"use client";

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

type Theme = "light" | "dark" | "auto";

interface ThemeContextType {
  theme: Theme;
  setTheme: (theme: Theme) => void;
  isDark: boolean;
}

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

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setTheme] = useState<Theme>("light");
  const [isDark, setIsDark] = useState(false);

  useEffect(() => {
    // 从 localStorage 获取保存的主题
    const savedTheme = localStorage.getItem("theme") as Theme;
    if (savedTheme && ["light", "dark", "auto"].includes(savedTheme)) {
      setTheme(savedTheme);
    }
  }, []);

  useEffect(() => {
    // 保存主题到 localStorage
    localStorage.setItem("theme", theme);

    // 应用主题
    const root = document.documentElement;
    const body = document.body;

    if (theme === "auto") {
      // 跟随系统主题
      const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)");
      const handleChange = (e: MediaQueryListEvent) => {
        setIsDark(e.matches);
        if (e.matches) {
          root.classList.add("dark");
          body.classList.add("dark");
        } else {
          root.classList.remove("dark");
          body.classList.remove("dark");
        }
      };

      setIsDark(mediaQuery.matches);
      if (mediaQuery.matches) {
        root.classList.add("dark");
        body.classList.add("dark");
      } else {
        root.classList.remove("dark");
        body.classList.remove("dark");
      }

      mediaQuery.addEventListener("change", handleChange);
      return () => mediaQuery.removeEventListener("change", handleChange);
    } else {
      // 手动设置主题
      setIsDark(theme === "dark");
      if (theme === "dark") {
        root.classList.add("dark");
        body.classList.add("dark");
      } else {
        root.classList.remove("dark");
        body.classList.remove("dark");
      }
    }
  }, [theme]);

  const value = {
    theme,
    setTheme,
    isDark,
  };

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

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