fix(health-monitoring): resolve HealthMonitoring-013,014,016 — shorter-timeout cadence, options validation, injected TimeProvider; HealthMonitoring-015 left open (cross-module design decision)

src/ScadaLink.HealthMonitoring/ServiceCollectionExtensions.cs

@@ -1,4 +1,6 @@
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+using Microsoft.Extensions.Options;
 
 namespace ScadaLink.HealthMonitoring;
 
@@ -10,6 +12,7 @@ public static class ServiceCollectionExtensions
     /// </summary>
     public static IServiceCollection AddSiteHealthMonitoring(this IServiceCollection services)
     {
+        AddOptionsValidation(services);
         services.AddSingleton<ISiteHealthCollector, SiteHealthCollector>();
         services.AddHostedService<HealthReportSender>();
         return services;
@@ -21,6 +24,7 @@ public static class ServiceCollectionExtensions
     /// </summary>
     public static IServiceCollection AddHealthMonitoring(this IServiceCollection services)
     {
+        AddOptionsValidation(services);
         services.AddSingleton<ISiteHealthCollector, SiteHealthCollector>();
         return services;
     }
@@ -32,10 +36,27 @@ public static class ServiceCollectionExtensions
     /// </summary>
     public static IServiceCollection AddCentralHealthAggregation(this IServiceCollection services)
     {
+        AddOptionsValidation(services);
         services.AddSingleton<CentralHealthAggregator>();
         services.AddSingleton<ICentralHealthAggregator>(sp => sp.GetRequiredService<CentralHealthAggregator>());
         services.AddHostedService(sp => sp.GetRequiredService<CentralHealthAggregator>());
         services.AddHostedService<CentralHealthReportLoop>();
         return services;
     }
+
+    /// <summary>
+    /// HealthMonitoring-014: register the <see cref="HealthMonitoringOptionsValidator"/>
+    /// so a misconfigured <c>ScadaLink:HealthMonitoring</c> section (zero/negative
+    /// intervals, or a <c>CentralOfflineTimeout</c> shorter than
+    /// <c>OfflineTimeout</c>) is rejected with a clear, key-naming message when the
+    /// hosted services resolve their options at startup — rather than crashing
+    /// later inside a <see cref="PeriodicTimer"/> constructor with an opaque
+    /// <see cref="ArgumentOutOfRangeException"/>. Idempotent so it is safe when
+    /// more than one of the registration methods above is called.
+    /// </summary>
+    private static void AddOptionsValidation(IServiceCollection services)
+    {
+        services.TryAddEnumerable(
+            ServiceDescriptor.Singleton<IValidateOptions<HealthMonitoringOptions>, HealthMonitoringOptionsValidator>());
+    }
 }