add markdown-language-features to sqlops (#2338)

extensions/markdown-language-features/src/features/foldingProvider.ts

@@ -0,0 +1,50 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+import { MarkdownEngine } from '../markdownEngine';
+import { TableOfContentsProvider } from '../tableOfContentsProvider';
+
+const rangeLimit = 5000;
+
+export default class MarkdownFoldingProvider implements vscode.FoldingRangeProvider {
+
+	constructor(
+		private readonly engine: MarkdownEngine
+	) { }
+
+	public async provideFoldingRanges(
+		document: vscode.TextDocument,
+		_: vscode.FoldingContext,
+		_token: vscode.CancellationToken
+	): Promise<vscode.FoldingRange[]> {
+		const tocProvider = new TableOfContentsProvider(this.engine, document);
+		let toc = await tocProvider.getToc();
+		if (toc.length > rangeLimit) {
+			toc = toc.slice(0, rangeLimit);
+		}
+
+		const foldingRanges = toc.map((entry, startIndex) => {
+			const start = entry.line;
+			let end: number | undefined = undefined;
+			for (let i = startIndex + 1; i < toc.length; ++i) {
+				if (toc[i].level <= entry.level) {
+					end = toc[i].line - 1;
+					if (document.lineAt(end).isEmptyOrWhitespace && end >= start + 1) {
+						end = end - 1;
+					}
+					break;
+				}
+			}
+			return new vscode.FoldingRange(
+				start,
+				typeof end === 'number' ? end : document.lineCount - 1);
+		});
+
+
+		return foldingRanges;
+	}
+}