index.js

"use strict";

const VIM_MODELINE = /(?:(?:^|[ \t])(?:vi|Vi(?=m))(?:m[<=>]?[0-9]+|m)?|[ \t]ex)(?=:(?=[ \t]*set?[ \t][^\r\n:]+:)|:(?![ \t]*set?[ \t]))(?:(?:[ \t]*:[ \t]*|[ \t])\w*(?:[ \t]*=(?:[^\\\s]|\\.)*)?)*[ \t:](?:filetype|ft|syntax)[ \t]*=(\w+)(?=$|\s|:)/i;
const {CompositeDisposable, Disposable} = require("atom");

module.exports = {
	disposables: null,
	
	activate(){
		this.disposables && this.disposables.dispose();
		this.disposables = new CompositeDisposable(
			new Disposable(() => this.disposables = null),
			atom.packages.onDidActivateInitialPackages(() => {
				atom.workspace.observeTextEditors(this.updateHelpGrammar.bind(this));
			})
		);
	},
	
	deactivate(){
		if(this.disposables){
			this.disposables.dispose();
		}
	},
	
	updateHelpGrammar(editor){
		if(!atom.workspace.isTextEditor(editor))
			return; // Not even a real editor
		
		const path = editor.getPath();
		if(/\.txt$/i.test(path) && VIM_MODELINE.test(editor.getText()) && "help" === RegExp.lastParen)
			editor.setGrammar(atom.grammars.grammarForScopeName("text.vim-help"));
	},
};