Add worldwide monolingual layer as default when language matches (#205)

js/LayersConfig.js

@@ -9,6 +9,7 @@ BR.LayersConfig = L.Class.extend({
         this._addLeafletProvidersLayers();
         this._customizeLayers();
         this.loadDefaultLayers();
+        this._addLanguageDefaultLayer();
     },
 
     loadDefaultLayers: function() {
@@ -80,6 +81,34 @@ BR.LayersConfig = L.Class.extend({
         BR.layerIndex['1017'].geometry = BR.confLayers.osmapaPl;
     },
 
+    _addLanguageDefaultLayer: function() {
+        // language code -> layer id
+        var languageLayersMap = {};
+        var i;
+
+        for (i = 0; i < BR.confLayers.languageDefaultLayers.length; i++) {
+            var id = BR.confLayers.languageDefaultLayers[i];
+            var layer = BR.layerIndex[id];
+            if (layer) {
+                var layerLanguage = layer.properties['language_code'];
+                if (layerLanguage) {
+                    languageLayersMap[layerLanguage] = id;
+                }
+            }
+        }
+
+        // iterate language code hierarchy, e.g ["de-DE", "de", "en"] (includes `i18next.options.fallbackLng`)
+        for (i = 0; i < i18next.languages.length; i++) {
+            var language = i18next.languages[i];
+            var layerId = languageLayersMap[language];
+
+            if (layerId) {
+                this.defaultBaseLayers.unshift(layerId);
+                break;
+            }
+        }
+    },
+
     isDefaultLayer: function(id, overlay) {
         var result = false;
         if (overlay) {

layers/config/config.js

@@ -2,12 +2,18 @@ BR.confLayers = {};
 
 BR.confLayers.defaultBaseLayers = [
     'standard',
-    'osm-mapnik-german_style',
     'OpenTopoMap',
     'Stamen.Terrain',
     'Esri.WorldImagery'
 ];
 
+// worldwide monolingual layers to add as default when browser language matches
+BR.confLayers.languageDefaultLayers = [
+    'osm-mapnik-german_style',
+    'osmfr',
+    '1021' // sputnik.ru
+];
+
 BR.confLayers.defaultOverlays =  [
     'HikeBike.HillShading',
     'Waymarked_Trails-Cycling',