// SPDX-License-Identifier: MIT

use core::fmt;
#[cfg(feature = "serde")]
use serde::de::{self, Deserializer};
#[cfg(feature = "serde")]
use serde::Deserialize;

/// A color
#[derive(Copy, Clone)]
#[repr(transparent)]
pub struct Color {
    pub data: u32,
}

impl Color {
    /// Create a new color from RGB
    pub const fn rgb(r: u8, g: u8, b: u8) -> Self {
        Color {
            data: 0xFF000000 | ((r as u32) << 16) | ((g as u32) << 8) | (b as u32),
        }
    }

    /// Set the alpha
    pub const fn rgba(r: u8, g: u8, b: u8, a: u8) -> Self {
        Color {
            data: ((a as u32) << 24) | ((r as u32) << 16) | ((g as u32) << 8) | (b as u32),
        }
    }

    /// Get the r value
    pub fn r(&self) -> u8 {
        ((self.data & 0x00FF0000) >> 16) as u8
    }

    /// Get the g value
    pub fn g(&self) -> u8 {
        ((self.data & 0x0000FF00) >> 8) as u8
    }

    /// Get the b value
    pub fn b(&self) -> u8 {
        (self.data & 0x000000FF) as u8
    }

    /// Get the alpha value
    pub fn a(&self) -> u8 {
        ((self.data & 0xFF000000) >> 24) as u8
    }

    /// Interpolate between two colors
    pub fn interpolate(start_color: Color, end_color: Color, scale: f64) -> Color {
        let r = Color::interp(start_color.r(), end_color.r(), scale);
        let g = Color::interp(start_color.g(), end_color.g(), scale);
        let b = Color::interp(start_color.b(), end_color.b(), scale);
        let a = Color::interp(start_color.a(), end_color.a(), scale);
        Color::rgba(r, g, b, a)
    }

    fn interp(start_color: u8, end_color: u8, scale: f64) -> u8 {
        ((end_color as f64 - start_color as f64) * scale + start_color as f64) as u8
    }
}

/// Compare two colors (Do not take care of alpha)
impl PartialEq for Color {
    fn eq(&self, other: &Color) -> bool {
        self.r() == other.r() && self.g() == other.g() && self.b() == other.b()
    }
}

impl fmt::Debug for Color {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        write!(f, "{:#010X}", { self.data })
    }
}

#[cfg(feature = "serde")]
impl<'de> Deserialize<'de> for Color {
    fn deserialize<D>(deserializer: D) -> Result<Color, D::Error>
        where
            D: Deserializer<'de>,
    {
        deserializer.deserialize_i32(ColorVisitor)
    }
}

#[cfg(feature = "serde")]
struct ColorVisitor;

#[cfg(feature = "serde")]
impl<'de> de::Visitor<'de> for ColorVisitor {
    type Value = Color;

    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        formatter.write_str("Color specification in HEX format '#ARGB'")
    }

    fn visit_str<E>(self, color_spec: &str) -> Result<Self::Value, E>
        where
            E: de::Error,
    {
        if color_spec.len() != 9 {
            return Err(E::custom(format!("Color spec must be of format '#AARRGGBB' ('{}')", color_spec)))
        }

        if &color_spec[0..1] != "#" {
            return Err(E::custom(format!("Color spec must begin with '#' ('{}')", color_spec)));
        }

        let a = u8::from_str_radix(&color_spec[1..3], 16)
            .map_err(|e| E::custom(e))?;
        let r = u8::from_str_radix(&color_spec[3..5], 16)
            .map_err(|e| E::custom(e.to_string()))?;
        let g = u8::from_str_radix(&color_spec[5..7], 16)
            .map_err(|e| E::custom(e.to_string()))?;
        let b = u8::from_str_radix(&color_spec[7..9], 16)
            .map_err(|e| E::custom(e.to_string()))?;

        Ok(Color::rgba(r, g, b, a))
    }
}

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

    #[test]
    fn partial_eq() {
        assert_eq!(Color::rgb(1, 2, 3), Color::rgba(1, 2, 3, 200));
        assert_ne!(Color::rgb(1, 2, 3), Color::rgba(11, 2, 3, 200));
        assert_eq!(Color::rgba(1, 2, 3, 200), Color::rgba(1, 2, 3, 200));
    }

    #[test]
    fn alignment() {
        assert_eq!(4, core::mem::size_of::<Color>());
        assert_eq!(8, core::mem::size_of::<[Color; 2]>());
        assert_eq!(12, core::mem::size_of::<[Color; 3]>());
        assert_eq!(16, core::mem::size_of::<[Color; 4]>());
        assert_eq!(20, core::mem::size_of::<[Color; 5]>());
    }

    #[cfg(features = "serde")]
    mod serde {
        use serde_derive::Deserialize;
        use toml;
        use crate::Color;

        #[derive(Deserialize)]
        struct TestColor {
            color: Color,
        }

        #[test]
        fn deserialize_ok() {
            let color_spec = r##"color = "#00010203""##;
            let test_color: TestColor = toml::from_str(color_spec).expect("Color spec did not parse correctly");
            assert_eq!(test_color.color.a(), 0, "Alpha channel incorrect");
            assert_eq!(test_color.color.r(), 1, "Red channel incorrect");
            assert_eq!(test_color.color.g(), 2, "Green channel incorrect");
            assert_eq!(test_color.color.b(), 3, "Blue channel incorrect");
        }

        #[test]
        fn deserialize_hex() {
            let color_spec = r##"color = "#AABBCCDD""##;
            let _: TestColor = toml::from_str(color_spec).expect("Color spec did not parse HEX correctly");
        }

        #[test]
        fn deserialize_no_hash() {
            let color_spec = r##"color = "$00010203""##;
            let test_color: Result<TestColor, _> = toml::from_str(color_spec);
            assert!(test_color.is_err(), "Color spec should not parse correctly without leading '#'");
            assert!(test_color.err().unwrap().to_string().contains("must begin with '#'"));
        }

        #[test]
        fn deserialize_not_hex() {
            let color_spec = r##"color = "#GG010203""##;
            let test_color: Result<TestColor, _> = toml::from_str(color_spec);
            assert!(test_color.is_err(), "Color spec should not parse invalid HEX correctly");
            assert!(test_color.err().unwrap().to_string().contains("invalid digit"));
        }

        #[test]
        fn deserialize_str_too_long() {
            let color_spec = r##"color = "#0001020304""##;
            let test_color: Result<TestColor, _> = toml::from_str(color_spec);
            assert!(test_color.is_err(), "Color spec should not parse invalid spec correctly");
            assert!(test_color.err().unwrap().to_string().contains("must be of format '#AARRGGBB'"));
        }

        #[test]
        fn deserialize_str_too_short() {
            let color_spec = r##"color = "#000102""##;
            let test_color: Result<TestColor, _> = toml::from_str(color_spec);
            assert!(test_color.is_err(), "Color spec should not parse invalid spec correctly");
            assert!(test_color.err().unwrap().to_string().contains("must be of format '#AARRGGBB'"));
        }
    }
}