"use client"

import React, { createContext, useContext, useEffect, useState, useCallback } from "react"
import { useTheme as useNextTheme } from "next-themes"
import type { Theme } from "./types"
import { getStoredThemeId, setStoredThemeId } from "./storage"
import { getAvailableThemes } from "./parser"

/**
 * 主题上下文类型定义
 */
interface ThemeContextValue {
  /** 所有可用主题列表 */
  themes: Theme[]
  /** 当前激活的主题对象 */
  currentTheme: Theme | null
  /** 当前激活的主题 ID */
  currentThemeId: string | null
  /** 设置主题的方法 */
  setTheme: (themeId: string) => void
  /** 是否正在加载主题 */
  isLoading: boolean
}

const ThemeContext = createContext<ThemeContextValue | null>(null)

/**
 * 自定义主题 Hook
 * 必须在 CustomThemeProvider 内部使用
 */
export function useCustomTheme() {
  const context = useContext(ThemeContext)
  if (!context) {
    throw new Error("useCustomTheme must be used within CustomThemeProvider")
  }
  return context
}

/**
 * 自定义主题提供者
 * 管理用户选择的界面外观主题（配色方案），独立于明暗模式
 */
export function CustomThemeProvider({ children }: { children: React.ReactNode }) {
  const [themes, setThemes] = useState<Theme[]>([])
  const [currentThemeId, setCurrentThemeId] = useState<string | null>(null)
  const [isLoading, setIsLoading] = useState(true)
  const [mounted, setMounted] = useState(false)
  const { resolvedTheme } = useNextTheme()

  /* 加载所有可用主题 */
  useEffect(() => {
    async function loadThemes() {
      const availableThemes = await getAvailableThemes()
      const storedId = getStoredThemeId()

      setThemes(availableThemes)
      setCurrentThemeId(storedId)
      setIsLoading(false)
    }

    loadThemes()
  }, [])

  /* 确保组件已挂载，避免水合不一致 */
  useEffect(() => {
    setMounted(true)
  }, [])

  /**
   * 将主题颜色应用到 DOM
   * @param theme - 要应用的主题
   * @param isDark - 是否为暗色模式
   */
  const applyThemeColors = useCallback((theme: Theme, isDark: boolean) => {
    if (typeof window === "undefined") return

    const root = document.documentElement
    const colors = isDark ? theme.colors.dark : theme.colors.light

    /* 应用所有 CSS 变量到根元素 */
    Object.entries(colors).forEach(([key, value]) => {
      root.style.setProperty(`--${ key }`, value)
    })
  }, [])

  /* 当主题 ID 或模式改变时，重新应用颜色 */
  useEffect(() => {
    if (!mounted || !currentThemeId || themes.length === 0) return

    const theme = themes.find(t => t.id === currentThemeId)
    if (!theme) return

    /* 使用 next-themes 的 resolvedTheme，它会自动处理系统偏好 */
    const isDark = resolvedTheme === "dark"
    applyThemeColors(theme, isDark)
  }, [currentThemeId, resolvedTheme, themes, mounted, applyThemeColors])

  /**
   * 设置主题
   * @param themeId - 要设置的主题 ID
   */
  const setTheme = useCallback((themeId: string) => {
    const theme = themes.find(t => t.id === themeId)
    if (!theme) return

    setCurrentThemeId(themeId)
    setStoredThemeId(themeId)

    /* 根据当前解析的主题模式计算是否为暗色 */
    const isDark = resolvedTheme === "dark"
    applyThemeColors(theme, isDark)
  }, [themes, resolvedTheme, applyThemeColors])

  const currentTheme = themes.find(t => t.id === currentThemeId) || null

  return (
    <ThemeContext.Provider
      value={{
        themes,
        currentTheme,
        currentThemeId,
        setTheme,
        isLoading
      }}
    >
      {children}
    </ThemeContext.Provider>
  )
}