/** Parse #RRGGBB to RGB components */
function hexToRgb(hex: string): [number, number, number] {
  const n = hex.replace("#", "");
  if (n.length !== 6) return [0, 0, 0];
  return [
    Number.parseInt(n.slice(0, 2), 16),
    Number.parseInt(n.slice(2, 4), 16),
    Number.parseInt(n.slice(4, 6), 16),
  ];
}

function rgbToHex(r: number, g: number, b: number): string {
  const c = (x: number) =>
    Math.max(0, Math.min(255, Math.round(x))).toString(16).padStart(2, "0");
  return `#${c(r)}${c(g)}${c(b)}`;
}

/** Linear mix between two hex colors (0 = a, 1 = b). */
export function mixHex(a: string, b: string, t: number): string {
  const u = Math.max(0, Math.min(1, t));
  const [ar, ag, ab] = hexToRgb(a);
  const [br, bg, bb] = hexToRgb(b);
  return rgbToHex(
    ar + (br - ar) * u,
    ag + (bg - ag) * u,
    ab + (bb - ab) * u
  );
}