--- /dev/null
+/**
+ * negotiator
+ * Copyright(c) 2012 Isaac Z. Schlueter
+ * Copyright(c) 2014 Federico Romero
+ * Copyright(c) 2014-2015 Douglas Christopher Wilson
+ * MIT Licensed
+ */
+
+module.exports = preferredMediaTypes;
+preferredMediaTypes.preferredMediaTypes = preferredMediaTypes;
+
+function parseAccept(accept) {
+ var accepts = splitMediaTypes(accept);
+
+ for (var i = 0, j = 0; i < accepts.length; i++) {
+ var mediaType = parseMediaType(accepts[i].trim(), i);
+
+ if (mediaType) {
+ accepts[j++] = mediaType;
+ }
+ }
+
+ // trim accepts
+ accepts.length = j;
+
+ return accepts;
+};
+
+function parseMediaType(s, i) {
+ var match = s.match(/\s*(\S+?)\/([^;\s]+)\s*(?:;(.*))?/);
+ if (!match) return null;
+
+ var type = match[1],
+ subtype = match[2],
+ full = "" + type + "/" + subtype,
+ params = {},
+ q = 1;
+
+ if (match[3]) {
+ params = match[3].split(';').map(function(s) {
+ return s.trim().split('=');
+ }).reduce(function (set, p) {
+ var name = p[0].toLowerCase();
+ var value = p[1];
+
+ set[name] = value && value[0] === '"' && value[value.length - 1] === '"'
+ ? value.substr(1, value.length - 2)
+ : value;
+
+ return set;
+ }, params);
+
+ if (params.q != null) {
+ q = parseFloat(params.q);
+ delete params.q;
+ }
+ }
+
+ return {
+ type: type,
+ subtype: subtype,
+ params: params,
+ q: q,
+ i: i,
+ full: full
+ };
+}
+
+function getMediaTypePriority(type, accepted, index) {
+ var priority = {o: -1, q: 0, s: 0};
+
+ for (var i = 0; i < accepted.length; i++) {
+ var spec = specify(type, accepted[i], index);
+
+ if (spec && (priority.s - spec.s || priority.q - spec.q || priority.o - spec.o) < 0) {
+ priority = spec;
+ }
+ }
+
+ return priority;
+}
+
+function specify(type, spec, index) {
+ var p = parseMediaType(type);
+ var s = 0;
+
+ if (!p) {
+ return null;
+ }
+
+ if(spec.type.toLowerCase() == p.type.toLowerCase()) {
+ s |= 4
+ } else if(spec.type != '*') {
+ return null;
+ }
+
+ if(spec.subtype.toLowerCase() == p.subtype.toLowerCase()) {
+ s |= 2
+ } else if(spec.subtype != '*') {
+ return null;
+ }
+
+ var keys = Object.keys(spec.params);
+ if (keys.length > 0) {
+ if (keys.every(function (k) {
+ return spec.params[k] == '*' || (spec.params[k] || '').toLowerCase() == (p.params[k] || '').toLowerCase();
+ })) {
+ s |= 1
+ } else {
+ return null
+ }
+ }
+
+ return {
+ i: index,
+ o: spec.i,
+ q: spec.q,
+ s: s,
+ }
+
+}
+
+function preferredMediaTypes(accept, provided) {
+ // RFC 2616 sec 14.2: no header = */*
+ var accepts = parseAccept(accept === undefined ? '*/*' : accept || '');
+
+ if (!provided) {
+ // sorted list of all types
+ return accepts.filter(isQuality).sort(compareSpecs).map(function getType(spec) {
+ return spec.full;
+ });
+ }
+
+ var priorities = provided.map(function getPriority(type, index) {
+ return getMediaTypePriority(type, accepts, index);
+ });
+
+ // sorted list of accepted types
+ return priorities.filter(isQuality).sort(compareSpecs).map(function getType(priority) {
+ return provided[priorities.indexOf(priority)];
+ });
+}
+
+function compareSpecs(a, b) {
+ return (b.q - a.q) || (b.s - a.s) || (a.o - b.o) || (a.i - b.i) || 0;
+}
+
+function isQuality(spec) {
+ return spec.q > 0;
+}
+
+function quoteCount(string) {
+ var count = 0;
+ var index = 0;
+
+ while ((index = string.indexOf('"', index)) !== -1) {
+ count++;
+ index++;
+ }
+
+ return count;
+}
+
+function splitMediaTypes(accept) {
+ var accepts = accept.split(',');
+
+ for (var i = 1, j = 0; i < accepts.length; i++) {
+ if (quoteCount(accepts[j]) % 2 == 0) {
+ accepts[++j] = accepts[i];
+ } else {
+ accepts[j] += ',' + accepts[i];
+ }
+ }
+
+ // trim accepts
+ accepts.length = j + 1;
+
+ return accepts;
+}