move data stores into their own folders like the go project

dotnet/SafelyYou/Data/Devices.cs

@@ -0,0 +1,93 @@
+using System.Collections.Concurrent;
+
+namespace SafelyYou.Data;
+
+public readonly record struct DeviceId(string Value);
+
+
+public sealed class KnownDevices
+{
+    private readonly HashSet<DeviceId> _knownDevices;
+
+    public KnownDevices(HashSet<DeviceId> knownDevices) => _knownDevices = knownDevices;
+
+    public bool Contains(DeviceId deviceId) => _knownDevices.Contains(deviceId);
+}
+
+public sealed class DeviceHeartBeatHistory
+{
+    private readonly Lock _lock = new();
+
+    public enum AddResult { Added, OutOfSequence }
+
+    public long NumberOfHeartBeats { get; private set; }
+    public DateTimeOffset? FirstHeartBeat { get; private set; }
+    public DateTimeOffset? LastHeartBeat { get; private set; }
+
+
+    public AddResult Add(DateTimeOffset sentAt)
+    {
+        lock (_lock)
+        {
+            // Reject heartbeats that arrive before the latest registered time.
+            // Gaps are fine: uptime can be derived from first, last, and count.
+            if (LastHeartBeat is null)
+            {
+                FirstHeartBeat = sentAt;
+                LastHeartBeat = sentAt;
+                NumberOfHeartBeats = 1;
+                return AddResult.Added;
+            }
+
+            if (sentAt < LastHeartBeat)
+                return AddResult.OutOfSequence;
+
+            // note: does not account for rejecting heartbeats that come between the one minute window.
+            LastHeartBeat = sentAt;
+            NumberOfHeartBeats++;
+            return AddResult.Added;
+        }
+    }
+}
+
+public sealed class HeartBeatHistories
+{
+    private readonly ConcurrentDictionary<DeviceId, DeviceHeartBeatHistory> _histories = new();
+    private readonly Lock _lock = new ();
+
+    public DeviceHeartBeatHistory.AddResult Add(DeviceId deviceId, DateTimeOffset sentAt)
+    {
+        if (!_histories.TryGetValue(deviceId, out var history))
+        {
+            lock (_lock)
+            {
+                history = new();
+                _histories[deviceId] = history;
+            }
+        }
+
+        return history.Add(sentAt);
+    }
+
+    public double Uptime(DeviceId deviceId)
+    {
+        if (!_histories.TryGetValue(deviceId, out var history)) return 0;
+        
+        var heartBeatMinutes = 
+            (history.FirstHeartBeat, history.LastHeartBeat) switch
+            {
+                ({} first, {} second ) => (second - first).TotalMinutes,
+                (not null, null) => 1,
+                (null, _) => 0
+            };
+
+        if (heartBeatMinutes == 0) return 0L;
+
+        var uptime = (history.NumberOfHeartBeats / heartBeatMinutes) * 100L;
+        return uptime;
+    }
+}
+
+
+
+