 0xFF));
    pub const ORANGE: Self = Self::Rgba(RgbaColor::new(0xFF, 0x85, 0x1B, 0xFF));
    pub const YELLOW: Self = Self::Rgba(RgbaColor::new(0xFF, 0xDC, 0x00, 0xFF));
    pub const OLIVE: Self = Self::Rgba(RgbaColor::new(0x3D, 0x99, 0x70, 0xFF));
    pub const GREEN: Self = Self::Rgba(RgbaColor::new(0x2E, 0xCC, 0x40, 0xFF));
    pub const LIME: Self = Self::Rgba(RgbaColor::new(0x01, 0xFF, 0x70, 0xFF));

    /// Convert this color to RGBA.
    pub fn to_rgba(self) -> RgbaColor {
        match self {
            Self::Rgba(rgba) => rgba,
            Self::Cmyk(cmyk) => cmyk.to_rgba(),
        }
    }
}

impl Debug for Color {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        match self {
            Self::Rgba(c) => Debug::fmt(c, f),
            Self::Cmyk(c) => Debug::fmt(c, f),
        }
    }
}

impl<T> From<T> for Color
where
    T: Into<RgbaColor>,
{
    fn from(rgba: T) -> Self {
        Self::Rgba(rgba.into())
    }
}

/// An 8-bit RGBA color.
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub struct RgbaColor {
    /// Red channel.
    pub r: u8,
    /// Green channel.
    pub g: u8,
    /// Blue channel.
    pub b: u8,
    /// Alpha channel.
    pub a: u8,
}

impl RgbaColor {
    /// Construct a new RGBA color.
    pub const fn new(r: u8, g: u8, b: u8, a: u8) -> Self {
        Self { r, g, b, a }
    }

    /// Construct a new, opaque gray color.
    pub const fn gray(luma: u8) -> Self {
        Self::new(luma, luma, luma, 255)
    }
}

impl FromStr for RgbaColor {
    type Err = &'static str;

    /// Constructs a new color from hex strings like the following:
    /// - `#aef` (shorthand, with leading hashtag),
    /// - `7a03c2` (without alpha),
    /// - `abcdefff` (with alpha).
    ///
    /// The hashtag is optional and both lower and upper case are fine.
    fn from_str(hex_str: &str) -> Result<Self, Self::Err> {
        let hex_str = hex_str.strip_prefix('#').unwrap_or(hex_str);
        if hex_str.chars().any(|c| !c.is_ascii_hexdigit()) {
            return Err("string contains non-hexadecimal letters");
        }

        let len = hex_str.len();
        let long = len == 6 || len == 8;
        let short = len == 3 || len == 4;
        let alpha = len == 4 || len == 8;

        if !long && !short {
            return Err("string has wrong length");
        }

        let mut values: [u8; 4] = [255; 4];

        for elem in if alpha { 0 .. 4 } else { 0 .. 3 } {
            let item_len = if long { 2 } else { 1 };
            let pos = elem * item_len;

            let item = &hex_str[pos .. (pos + item_len)];
            values[elem] = u8::from_str_radix(item, 16).unwrap();

            if short {
                // Duplicate number for shorthand notation, i.e. `a` -> `aa`
                values[elem] += values[elem] * 16;
            }
        }

        Ok(Self::new(values[0], values[1], values[2], values[3]))
    }
}

impl From<SynColor> for RgbaColor {
    fn from(color: SynColor) -> Self {
        Self::new(color.r, color.b, color.g, color.a)
    }
}

impl Debug for RgbaColor {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        if f.alternate() {
            write!(
                f,
                "rgba({:02}, {:02}, {:02}, {:02})",
                self.r, self.g, self.b, self.a,
            )?;
        } else {
            write!(f, "#{:02x}{:02x}{:02x}", self.r, self.g, self.b)?;
            if self.a != 255 {
                write!(f, "{:02x}", self.a)?;
            }
        }
        Ok(())
    }
}

/// An 8-bit CMYK color.
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub struct CmykColor {
    /// The cyan component.
    pub c: u8,
    /// The magenta component.
    pub m: u8,
    /// The yellow component.
    pub y: u8,
    /// The key (black) component.
    pub k: u8,
}

impl CmykColor {
    /// Construct a new CMYK color.
    pub const fn new(c: u8, m: u8, y: u8, k: u8) -> Self {
        Self { c, m, y, k }
    }

    /// Construct a new, opaque gray color as a fraction of true black.
    pub fn gray(luma: u8) -> Self {
        Self::new(
            (luma as f64 * 0.75) as u8,
            (luma as f64 * 0.68) as u8,
            (luma as f64 * 0.67) as u8,
            (luma as f64 * 0.90) as u8,
        )
    }

    /// Convert this color to RGBA.
    pub fn to_rgba(self) -> RgbaColor {
        let k = self.k as f32 / 255.0;
        let f = |c| {
            let c = c as f32 / 255.0;
            (255.0 * (1.0 - c) * (1.0 - k)).round() as u8
        };

        RgbaColor {
            r: f(self.c),
            g: f(self.m),
            b: f(self.y),
            a: 255,
        }
    }
}

impl Debug for CmykColor {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let g = |c| 100.0 * (c as f64 / 255.0);
        write!(
            f,
            "cmyk({:.1}%, {:.1}%, {:.1}%, {:.1}%)",
            g(self.c),
            g(self.m),
            g(self.y),
            g(self.k),
        )
    }
}

impl From<CmykColor> for Color {
    fn from(cmyk: CmykColor) -> Self {
        Self::Cmyk(cmyk)
    }
}

/// A stroke of a geometric shape.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
pub struct Stroke {
    /// The stroke's paint.
    pub paint: Paint,
    /// The stroke's thickness.
    pub thickness: Length,
}

impl Default for Stroke {
    fn default() -> Self {
        Self {
            paint: Paint::Solid(Color::BLACK.into()),
            thickness: Length::pt(1.0),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_parse_color_strings() {
        #[track_caller]
        fn test(hex: &str, r: u8, g: u8, b: u8, a: u8) {
            assert_eq!(RgbaColor::from_str(hex), Ok(RgbaColor::new(r, g, b, a)));
        }

        test("f61243ff", 0xf6, 0x12, 0x43, 0xff);
        test("b3d8b3", 0xb3, 0xd8, 0xb3, 0xff);
        test("fCd2a9AD", 0xfc, 0xd2, 0xa9, 0xad);
        test("233", 0x22, 0x33, 0x33, 0xff);
        test("111b", 0x11, 0x11, 0x11, 0xbb);
    }

    #[test]
    fn test_parse_invalid_colors() {
        #[track_caller]
        fn test(hex: &str, message: &str) {
            assert_eq!(RgbaColor::from_str(hex), Err(message));
        }

        test("a5", "string has wrong length");
        test("12345", "string has wrong length");
        test("f075ff011", "string has wrong length");
        test("hmmm", "string contains non-hexadecimal letters");
        test("14B2AH", "string contains non-hexadecimal letters");
    }
}