import MutationQueue from "./MutationQueue"
// Diff provides diffing utilities to morph existing DOM elements
// into the target HTML string.
//
// Example:
// Diff.innerHTML(body, "This is my new content
")
//
// Whatever contents will be in the body, they will be re-used and morphed
// into the new DOM defined by a simple HTML string. This is useful for
// Single Page Applications that use server rendered content. The server
// responds with the pre-rendered HTML and we can simply morph our current
// contents into the next page.
export default class Diff {
static persistentClasses = new Set()
static persistentAttributes = new Set()
static mutations: MutationQueue = new MutationQueue()
// innerHTML will diff the element with the given HTML string and apply DOM mutations.
static innerHTML(aRoot: HTMLElement, html: string): Promise {
let container = document.createElement("main")
container.innerHTML = html
return new Promise((resolve, _) => {
Diff.childNodes(aRoot, container)
this.mutations.wait(resolve)
})
}
// root will diff the document root element with the given HTML string and apply DOM mutations.
static root(aRoot: HTMLElement, html: string) {
return new Promise((resolve, _) => {
let rootContainer = document.createElement("html")
rootContainer.innerHTML = html.replace("", "")
Diff.childNodes(aRoot.getElementsByTagName("body")[0], rootContainer.getElementsByTagName("body")[0])
this.mutations.wait(resolve)
})
}
// childNodes diffs the child nodes of 2 given elements and applies DOM mutations.
static childNodes(aRoot: Node, bRoot: Node) {
let aChild = [...aRoot.childNodes]
let bChild = [...bRoot.childNodes]
let numNodes = Math.max(aChild.length, bChild.length)
for(let i = 0; i < numNodes; i++) {
let a = aChild[i]
// Remove nodes at the end of a that do not exist in b
if(i >= bChild.length) {
this.mutations.queue(() => aRoot.removeChild(a))
continue
}
let b = bChild[i]
// If a doesn't have that many nodes, simply append at the end of a
if(i >= aChild.length) {
this.mutations.queue(() => aRoot.appendChild(b))
continue
}
// If it's a completely different HTML tag or node type, replace it
if(a.nodeName !== b.nodeName || a.nodeType !== b.nodeType) {
this.mutations.queue(() => aRoot.replaceChild(b, a))
continue
}
// Text node:
// We don't need to check for b to be a text node as well because
// we eliminated different node types in the previous condition.
if(a.nodeType === Node.TEXT_NODE) {
this.mutations.queue(() => a.textContent = b.textContent)
continue
}
// HTML element:
if(a.nodeType === Node.ELEMENT_NODE) {
let elemA = a as HTMLElement
let elemB = b as HTMLElement
let removeAttributes: Attr[] = []
for(let x = 0; x < elemA.attributes.length; x++) {
let attrib = elemA.attributes[x]
if(attrib.specified) {
if(!elemB.hasAttribute(attrib.name) && !Diff.persistentAttributes.has(attrib.name)) {
removeAttributes.push(attrib)
}
}
}
this.mutations.queue(() => {
for(let attr of removeAttributes) {
elemA.removeAttributeNode(attr)
}
})
for(let x = 0; x < elemB.attributes.length; x++) {
let attrib = elemB.attributes[x]
if(!attrib.specified) {
continue
}
// If the attribute value is exactly the same, skip this attribute.
if(elemA.getAttribute(attrib.name) === attrib.value) {
continue
}
if(attrib.name === "class") {
let classesA = elemA.classList
let classesB = elemB.classList
let removeClasses: string[] = []
for(let className of classesA) {
if(!classesB.contains(className) && !Diff.persistentClasses.has(className)) {
removeClasses.push(className)
}
}
this.mutations.queue(() => {
for(let className of removeClasses) {
classesA.remove(className)
}
for(let className of classesB) {
if(!classesA.contains(className)) {
classesA.add(className)
}
}
})
continue
}
this.mutations.queue(() => elemA.setAttribute(attrib.name, attrib.value))
}
// Special case: Apply state of input elements
if(elemA !== document.activeElement && elemA instanceof HTMLInputElement && elemB instanceof HTMLInputElement) {
this.mutations.queue(() => {
(elemA as HTMLInputElement).value = (elemB as HTMLInputElement).value
})
}
}
// Never diff the contents of web components
if(a.nodeName.includes("-")) {
continue
}
// Child nodes
Diff.childNodes(a, b)
}
}
}