/**
 * Convert a hex colour code to RGB.
 * @param {String} hex Hex colour code.
 */
export function hex2rgb(hex: string) {
    if (/^#([A-Fa-f0-9]{3}){1,2}$/.test(hex)) {
        let colorArr = hex.substring(1).split('');

        if (colorArr.length === 3) {
            colorArr = [
                colorArr[0],
                colorArr[0],
                colorArr[1],
                colorArr[1],
                colorArr[2],
                colorArr[2],
            ];
        }

        const color = `0x${colorArr.join('')}`;

        // FIXME: `>>` operand can validly take a string value
        const r = ((color as any) >> 16) & 255;
        const g = ((color as any) >> 8) & 255;
        const b = (color as any) & 255;

        return [r, g, b].join(', ');
    }

    throw new Error('Bad Hex');
}

export function luminance(str) {
    const [r, g, b] = str.split(', ');
    var a = [r, g, b].map(function (v) {
        v /= 255;
        return v <= 0.03928 ? v / 12.92 : Math.pow((v + 0.055) / 1.055, 2.4);
    });
    return a[0] * 0.2126 + a[1] * 0.7152 + a[2] * 0.0722;
}

export function contrastRatio(color1luminance, color2luminance) {
    const ratio =
        color1luminance > color2luminance
            ? (color2luminance + 0.05) / (color1luminance + 0.05)
            : (color1luminance + 0.05) / (color2luminance + 0.05);

    return ratio;
}

export function isAAAPassing(ratio, textSize = 'small') {
    if (textSize === 'large') {
        return ratio < 1 / 4.5;
    }
    return ratio < 1 / 7;
}

export function isAAPassing(ratio, textSize = 'small') {
    if (textSize === 'large') {
        return ratio < 1 / 3;
    }
    return ratio < 1 / 4.5;
}