extensions/html-language-features/client/src/htmlClient.ts/insertRequestor
export function startClient(context: ExtensionContext, newLanguageClient: LanguageClientConstructor, runtime: Runtime) {

	let toDispose = context.subscriptions;


	let documentSelector = ['html', 'handlebars'];
	let embeddedLanguages = { css: true, javascript: true };

	let rangeFormatting: Disposable | undefined = undefined;

	// Options to control the language client
	let clientOptions: LanguageClientOptions = {
		documentSelector,
		synchronize: {
			configurationSection: ['html', 'css', 'javascript'], // the settings to synchronize
		},
		initializationOptions: {
			embeddedLanguages,
			handledSchemas: ['file'],
			provideFormatter: false, // tell the server to not provide formatting capability and ignore the `html.format.enable` setting.
			customCapabilities: { rangeFormatting: { editLimit: 10000 } }
		},
		middleware: {
			// testing the replace / insert mode
			provideCompletionItem(document: TextDocument, position: Position, context: CompletionContext, token: CancellationToken, next: ProvideCompletionItemsSignature): ProviderResult<CompletionItem[] | CompletionList> {
				function updateRanges(item: CompletionItem) {
					const range = item.range;
					if (range instanceof Range && range.end.isAfter(position) && range.start.isBeforeOrEqual(position)) {
						item.range = { inserting: new Range(range.start, position), replacing: range };
					}
				}
				function updateProposals(r: CompletionItem[] | CompletionList | null | undefined): CompletionItem[] | CompletionList | null | undefined {
					if (r) {
						(Array.isArray(r) ? r : r.items).forEach(updateRanges);
					}
					return r;
				}
				const isThenable = <T>(obj: ProviderResult<T>): obj is Thenable<T> => obj && (<any>obj)['then'];

				const r = next(document, position, context, token);
				if (isThenable<CompletionItem[] | CompletionList | null | undefined>(r)) {
					return r.then(updateProposals);
				}
				return updateProposals(r);
			}
		}
	};

	// Create the language client and start the client.
	let client = newLanguageClient('html', localize('htmlserver.name', 'HTML Language Server'), clientOptions);
	client.registerProposedFeatures();

	let disposable = client.start();
	toDispose.push(disposable);
	client.onReady().then(() => {

		toDispose.push(serveFileSystemRequests(client, runtime));

		const customDataSource = getCustomDataSource(runtime, context.subscriptions);

		client.sendNotification(CustomDataChangedNotification.type, customDataSource.uris);
		customDataSource.onDidChange(() => {
			client.sendNotification(CustomDataChangedNotification.type, customDataSource.uris);
		});
		client.onRequest(CustomDataContent.type, customDataSource.getContent);


		const insertRequestor = (kind: 'autoQuote' | 'autoClose', document: TextDocument, position: Position): Promise<string> => {
			let param: AutoInsertParams = {
				kind,
				textDocument: client.code2ProtocolConverter.asTextDocumentIdentifier(document),
				position: client.code2ProtocolConverter.asPosition(position)
			};
			return client.sendRequest(AutoInsertRequest.type, param);
		};
		let disposable = activateAutoInsertion(insertRequestor, { html: true, handlebars: true }, runtime);
		toDispose.push(disposable);

		disposable = client.onTelemetry(e => {
			runtime.telemetry?.sendTelemetryEvent(e.key, e.data);
		});
		toDispose.push(disposable);

		// manually register / deregister format provider based on the `html.format.enable` setting avoiding issues with late registration. See #71652.
		updateFormatterRegistration();
		toDispose.push({ dispose: () => rangeFormatting && rangeFormatting.dispose() });
		toDispose.push(workspace.onDidChangeConfiguration(e => e.affectsConfiguration(SettingIds.formatEnable) && updateFormatterRegistration()));

		client.sendRequest(SemanticTokenLegendRequest.type).then(legend => {
			if (legend) {
				const provider: DocumentSemanticTokensProvider & DocumentRangeSemanticTokensProvider = {
					provideDocumentSemanticTokens(doc) {
						const params: SemanticTokenParams = {
							textDocument: client.code2ProtocolConverter.asTextDocumentIdentifier(doc),
						};
						return client.sendRequest(SemanticTokenRequest.type, params).then(data => {
							return data && new SemanticTokens(new Uint32Array(data));
						});
					},
					provideDocumentRangeSemanticTokens(doc, range) {
						const params: SemanticTokenParams = {
							textDocument: client.code2ProtocolConverter.asTextDocumentIdentifier(doc),
							ranges: [client.code2ProtocolConverter.asRange(range)]
						};
						return client.sendRequest(SemanticTokenRequest.type, params).then(data => {
							return data && new SemanticTokens(new Uint32Array(data));
						});
					}
				};
				toDispose.push(languages.registerDocumentSemanticTokensProvider(documentSelector, provider, new SemanticTokensLegend(legend.types, legend.modifiers)));
			}
		});
	});

	function updateFormatterRegistration() {
		const formatEnabled = workspace.getConfiguration().get(SettingIds.formatEnable);
		if (!formatEnabled && rangeFormatting) {
			rangeFormatting.dispose();
			rangeFormatting = undefined;
		} else if (formatEnabled && !rangeFormatting) {
			rangeFormatting = languages.registerDocumentRangeFormattingEditProvider(documentSelector, {
				provideDocumentRangeFormattingEdits(document: TextDocument, range: Range, options: FormattingOptions, token: CancellationToken): ProviderResult<TextEdit[]> {
					const filesConfig = workspace.getConfiguration('files', document);
					const fileFormattingOptions = {
						trimTrailingWhitespace: filesConfig.get<boolean>('trimTrailingWhitespace'),
						trimFinalNewlines: filesConfig.get<boolean>('trimFinalNewlines'),
						insertFinalNewline: filesConfig.get<boolean>('insertFinalNewline'),
					};
					let params: DocumentRangeFormattingParams = {
						textDocument: client.code2ProtocolConverter.asTextDocumentIdentifier(document),
						range: client.code2ProtocolConverter.asRange(range),
						options: client.code2ProtocolConverter.asFormattingOptions(options, fileFormattingOptions)
					};
					return client.sendRequest(DocumentRangeFormattingRequest.type, params, token).then(
						client.protocol2CodeConverter.asTextEdits,
						(error) => {
							client.handleFailedRequest(DocumentRangeFormattingRequest.type, error, []);
							return Promise.resolve([]);
						}
					);
				}
			});
		}
	}

	const regionCompletionRegExpr = /^(\s*)(<(!(-(-\s*(#\w*)?)?)?)?)?$/;
	const htmlSnippetCompletionRegExpr = /^(\s*)(<(h(t(m(l)?)?)?)?)?$/;
	toDispose.push(languages.registerCompletionItemProvider(documentSelector, {
		provideCompletionItems(doc, pos) {
			const results: CompletionItem[] = [];
			let lineUntilPos = doc.getText(new Range(new Position(pos.line, 0), pos));
			let match = lineUntilPos.match(regionCompletionRegExpr);
			if (match) {
				let range = new Range(new Position(pos.line, match[1].length), pos);
				let beginProposal = new CompletionItem('#region', CompletionItemKind.Snippet);
				beginProposal.range = range;
				beginProposal.insertText = new SnippetString('<!-- #region $1-->');
				beginProposal.documentation = localize('folding.start', 'Folding Region Start');
				beginProposal.filterText = match[2];
				beginProposal.sortText = 'za';
				results.push(beginProposal);
				let endProposal = new CompletionItem('#endregion', CompletionItemKind.Snippet);
				endProposal.range = range;
				endProposal.insertText = new SnippetString('<!-- #endregion -->');
				endProposal.documentation = localize('folding.end', 'Folding Region End');
				endProposal.filterText = match[2];
				endProposal.sortText = 'zb';
				results.push(endProposal);
			}
			let match2 = lineUntilPos.match(htmlSnippetCompletionRegExpr);
			if (match2 && doc.getText(new Range(new Position(0, 0), pos)).match(htmlSnippetCompletionRegExpr)) {
				let range = new Range(new Position(pos.line, match2[1].length), pos);
				let snippetProposal = new CompletionItem('HTML sample', CompletionItemKind.Snippet);
				snippetProposal.range = range;
				const content = ['<!DOCTYPE html>',
					'<html>',
					'<head>',
					'\t<meta charset=\'utf-8\'>',
					'\t<meta http-equiv=\'X-UA-Compatible\' content=\'IE=edge\'>',
					'\t<title>${1:Page Title}</title>',
					'\t<meta name=\'viewport\' content=\'width=device-width, initial-scale=1\'>',
					'\t<link rel=\'stylesheet\' type=\'text/css\' media=\'screen\' href=\'${2:main.css}\'>',
					'\t<script src=\'${3:main.js}\'></script>',
					'</head>',
					'<body>',
					'\t$0',
					'</body>',
					'</html>'].join('\n');
				snippetProposal.insertText = new SnippetString(content);
				snippetProposal.documentation = localize('folding.html', 'Simple HTML5 starting point');
				snippetProposal.filterText = match2[2];
				snippetProposal.sortText = 'za';
				results.push(snippetProposal);
			}
			return results;
		}
	}));

	const promptForLinkedEditingKey = 'html.promptForLinkedEditing';
	if (extensions.getExtension('formulahendry.auto-rename-tag') !== undefined && (context.globalState.get(promptForLinkedEditingKey) !== false)) {
		const config = workspace.getConfiguration('editor', { languageId: 'html' });
		if (!config.get('linkedEditing') && !config.get('renameOnType')) {
			const activeEditorListener = window.onDidChangeActiveTextEditor(async e => {
				if (e && documentSelector.indexOf(e.document.languageId) !== -1) {
					context.globalState.update(promptForLinkedEditingKey, false);
					activeEditorListener.dispose();
					const configure = localize('configureButton', 'Configure');
					const res = await window.showInformationMessage(localize('linkedEditingQuestion', 'VS Code now has built-in support for auto-renaming tags. Do you want to enable it?'), configure);
					if (res === configure) {
						commands.executeCommand('workbench.action.openSettings', SettingIds.linkedEditing);
					}
				}
			});
			toDispose.push(activeEditorListener);
		}
	}

}