export type HsvColor = {
  h: number;
  s: number;
  v: number;
};

function normalizeHue(value: number): number {
  if (!Number.isFinite(value)) return 0;
  return ((value % 360) + 360) % 360;
}

export function clampNumber(value: number, min: number, max: number): number {
  if (!Number.isFinite(value)) return min;
  return Math.max(min, Math.min(max, value));
}

export function normalizeHexColor(hex: string | null | undefined): string | null {
  if (typeof hex !== "string") return null;

  const raw = hex.trim();
  if (!raw) return null;

  const hashless = raw.startsWith("#") ? raw.slice(1) : raw;
  if (![3, 6].includes(hashless.length)) return null;
  if (!/^[\da-f]+$/i.test(hashless)) return null;

  if (hashless.length === 3) {
    const expanded = hashless
      .split("")
      .map((char) => `${char}${char}`)
      .join("");
    return `#${expanded.toLowerCase()}`;
  }

  return `#${hashless.toLowerCase()}`;
}

export function hexToHsv(hex: string): HsvColor {
  const normalized = normalizeHexColor(hex);
  if (!normalized) {
    throw new Error(`Invalid hex color: ${hex}`);
  }

  const value = normalized.slice(1);
  const r = Number.parseInt(value.slice(0, 2), 16) / 255;
  const g = Number.parseInt(value.slice(2, 4), 16) / 255;
  const b = Number.parseInt(value.slice(4, 6), 16) / 255;
  const max = Math.max(r, g, b);
  const min = Math.min(r, g, b);
  const delta = max - min;

  let hue = 0;
  if (delta !== 0) {
    if (max === r) {
      hue = ((g - b) / delta) % 6;
    } else if (max === g) {
      hue = (b - r) / delta + 2;
    } else {
      hue = (r - g) / delta + 4;
    }
  }

  hue = normalizeHue(hue * 60);

  return {
    h: hue,
    s: max === 0 ? 0 : delta / max,
    v: max,
  };
}

export function hsvToHex(color: HsvColor): string {
  const hue = normalizeHue(color.h);
  const saturation = clampNumber(color.s, 0, 1);
  const value = clampNumber(color.v, 0, 1);
  const chroma = value * saturation;
  const hueSegment = hue / 60;
  const x = chroma * (1 - Math.abs((hueSegment % 2) - 1));
  const match = value - chroma;

  let red = 0;
  let green = 0;
  let blue = 0;

  if (hueSegment >= 0 && hueSegment < 1) {
    red = chroma;
    green = x;
  } else if (hueSegment >= 1 && hueSegment < 2) {
    red = x;
    green = chroma;
  } else if (hueSegment >= 2 && hueSegment < 3) {
    green = chroma;
    blue = x;
  } else if (hueSegment >= 3 && hueSegment < 4) {
    green = x;
    blue = chroma;
  } else if (hueSegment >= 4 && hueSegment < 5) {
    red = x;
    blue = chroma;
  } else {
    red = chroma;
    blue = x;
  }

  const toHex = (channel: number) =>
    Math.round((channel + match) * 255)
      .toString(16)
      .padStart(2, "0");

  return `#${toHex(red)}${toHex(green)}${toHex(blue)}`;
}