const VARIANT_PARAMETER = 'v'
const HASH = '#'
const QUERY = '?'

function splitSrc(src: string) {
	const hashAt = src.indexOf(HASH)
	const withoutHash = hashAt === -1 ? src : src.slice(0, hashAt)
	const hash = hashAt === -1 ? '' : src.slice(hashAt)
	const queryAt = withoutHash.indexOf(QUERY)
	if (queryAt === -1) {
		return { base: withoutHash, query: '', hash }
	}
	return {
		base: withoutHash.slice(0, queryAt),
		query: withoutHash.slice(queryAt + 1),
		hash,
	}
}

export function variantOfSrc(src: string | undefined | null) {
	if (!src) {
		return null
	}
	const name = new URLSearchParams(splitSrc(src).query).get(VARIANT_PARAMETER)
	return name === null || name === '' ? null : name
}

export function withVariant(src: string, name: string) {
	const { base, query, hash } = splitSrc(src)
	const params = new URLSearchParams(query)
	params.delete(VARIANT_PARAMETER)
	const kept = params.toString()
	const parts = [kept, name === '' ? '' : `${VARIANT_PARAMETER}=${encodeURIComponent(name)}`]
	const next = parts.filter((part) => part !== '').join('&')
	return `${base}${next === '' ? '' : QUERY + next}${hash}`
}

export function bodyHasVariantImage(html: string) {
	const document = new DOMParser().parseFromString(html, 'text/html')
	return Array.from(document.querySelectorAll('img')).some(
		(image) => variantOfSrc(image.getAttribute('src')) !== null,
	)
}