layouts/partials/themeSwitcher.html


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{{ $style := "light-without-switcher" }}
{{ if and (isset site.Params "style") (ne site.Params.style "") }}
    {{ $style = site.Params.style | lower }}
{{ end }}

{{ if not (in (slice "light-without-switcher" "dark-without-switcher" "auto-without-switcher") $style) }}
    <button class="theme-switcher">
        {{ i18n "darkTheme" | humanize }}
    </button>

    <script>
    const STORAGE_KEY = 'user-color-scheme'
    const defaultTheme = {{ $style }}

    let currentTheme
    let switchButton
    let autoDefinedScheme = window.matchMedia('(prefers-color-scheme: dark)')

    const autoChangeScheme = e => {
        currentTheme = e.matches ? 'dark' : 'light'
        document.documentElement.setAttribute('data-theme', currentTheme)
        changeButtonText()
    }

    document.addEventListener('DOMContentLoaded', function() {
        switchButton = document.querySelector('.theme-switcher')
        currentTheme = detectCurrentScheme()
        if (currentTheme == 'dark') {
            document.documentElement.setAttribute('data-theme', 'dark')
        }
        if (currentTheme == 'auto') {
            autoChangeScheme(autoDefinedScheme);
            autoDefinedScheme.addListener(autoChangeScheme);
        }
        changeButtonText()
        switchButton.addEventListener('click', switchTheme, false)
    })

    function detectCurrentScheme() {
        if (localStorage.getItem(STORAGE_KEY)) {
            return localStorage.getItem(STORAGE_KEY)
        } 
        if (defaultTheme) {
            return defaultTheme
        } 
        if (!window.matchMedia) {
            return 'light'
        } 
        if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
            return 'dark'
        }
        return 'light'
    }

    function changeButtonText()
    {   
        switchButton.textContent = currentTheme == 'dark' ?  {{ i18n "lightTheme" | humanize }} : {{ i18n "darkTheme" | humanize }}
    }

    function switchTheme(e) {
        if (currentTheme == 'dark') {
            localStorage.setItem(STORAGE_KEY, 'light')
            document.documentElement.setAttribute('data-theme', 'light')
            currentTheme = 'light'
        } else {
            localStorage.setItem(STORAGE_KEY, 'dark')
            document.documentElement.setAttribute('data-theme', 'dark')
            currentTheme = 'dark'
        }
        changeButtonText()
    }
    </script>
{{ end }}