import * as vscode from 'vscode';

const fnRegex = /^\t*(.*)err\s?:=.+?$/

export function activate(context: vscode.ExtensionContext) {
	context.subscriptions.push(
		vscode.languages.registerCodeActionsProvider(
			'go',
			new ErrorsWrapper(),
			{ providedCodeActionKinds: ErrorsWrapper.providedCodeActionKinds }
		)
	);
	context.subscriptions.push(
		vscode.commands.registerCommand('gotools.wrap-error', wrapError)
	);
}

export function deactivate() { }

export class ErrorsWrapper implements vscode.CodeActionProvider {

	public static readonly providedCodeActionKinds = [
		vscode.CodeActionKind.RefactorRewrite
	];

	public provideCodeActions(document: vscode.TextDocument, range: vscode.Range): vscode.CodeAction[] | undefined {
		const editor = vscode.window.activeTextEditor;
		if (!editor) {
			return undefined;
		}
		const line = document.lineAt(editor.selection.start.line);
		if (!fnRegex.test(line.text)) {
			return undefined;
		}
		const action = new vscode.CodeAction('Add error checking', vscode.CodeActionKind.RefactorRewrite);
		action.command = { command: 'gotools.wrap-error', title: 'Add error checking block', tooltip: '' };
		return [
			action,
		];
	}
}

const wrapError = () => {
	const editor = vscode.window.activeTextEditor;
	if (!editor) {
		return;
	}
	const document = editor.document;
	const line = document.lineAt(editor.selection.start.line);
	const matches = line.text.match(fnRegex);
	if (matches == null || matches.length == 0) {
		return;
	}
	const extravars = matches[1].split(',').map(x => x.trim()).filter(x => x);
	if (extravars.filter(x => x != "_").length > 0) {
		editor.insertSnippet(
			new vscode.SnippetString(`\nif err != nil {\n\t\${1:return \${2:nil, }\${3:err}}\n}\n`),
			new vscode.Position(line.range.end.line, line.range.end.character + line.firstNonWhitespaceCharacterIndex),
		)
	} else {
		editor.insertSnippet(
			new vscode.SnippetString(`if `),
			new vscode.Position(line.range.start.line, line.range.start.character + line.firstNonWhitespaceCharacterIndex),
		)
		editor.insertSnippet(
			new vscode.SnippetString(`; err != nil {\n\t\${1:return \${2:nil, }\${3:err}}\n}\n`),
			new vscode.Position(line.range.end.line, line.range.end.character + line.firstNonWhitespaceCharacterIndex + 3),
			{
				undoStopAfter: true,
				undoStopBefore: false,
			}
		)
	}
};