/** HEX · RGB · HSV 변환 (색상 팔레트 UI용) */

export interface Rgb {
  r: number;
  g: number;
  b: number;
}

export interface Hsv {
  /** 0–360 */
  h: number;
  /** 0–1 */
  s: number;
  /** 0–1 */
  v: number;
}

function clamp(n: number, min: number, max: number): number {
  return Math.max(min, Math.min(max, n));
}

export function normalizeHex6(hex: string): string {
  const h = hex.trim();
  if (/^#[0-9A-Fa-f]{6}$/.test(h)) return h.toUpperCase();
  if (/^#[0-9A-Fa-f]{3}$/.test(h)) {
    const c = h.slice(1);
    return ('#' + c[0] + c[0] + c[1] + c[1] + c[2] + c[2]).toUpperCase();
  }
  return '#2962FF';
}

export function hexToRgb(hex: string): Rgb {
  const h = normalizeHex6(hex).slice(1);
  return {
    r: parseInt(h.slice(0, 2), 16),
    g: parseInt(h.slice(2, 4), 16),
    b: parseInt(h.slice(4, 6), 16),
  };
}

export function rgbToHex(r: number, g: number, b: number): string {
  const to = (n: number) => clamp(Math.round(n), 0, 255).toString(16).padStart(2, '0');
  return `#${to(r)}${to(g)}${to(b)}`.toUpperCase();
}

export function rgbToHsv({ r, g, b }: Rgb): Hsv {
  const rn = r / 255;
  const gn = g / 255;
  const bn = b / 255;
  const max = Math.max(rn, gn, bn);
  const min = Math.min(rn, gn, bn);
  const d = max - min;
  let h = 0;
  if (d !== 0) {
    if (max === rn) h = ((gn - bn) / d) % 6;
    else if (max === gn) h = (bn - rn) / d + 2;
    else h = (rn - gn) / d + 4;
    h *= 60;
    if (h < 0) h += 360;
  }
  const s = max === 0 ? 0 : d / max;
  return { h, s, v: max };
}

export function hsvToRgb({ h, s, v }: Hsv): Rgb {
  const c = v * s;
  const x = c * (1 - Math.abs(((h / 60) % 2) - 1));
  const m = v - c;
  let rp = 0;
  let gp = 0;
  let bp = 0;
  if (h < 60) { rp = c; gp = x; }
  else if (h < 120) { rp = x; gp = c; }
  else if (h < 180) { gp = c; bp = x; }
  else if (h < 240) { gp = x; bp = c; }
  else if (h < 300) { rp = x; bp = c; }
  else { rp = c; bp = x; }
  return {
    r: Math.round((rp + m) * 255),
    g: Math.round((gp + m) * 255),
    b: Math.round((bp + m) * 255),
  };
}

export function hexToHsv(hex: string): Hsv {
  return rgbToHsv(hexToRgb(hex));
}

export function hsvToHex(hsv: Hsv): string {
  const { r, g, b } = hsvToRgb(hsv);
  return rgbToHex(r, g, b);
}

/** 채도·명도 영역 배경 (hue 고정) */
export function svPanelBackground(hue: number): string {
  const pure = hsvToHex({ h: hue, s: 1, v: 1 });
  return `linear-gradient(to top, #000, transparent), linear-gradient(to right, #fff, ${pure})`;
}

/** 색상(Hue) 슬라이더 배경 */
export const HUE_SLIDER_BG =
  'linear-gradient(to right, #f00 0%, #ff0 17%, #0f0 33%, #0ff 50%, #00f 67%, #f0f 83%, #f00 100%)';