patterns/observer/heatindexdisplay.d

module observer.heatindexdisplay;

import observer.displayelement;
import observer.observer;
import observer.weatherdata;
import std.stdio : writeln;

class HeatIndexDisplay : Observer, DisplayElement
{
private:
    float heatIndex;
    WeatherData weatherData;

    float computeHeatIndex(float t, float 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:
    this(WeatherData weatherData)
    {
        this.weatherData = weatherData;
        weatherData.registerObserver(this);
    }

    override void update()
    {
        this.heatIndex = computeHeatIndex(weatherData.getTemperature, weatherData.getHumidity);
        display();
    }

    override void display()
    {
        writeln("Heat index is ", heatIndex);
    }
}