Add event-based LogMonitor state changes to better handle batch reads (#59)

* Add event-based LogMonitor state changes to better handle batch reads

Pre-reading hackily used read-all to suppress notifications. But that broke some assumptions about what read-all meant. Furthermore, the Core UI told plugins about read-all rather than the log monitor telling them -- which is really what should be telling them.

To address these concerns, LogMonitor now provides an event that both the PluginCore and PluginEventHandler listens to or tracking logging state allowing more granular information about the activities of LogMonitor, including distinguishing between ReadAll and Pre-read batches. Plugins no longer need to track if LogMonitor is in batch-read mode or not -- PluginCore now provides it. 

I've also converted all built-in plugins to use the new event-based system. The old system is marked deprecated and will go away once other known contributed plugins have converted to the new system.

* Change LogMonitorState enum to [Flags], drop 'None' state

As requested, and did associated simplifications and cleanup that followed.

ObservatoryCore/LogMonitor.cs

@@ -4,7 +4,6 @@ using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.InteropServices;
-using System.Text.Json.Serialization;
 using Observatory.Framework;
 using Observatory.Framework.Files;
 
@@ -34,6 +33,7 @@ namespace Observatory
             currentLine = new();
             journalTypes = JournalReader.PopulateEventClasses();
             InitializeWatchers(string.Empty);
+            SetLogMonitorState(LogMonitorState.Idle);
         }
 
         #endregion
@@ -50,7 +50,7 @@ namespace Observatory
             }
             journalWatcher.EnableRaisingEvents = true;
             statusWatcher.EnableRaisingEvents = true;
-            monitoring = true;
+            SetLogMonitorState(LogMonitorState.Realtime);
             JournalPoke();
         }
 
@@ -58,7 +58,7 @@ namespace Observatory
         {
             journalWatcher.EnableRaisingEvents = false;
             statusWatcher.EnableRaisingEvents = false;
-            monitoring = false;
+            SetLogMonitorState(LogMonitorState.Idle);
         }
 
         public void ChangeWatchedDirectory(string path)
@@ -70,12 +70,13 @@ namespace Observatory
 
         public bool IsMonitoring()
         {
-            return monitoring;
+            return (currentState & LogMonitorState.Realtime) == LogMonitorState.Realtime;
         }
 
+        // TODO(fredjk_gh): Remove?
         public bool ReadAllInProgress()
         {
-            return readall;
+            return LogMonitorStateChangedEventArgs.IsBatchRead(currentState);
         }
 
         public void ReadAllJournals()
@@ -87,7 +88,8 @@ namespace Observatory
         {
             // Prevent pre-reading when starting monitoring after reading all.
             firstStartMonitor = false;
-            readall = true;
+            SetLogMonitorState(currentState | LogMonitorState.Batch);
+
             DirectoryInfo logDirectory = GetJournalFolder(path);
             var files = logDirectory.GetFiles("Journal.????????????.??.log");
             var readErrors = new List<(Exception ex, string file, string line)>();
@@ -98,13 +100,15 @@ namespace Observatory
             }
 
             ReportErrors(readErrors);
-            readall = false;
+            SetLogMonitorState(currentState & ~LogMonitorState.Batch);
         }
 
         public void PrereadJournals()
         {
             if (!Properties.Core.Default.TryPrimeSystemContextOnStartMonitor) return;
 
+            SetLogMonitorState(currentState | LogMonitorState.PreRead);
+
             DirectoryInfo logDirectory = GetJournalFolder(Properties.Core.Default.JournalFolder);
             var files = logDirectory.GetFiles("Journal.????????????.??.log");
 
@@ -156,15 +160,16 @@ namespace Observatory
                 linesToRead = lastSystemLines;
             }
 
-            readall = true;
             ReportErrors(ProcessLines(linesToRead, "Pre-read"));
-            readall = false;
+            SetLogMonitorState(currentState & ~LogMonitorState.PreRead);
         }
 
         #endregion
 
         #region Public Events
 
+        public event EventHandler<LogMonitorStateChangedEventArgs> LogMonitorStateChanged;
+
         public event EventHandler<JournalEventArgs> JournalEntry;
 
         public event EventHandler<JournalEventArgs> StatusUpdate;
@@ -177,14 +182,27 @@ namespace Observatory
         private FileSystemWatcher statusWatcher;
         private Dictionary<string, Type> journalTypes;
         private Dictionary<string, int> currentLine;
+        private LogMonitorState currentState = LogMonitorState.Idle; // Change via #SetLogMonitorState
         private bool monitoring = false;
-        private bool readall = false;
         private bool firstStartMonitor = true;
 
         #endregion
 
         #region Private Methods
 
+        private void SetLogMonitorState(LogMonitorState newState)
+        {
+            var oldState = currentState;
+            currentState = newState;
+            LogMonitorStateChanged?.Invoke(this, new LogMonitorStateChangedEventArgs
+            {
+                PreviousState = oldState,
+                NewState = newState
+            });;
+
+            System.Diagnostics.Debug.WriteLine("LogMonitor State change: {0} -> {1}", oldState, newState);
+        }
+
         private void InitializeWatchers(string path)
         {
             DirectoryInfo logDirectory = GetJournalFolder(path);

ObservatoryCore/PluginManagement/PluginCore.cs

@@ -11,6 +11,7 @@ namespace Observatory.PluginManagement
 
         private readonly NativeVoice NativeVoice;
         private readonly NativePopup NativePopup;
+        private LogMonitorState currentLogMonitorState = LogMonitorState.Idle;
 
         public PluginCore()
         {
@@ -18,6 +19,11 @@ namespace Observatory.PluginManagement
             NativePopup = new();
         }
 
+        internal void OnLogMonitorStateChanged(object sender, LogMonitorStateChangedEventArgs e)
+        {
+            currentLogMonitorState = e.NewState;
+        }
+
         public string Version => System.Reflection.Assembly.GetEntryAssembly().GetName().Version.ToString();
 
         public Status GetStatus()
@@ -34,7 +40,7 @@ namespace Observatory.PluginManagement
         {
             var guid = Guid.Empty;
 
-            if (!LogMonitor.GetInstance.ReadAllInProgress())
+            if (!IsLogMonitorBatchReading)
             {
                 if (notificationArgs.Rendering.HasFlag(NotificationRendering.PluginNotifier))
                 {
@@ -63,7 +69,7 @@ namespace Observatory.PluginManagement
 
         public void UpdateNotification(Guid id, NotificationArgs notificationArgs)
         {
-            if (!LogMonitor.GetInstance.ReadAllInProgress())
+            if (!IsLogMonitorBatchReading)
             {
 
                 if (notificationArgs.Rendering.HasFlag(NotificationRendering.PluginNotifier))
@@ -134,6 +140,16 @@ namespace Observatory.PluginManagement
             get => Observatory.HttpClient.Client;
         }
 
+        public LogMonitorState CurrentLogMonitorState
+        {
+            get => currentLogMonitorState;
+        }
+
+        public bool IsLogMonitorBatchReading
+        {
+            get => LogMonitorStateChangedEventArgs.IsBatchRead(currentLogMonitorState);
+        }
+
         public event EventHandler<NotificationArgs> Notification;
     }
 }

ObservatoryCore/PluginManagement/PluginEventHandler.cs

@@ -61,6 +61,21 @@ namespace Observatory.PluginManagement
             }
         }
 
+        internal void OnLogMonitorStateChanged(object sender, LogMonitorStateChangedEventArgs e)
+        {
+            foreach (var worker in observatoryWorkers)
+            {
+                try
+                {
+                    worker.LogMonitorStateChanged(e);
+                }
+                catch (Exception ex)
+                {
+                    RecordError(ex, worker.Name, "LogMonitorStateChanged event");
+                }
+            }
+        }
+
         public void OnNotificationEvent(object source, NotificationArgs notificationArgs)
         {
             foreach (var notifier in observatoryNotifiers)

ObservatoryCore/PluginManagement/PluginManager.cs

@@ -46,8 +46,10 @@ namespace Observatory.PluginManagement
 
             logMonitor.JournalEntry += pluginHandler.OnJournalEvent;
             logMonitor.StatusUpdate += pluginHandler.OnStatusUpdate;
+            logMonitor.LogMonitorStateChanged += pluginHandler.OnLogMonitorStateChanged;
 
             var core = new PluginCore();
+            logMonitor.LogMonitorStateChanged += core.OnLogMonitorStateChanged;
 
             List<IObservatoryPlugin> errorPlugins = new();
             

ObservatoryCore/UI/ViewModels/CoreViewModel.cs

@@ -65,8 +65,10 @@ namespace Observatory.UI.ViewModels
 
         public void ReadAll()
         {
+            // TODO(fredjk_gh): remove.
             SetWorkerReadAllState(true);
             LogMonitor.GetInstance.ReadAllJournals();
+            // TODO(fredjk_gh): remove.
             SetWorkerReadAllState(false);
         }
 
@@ -82,8 +84,10 @@ namespace Observatory.UI.ViewModels
             else
             {
                 // HACK: Find a better way of suppressing notifications when pre-reading.
+                // TODO(fredjk_gh): remove.
                 SetWorkerReadAllState(true);
                 logMonitor.Start();
+                // TODO(fredjk_gh): remove.
                 SetWorkerReadAllState(false);
                 ToggleButtonText = "Stop Monitor";
             }
@@ -138,6 +142,7 @@ namespace Observatory.UI.ViewModels
             get { return tabs; }
         }
 
+        // TODO(fredjk_gh): remove.
         private void SetWorkerReadAllState(bool isReadingAll)
         {
             foreach (var worker in workers)