(function(Prism) {

	var handlebars_pattern = /\{\{\{[\s\S]+?\}\}\}|\{\{[\s\S]+?\}\}/g;

	Prism.languages.handlebars = Prism.languages.extend('markup', {
		'handlebars': {
			pattern: handlebars_pattern,
			inside: {
				'delimiter': {
					pattern: /^\{\{\{?|\}\}\}?$/i,
					alias: 'punctuation'
				},
				'string': /(["'])(\\?.)*?\1/,
				'number': /\b-?(0x[\dA-Fa-f]+|\d*\.?\d+([Ee][+-]?\d+)?)\b/,
				'boolean': /\b(true|false)\b/,
				'block': {
					pattern: /^(\s*~?\s*)[#\/]\S+?(?=\s*~?\s*$|\s)/i,
					lookbehind: true,
					alias: 'keyword'
				},
				'brackets': {
					pattern: /\[[^\]]+\]/,
					inside: {
						punctuation: /\[|\]/,
						variable: /[\s\S]+/
					}
				},
				'punctuation': /[!"#%&'()*+,.\/;<=>@\[\\\]^`{|}~]/,
				'variable': /[^!"#%&'()*+,.\/;<=>@\[\\\]^`{|}~\s]+/
			}
		}
	});

	// Comments are inserted at top so that they can
	// surround markup
	Prism.languages.insertBefore('handlebars', 'tag', {
		'handlebars-comment': {
			pattern: /\{\{![\s\S]*?\}\}/,
			alias: ['handlebars','comment']
		}
	});

	// Tokenize all inline Handlebars expressions that are wrapped in {{ }} or {{{ }}}
	// This allows for easy Handlebars + markup highlighting
	Prism.hooks.add('before-highlight', function(env) {
		if (env.language !== 'handlebars') {
			return;
		}

		env.tokenStack = [];

		env.backupCode = env.code;
		env.code = env.code.replace(handlebars_pattern, function(match) {
			var i = env.tokenStack.length;
			// Check for existing strings
			while (env.backupCode.indexOf('___HANDLEBARS' + i + '___') !== -1)
				++i;

			// Create a sparse array
			env.tokenStack[i] = match;

			return '___HANDLEBARS' + i + '___';
		});
	});

	// Restore env.code for other plugins (e.g. line-numbers)
	Prism.hooks.add('before-insert', function(env) {
		if (env.language === 'handlebars') {
			env.code = env.backupCode;
			delete env.backupCode;
		}
	});

	// Re-insert the tokens after highlighting
	// and highlight them with defined grammar
	Prism.hooks.add('after-highlight', function(env) {
		if (env.language !== 'handlebars') {
			return;
		}

		for (var i = 0, keys = Object.keys(env.tokenStack); i < keys.length; ++i) {
			var k = keys[i];
			var t = env.tokenStack[k];

			// The replace prevents $$, $&, $`, $', $n, $nn from being interpreted as special patterns
			env.highlightedCode = env.highlightedCode.replace('___HANDLEBARS' + k + '___', Prism.highlight(t, env.grammar, 'handlebars').replace(/\$/g, '$$$$'));
		}

		env.element.innerHTML = env.highlightedCode;
	});

}(Prism));