99 lines
3.0 KiB
JavaScript
99 lines
3.0 KiB
JavaScript
import { getTagName } from './utility.service.js'
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import { unescape } from 'lodash'
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/**
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* This is a not-so-tiny purpose-built HTML parser/processor. This parses html
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* and converts it into a tree structure representing tag openers/closers and
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* children.
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*
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* Structure follows this pattern: [opener, [...children], closer] except root
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* node which is just [...children]. Text nodes can only be within children and
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* are represented as strings.
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*
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* Intended use is to convert HTML structure and then recursively iterate over it
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* most likely using a map. Very useful for dynamically rendering html replacing
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* tags with JSX elements in a render function.
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*
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* known issue: doesn't handle CDATA so CDATA might not work well
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* known issue: doesn't handle HTML comments
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*
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* @param {Object} input - input data
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* @return {string} processed html
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*/
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export const convertHtmlToTree = (html = '') => {
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// Elements that are implicitly self-closing
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// https://developer.mozilla.org/en-US/docs/Glossary/empty_element
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const emptyElements = new Set([
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'area', 'base', 'br', 'col', 'embed', 'hr', 'img', 'input',
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'keygen', 'link', 'meta', 'param', 'source', 'track', 'wbr'
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])
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// TODO For future - also parse HTML5 multi-source components?
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const buffer = [] // Current output buffer
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const levels = [['', buffer]] // How deep we are in tags and which tags were there
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let textBuffer = '' // Current line content
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let tagBuffer = null // Current tag buffer, if null = we are not currently reading a tag
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const getCurrentBuffer = () => {
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return levels[levels.length - 1][1]
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}
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const flushText = () => { // Processes current line buffer, adds it to output buffer and clears line buffer
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if (textBuffer === '') return
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getCurrentBuffer().push(textBuffer)
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textBuffer = ''
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}
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const handleSelfClosing = (tag) => {
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getCurrentBuffer().push([tag])
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}
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const handleOpen = (tag) => {
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const curBuf = getCurrentBuffer()
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const newLevel = [unescape(tag), []]
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levels.push(newLevel)
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curBuf.push(newLevel)
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}
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const handleClose = (tag) => {
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const currentTag = levels[levels.length - 1]
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if (getTagName(levels[levels.length - 1][0]) === getTagName(tag)) {
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currentTag.push(tag)
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levels.pop()
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} else {
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getCurrentBuffer().push(tag)
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}
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}
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for (let i = 0; i < html.length; i++) {
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const char = html[i]
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if (char === '<' && tagBuffer === null) {
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flushText()
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tagBuffer = char
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} else if (char !== '>' && tagBuffer !== null) {
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tagBuffer += char
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} else if (char === '>' && tagBuffer !== null) {
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tagBuffer += char
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const tagFull = tagBuffer
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tagBuffer = null
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const tagName = getTagName(tagFull)
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if (tagFull[1] === '/') {
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handleClose(tagFull)
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} else if (emptyElements.has(tagName) || tagFull[tagFull.length - 2] === '/') {
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// self-closing
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handleSelfClosing(tagFull)
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} else {
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handleOpen(tagFull)
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}
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} else {
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textBuffer += char
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}
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}
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if (tagBuffer) {
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textBuffer += tagBuffer
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}
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flushText()
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return buffer
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}
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