'use client';

import React, { createContext, useContext, useEffect, useState } from 'react';

type Theme = 'light' | 'dark' | 'system';

interface ThemeContextType {
  theme: Theme;
  resolvedTheme: 'light' | 'dark';
  setTheme: (theme: Theme) => void;
  toggleTheme: () => void;
}

const ThemeContext = createContext<ThemeContextType | undefined>(undefined);

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setThemeState] = useState<Theme>('system');
  const [resolvedTheme, setResolvedTheme] = useState<'light' | 'dark'>('light');

  // İlk mount'da localStorage'dan tema oku
  useEffect(() => {
    const stored = localStorage.getItem('theme') as Theme | null;
    if (stored && ['light', 'dark', 'system'].includes(stored)) {
      setThemeState(stored);
    }
  }, []);

  // Tema değiştiğinde doc'a uygula ve localStorage'a kaydet
  useEffect(() => {
    const root = document.documentElement;

    const applyTheme = (isDark: boolean) => {
      if (isDark) {
        root.classList.add('dark');
        setResolvedTheme('dark');
      } else {
        root.classList.remove('dark');
        setResolvedTheme('light');
      }
    };

    if (theme === 'system') {
      const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
      applyTheme(mediaQuery.matches);

      const handler = (e: MediaQueryListEvent) => applyTheme(e.matches);
      mediaQuery.addEventListener('change', handler);
      return () => mediaQuery.removeEventListener('change', handler);
    } else {
      applyTheme(theme === 'dark');
    }

    localStorage.setItem('theme', theme);
  }, [theme]);

  const setTheme = (newTheme: Theme) => {
    setThemeState(newTheme);
  };

  const toggleTheme = () => {
    setThemeState(prev => {
      if (prev === 'light') return 'dark';
      if (prev === 'dark') return 'light';
      // system -> şu anki resolved'ın tersi
      return resolvedTheme === 'dark' ? 'light' : 'dark';
    });
  };

  return (
    <ThemeContext.Provider value={{ theme, resolvedTheme, setTheme, toggleTheme }}>
      {children}
    </ThemeContext.Provider>
  );
}

export function useTheme() {
  const context = useContext(ThemeContext);
  if (!context) {
    throw new Error('useTheme must be used within a ThemeProvider');
  }
  return context;
}