colour-helper.ts

export const presetColours = {
  blue: {
    hue: 240,
    saturation: 100,
    color_temp: 0
  },
  red: {
    hue: 0,
    saturation: 100,
    color_temp: 0
  },
  yellow: {
    hue: 60,
    saturation: 100,
    color_temp: 0
  },
  green: {
    hue: 120,
    saturation: 100,
    color_temp: 0
  },
  white: {
    color_temp: 4500
  },
  daylightwhite: {
    color_temp: 5500
  },
  warmwhite: {
    color_temp: 2700
  }
}

export const hexToHsl = (hex: string) => {
  if (hex.toLowerCase() === '#000000') return console.error('Cannot set light to black');
  let result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);

  let r = parseInt(result[1], 16);
  let g = parseInt(result[2], 16);
  let b = parseInt(result[3], 16);

  r /= 255, g /= 255, b /= 255;

  let max = Math.max(r, g, b), min = Math.min(r, g, b);
  let h, s, l = (max + min) / 2;

  if(max == min){
    h = s = 0; // achromatic
  } else {
    let d = max - min;
    s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
    switch(max) {
        case r: h = (g - b) / d + (g < b ? 6 : 0); break;
        case g: h = (b - r) / d + 2; break;
        case b: h = (r - g) / d + 4; break;
    }
    h /= 6;
  }

  s = s * 100;
  s = Math.round(s);
  l = l * 100;
  l = Math.round(l);
  h = Math.round(360 * h);

  return {
    hue: h,
    saturation: s,
    brightness: l
  };
}

export const temperature = (temp: string) => {
  let t = parseInt(temp.slice(0,-1));

  if(t<2500||t>6500) return console.error('Colour temperature should be between 2500K and 6500K.');

  return{
    color_temp: t
  };
}

export const getColour = (colour: string) => {
  colour = colour.toLowerCase();
  if (colour.startsWith('#')) return hexToHsl(colour);
  if (colour.endsWith('k')) return temperature(colour);
  if (Object.keys(presetColours).includes(colour)) return presetColours[colour];
  throw new Error('Invalid Colour');
}