View: frontend/src/components/theme-provider.tsx

← full-stack-fastapi-template / frontend/src/components/theme-provider.tsx

import {
  createContext,
  useCallback,
  useContext,
  useEffect,
  useState,
} from "react"

export type Theme = "dark" | "light" | "system"

type ThemeProviderProps = {
  children: React.ReactNode
  defaultTheme?: Theme
  storageKey?: string
}

type ThemeProviderState = {
  theme: Theme
  resolvedTheme: "dark" | "light"
  setTheme: (theme: Theme) => void
}

const initialState: ThemeProviderState = {
  theme: "system",
  resolvedTheme: "light",
  setTheme: () => null,
}

const ThemeProviderContext = createContext<ThemeProviderState>(initialState)

export function ThemeProvider({
  children,
  defaultTheme = "system",
  storageKey = "vite-ui-theme",
  ...props
}: ThemeProviderProps) {
  const [theme, setTheme] = useState<Theme>(
    () => (localStorage.getItem(storageKey) as Theme) || defaultTheme,
  )

  const getResolvedTheme = useCallback((theme: Theme): "dark" | "light" => {
    if (theme === "system") {
      return window.matchMedia("(prefers-color-scheme: dark)").matches
        ? "dark"
        : "light"
    }
    return theme
  }, [])

  const [resolvedTheme, setResolvedTheme] = useState<"dark" | "light">(() =>
    getResolvedTheme(theme),
  )

  const updateTheme = useCallback((newTheme: Theme) => {
    const root = window.document.documentElement

    root.classList.remove("light", "dark")

    if (newTheme === "system") {
      const systemTheme = window.matchMedia("(prefers-color-scheme: dark)")
        .matches
        ? "dark"
        : "light"

      root.classList.add(systemTheme)
      return
    }

    root.classList.add(newTheme)
  }, [])

  useEffect(() => {
    updateTheme(theme)
    setResolvedTheme(getResolvedTheme(theme))

    const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)")

    const handleChange = () => {
      if (theme === "system") {
        updateTheme("system")
        setResolvedTheme(getResolvedTheme("system"))
      }
    }

    mediaQuery.addEventListener("change", handleChange)

    return () => {
      mediaQuery.removeEventListener("change", handleChange)
    }
  }, [theme, updateTheme, getResolvedTheme])

  const value = {
    theme,
    resolvedTheme,
    setTheme: (theme: Theme) => {
      localStorage.setItem(storageKey, theme)
      setTheme(theme)
    },
  }

  return (
    <ThemeProviderContext.Provider {...props} value={value}>
      {children}
    </ThemeProviderContext.Provider>
  )
}

export const useTheme = () => {
  const context = useContext(ThemeProviderContext)

  if (context === undefined)
    throw new Error("useTheme must be used within a ThemeProvider")

  return context
}


1	import {
2	createContext,
3	useCallback,
4	useContext,
5	useEffect,
6	useState,
7	} from "react"
8
9	export type Theme = "dark" \| "light" \| "system"
10
11	type ThemeProviderProps = {
12	children: React.ReactNode
13	defaultTheme?: Theme
14	storageKey?: string
15	}
16
17	type ThemeProviderState = {
18	theme: Theme
19	resolvedTheme: "dark" \| "light"
20	setTheme: (theme: Theme) => void
21	}
22
23	const initialState: ThemeProviderState = {
24	theme: "system",
25	resolvedTheme: "light",
26	setTheme: () => null,
27	}
28
29	const ThemeProviderContext = createContext<ThemeProviderState>(initialState)
30
31	export function ThemeProvider({
32	children,
33	defaultTheme = "system",
34	storageKey = "vite-ui-theme",
35	...props
36	}: ThemeProviderProps) {
37	const [theme, setTheme] = useState<Theme>(
38	() => (localStorage.getItem(storageKey) as Theme) \|\| defaultTheme,
39	)
40
41	const getResolvedTheme = useCallback((theme: Theme): "dark" \| "light" => {
42	if (theme === "system") {
43	return window.matchMedia("(prefers-color-scheme: dark)").matches
44	? "dark"
45	: "light"
46	}
47	return theme
48	}, [])
49
50	const [resolvedTheme, setResolvedTheme] = useState<"dark" \| "light">(() =>
51	getResolvedTheme(theme),
52	)
53
54	const updateTheme = useCallback((newTheme: Theme) => {
55	const root = window.document.documentElement
56
57	root.classList.remove("light", "dark")
58
59	if (newTheme === "system") {
60	const systemTheme = window.matchMedia("(prefers-color-scheme: dark)")
61	.matches
62	? "dark"
63	: "light"
64
65	root.classList.add(systemTheme)
66	return
67	}
68
69	root.classList.add(newTheme)
70	}, [])
71
72	useEffect(() => {
73	updateTheme(theme)
74	setResolvedTheme(getResolvedTheme(theme))
75
76	const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)")
77
78	const handleChange = () => {
79	if (theme === "system") {
80	updateTheme("system")
81	setResolvedTheme(getResolvedTheme("system"))
82	}
83	}
84
85	mediaQuery.addEventListener("change", handleChange)
86
87	return () => {
88	mediaQuery.removeEventListener("change", handleChange)
89	}
90	}, [theme, updateTheme, getResolvedTheme])
91
92	const value = {
93	theme,
94	resolvedTheme,
95	setTheme: (theme: Theme) => {
96	localStorage.setItem(storageKey, theme)
97	setTheme(theme)
98	},
99	}
100
101	return (
102	<ThemeProviderContext.Provider {...props} value={value}>
103	{children}
104	</ThemeProviderContext.Provider>
105	)
106	}
107
108	export const useTheme = () => {
109	const context = useContext(ThemeProviderContext)
110
111	if (context === undefined)
112	throw new Error("useTheme must be used within a ThemeProvider")
113
114	return context
115	}
116