import java.awt.*;

public class ObsMath {

   public static final int    PAD   = -1000;


   public static int heatStressTempCalc (int tdry, int RH, int statHeight) {
      // Calculates heat stress temperature (deg. C) from
      // dry temperature (deg. C) and relative humidity (%)
      // Uses station height for station level pressure calculation

      int twet = wetTempCalc (tdry, RH, statHeight);
      return (int) Math.round ((tdry + twet) / 2.);
   }

   public static int heatStressIndexCalc (int temp) {

      // Calculates heat stress index from heat stress temperature

      int index = PAD;
      if (temp > 22 && temp <= 24)
     index = 1;
      else if (temp > 24 && temp <= 26)
     index = 2;
      else if (temp > 26 && temp <= 28)
     index = 3;
      else if (temp > 28 && temp <= 30)
     index = 4;
      else if (temp > 30)
     index = 5;

      return index;
   }


   private static int wetTempCalc (int tdry, int RH, int statHeight) {
      // Calculates wet temperature (deg. C) from dry temperature (deg. C) and relative humidity (%)
      // Uses station height for station level pressure calculation

      double twx, twn, twi=99999., EsTw, Ei, Ri=99999.;
      double pst = 101.3 * Math.pow (( 293. - 0.0065 * statHeight )/293., 5.26);
      double Psych = 0.000792 * pst;
      double EsTd = 0.611 * Math.exp( 17.27 * tdry / (237.3 + tdry));
      double R = RH / 100.;
      double E = R * EsTd;
      if ( Math.abs (E-0.611) < 0.0022 )
         twn = 0.;
      else
         twn = 13.7406 / ( 1./Math.log (E/.611) - .05791 );
      twx = tdry;

      while (Math.abs (R - Ri) >= 0.005) {
     twi = (twn + twx)/2.;
     EsTw = 0.611 * Math.exp( 17.27 * twi / (237.3 + twi) );
     Ei = EsTw - Psych * (tdry - twi) * ( 1 + 0.00115*twi);
     Ri = Ei / EsTd ;
     if ( Ri > R )
        twx = twi;
     else
        twn = twi;
      }

      return (int) Math.round (twi);
   }

}