import { clampNum } from "../shared/math.js";
import { prefersColorSchemeDark } from "../shared/media.js";

export const STORAGE_KEY = "siteThemeV1";
export const RADIUS_IDS = ["soft", "medium", "strong"];
export const THEME_MODE_IDS = ["system", "light", "dark"];
export const FONT_IDS = ["merriweather", "mono", "geologica"];

const LEGACY_FONT_MAP = {
  onest: "geologica",
  anonymous: "mono",
};

export function normalizeFontId(font) {
  if (LEGACY_FONT_MAP[font]) return LEGACY_FONT_MAP[font];
  return FONT_IDS.includes(font) ? font : defaultThemeState().font;
}
export const MESH_BG_IDS = ["on", "off"];

export const PICK = {
  sMin: 30,
  sMax: 100,
  lMin: 20,
  lMax: 70,
};
export const S_RANGE = PICK.sMax - PICK.sMin;
export const L_RANGE = PICK.lMax - PICK.lMin;

export function defaultThemeState() {
  return { mode: "system", h: 210, s: 90, l: 40, radius: "medium", font: "geologica", meshBg: "on" };
}

export function effectiveThemeMode(state) {
  if (state.mode === "system") return prefersColorSchemeDark() ? "dark" : "light";
  return state.mode;
}

export function readThemeState() {
  try {
    const raw = localStorage.getItem(STORAGE_KEY);
    if (!raw) return defaultThemeState();
    const o = JSON.parse(raw);
    const base = defaultThemeState();
    const hRaw = o.h ?? o.hue;
    const h = clampNum(hRaw, 0, 360, base.h);
    const s = clampNum(o.s ?? o.sat, PICK.sMin, PICK.sMax, base.s);
    const lRaw = o.l ?? o.light;
    const l = clampNum(lRaw, PICK.lMin, PICK.lMax, base.l);
    const mode =
      o.mode === "light" || o.mode === "dark" || o.mode === "system" ? o.mode : base.mode;
    const radius = RADIUS_IDS.includes(o.radius) ? o.radius : base.radius;
    const font = normalizeFontId(o.font ?? base.font);
    const meshBg = MESH_BG_IDS.includes(o.meshBg) ? o.meshBg : base.meshBg;
    return { mode, h, s, l, radius, font, meshBg };
  } catch {
    return defaultThemeState();
  }
}

export function writeThemeState(state) {
  localStorage.setItem(
    STORAGE_KEY,
    JSON.stringify({
      mode: state.mode,
      h: state.h,
      s: state.s,
      l: state.l,
      radius: state.radius,
      font: state.font,
      meshBg: state.meshBg,
    }),
  );
}

export function hslToRgb(h, s, l) {
  const H = (((h % 360) + 360) % 360) / 360;
  const S = Math.min(100, Math.max(0, s)) / 100;
  const L = Math.min(100, Math.max(0, l)) / 100;
  let r;
  let g;
  let b;
  if (S === 0) {
    r = g = b = L;
  } else {
    const hue2rgb = (p, q, t) => {
      let T = t;
      if (T < 0) T += 1;
      if (T > 1) T -= 1;
      if (T < 1 / 6) return p + (q - p) * 6 * T;
      if (T < 1 / 2) return q;
      if (T < 2 / 3) return p + (q - p) * (2 / 3 - T) * 6;
      return p;
    };
    const q = L < 0.5 ? L * (1 + S) : L + S - L * S;
    const p = 2 * L - q;
    r = hue2rgb(p, q, H + 1 / 3);
    g = hue2rgb(p, q, H);
    b = hue2rgb(p, q, H - 1 / 3);
  }
  return [Math.round(r * 255), Math.round(g * 255), Math.round(b * 255)];
}

export function relativeLuminance(rgb) {
  const lin = rgb.map((v) => {
    const x = v / 255;
    return x <= 0.03928 ? x / 12.92 : Math.pow((x + 0.055) / 1.055, 2.4);
  });
  return 0.2126 * lin[0] + 0.7152 * lin[1] + 0.0722 * lin[2];
}

export function applyThemeState(state) {
  const root = document.documentElement;
  root.dataset.theme = effectiveThemeMode(state);
  root.dataset.radius = state.radius;
  root.dataset.font = state.font;
  root.dataset.meshBg = state.meshBg === "off" ? "off" : "on";
  root.style.setProperty("--theme-h", String(state.h));
  root.style.setProperty("--theme-s", String(state.s));
  root.style.setProperty("--theme-l", String(state.l));
  const rgb = hslToRgb(state.h, state.s, state.l);
  const lum = relativeLuminance(rgb);
  root.style.setProperty("--on-accent", lum > 0.58 ? "hsl(220 14% 12%)" : "hsl(0 0% 98%)");
  window.dispatchEvent(new CustomEvent("site-theme-applied", { bubbles: true }));
}

export function drawSLPlane(canvas, hue) {
  const ctx = canvas.getContext("2d", { willReadFrequently: true });
  const w = canvas.width;
  const h = canvas.height;
  const img = ctx.createImageData(w, h);
  const { data } = img;
  for (let y = 0; y < h; y++) {
    const l = PICK.lMax - (y / (h - 1 || 1)) * L_RANGE;
    for (let x = 0; x < w; x++) {
      const s = PICK.sMin + (x / (w - 1 || 1)) * S_RANGE;
      const [r, g, b] = hslToRgb(hue, s, l);
      const i = (y * w + x) * 4;
      data[i] = r;
      data[i + 1] = g;
      data[i + 2] = b;
      data[i + 3] = 255;
    }
  }
  ctx.putImageData(img, 0, 0);
}

export function updateKnob(knob, s, l) {
  if (!knob) return;
  knob.style.left = `${((s - PICK.sMin) / S_RANGE) * 100}%`;
  knob.style.top = `${(1 - (l - PICK.lMin) / L_RANGE) * 100}%`;
}