#![cfg(feature = "ogp_images")]

use image::{Pixel, Rgb, Rgba};
use pronouns_today::util::pcg64;

pub fn generate_color_pair(state: &mut u128) -> ([u8; 3], [u8; 3]) {
	let mut background = random_color(state);
	let mut foreground;
	loop {
		foreground = random_color(state);
		if meets_criteria(&foreground, &background) {
			break;
		}
		background = random_color(state);
		if meets_criteria(&foreground, &background) {
			break;
		}
	}
	(foreground, background)
}

pub fn generate_color_pair_rgba(state: &mut u128) -> (Rgba<u8>, Rgba<u8>) {
	let (color1, color2) = generate_color_pair(state);

	let (color1, color2): (Rgb<u8>, Rgb<u8>) = (
		color1.into(),
		color2.into(),
	);

	(color1.to_rgba(), color2.to_rgba())
}

pub fn relative_lum(color: &[u8; 3]) -> f32 {
	let color_mapped: Vec<f32> = color.iter()
		.map(|val| {
			let val = *val as f32 / 255.0;
			if val < 0.03928 {
				val / 12.92
			} else {
				((val+0.055)/1.055).powf(2.4)
			}
		})
		.collect();
	return 0.2126 * color_mapped[0] + 0.7152 * color_mapped[1] + 0.0722 * color_mapped[2]
}

pub fn check_contrast(color1: &[u8; 3], color2: &[u8; 3]) -> f32 {
	let a = 0.05 + relative_lum(color1);
	let b = 0.05 + relative_lum(color2);
	(a / b).max(b / a)
}

pub fn get_saturation(color: &[u8; 3]) -> f32 {
	let chroma_max = *(color.iter().max().unwrap());
	let chroma_min = *(color.iter().min().unwrap());
	return ((chroma_max - chroma_min) as f32) / chroma_max as f32;
}

pub fn random_color(state: &mut u128) -> [u8; 3] {
	let random = pcg64(state).to_le_bytes();
	return [
		random[0],
		random[1],
		random[2],
	]
}

pub fn meets_criteria(foreground: &[u8; 3], background: &[u8; 3]) -> bool {
	return check_contrast(foreground, background) >= 5.0 &&
		   get_saturation(background) < 0.65 &&
		   get_saturation(foreground) < 0.65
}