#21 - Implemented the folding provider for front matter

src/extension.ts

@@ -5,6 +5,7 @@ import { Project } from './commands/Project';
 import { Template } from './commands/Template';
 import { COMMAND_NAME } from './constants/Extension';
 import { TaxonomyType } from './models';
+import { MarkdownFoldingProvider } from './providers/MarkdownFoldingProvider';
 import { TagType } from './viewpanel/TagType';
 import { ExplorerView } from './webview/ExplorerView';
 
@@ -13,6 +14,8 @@ let statusDebouncer: { (fnc: any, time: number): void; };
 let editDebounce: { (fnc: any, time: number): void; };
 let collection: vscode.DiagnosticCollection;
 
+const mdSelector: vscode.DocumentSelector = { language: 'markdown', scheme: 'file' };
+
 export async function activate({ subscriptions, extensionUri }: vscode.ExtensionContext) {
 	collection = vscode.languages.createDiagnosticCollection('frontMatter');
 
@@ -23,6 +26,8 @@ export async function activate({ subscriptions, extensionUri }: vscode.Extension
 		}
 	});
 
+	vscode.languages.registerFoldingRangeProvider(mdSelector, new MarkdownFoldingProvider());
+
 	let insertTags = vscode.commands.registerCommand(COMMAND_NAME.insertTags, async () => {
 		await vscode.commands.executeCommand('workbench.view.extension.frontmatter-explorer');
 		await vscode.commands.executeCommand('workbench.action.focusSideBar');

src/providers/MarkdownFoldingProvider.ts

@@ -0,0 +1,26 @@
+import { CancellationToken, FoldingContext, FoldingRange, FoldingRangeKind, FoldingRangeProvider, TextDocument } from 'vscode';
+
+export class MarkdownFoldingProvider implements FoldingRangeProvider {
+
+  public async provideFoldingRanges(document: TextDocument, context: FoldingContext, token: CancellationToken): Promise<FoldingRange[]> {
+    const ranges: FoldingRange[] = [];
+
+    const lines = document.getText().split('\n');
+    let start: number | null = null;
+    let end: number | null = null;
+
+    for (let i = 0; i < lines.length; i++) {
+      const line = lines[i];
+      if (line.startsWith('---')) {
+        if (i === 0 && start === null) {
+          start = i;
+        } else if (start !== null && end === null) {
+          end = i;
+          ranges.push(new FoldingRange(start, end, FoldingRangeKind.Region));
+          return ranges;
+        }
+      }
+    }
+    return ranges;
+  }
+}