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package jscl.math.operator;

import jscl.math.*;
import jscl.math.function.Pow;
import jscl.mathml.MathML;
import jscl.text.ParserUtils;

import javax.annotation.Nonnull;

/**
 * User: serso
 * Date: 12/15/11
 * Time: 10:32 PM
 */
public class DoubleFactorial extends PostfixFunction {

	public static final String NAME = "!!";

	public DoubleFactorial(Generic expression) {
		super(NAME, new Generic[]{expression});
	}

	private DoubleFactorial(Generic[] parameter) {
		super(NAME, ParserUtils.copyOf(parameter, 1));
	}

	@Override
	public int getMinParameters() {
		return 1;
	}

	public Generic selfExpand() {
		return expressionValue();
	}

	@Override
	public Generic selfNumeric() {
		final Generic parameter = parameters[0];
		if (parameter.isInteger()) {
			int n = parameter.integerValue().intValue();
			if (n < 0) {
				//return expressionValue();
				throw new ArithmeticException("Cannot take factorial from negative integer!");
			}

			Generic result;
			if (n == 0) {
				result = JsclInteger.valueOf(1);
			} else {
				int i;
				if (n % 2 != 0) {
					// odd
					i = 1;
				} else {
					// even
					i = 2;
				}

				result = JsclInteger.valueOf(i);
				for (; i < n; i += 2) {
					ParserUtils.checkInterruption();
					result = result.multiply(JsclInteger.valueOf(i + 2));
				}
			}

			if (result instanceof JsclInteger) {
				return new NumericWrapper(((JsclInteger) result));
			} else {
				throw new NotIntegerException();
			}

		} else {
			throw new NotIntegerException();
		}
	}

	public void toMathML(MathML element, Object data) {
		int exponent = data instanceof Integer ? (Integer) data : 1;
		if (exponent == 1) bodyToMathML(element);
		else {
			MathML e1 = element.element("msup");
			bodyToMathML(e1);
			MathML e2 = element.element("mn");
			e2.appendChild(element.text(String.valueOf(exponent)));
			e1.appendChild(e2);
			element.appendChild(e1);
		}
	}

	@Nonnull
	@Override
	public Operator newInstance(@Nonnull Generic[] parameters) {
		return new DoubleFactorial(parameters);
	}

	void bodyToMathML(MathML element) {
		MathML e1 = element.element("mrow");
		try {
			JsclInteger en = parameters[0].integerValue();
			en.toMathML(e1, null);
		} catch (NotIntegerException e) {
			try {
				Variable v = parameters[0].variableValue();
				if (v instanceof Pow) {
					GenericVariable.valueOf(parameters[0]).toMathML(e1, null);
				} else v.toMathML(e1, null);
			} catch (NotVariableException e2) {
				GenericVariable.valueOf(parameters[0]).toMathML(e1, null);
			}
		}
		MathML e2 = element.element("mo");
		e2.appendChild(element.text("!!"));
		e1.appendChild(e2);
		element.appendChild(e1);
	}

	@Nonnull
	public Variable newInstance() {
		return new DoubleFactorial((Generic) null);
	}
}