From 61842a204eb6b12febfd101510f130d58e307d5d Mon Sep 17 00:00:00 2001
From: Jack Stratton <jack@phroa.net>
Date: Tue, 20 Jul 2021 16:42:50 -0700
Subject: [PATCH] Set up a background service for notifications

---
 phms/BackgroundService.cs | 66 +++++++++++++++++++++++++++++++++++++++
 phms/MainActivity.cs      | 14 ++++++---
 phms/phms.csproj          |  1 +
 3 files changed, 77 insertions(+), 4 deletions(-)
 create mode 100644 phms/BackgroundService.cs

diff --git a/phms/BackgroundService.cs b/phms/BackgroundService.cs
new file mode 100644
index 0000000..8db720c
--- /dev/null
+++ b/phms/BackgroundService.cs
@@ -0,0 +1,66 @@
+using System;
+using Android.App;
+using Android.Content;
+using Android.OS;
+
+namespace phms
+{
+    using R = Resource;
+    
+    [Service(Enabled = true)]
+    public class BackgroundService : Service
+    {
+        public const string UpdateNotificationAction = "phms.backgroundservice.updatenotification";
+        
+        private const int NotificationId = 39;
+        
+        private NotificationChannel? _notificationChannel;
+        private Binder? _binder;
+
+        public override IBinder OnBind(Intent? intent)
+        {
+            return _binder ??= new Binder();
+        }
+
+        public override void OnCreate()
+        {
+            base.OnCreate();
+            _notificationChannel ??= new NotificationChannel("phms", "phms", NotificationImportance.High);
+
+            Notify("Service OnCreate");
+        }
+
+        public override StartCommandResult OnStartCommand(Intent? intent, StartCommandFlags flags, int startId)
+        {
+            var ret = base.OnStartCommand(intent, flags, startId);
+
+            if (intent?.Action == UpdateNotificationAction)
+            {
+                Notify(intent.Extras?.GetString("message") ?? "Something important!");
+            }
+            
+            return ret;
+        }
+
+        private void Notify(string message)
+        {
+            if (!GetNotificationManager().NotificationChannels.Contains(_notificationChannel))
+            {
+                GetNotificationManager().CreateNotificationChannel(_notificationChannel);
+            }
+            
+            var n = new Notification.Builder(this, _notificationChannel?.Id)
+                .SetContentTitle("phms")
+                .SetContentText(message)
+                .SetSmallIcon(Android.Resource.Drawable.SymDefAppIcon)
+                .Build();
+ 
+            GetNotificationManager().Notify(NotificationId, n);
+        }
+
+        private NotificationManager GetNotificationManager()
+        {
+            return (NotificationManager) (GetSystemService(NotificationService) ?? throw new Exception("Couldn't get a notification service"));
+        }
+    }
+}
\ No newline at end of file
diff --git a/phms/MainActivity.cs b/phms/MainActivity.cs
index 49dbc37..a76c362 100644
--- a/phms/MainActivity.cs
+++ b/phms/MainActivity.cs
@@ -49,15 +49,21 @@ namespace phms
                     conn.Open();
                     using var cmd = new NpgsqlCommand("SHOW server_version", conn);
                     var result = cmd.ExecuteScalar();
-                    Snackbar.Make(connect, $"Success, {result}", Snackbar.LengthShort).Show();
+                    SendNotification($"Success, {result}");
                 }
                 catch
                 {
-                    Console.WriteLine();
-                    Snackbar.Make(connect, "Failure", Snackbar.LengthShort).Show();
-                    throw;
+                    SendNotification("Failed!");
                 }
             };
         }
+
+        private void SendNotification(string message)
+        {
+            var intent = new Intent(this, typeof(BackgroundService));
+            intent.SetAction(BackgroundService.UpdateNotificationAction);
+            intent.PutExtra("message", message);
+            StartService(intent);
+        }
     }
 }
\ No newline at end of file
diff --git a/phms/phms.csproj b/phms/phms.csproj
index c211677..a59ab08 100644
--- a/phms/phms.csproj
+++ b/phms/phms.csproj
@@ -57,6 +57,7 @@
         <Reference Include="Mono.Android" />
     </ItemGroup>
     <ItemGroup>
+        <Compile Include="BackgroundService.cs" />
         <Compile Include="MainActivity.cs" />
         <Compile Include="Resources\Resource.Designer.cs" />
         <Compile Include="Properties\AssemblyInfo.cs" />
-- 
2.45.2