export type RgbTuple = readonly [number, number, number];

export interface AccentVariables {
  "--nodedc-accent-rgb": string;
  "--nodedc-on-accent-rgb": string;
}

function clampChannel(value: number): number {
  return Math.max(0, Math.min(255, Math.round(value)));
}

function linearChannel(channel: number): number {
  const normalized = clampChannel(channel) / 255;
  return normalized <= 0.04045
    ? normalized / 12.92
    : ((normalized + 0.055) / 1.055) ** 2.4;
}

export function relativeLuminance(rgb: RgbTuple): number {
  const [red, green, blue] = rgb.map(linearChannel) as [number, number, number];
  return red * 0.2126 + green * 0.7152 + blue * 0.0722;
}

export function readableTextRgb(rgb: RgbTuple): RgbTuple {
  return relativeLuminance(rgb) > 0.46 ? [11, 17, 23] : [247, 248, 244];
}

export function rgbTuple(value: RgbTuple): string {
  return value.map(clampChannel).join(" ");
}

export function createAccentVariables(accent: RgbTuple): AccentVariables {
  return {
    "--nodedc-accent-rgb": rgbTuple(accent),
    "--nodedc-on-accent-rgb": rgbTuple(readableTextRgb(accent)),
  };
}