'use client';

/**
 * ThemeSessionBridge (THEME-03 / D-16, D-17).
 *
 * On session load and after sign-in, compares session.user.theme to the
 * next-themes useTheme() value and calls setTheme(session.user.theme) if
 * different. Server is canonical; this is the bridge that enforces it.
 *
 * Renders nothing.
 */

import { useEffect } from 'react';
import { useTheme } from 'next-themes';
import { useSession } from '@/lib/auth-client';

type SessionUserWithTheme = { theme?: 'light' | 'dark' | 'system' | string };

export function ThemeSessionBridge() {
  const { data: session } = useSession();
  const { theme, setTheme } = useTheme();

  useEffect(() => {
    if (!session?.user) return;
    const serverTheme = (session.user as SessionUserWithTheme).theme;
    if (
      serverTheme === 'light' ||
      serverTheme === 'dark' ||
      serverTheme === 'system'
    ) {
      if (serverTheme !== theme) {
        setTheme(serverTheme);
      }
    }
  }, [session?.user, theme, setTheme]);

  return null;
}