export function expandEmmetAbbreviation()

in extensions/emmet/src/abbreviationActions.ts [229:349]
103 lines of code
34 McCabe index (conditional complexity)

export function expandEmmetAbbreviation(args: any): Thenable<boolean | undefined> {
	if (!validate() || !vscode.window.activeTextEditor) {
		return fallbackTab();
	}

	args = args || {};
	if (!args['language']) {
		args['language'] = vscode.window.activeTextEditor.document.languageId;
	} else {
		const excludedLanguages = vscode.workspace.getConfiguration('emmet')['excludeLanguages'] ? vscode.workspace.getConfiguration('emmet')['excludeLanguages'] : [];
		if (excludedLanguages.indexOf(vscode.window.activeTextEditor.document.languageId) > -1) {
			return fallbackTab();
		}
	}
	const syntax = getSyntaxFromArgs(args);
	if (!syntax) {
		return fallbackTab();
	}

	const editor = vscode.window.activeTextEditor;
	let rootNode: Node | undefined;
	let usePartialParsing = vscode.workspace.getConfiguration('emmet')['optimizeStylesheetParsing'] === true;
	if (editor.selections.length === 1 && isStyleSheet(editor.document.languageId) && usePartialParsing && editor.document.lineCount > 1000) {
		rootNode = parsePartialStylesheet(editor.document, editor.selection.isReversed ? editor.selection.anchor : editor.selection.active);
	} else {
		rootNode = parseDocument(editor.document, false);
	}

	// When tabbed on a non empty selection, do not treat it as an emmet abbreviation, and fallback to tab instead
	if (vscode.workspace.getConfiguration('emmet')['triggerExpansionOnTab'] === true && editor.selections.find(x => !x.isEmpty)) {
		return fallbackTab();
	}

	let abbreviationList: ExpandAbbreviationInput[] = [];
	let firstAbbreviation: string;
	let allAbbreviationsSame: boolean = true;
	const helper = getEmmetHelper();

	let getAbbreviation = (document: vscode.TextDocument, selection: vscode.Selection, position: vscode.Position, syntax: string): [vscode.Range | null, string, string] => {
		let rangeToReplace: vscode.Range = selection;
		let abbr = document.getText(rangeToReplace);
		if (!rangeToReplace.isEmpty) {
			let extractedResults = helper.extractAbbreviationFromText(abbr);
			if (extractedResults) {
				return [rangeToReplace, extractedResults.abbreviation, extractedResults.filter];
			}
			return [null, '', ''];
		}

		const currentLine = editor.document.lineAt(position.line).text;
		const textTillPosition = currentLine.substr(0, position.character);

		// Expand cases like <div to <div></div> explicitly
		// else we will end up with <<div></div>
		if (syntax === 'html') {
			let matches = textTillPosition.match(/<(\w+)$/);
			if (matches) {
				abbr = matches[1];
				rangeToReplace = new vscode.Range(position.translate(0, -(abbr.length + 1)), position);
				return [rangeToReplace, abbr, ''];
			}
		}
		let extractedResults = helper.extractAbbreviation(editor.document, position, false);
		if (!extractedResults) {
			return [null, '', ''];
		}

		let { abbreviationRange, abbreviation, filter } = extractedResults;
		return [new vscode.Range(abbreviationRange.start.line, abbreviationRange.start.character, abbreviationRange.end.line, abbreviationRange.end.character), abbreviation, filter];
	};

	let selectionsInReverseOrder = editor.selections.slice(0);
	selectionsInReverseOrder.sort((a, b) => {
		const posA = a.isReversed ? a.anchor : a.active;
		const posB = b.isReversed ? b.anchor : b.active;
		return posA.compareTo(posB) * -1;
	});

	selectionsInReverseOrder.forEach(selection => {
		let position = selection.isReversed ? selection.anchor : selection.active;
		let [rangeToReplace, abbreviation, filter] = getAbbreviation(editor.document, selection, position, syntax);
		if (!rangeToReplace) {
			return;
		}
		if (!helper.isAbbreviationValid(syntax, abbreviation)) {
			return;
		}
		let currentNode = getNode(rootNode, position, true);
		let validateLocation = true;
		let syntaxToUse = syntax;

		if (editor.document.languageId === 'html') {
			if (isStyleAttribute(currentNode, position)) {
				syntaxToUse = 'css';
				validateLocation = false;
			} else {
				const embeddedCssNode = getEmbeddedCssNodeIfAny(editor.document, currentNode, position);
				if (embeddedCssNode) {
					currentNode = getNode(embeddedCssNode, position, true);
					syntaxToUse = 'css';
				}
			}
		}

		if (validateLocation && !isValidLocationForEmmetAbbreviation(editor.document, rootNode, currentNode, syntaxToUse, position, rangeToReplace)) {
			return;
		}

		if (!firstAbbreviation) {
			firstAbbreviation = abbreviation;
		} else if (allAbbreviationsSame && firstAbbreviation !== abbreviation) {
			allAbbreviationsSame = false;
		}

		abbreviationList.push({ syntax: syntaxToUse, abbreviation, rangeToReplace, filter });
	});

	return expandAbbreviationInRange(editor, abbreviationList, allAbbreviationsSame).then(success => {
		return success ? Promise.resolve(undefined) : fallbackTab();
	});
}