package calculator.functions;
   
   import java.math.BigDecimal;
   
   import calculator.Expression;
   import calculator.IllegalConstruction;
   import calculator.atoms.Complex;
   import calculator.atoms.IntegerAtom;
   import calculator.atoms.Rationnal;
  import calculator.atoms.Real;
  import ch.obermuhlner.math.big.BigDecimalMath;
  
  /**
   * This class represents the arithmetic unary operation "acos".
   * The class extends an abstract superclass UnaryFunction.
   */
  public final class Arccosinus extends UnaryFunction {
  
  	/**
  	 * Class constructor specifying an Expression to apply the arccosine function.
  	 *
  	 * @param arg The Expression to apply the operation on
  	 * @throws IllegalConstruction If a null argument is passed
  	 */
  	public Arccosinus(Expression arg) throws IllegalConstruction {
  		super(arg);
  		symbol = "acos";
  	}
  
  	@Override
  	public Real op(Real r) {
  		if (r.isNan() || r.isMinusInf() || r.isPlusInf()) {
  			return Real.nan();
  		}
  
  		if (r.getValue().compareTo(new BigDecimal(-1)) <= -1 // r < -1
  				|| r.getValue().compareTo(new BigDecimal(1)) >= 1) // r > 1
  			return Real.nan();
  
  		BigDecimal acosVal = BigDecimalMath.acos(r.getValue(), Real.context);
  		return new Real(acosVal);
  	}
  
  	@Override
  	public IntegerAtom op(IntegerAtom i) {
  		double acosVal = Math.acos(i.getValue());
  		return new IntegerAtom((int) Math.round(acosVal));
  	}
  
  	@Override
  	public Complex op(Complex c) {
  		org.apache.commons.numbers.complex.Complex val = c.getValue().acos();
  		return new Complex(val);
  	}
  
  	@Override
  	public Rationnal op(Rationnal q) {
  		double val = q.getValue().doubleValue();
  		if (val < -1.0 || val > 1.0) {
  			throw new ArithmeticException("Domain error: Arccosinus requires input in the range [-1, 1].");
  		}
  		double acosVal = Math.acos(val);
  		return new Rationnal(org.apache.commons.numbers.fraction.Fraction.from(acosVal));
  	}
  }