fix: parse accept-language prefixes

lib/header.js

@@ -70,7 +70,6 @@ exports.selections = function (header, preferences, options) {
 //       weight = OWS ";" OWS "q=" qvalue
 //       qvalue = ( "0" [ "." 0*3DIGIT ] ) / ( "1" [ "." 0*3("0") ] )
 
-
 internals.parse = function (raw, preferences, options) {
 
     // Normalize header (remove spaces and tabs)
@@ -83,7 +82,18 @@ internals.parse = function (raw, preferences, options) {
     if (preferences) {
         for (let i = 0; i < preferences.length; ++i) {
             const preference = preferences[i];
-            lowers.set(preference.toLowerCase(), { orig: preference, pos: i });
+            const lowerPreference = preference.toLowerCase();
+            lowers.set(lowerPreference, { orig: preference, pos: i });
+            if ( options.type === 'accept-language') {
+                const languageParts = lowerPreference.split('-');
+                languageParts.pop();
+
+                while (languageParts.length) {
+                    lowers.set(languageParts.join('-'), { orig: preference, pos: i });
+                    languageParts.pop();
+                }
+
+            }
         }
     }
 
@@ -124,13 +134,16 @@ internals.parse = function (raw, preferences, options) {
             specificity: options.specificity ? token.split('-') : null
         };
 
-        if (preferences &&
-            lowers.has(token)) {
-
+        if (preferences && lowers.has(token)) {
             selection.pref = lowers.get(token).pos;
         }
 
-        map.add(selection.token);
+        if (preferences && lowers.has(selection.token)) {
+            map.add(lowers.get(selection.token).orig);
+        }
+        else {
+            map.add(selection.token);
+        }
 
         // Parse q=value
 
@@ -210,6 +223,13 @@ internals.sort = function (a, b) {
         return b.q - a.q;
     }
 
+    if (a.specificity &&
+        a.specificity[0] === b.specificity[0] &&
+        a.specificity.length !== b.specificity.length) {
+
+        return b.specificity.length - a.specificity.length;
+    }
+
     if (b.pref !== a.pref) {
         if (a.pref === undefined) {
             return bFirst;
@@ -222,12 +242,5 @@ internals.sort = function (a, b) {
         return a.pref - b.pref;
     }
 
-    if (a.specificity &&
-        a.specificity[0] === b.specificity[0] &&
-        a.specificity.length !== b.specificity.length) {
-
-        return b.specificity.length - a.specificity.length;
-    }
-
     return a.pos - b.pos;
 };

test/language.js

@@ -72,12 +72,12 @@ describe('language()', () => {
 
     it('returns preference with highest specificity', () => {
 
-        expect(Accept.language('da, en, en-GB', ['en', 'en-GB'])).to.equal('en');
+        expect(Accept.language('da, en, en-GB', ['en', 'en-GB'])).to.equal('en-GB');
         expect(Accept.language('da, en, en-GB', ['en-GB', 'en'])).to.equal('en-GB');
         expect(Accept.language('en, en-GB, en-US')).to.equal('en-gb');
     });
 
-    it('return language with heighest weight', () => {
+    it('returns language with heighest weight', () => {
 
         const language = Accept.language('da;q=0.5, en;q=1', ['da', 'en']);
         expect(language).to.equal('en');
@@ -88,6 +88,12 @@ describe('language()', () => {
         const language = Accept.language('da, en-GB, en', ['en-us', 'en-gb']); // en-GB vs en-gb
         expect(language).to.equal('en-gb');
     });
+
+    it('returns a more specific preference if a less specific one is requested', () => {
+
+        const language = Accept.language('de-LI,de', ['en-us', 'de-de']);
+        expect(language).to.equal('de-de');
+    });
 });
 
 
@@ -123,15 +129,16 @@ describe('languages()', () => {
         expect(languages).to.equal(['da', 'en-gb', 'es', 'en']);
     });
 
-    it('return empty array when no header is present', () => {
+    it('returns empty array when no header is present', () => {
 
         const languages = Accept.languages();
         expect(languages).to.equal([]);
     });
 
-    it('return empty array when header is empty', () => {
+    it('returns empty array when header is empty', () => {
 
         const languages = Accept.languages('');
         expect(languages).to.equal([]);
     });
+
 });