Ch2Weather first version

Ch2Weather/Weather.cs

@@ -0,0 +1,95 @@
+namespace Ch2Weather;
+
+public record struct WeatherRecord(double Temperature, double Humidity, double Pressure);
+
+public interface IWeatherSubject {
+    void Subscribe(IWeatherObserver o);
+    void Unsubscribe(IWeatherObserver o);
+    void NotifyObservers();
+}
+
+public interface IWeatherObserver {
+    void Update(WeatherRecord wr);
+}
+
+public interface IWeatherDisplay {
+    void Display();
+}
+
+public class WeatherData(WeatherRecord weatherRecord) : IWeatherSubject {
+    private readonly List<IWeatherObserver> _observers = [];
+    private WeatherRecord _weatherRecord = weatherRecord;
+
+    public WeatherRecord WeatherRecord {
+        get => _weatherRecord;
+        set {
+            _weatherRecord = value;
+            NotifyObservers();
+        }
+    }
+
+    public void Subscribe(IWeatherObserver o) {
+        _observers.Add(o);
+    }
+
+    public void Unsubscribe(IWeatherObserver o) {
+        _observers.Remove(o);
+    }
+
+    public void NotifyObservers() {
+        foreach (var o in _observers) {
+            o.Update(_weatherRecord);
+        }
+    }
+}
+
+public class CurrentConditionsDisplay : IWeatherObserver, IWeatherDisplay {
+    private IWeatherSubject _subject;
+    private double _temperature = 0;
+    private double _humidity = 0;
+    
+    public CurrentConditionsDisplay(IWeatherSubject subject) {
+        _subject = subject;
+        subject.Subscribe(this);
+    }
+
+    public void Update(WeatherRecord wr) {
+        _temperature = wr.Temperature;
+        _humidity = wr.Humidity;
+        Display();
+    }
+
+    public void Display() {
+        Console.WriteLine($"Current conditions: {_temperature}C degrees and {_humidity}% humidity.");
+    }
+}
+
+public class HeatIndexDisplay : IWeatherObserver, IWeatherDisplay {
+    private IWeatherSubject _subject;
+    private WeatherRecord _weatherRecord = new WeatherRecord(0,0,0);
+
+    public HeatIndexDisplay(IWeatherSubject subject) {
+        _subject = subject;
+        subject.Subscribe(this);
+    }
+    
+    private double ComputeHeatIndex(double t, double rh) {
+        return (16.923 + (0.185212 * t) + (5.37941 * rh) - (0.100254 * t * rh) +
+                (0.00941695 * (t * t)) + (0.00728898 * (rh * rh)) +
+                (0.000345372 * (t * t * rh)) - (0.000814971 * (t * rh * rh)) +
+                (0.0000102102 * (t * t * rh * rh)) - (0.000038646 * (t * t * t)) + (0.0000291583 *
+                    (rh * rh * rh)) + (0.00000142721 * (t * t * t * rh)) +
+                (0.000000197483 * (t * rh * rh * rh)) - (0.0000000218429 * (t * t * t * rh * rh)) +
+                0.000000000843296 * (t * t * rh * rh * rh)) -
+               (0.0000000000481975 * (t * t * t * rh * rh * rh));
+    }  
+    public void Update(WeatherRecord wr) {
+        _weatherRecord = wr;
+        Display();
+    }
+
+    public void Display() {
+        var heatIndex = ComputeHeatIndex(_weatherRecord.Temperature, _weatherRecord.Humidity);
+        Console.WriteLine($"Heat Index is {heatIndex}");
+    }
+}