add a little progress dialog while downloading the database

EDDB/API.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading.Tasks;
 using System.IO;
 using System.Net;
 using System.Collections.Generic;
@@ -17,10 +18,14 @@ namespace NonaBGS.EDDB {
         private string stations_file_short = null;
 
         public delegate void DatabaseAvailableDelegate();
+        public delegate void DatabaseUpdateProgressDelegate();
 
         public event DatabaseAvailableDelegate SystemsAvailable;
         public event DatabaseAvailableDelegate StationsAvailable;
 
+        public event DatabaseUpdateProgressDelegate DatabaseUpdateProgress;
+        public event DatabaseUpdateProgressDelegate DatabaseUpdateFinished;
+
         public string SystemsFile => systems_file;
         public string StationsFile => stations_file;
         public string StationsFileShort => stations_file_short;
@@ -39,14 +44,26 @@ namespace NonaBGS.EDDB {
             systems_file = Path.Combine(this.cache_folder, "systems_populated.json");
             stations_file = Path.Combine(this.cache_folder, "stations.json");
             stations_file_short = Path.Combine(this.cache_folder, "stations_short.json");
+
+            this.StationsAvailable += API_StationsAvailable;
+        }
+
+        private void API_StationsAvailable() {
+            TranslateStations();
+            DatabaseUpdateFinished?.Invoke();
         }
 
         private void DownloadFile(string url, string file, DatabaseAvailableDelegate notifier) {
             WebClient client = new WebClient();
             client.DownloadFileCompleted += Client_DownloadFileCompleted;
+            client.DownloadProgressChanged += Client_DownloadProgressChanged;
             client.DownloadFileAsync(new Uri(url), file, notifier);
         }
 
+        private void Client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e) {
+            DatabaseUpdateProgress?.Invoke();
+        }
+
         private void Client_DownloadFileCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e) {
             DatabaseAvailableDelegate notifier = e.UserState as DatabaseAvailableDelegate;
             notifier?.Invoke();
@@ -69,7 +86,6 @@ namespace NonaBGS.EDDB {
             using (var str = new StreamReader(StationsFile)) {
                 using (var reader = new JsonTextReader(str)) {
                     JArray obj = (JArray)JToken.ReadFrom(reader);
-                    
 
                     foreach (JObject child in obj.Children<JObject>()) {
                         int system_id = child.Value<int>("system_id");
@@ -79,6 +95,8 @@ namespace NonaBGS.EDDB {
                             systems.Add(system_id, new List<string>());
                         }
 
+                        DatabaseUpdateProgress?.Invoke();
+
                         systems[system_id].Add(name);
                     }
                 }