package org.matheclipse.core.reflection.system;

import org.matheclipse.core.builtin.function.NumericQ;
import org.matheclipse.core.eval.exception.Validate;
import org.matheclipse.core.eval.interfaces.IFunctionEvaluator;
import org.matheclipse.core.expression.F;
import org.matheclipse.core.interfaces.IAST;
import org.matheclipse.core.interfaces.IComplex;
import org.matheclipse.core.interfaces.IComplexNum;
import org.matheclipse.core.interfaces.IExpr;
import org.matheclipse.core.interfaces.INumber;
import org.matheclipse.core.interfaces.ISignedNumber;
import org.matheclipse.core.interfaces.ISymbol;

/**
 * Gets the sign value of a number. See Wikipedia - Sign
 * function
 * 
 */
public class Sign implements IFunctionEvaluator {

	public Sign() {
	}

	public IExpr evaluate(final IAST ast) {
		Validate.checkSize(ast, 2);

		IExpr arg1 = ast.arg1();
		if (arg1.isNumber()) {
			return numberSign((INumber) arg1);
		}
		if (NumericQ.CONST.apply(arg1)) {
			IExpr result = F.evaln(arg1);
			if (result.isSignedNumber()) {
				return numberSign((INumber) result);
			}
		}
		return null;
	}

	public IExpr numberSign(INumber arg1) {
		if (arg1.isSignedNumber()) {
			final int signum = ((ISignedNumber) arg1).sign();
			return F.integer(signum);
		} else if (arg1.isComplex()) {
			IComplex c = (IComplex) arg1;
			return F.Times(c, F.Power(c.eabs(), F.CN1));
		} else if (arg1.isComplexNumeric()) {
			IComplexNum c = (IComplexNum) arg1;
			return c.divide(F.num(c.dabs()));
		}
		return null;
	}

	public IExpr numericEval(final IAST ast) {
		return evaluate(ast);
	}

	public void setUp(final ISymbol symbol) {
		symbol.setAttributes(ISymbol.LISTABLE);
	}

}