first commit

Services/FileMonitorStateService.cs

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+using HanaToolbox.Logging;
+using HanaToolbox.Services.Interfaces;
+
+namespace HanaToolbox.Services;
+
+/// <summary>
+/// File-based alert state persistence.
+/// Each key maps to /etc/hanatoolbox/state/&lt;key&gt;.state containing a plain-text value.
+/// </summary>
+public sealed class FileMonitorStateService(AppLogger logger) : IMonitorStateService
+{
+    private static readonly string StateDir = Config.ConfigService.StateDirectory;
+
+    public string? GetState(string key)
+    {
+        var path = StatePath(key);
+        if (!File.Exists(path)) return null;
+
+        try { return File.ReadAllText(path).Trim(); }
+        catch { return null; }
+    }
+
+    public void SetState(string key, string value)
+    {
+        try
+        {
+            Directory.CreateDirectory(StateDir);
+            File.WriteAllText(StatePath(key), value);
+        }
+        catch (Exception ex)
+        {
+            logger.Warning($"Could not write state for '{key}': {ex.Message}");
+        }
+    }
+
+    private static string StatePath(string key) =>
+        Path.Combine(StateDir, $"{key}.state");
+}