feature: Observation Ingest, Synchronous Alert Detection, and Alert Lifecycle

VigilCareClinicalAPI/Services/PlausibilityValidator.cs

@@ -0,0 +1,35 @@
+public static class PlausibilityValidator
+{
+    // Plausible ranges define the outer boundary of physically possible values.
+    // These are NOT clinical thresholds — they catch device malfunctions and typos.
+    // A heart rate of 300 is clinically impossible; 150 is critical but possible.
+    private static readonly Dictionary<string, (decimal Min, decimal Max)> _ranges = new()
+    {
+        ["HEART_RATE"]       = (1,    300),
+        ["TEMP_C"]           = (20,   50),
+        ["POTASSIUM_MEQ_L"]  = (0.1m, 15),
+        ["SPO2"]             = (50,   100),
+        ["RESP_RATE"]        = (1,    80),
+        ["WBC_K_UL"]         = (0.1m, 500),
+        ["GLUCOSE_MG_DL"]    = (10,   1500),
+    };
+
+    public static bool IsPlausible(string observationCode, decimal value, out string? reason)
+    {
+        if (!_ranges.TryGetValue(observationCode, out var range))
+        {
+            // Unknown codes pass plausibility — threshold lookup will validate the code
+            reason = null;
+            return true;
+        }
+
+        if (value < range.Min || value > range.Max)
+        {
+            reason = $"Value {value} is outside the plausible range [{range.Min}–{range.Max}] for {observationCode}.";
+            return false;
+        }
+
+        reason = null;
+        return true;
+    }
+}