use palette;
use std::fmt;

// Copy could be reconsidered, but eh
// TODO only pub so we can construct constants elsewhere. need const fn.
#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
pub struct Color(pub [f32; 4]);

impl fmt::Display for Color {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "Color(r={}, g={}, b={}, a={})",
            self.0[0], self.0[1], self.0[2], self.0[3]
        )
    }
}

impl Color {
    pub const BLACK: Color = Color([0.0, 0.0, 0.0, 1.0]);
    pub const WHITE: Color = Color([1.0, 1.0, 1.0, 1.0]);
    pub const RED: Color = Color([1.0, 0.0, 0.0, 1.0]);
    pub const GREEN: Color = Color([0.0, 1.0, 0.0, 1.0]);
    pub const BLUE: Color = Color([0.0, 0.0, 1.0, 1.0]);
    pub const CYAN: Color = Color([0.0, 1.0, 1.0, 1.0]);
    pub const YELLOW: Color = Color([1.0, 1.0, 0.0, 1.0]);
    pub const PURPLE: Color = Color([0.5, 0.0, 0.5, 1.0]);

    // TODO should assert stuff about the inputs

    pub fn rgb(r: usize, g: usize, b: usize) -> Color {
        Color::rgba(r, g, b, 1.0)
    }

    pub fn rgb_f(r: f32, g: f32, b: f32) -> Color {
        Color([r, g, b, 1.0])
    }

    pub fn rgba(r: usize, g: usize, b: usize, a: f32) -> Color {
        Color([
            (r as f32) / 255.0,
            (g as f32) / 255.0,
            (b as f32) / 255.0,
            a,
        ])
    }

    pub fn rgba_f(r: f32, g: f32, b: f32, a: f32) -> Color {
        Color([r, g, b, a])
    }

    pub fn grey(f: f32) -> Color {
        Color([f, f, f, 1.0])
    }

    // Deterministically shift a color's brightness based on an ID.
    pub fn shift(&self, id: usize) -> Color {
        use palette::Shade;

        // TODO this needs tuning. too easy to get too light/dark, but also too easy to have too few
        // variants. should maybe just manually come up with a list of 100 colors, hardcode in, modulo.
        let variants = 10;
        let half_variants = variants / 2;
        let modulo = id % variants;
        let scale = 1.0 / (variants as f32);

        let color = palette::Srgb::new(self.0[0], self.0[1], self.0[2]).into_linear();
        let new_color = if modulo < half_variants {
            color.lighten(scale * (modulo as f32))
        } else {
            color.darken(scale * ((modulo - half_variants) as f32))
        };
        Color([new_color.red, new_color.green, new_color.blue, 1.0])
    }

    pub fn alpha(&self, a: f32) -> Color {
        Color([self.0[0], self.0[1], self.0[2], a])
    }
}