Chore: Refactor htmlpack for mobile compatibility (#12174)

packages/htmlpack/utils/parseHtmlAsync.ts

@@ -0,0 +1,79 @@
+const htmlparser2 = require('@joplin/fork-htmlparser2');
+
+export type HtmlAttrs = Record<string, string>;
+
+interface Callbacks {
+	onopentag: (name: string, attrs: HtmlAttrs)=> Promise<void>;
+	ontext: (text: string)=> Promise<void>;
+	onclosetag: (name: string)=> Promise<void>;
+}
+
+enum EventTypes {
+	OpenTag,
+	Text,
+	CloseTag,
+}
+
+interface OpenTagEvent {
+	type: EventTypes.OpenTag;
+	name: string;
+	attrs: HtmlAttrs;
+}
+
+interface TextEvent {
+	type: EventTypes.Text;
+	decodedText: string;
+}
+
+interface CloseTagEvent {
+	type: EventTypes.CloseTag;
+	name: string;
+}
+
+type ParserEvent = OpenTagEvent|TextEvent|CloseTagEvent;
+
+const parseHtmlAsync = async (html: string, callbacks: Callbacks) => {
+	const events: ParserEvent[] = [];
+	const parser = new htmlparser2.Parser({
+		onopentag: (name: string, attrs: HtmlAttrs) => {
+			events.push({
+				type: EventTypes.OpenTag,
+				name,
+				attrs,
+			});
+		},
+
+		ontext: (decodedText: string) => {
+			events.push({
+				type: EventTypes.Text,
+				decodedText,
+			});
+		},
+
+		onclosetag: (name: string) => {
+			events.push({
+				type: EventTypes.CloseTag,
+				name,
+			});
+		},
+
+	}, { decodeEntities: true });
+
+	parser.write(html);
+	parser.end();
+
+	for (const event of events) {
+		if (event.type === EventTypes.OpenTag) {
+			await callbacks.onopentag(event.name, event.attrs);
+		} else if (event.type === EventTypes.CloseTag) {
+			await callbacks.onclosetag(event.name);
+		} else if (event.type === EventTypes.Text) {
+			await callbacks.ontext(event.decodedText);
+		} else {
+			const exhaustivenessCheck: never = event;
+			throw new Error(`Unknown event type: ${exhaustivenessCheck}`);
+		}
+	}
+};
+
+export default parseHtmlAsync;