type RGB = [number, number, number];

const grey: RGB = [237, 242, 246]; // grey-200
const red: RGB = [221, 103, 81]; // red-600
const yellow: RGB = [250, 200, 82]; // yellow-500
const lightGreen: RGB = [120, 222, 163]; // green-500
const darkGreen: RGB = [91, 183, 130]; // green-600

const blendColorValue = (v1: number, v2: number, weight: number): number => {
  return v1 * (1 - weight) + v2 * weight;
};

const blendColors = (c1: RGB, c2: RGB, weight: number): RGB => {
  const [r1, g1, b1] = c1;
  const [r2, g2, b2] = c2;
  return [
    blendColorValue(r1, r2, weight),
    blendColorValue(g1, g2, weight),
    blendColorValue(b1, b2, weight),
  ];
};

const getRGBString = (color: RGB): string => {
  const [r, g, b] = color;
  return `rgb(${Math.floor(r)}, ${Math.floor(g)}, ${Math.floor(b)})`;
};

export const getBlendedColorForRating = (rating: number): string => {
  const scale = Math.floor(rating);
  const weight = rating % 1;
  let colors: [RGB, RGB];

  switch (scale) {
    case 0:
      return getRGBString(grey);
    case 1:
      colors = [red, yellow];
      break;
    case 2:
      colors = [yellow, lightGreen];
      break;
    case 3:
      colors = [lightGreen, darkGreen];
      break;
    case 4:
    default:
      return getRGBString(darkGreen);
  }

  const blendedColor = blendColors(colors[0], colors[1], weight);
  return getRGBString(blendedColor);
};