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"use client";

import { useEffect, useState } from "react";
import { resolveTheme, type Theme, type Mode } from "@/lib/themes";

const STORAGE_KEY = "app-theme";

interface Stored {
  theme?: Theme;
  mode?: Mode;
}

export function useTheme() {
  const [theme, setThemeState] = useState<Theme>("humdrum");
  const [mode, setModeState] = useState<Mode>("auto");

  // hydrate from localStorage
  useEffect(() => {
    try {
      const raw = localStorage.getItem(STORAGE_KEY);
      if (raw) {
        const parsed = JSON.parse(raw) as Stored;
        if (parsed.theme) setThemeState(parsed.theme);
        if (parsed.mode) setModeState(parsed.mode);
      }
    } catch {}
  }, []);

  // apply whenever theme or mode change
  useEffect(() => {
    const applied = resolveTheme(theme, mode);
    document.documentElement.dataset.theme = applied;
    try {
      localStorage.setItem(STORAGE_KEY, JSON.stringify({ theme, mode }));
      document.cookie = `app-theme=${applied}; Path=/; Max-Age=31536000; SameSite=Lax`;
    } catch {}
  }, [theme, mode]);

  // react to system preference changes if mode === "auto"
  useEffect(() => {
    if (mode !== "auto") return;
    const mql = window.matchMedia("(prefers-color-scheme: dark)");
    const handler = () => {
      document.documentElement.dataset.theme = resolveTheme(theme, "auto");
    };
    mql.addEventListener("change", handler);
    return () => mql.removeEventListener("change", handler);
  }, [theme, mode]);

  return {
    theme,
    mode,
    setTheme: setThemeState,
    setMode: setModeState,
  };
}