Add global holidays to calendar, fix volume mute display

Helpers/Holidays.js

@@ -0,0 +1,51 @@
+var _countryCode = null;
+var _holidaysCache = {};
+
+function getCountryCode(callback) {
+    if (_countryCode) {
+        callback(_countryCode);
+        return;
+    }
+    var xhr = new XMLHttpRequest();
+    xhr.open("GET", "http://ip-api.com/json/", true);
+    xhr.onreadystatechange = function() {
+        if (xhr.readyState === XMLHttpRequest.DONE && xhr.status === 200) {
+            var response = JSON.parse(xhr.responseText);
+            _countryCode = response.countryCode;
+            callback(_countryCode);
+        }
+    }
+    xhr.send();
+}
+
+function getHolidays(year, countryCode, callback) {
+    var cacheKey = year + "-" + countryCode;
+    if (_holidaysCache[cacheKey]) {
+        callback(_holidaysCache[cacheKey]);
+        return;
+    }
+    var url = "https://date.nager.at/api/v3/PublicHolidays/" + year + "/" + countryCode;
+    var xhr = new XMLHttpRequest();
+    xhr.open("GET", url, true);
+    xhr.onreadystatechange = function() {
+        if (xhr.readyState === XMLHttpRequest.DONE && xhr.status === 200) {
+            var holidays = JSON.parse(xhr.responseText);
+            _holidaysCache[cacheKey] = holidays;
+            callback(holidays);
+        }
+    }
+    xhr.send();
+}
+
+function getHolidaysForMonth(year, month, callback) {
+    getCountryCode(function(countryCode) {
+        getHolidays(year, countryCode, function(holidays) {
+            // 0-based months (0=Jan, 11=Dec)
+            var filtered = holidays.filter(function(h) {
+                var date = new Date(h.date);
+                return date.getFullYear() === year && date.getMonth() === month;
+            });
+            callback(filtered);
+        });
+    });
+}