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use std::num::NonZeroUsize;

use almost::equal;
use palette::{convert::FromColorUnclamped, ClampAssign, FromColor, Oklcha, Srgb, Srgba};

/// Get an array of 100 colors with a specific hue and chroma
/// over the full range of lightness.
/// Colors which are not valid Srgba will fallback to a color with the nearest valid chroma.
pub fn steps<C>(c: C, len: NonZeroUsize) -> Vec<Srgba>
where
    Oklcha: FromColor<C>,
{
    let mut c = Oklcha::from_color(c);
    let mut steps = Vec::with_capacity(len.get());

    for i in 0..len.get() {
        let lightness = i as f32 / (len.get() - 1) as f32;
        c.l = lightness;
        steps.push(oklch_to_srgba_nearest_chroma(c))
    }
    steps
}

/// get the index for a new color some steps away from a base color
pub fn get_index(base_index: usize, steps: usize, step_len: usize, is_dark: bool) -> Option<usize> {
    if is_dark {
        base_index.checked_add(steps)
    } else {
        base_index.checked_sub(steps)
    }
    .filter(|i| *i < step_len)
}

/// get surface color given a base and some steps
pub fn get_surface_color(
    base_index: usize,
    steps: usize,
    step_array: &Vec<Srgba>,
    mut is_dark: bool,
    fallback: &Srgba,
) -> Srgba {
    assert!(step_array.len() == 100);

    is_dark = is_dark || base_index < 91;

    *get_index(base_index, steps, step_array.len(), is_dark)
        .and_then(|i| step_array.get(i))
        .unwrap_or(fallback)
}

/// get text color given a base background color
pub fn get_text(
    base_index: usize,
    step_array: &Vec<Srgba>,
    fallback: &Srgba,
    tint_array: Option<&Vec<Srgba>>,
) -> Srgba {
    assert!(step_array.len() == 100);
    let step_array = if let Some(tint_array) = tint_array {
        assert!(tint_array.len() == 100);
        tint_array
    } else {
        step_array
    };

    let is_dark = base_index < 60;

    let index = get_index(base_index, 70, step_array.len(), is_dark)
        .or_else(|| get_index(base_index, 50, step_array.len(), is_dark))
        .unwrap_or_else(|| if is_dark { 99 } else { 0 });

    *step_array.get(index).unwrap_or(fallback)
}

/// get the index into the steps array for a given color
/// the index is the lightness value of the color converted to Oklcha, scaled to the range [0, 100]
pub fn color_index<C>(c: C, array_len: usize) -> usize
where
    Oklcha: FromColor<C>,
{
    let c = Oklcha::from_color(c);
    ((c.l * array_len as f32).round() as usize).clamp(0, array_len - 1)
}

/// find the nearest chroma which makes our color a valid color in Srgba
pub fn oklch_to_srgba_nearest_chroma(mut c: Oklcha) -> Srgba {
    let mut r_chroma = c.chroma;
    let mut l_chroma = 0.0;
    // exit early if we found it right away
    let mut new_c = Srgba::from_color_unclamped(c);

    if is_valid_srgb(new_c) {
        new_c.clamp_assign();
        return new_c;
    }

    // is this an excessive depth to search?
    for _ in 0..64 {
        let new_c = Srgba::from_color_unclamped(c);
        if is_valid_srgb(new_c) {
            l_chroma = c.chroma;
            c.chroma = (c.chroma + r_chroma) / 2.0;
        } else {
            r_chroma = c.chroma;
            c.chroma = (c.chroma + l_chroma) / 2.0;
        }
    }
    Srgba::from_color(c)
}

/// checks that the color is valid srgb
pub fn is_valid_srgb(c: Srgba) -> bool {
    (equal(c.red, Srgb::max_red()) || (c.red >= Srgb::min_red() && c.red <= Srgb::max_red()))
        && (equal(c.blue, Srgb::max_blue())
            || (c.blue >= Srgb::min_blue() && c.blue <= Srgb::max_blue()))
        && (equal(c.green, Srgb::max_green())
            || (c.green >= Srgb::min_green() && c.green <= Srgb::max_green()))
}

#[cfg(test)]
mod tests {
    use almost::equal;
    use palette::{OklabHue, Srgba};

    use super::{is_valid_srgb, oklch_to_srgba_nearest_chroma};

    #[test]
    fn test_valid_check() {
        assert!(is_valid_srgb(Srgba::new(1.0, 1.0, 1.0, 1.0)));
        assert!(is_valid_srgb(Srgba::new(0.0, 0.0, 0.0, 1.0)));
        assert!(is_valid_srgb(Srgba::new(0.5, 0.5, 0.5, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(-0.1, 0.0, 0.0, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(0.0, -0.1, 0.0, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(-0.0, 0.0, -0.1, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(-100.1, 0.0, 0.0, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(0.0, -100.1, 0.0, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(-0.0, 0.0, -100.1, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(1.1, 0.0, 0.0, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(0.0, 1.1, 0.0, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(-0.0, 0.0, 1.1, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(100.1, 0.0, 0.0, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(0.0, 100.1, 0.0, 1.0)));
        assert!(!is_valid_srgb(Srgba::new(-0.0, 0.0, 100.1, 1.0)));
    }

    #[test]
    fn test_conversion_boundaries() {
        let c1 = palette::Oklcha::new(0.0, 0.288, OklabHue::from_degrees(0.0), 1.0);
        let srgb = oklch_to_srgba_nearest_chroma(c1);
        equal(srgb.red, 0.0);
        equal(srgb.blue, 0.0);
        equal(srgb.green, 0.0);

        let c1 = palette::Oklcha::new(1.0, 0.288, OklabHue::from_degrees(0.0), 1.0);
        let srgb = oklch_to_srgba_nearest_chroma(c1);

        equal(srgb.red, 1.0);
        equal(srgb.blue, 1.0);
        equal(srgb.green, 1.0);
    }

    #[test]
    fn test_conversion_colors() {
        let c1 = palette::Oklcha::new(0.4608, 0.11111, OklabHue::new(57.31), 1.0);
        let srgb = oklch_to_srgba_nearest_chroma(c1).into_format::<u8, u8>();
        assert!(srgb.red == 133);
        assert!(srgb.green == 69);
        assert!(srgb.blue == 0);

        let c1 = palette::Oklcha::new(0.30, 0.08, OklabHue::new(35.0), 1.0);
        let srgb = oklch_to_srgba_nearest_chroma(c1).into_format::<u8, u8>();
        assert!(srgb.red == 78);
        assert!(srgb.green == 27);
        assert!(srgb.blue == 15);

        let c1 = palette::Oklcha::new(0.757, 0.146, OklabHue::new(301.2), 1.0);
        let srgb = oklch_to_srgba_nearest_chroma(c1).into_format::<u8, u8>();
        assert!(srgb.red == 192);
        assert!(srgb.green == 153);
        assert!(srgb.blue == 253);
    }

    #[test]
    fn test_conversion_fallback_colors() {
        let c1 = palette::Oklcha::new(0.70, 0.284, OklabHue::new(35.0), 1.0);
        let srgb = oklch_to_srgba_nearest_chroma(c1).into_format::<u8, u8>();
        assert!(srgb.red == 255);
        assert!(srgb.green == 103);
        assert!(srgb.blue == 65);

        let c1 = palette::Oklcha::new(0.757, 0.239, OklabHue::new(301.2), 1.0);
        let srgb = oklch_to_srgba_nearest_chroma(c1).into_format::<u8, u8>();
        assert!(srgb.red == 193);
        assert!(srgb.green == 152);
        assert!(srgb.blue == 255);

        let c1 = palette::Oklcha::new(0.163, 0.333, OklabHue::new(141.0), 1.0);
        let srgb = oklch_to_srgba_nearest_chroma(c1).into_format::<u8, u8>();
        assert!(srgb.red == 1);
        assert!(srgb.green == 19);
        assert!(srgb.blue == 0);
    }
}