litejs/app/accept.js

/*! litejs.com/MIT-LICENSE.txt */

module.exports = function(choices, priority) {
	var group = 0
	, ruleSeq = 0
	, rules = choices.constructor === Object ? Object.keys(choices) : choices
	, escapeRe = /[.+?^!:${}()|\[\]\/\\]/g
	, fnStr = 'return function(i){for(var m,t,l={q:null};(m=r.exec(i))&&(m='
	, reStr = 'var r=/(?:^|,\\s*)(?:('
	+ ('' + rules).replace(/[^,;]+|\s*;\s*(\w+)=("([^"]*)"|[^,;\s]*)|,/ig, function add(rule, key, token, qstr, offset) {
		if (key) {
			fnStr += ',' + key + ':unescape(m[' + (++group + 1) + ']!==void 0?m[' + (group + 1) + ']:m[' + (group++) + ']||"' + escape(qstr == null ? token : qstr ) + '")'
			return '(?=(?:"[^"]*"|[^,])*;\\s*' + key + '(?:=|\\*=utf-8\'\\w*\')("([^"]*)"|[^\\s,;]+)|)'
		}
		if (rule === ',') {
			return ')|('
		}
		fnStr += (offset ? '}:m[' : 'm[') + (++group) + ']?{rule:"' + rule + '",match:m[' + group + ']'
		if (choices !== rules) {
			fnStr += ',o:c[R[' + (ruleSeq++) + ']]'
		}

		function capture(j, re, to) {
			return /\*/.test(key[j]) ?
			((rule = rule.replace(re, to)), 'm[' + (++group) + ']') :
			'"' + (key[j] || '') + '"'
		}

		key = rule.match(/^(.+?)\/(.+?)(?:\+(.+))?$/)
		rule = rule.replace(escapeRe, '\\$&')
		if (key) {
			// type / [ tree. ] subtype [ +suffix ] [ ; parameters ]
			fnStr += ',type:' + capture(1, /(.*)\\\//, '($1)\\/')
			+ ',subtype:' + capture(2, /\/(.+?)(?=\\\+|$)/, '/($1)')
			+ ',suffix:' + capture(3, /\+(.+)/, '+($1)')
		}
		rule = rule.replace(/\*/g, '[^,;\\s\\/+]+?')

		return (offset ? rule : '(?:' + rule + '|[*\\/]+)') + add(0, 'q', 1)
	})
	+ '))\\s*(?=,|;|$)(?:"[^"]*"|[^,])*/gi;'

	return Function(
		'c,R',
		reStr +
		fnStr.replace(/m\[\d+\]\?(?!.*m\[\d+\]\?)/, '') +
		'});){t=1*m.q;if((m.q=t>=0&&t<1?t:1)>l.q' + (priority || '') + ')l=m}return l}'
	)(choices, rules)
}