use num::PrimInt;

pub fn scale8(i: u8, scale: u8) -> u8 {
    // borrowed from FastLED
    (i as u16 * scale as u16).wrapping_shr(8) as u8
}

pub fn avg7(i: i8, j: i8) -> i8 {
    i.unsigned_shr(1).wrapping_add(j.unsigned_shr(1)).wrapping_add(i & 0x1)
}

pub fn grad8(hash: u8, x: i8, y: i8) -> i8 {
    let mut u: i8;
    let mut v: i8;

    if hash & 4 != 0 {
        u = y; v = x;
    } else {
        u = x; v = y;
    }

    if hash & 1 != 0 {
        u = u.wrapping_neg();
    }
    if hash & 2 != 0 {
        v = v.wrapping_neg();
    }

    return avg7(u, v);
}

pub fn lerp7by8(a: i8, b: i8, frac: u8) -> i8 {
    if b > a {
        let delta: u8 = b.wrapping_sub(a) as u8;
        let scaled: u8 = scale8(delta as u8, frac);
        return a.wrapping_add(scaled as i8);
    } else {
        let delta: u8 = a.wrapping_sub(b) as u8;
        let scaled: u8 = scale8(delta as u8, frac);
        return a.wrapping_sub(scaled as i8);
    }
}

pub fn ease8InOutQuad(i: u8) -> u8 {
    let j = if i & 0x80 != 0 {
        255 - i
    } else {
        i
    };
    let jj = scale8(j, j);
    let jj2 = jj.unsigned_shl(1);
    if i & 0x80 == 0 {
        return jj2
    } else {
        return 255 - jj2;
    }
}