import { useEffect, useState } from "react";

export const RD_THEMES = ["paper", "sepia", "night"] as const;
export type RdTheme = (typeof RD_THEMES)[number];
export const RD_THEME_LABEL: Record<RdTheme, string> = { paper: "纸", sepia: "米", night: "夜" };
export const FONT_SIZES = [16, 18, 20, 22, 25, 28];

const KEY = "reader-prefs";

export interface ReaderPrefs {
  theme: RdTheme;
  sizeIdx: number;
}

export function useReaderPrefs() {
  const [prefs, setPrefs] = useState<ReaderPrefs>(() => {
    try {
      const p = JSON.parse(localStorage.getItem(KEY) ?? "") as ReaderPrefs;
      if (RD_THEMES.includes(p.theme) && Number.isInteger(p.sizeIdx) && p.sizeIdx >= 0 && p.sizeIdx < FONT_SIZES.length)
        return p;
    } catch {
      /* 首次使用或存了坏值 */
    }
    return { theme: "sepia", sizeIdx: 2 };
  });
  useEffect(() => localStorage.setItem(KEY, JSON.stringify(prefs)), [prefs]);

  return {
    prefs,
    fontSize: FONT_SIZES[prefs.sizeIdx],
    setTheme: (theme: RdTheme) => setPrefs((p) => ({ ...p, theme })),
    bump: (d: number) =>
      setPrefs((p) => ({ ...p, sizeIdx: Math.min(FONT_SIZES.length - 1, Math.max(0, p.sizeIdx + d)) })),
  };
}