import { ref } from 'vue'

import { useNativeTheme } from './native-theme.ts'
import { usePreferredThemes } from './preferred-theme.ts'
import { useThemeSettings } from './theme-settings.ts'
import { isDarkTheme } from './themes.ts'

export * from './themes.ts'

export default defineNuxtPlugin({
	name: 'theme',
	dependsOn: ['cosmetics'],
	setup(nuxtApp) {
		const $nativeTheme = useNativeTheme()

		const $preferredThemes = usePreferredThemes()

		function getPreferredNativeTheme() {
			const nativeTheme = $nativeTheme.value
			switch (nativeTheme) {
				case 'light':
					return $preferredThemes.light
				case 'dark':
				case 'unknown':
					if (import.meta.dev && import.meta.server && nativeTheme === 'unknown') {
						console.warn(
							'[theme] no client hint is available for request, using dark theme as default',
						)
					}

					return $preferredThemes.dark
			}
		}

		const $settings = useThemeSettings(() => getPreferredNativeTheme())

		useHead({ htmlAttrs: { class: () => [`${$settings.active}-mode`] } })

		function syncTheme() {
			$settings.active =
				$settings.preferred === 'system' ? getPreferredNativeTheme() : $settings.preferred
		}

		if (
			import.meta.server &&
			$settings.preferred === 'system' &&
			$nativeTheme.value !== 'unknown'
		) {
			// take advantage of the client hint
			syncTheme()
		}

		if (import.meta.client) {
			const $clientReady = ref(false)

			nuxtApp.hook('app:suspense:resolve', () => {
				$clientReady.value = true
			})

			watchEffect(() => $clientReady.value && syncTheme())
		}

		function cycle() {
			const nextTheme = isDarkTheme($settings.active)
				? $preferredThemes.light
				: $preferredThemes.dark

			$settings.preferred = nextTheme

			return nextTheme
		}

		return {
			provide: {
				theme: reactive({
					...toRefs($settings),
					/**
					 * Preferred themes for each mode.
					 */
					preferences: $preferredThemes,
					/**
					 * Current native (system) theme provided through client hint header or
					 * `prefers-color-scheme` media query.
					 */
					native: $nativeTheme,
					cycle,
				}),
			},
		}
	},
})