"use client";

import { createContext, useContext, useEffect, useState } from "react";
import { trpc } from "@/lib/trpc";

type ThemeContextValue = { isDark: boolean; toggleDark: () => void };

const ThemeContext = createContext<ThemeContextValue>({
  isDark: false,
  toggleDark: () => {},
});

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [isDark, setIsDark] = useState(false);
  const [localInit, setLocalInit] = useState(false);

  // 1. Start neutral; the user profile below owns the persisted theme.
  useEffect(() => {
    setLocalInit(true);
  }, []);

  // 2. Sync from DB once profile is loaded — overrides the localStorage value
  const { data: profile } = trpc.users.myProfile.useQuery(undefined, {
    enabled: localInit,
    retry: false,
  });

  const setTheme = trpc.users.setTheme.useMutation();

  useEffect(() => {
    if (!profile) return;
    const userThemeKey = `hellth-theme:${profile.id}`;
    const dbTheme = profile.theme;
    if (dbTheme === null || dbTheme === undefined) {
      const stored = localStorage.getItem(userThemeKey);
      const dark = stored === "dark";
      setIsDark(dark);
      document.documentElement.classList.toggle("dark", dark);
      return;
    }
    const dark = dbTheme === "dark";
    setIsDark(dark);
    document.documentElement.classList.toggle("dark", dark);
    localStorage.setItem(userThemeKey, dark ? "dark" : "light");
  }, [profile?.id, profile?.theme]);

  function toggleDark() {
    const next = !isDark;
    setIsDark(next);
    document.documentElement.classList.toggle("dark", next);
    const themeValue = next ? "dark" : "light";
    if (profile?.id) {
      localStorage.setItem(`hellth-theme:${profile.id}`, themeValue);
    }
    setTheme.mutate({ theme: themeValue });
  }

  return (
    <ThemeContext.Provider value={{ isDark, toggleDark }}>
      {children}
    </ThemeContext.Provider>
  );
}

export function useTheme() {
  return useContext(ThemeContext);
}