const spannerClassName = "non-nested-spanner"
const spannerQuerySelector = `.${spannerClassName}`

/**
 *
 * @param {Range} range
 * @returns {?HTMLSpanElement}
 */
export function getContainingSpanner(range) {
	let cursor = range.commonAncestorContainer
	if (cursor.classList == undefined) cursor = cursor.parentElement
	while (cursor.parentElement != null) {
		if (cursor.classList.contains(spannerClassName)) return cursor
		cursor = cursor.parentElement
	}
	return null
}

/**
 *
 * @param {Node} childNode
 * @returns {!HTMLSpanElement}
 */
export function createSpannerWrapping(childNode) {
	const spanner = document.createElement('span')
	spanner.classList.add(spannerClassName)
	spanner.appendChild(childNode)
	return spanner
}

function isEmptySpanner(spanner) {
	if (spanner.childNodes.length == 0) return true
	else if (spanner.childNodes.length == 1) {
		const node = spanner.childNodes[0]
		return node instanceof Text && node.length == 0
	}
	return false
}

/**
 *
 * @param {Range} range
 */
export function wrapInNonNestedSpanners(range) {
	const containingSpanner = getContainingSpanner(range)
	const result = []
	if (containingSpanner != null) {
		const endRange = document.createRange() // contents of the span after range
		endRange.selectNode(containingSpanner)
		endRange.setStart(range.endContainer, range.endOffset)
		const endContents = endRange.cloneContents()
		const wrappedSelectionContents = containingSpanner.cloneNode(false)
		wrappedSelectionContents.appendChild(range.cloneContents())
		endRange.deleteContents()
		range.deleteContents()
		const parent = containingSpanner.parentNode
		const next = containingSpanner.nextSibling
		parent.insertBefore(wrappedSelectionContents, next)
		result.push(wrappedSelectionContents)
		if (!isEmptySpanner(endContents.childNodes[0])) parent.insertBefore(endContents, next)
		if (isEmptySpanner(containingSpanner)) parent.removeChild(containingSpanner)
		const newSelection = document.createRange()
		newSelection.selectNode(wrappedSelectionContents)
		window.getSelection().removeAllRanges()
		window.getSelection().addRange(newSelection)
	} else {
		const contents = range.extractContents()
		const spanners = contents.querySelectorAll(spannerQuerySelector)
		let endRange = document.createRange() // range before the span
		for (let index = spanners.length-1; index>=0; index--) {
			const spanner = spanners[index]
			endRange.selectNodeContents(contents)
			endRange.setStartAfter(spanner)
			if (!endRange.collapsed) {
				const wrappedEndContents = createSpannerWrapping(endRange.extractContents())
				range.insertNode(wrappedEndContents)
				result.unshift(wrappedEndContents)
			}
			range.insertNode(spanner)
			result.unshift(spanner)
		}
		const rest = createSpannerWrapping(contents)
		if (!isEmptySpanner(rest)) {
			range.insertNode(rest)
			result.unshift(rest)
		}
	}
	return result
}