(function (Prism) {

	Prism.languages.diff = {
		'coord': [
			// Match all kinds of coord lines (prefixed by "+++", "---" or "***").
			/^(?:\*{3}|-{3}|\+{3}).*$/m,
			// Match "@@ ... @@" coord lines in unified diff.
			/^@@.*@@$/m,
			// Match coord lines in normal diff (starts with a number).
			/^\d+.*$/m
		]

		// deleted, inserted, unchanged, diff
	};

	/**
	 * A map from the name of a block to its line prefix.
	 *
	 * @type {Object<string, string>}
	 */
	var PREFIXES = {
		'deleted-sign': '-',
		'deleted-arrow': '<',
		'inserted-sign': '+',
		'inserted-arrow': '>',
		'unchanged': ' ',
		'diff': '!',
	};

	// add a token for each prefix
	Object.keys(PREFIXES).forEach(function (name) {
		var prefix = PREFIXES[name];

		var alias = [];
		if (!/^\w+$/.test(name)) { // "deleted-sign" -> "deleted"
			alias.push(/\w+/.exec(name)[0]);
		}
		if (name === "diff") {
			alias.push("bold");
		}

		Prism.languages.diff[name] = {
			// pattern: /^(?:[_].*(?:\r\n?|\n|(?![\s\S])))+/m
			pattern: RegExp('^(?:[' + prefix + '].*(?:\r\n?|\n|(?![\\s\\S])))+', 'm'),
			alias: alias
		};
	});

	// make prefixes available to Diff plugin
	Object.defineProperty(Prism.languages.diff, 'PREFIXES', {
		value: PREFIXES
	});

}(Prism));