feat: Refactor Patient and implement mean-reverting simulation

- Broke out the Patient struct and its related functions (initializePatient, updatePatient) into their own files (Patient.h, Patient.cpp) for better organization.

- Implemented the initial UpdateState logic in the updatePatient function using a mean-reverting model. This ensures that vital signs fluctuate realistically around a healthy baseline.

- Updated CMakeLists.txt to include the new Patient.cpp file in the build.

src/MedicalLib.cpp

@@ -10,22 +10,3 @@ double calculateBMI(double weight_kg, double height_m) {
     }
     return weight_kg / (height_m * height_m);
 }
-
-Patient initializePatient(int patientId) {
-    Patient patient;
-    patient.patientId = patientId;
-    patient.bloodPressureSystolic = 120.0;
-    patient.bloodPressureDiastolic = 80.0;
-    patient.heartRate = 75.0;
-    patient.respirationRate = 16.0;
-    patient.bodyTemperature = 37.0;
-    patient.oxygenSaturation = 98.0;
-    return patient;
-}
-
-void updatePatient(Patient& patient, double deltaTime_s) {
-    // For this initial implementation, we will not change the patient's vitals.
-    // This function serves as a placeholder for future, more complex simulation logic.
-    (void)patient;
-    (void)deltaTime_s;
-}

src/Patient.cpp

@@ -0,0 +1,59 @@
+#include "MedicalLib/Patient.h"
+#include <random>
+#include <algorithm> // For std::clamp
+
+// Helper function to generate random fluctuations
+double getFluctuation(double stddev) {
+    static std::random_device rd;
+    static std::mt19937 gen(rd());
+    std::normal_distribution<> d(0, stddev);
+    return d(gen);
+}
+
+Patient initializePatient(int patientId) {
+    Patient patient;
+    patient.patientId = patientId;
+    patient.bloodPressureSystolic = 120.0;
+    patient.bloodPressureDiastolic = 80.0;
+    patient.heartRate = 75.0;
+    patient.respirationRate = 16.0;
+    patient.bodyTemperature = 37.0;
+    patient.oxygenSaturation = 98.0;
+    return patient;
+}
+
+void updatePatient(Patient& patient, double deltaTime_s) {
+    // Baseline healthy values
+    const double baseline_hr = 75.0;
+    const double baseline_bp_systolic = 120.0;
+    const double baseline_bp_diastolic = 80.0;
+    const double baseline_rr = 16.0;
+    const double baseline_temp = 37.0;
+    const double baseline_spo2 = 98.0;
+
+    // Reversion speed (how quickly vitals return to baseline)
+    const double theta = 0.1;
+
+    // Standard deviations for random fluctuations per second
+    const double hr_stddev = 0.1;
+    const double bp_stddev = 0.1;
+    const double rr_stddev = 0.05;
+    const double temp_stddev = 0.01;
+    const double spo2_stddev = 0.02;
+
+    // Update vitals using a mean-reverting model
+    patient.heartRate += theta * (baseline_hr - patient.heartRate) * deltaTime_s + getFluctuation(hr_stddev * deltaTime_s);
+    patient.bloodPressureSystolic += theta * (baseline_bp_systolic - patient.bloodPressureSystolic) * deltaTime_s + getFluctuation(bp_stddev * deltaTime_s);
+    patient.bloodPressureDiastolic += theta * (baseline_bp_diastolic - patient.bloodPressureDiastolic) * deltaTime_s + getFluctuation(bp_stddev * deltaTime_s);
+    patient.respirationRate += theta * (baseline_rr - patient.respirationRate) * deltaTime_s + getFluctuation(rr_stddev * deltaTime_s);
+    patient.bodyTemperature += theta * (baseline_temp - patient.bodyTemperature) * deltaTime_s + getFluctuation(temp_stddev * deltaTime_s);
+    patient.oxygenSaturation += theta * (baseline_spo2 - patient.oxygenSaturation) * deltaTime_s + getFluctuation(spo2_stddev * deltaTime_s);
+
+    // Clamp values to within healthy physiological ranges
+    patient.heartRate = std::clamp(patient.heartRate, 60.0, 100.0);
+    patient.bloodPressureSystolic = std::clamp(patient.bloodPressureSystolic, 90.0, 120.0);
+    patient.bloodPressureDiastolic = std::clamp(patient.bloodPressureDiastolic, 60.0, 80.0);
+    patient.respirationRate = std::clamp(patient.respirationRate, 12.0, 20.0);
+    patient.bodyTemperature = std::clamp(patient.bodyTemperature, 36.5, 37.3);
+    patient.oxygenSaturation = std::clamp(patient.oxygenSaturation, 96.0, 100.0);
+}