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+/**
+ * This is a tiny purpose-built HTML parser/processor. This basically detects
+ * any type of visual newline and converts entire HTML into a array structure.
+ *
+ * Text nodes are represented as object with single property - text - containing
+ * the visual line. Intended usage is to process the array with .map() in which
+ * map function returns a string and resulting array can be converted back to html
+ * with a .join('').
+ *
+ * Generally this isn't very useful except for when you really need to either
+ * modify visual lines (greentext i.e. simple quoting) or do something with
+ * first/last line.
+ *
+ * known issue: doesn't handle CDATA so nested CDATA might not work well
+ *
+ * @param {Object} input - input data
+ * @return {(string|{ text: string })[]} processed html in form of a list.
+ */
+export const convertHtmlToLines = (html) => {
+ const handledTags = new Set(['p', 'br', 'div'])
+ const openCloseTags = new Set(['p', 'div'])
+
+ let buffer = [] // Current output buffer
+ const level = [] // How deep we are in tags and which tags were there
+ let textBuffer = '' // Current line content
+ let tagBuffer = null // Current tag buffer, if null = we are not currently reading a tag
+
+ // Extracts tag name from tag, i.e. <span a="b"> => span
+ const getTagName = (tag) => {
+ const result = /(?:<\/(\w+)>|<(\w+)\s?[^/]*?\/?>)/gi.exec(tag)
+ return result && (result[1] || result[2])
+ }
+
+ const flush = () => { // Processes current line buffer, adds it to output buffer and clears line buffer
+ if (textBuffer.trim().length > 0) {
+ buffer.push({ text: textBuffer })
+ } else {
+ buffer.push(textBuffer)
+ }
+ textBuffer = ''
+ }
+
+ const handleBr = (tag) => { // handles single newlines/linebreaks/selfclosing
+ flush()
+ buffer.push(tag)
+ }
+
+ const handleOpen = (tag) => { // handles opening tags
+ flush()
+ buffer.push(tag)
+ level.push(tag)
+ }
+
+ const handleClose = (tag) => { // handles closing tags
+ flush()
+ buffer.push(tag)
+ if (level[level.length - 1] === tag) {
+ level.pop()
+ }
+ }
+
+ for (let i = 0; i < html.length; i++) {
+ const char = html[i]
+ if (char === '<' && tagBuffer === null) {
+ tagBuffer = char
+ } else if (char !== '>' && tagBuffer !== null) {
+ tagBuffer += char
+ } else if (char === '>' && tagBuffer !== null) {
+ tagBuffer += char
+ const tagFull = tagBuffer
+ tagBuffer = null
+ const tagName = getTagName(tagFull)
+ if (handledTags.has(tagName)) {
+ if (tagName === 'br') {
+ handleBr(tagFull)
+ } else if (openCloseTags.has(tagName)) {
+ if (tagFull[1] === '/') {
+ handleClose(tagFull)
+ } else if (tagFull[tagFull.length - 2] === '/') {
+ // self-closing
+ handleBr(tagFull)
+ } else {
+ handleOpen(tagFull)
+ }
+ }
+ } else {
+ textBuffer += tagFull
+ }
+ } else if (char === '\n') {
+ handleBr(char)
+ } else {
+ textBuffer += char
+ }
+ }
+ if (tagBuffer) {
+ textBuffer += tagBuffer
+ }
+
+ flush()
+
+ return buffer
+}