import colors from "./colors.json";
import { hslToHex, hexToHsl, contrastRatio } from "./colors";
import { clamp } from "./math";

type Pallette = {
  bg: string;
  fg: string;
  red: string;
  green: string;
  shade1: string;
  shade2: string;
  shade3: string;
  shade4: string;
};

const MIN_CONTRAST = 3.0;
const FALLBACK_WHITE = "#ffffff";

const bg = colors.bg ?? "#0f0f10";
const fg = colors.fg ?? "#e6e6e6";
const redHue = colors.accentRedHue ?? 0;
const greenHue = colors.accentGreenHue ?? 140;
const sat = colors.accentSaturation ?? 65;
const light = colors.accentLightness ?? 60;
const steps = colors.shadeSteps ?? 4;

// generate accents
// ensure reasonable contrast with bg; if too low, nudge lightness
const fixContrast = (
  ref: string,
  hue: number,
  sat: number,
  lightness: number,
) => {
  let cur = hslToHex(hue, sat, lightness);
  let ctr = contrastRatio(cur, ref);
  let l = lightness;
  let tries = 0;
  while (ctr < MIN_CONTRAST && tries < 10) {
    l = clamp(l + 6, 0, 100); // make lighter
    cur = hslToHex(hue, sat, l);
    ctr = contrastRatio(cur, ref);
    tries++;
  }
  return cur;
};

const red = fixContrast(bg, redHue, sat, light);
const green = fixContrast(bg, greenHue, sat, light);

// generate 4 darker shades from fg towards bg by lightness interpolation
const { h: fgH, s: fgS, l: fgL } = hexToHsl(fg);
const { s: bgS, l: bgL } = hexToHsl(bg);
const shades: string[] = [];
for (let i = 1; i <= steps; i++) {
  const t = i / (steps + 1); // fraction towards bg
  const l = fgL + (bgL - fgL) * t;
  const s = fgS + (bgS - fgS) * t;
  const h = fgH; // keep fg hue
  shades.push(hslToHex(h, s, l));
}

const pallette: Pallette = {
  bg,
  fg,
  red,
  green,
  shade1: shades[0] ?? FALLBACK_WHITE,
  shade2: shades[1] ?? FALLBACK_WHITE,
  shade3: shades[2] ?? FALLBACK_WHITE,
  shade4: shades[3] ?? FALLBACK_WHITE,
};

function* createPalletteGenerator() {
  const keys = Object.keys(pallette) as (keyof Pallette)[];
  for (let key of keys) {
    yield [key, pallette[key]];
  }
}

const palletteGenerator = createPalletteGenerator();

export { pallette, palletteGenerator };
export type { Pallette };