Implement custom view counters

NostrStreamer/Services/ViewCounter.cs

@@ -0,0 +1,77 @@
+using System.Collections.Concurrent;
+
+namespace NostrStreamer.Services;
+
+public class ViewCounter
+{
+    private readonly ConcurrentDictionary<string, Dictionary<string, DateTime>> _sessions = new();
+
+    public void Activity(string key, string token)
+    {
+        if (!_sessions.ContainsKey(key))
+        {
+            _sessions.TryAdd(key, new());
+        }
+        if (_sessions.TryGetValue(key, out var x))
+        {
+            x[token] = DateTime.Now;
+        }
+    }
+
+    public void Decay()
+    {
+        foreach (var k in _sessions.Keys)
+        {
+            if (_sessions.TryGetValue(k, out var x))
+            {
+                _sessions[k] = x
+                    .Where(a => a.Value > DateTime.Now.Subtract(TimeSpan.FromMinutes(2)))
+                    .ToDictionary(a => a.Key, b => b.Value);
+
+                if (_sessions[k].Count == 0)
+                {
+                    _sessions.TryRemove(k, out _);
+                }
+            }
+        }
+    }
+
+    public int Current(string key)
+    {
+        if (_sessions.TryGetValue(key, out var x))
+        {
+            return x.Count;
+        }
+
+        return 0;
+    }
+}
+
+public class ViewCounterDecay : BackgroundService
+{
+    private readonly ViewCounter _viewCounter;
+    private readonly ILogger<ViewCounterDecay> _logger;
+
+    public ViewCounterDecay(ViewCounter viewCounter, ILogger<ViewCounterDecay> logger)
+    {
+        _viewCounter = viewCounter;
+        _logger = logger;
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            try
+            {
+                _viewCounter.Decay();
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Something went wrong");
+            }
+
+            await Task.Delay(TimeSpan.FromMinutes(1), stoppingToken);
+        }
+    }
+}