use crate::format::ser::{Ser, Sink, Source};

#[derive(Copy, Clone, Debug, Default)]
pub struct Pixel {
    pub r: u8,
    pub g: u8,
    pub b: u8,
}

impl Ser for Pixel {
    fn write(&self, sink: &mut impl std::io::Write) -> anyhow::Result<()> {
        sink.put((self.r, self.g, self.b))
    }

    fn read(source: &mut impl std::io::Read) -> anyhow::Result<Self> {
        let (r, g, b) = source.get()?;
        Ok(Self { r, g, b })
    }
}

impl Pixel {
    pub const BLACK: Pixel = Pixel { r: 0, g: 0, b: 0 };
    #[inline]
    pub fn distance(a: Pixel, b: Pixel) -> usize {
        let (rd, gd, bd) = (
            a.r.abs_diff(b.r) as usize,
            a.r.abs_diff(b.r) as usize,
            a.r.abs_diff(b.r) as usize,
        );
        // fast_sqrt(rd * rd + gd * gd + bd * bd)
        SQRT[rd + gd + bd]
    }

    #[inline]
    pub fn average(a: Pixel, b: Pixel) -> Pixel {
        Pixel {
            r: ((a.r as u16 + b.r as u16) >> 1) as u8,
            g: ((a.g as u16 + b.g as u16) >> 1) as u8,
            b: ((a.b as u16 + b.b as u16) >> 1) as u8,
        }
    }

    #[inline]
    pub fn scale(&self, factor: f32) -> Pixel {
        Pixel {
            r: ((self.r as f32) * factor).clamp(0.0, 255.0) as u8,
            g: ((self.g as f32) * factor).clamp(0.0, 255.0) as u8,
            b: ((self.b as f32) * factor).clamp(0.0, 255.0) as u8,
        }
    }
}

pub const SQRT: [usize; 256 * 3] = gen_sqrt_lookup();

const fn gen_sqrt_lookup<const N: usize>() -> [usize; N] {
    let mut arr = [0; N];
    let mut i = 0;
    while i < N {
        arr[i] = sqrt(i as f32) as usize;
        i += 1;
    }
    arr
}

const fn sqrt(x: f32) -> f32 {
    let a = 1.0;
    let a = (a + x / a) * 0.5;
    let a = (a + x / a) * 0.5;
    let a = (a + x / a) * 0.5;
    a
}

pub fn fast_sqrt(x: usize) -> usize {
    let a = 1;
    let a = (a + x / (a + 1)) / 2;
    let a = (a + x / (a + 1)) / 2;
    // let a = (a + x / (a + 1)) / 2;
    // let a = (a + x / (a + 1)) / 2;
    a
}