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package jscl.math.operator;

import jscl.math.Generic;
import jscl.math.JsclInteger;
import jscl.math.NotIntegerException;
import jscl.math.Variable;
import jscl.mathml.MathML;

import javax.annotation.Nonnull;

public class Product extends Operator {

	public static final String NAME = "∏";

	public Product(Generic expression, Generic variable, Generic n1, Generic n2) {
		super(NAME, new Generic[]{expression, variable, n1, n2});
	}

	private Product(Generic parameters[]) {
		super(NAME, parameters);
	}

	@Override
	public int getMinParameters() {
		return 4;
	}

	public Generic selfExpand() {
		Variable variable = parameters[1].variableValue();
		try {
			int n1 = parameters[2].integerValue().intValue();
			int n2 = parameters[3].integerValue().intValue();
			Generic a = JsclInteger.valueOf(1);
			for (int i = n1; i <= n2; i++) {
				a = a.multiply(parameters[0].substitute(variable, JsclInteger.valueOf(i)));
			}
			return a;
		} catch (NotIntegerException e) {
		}
		return expressionValue();
	}

	@Nonnull
	@Override
	protected String formatUndefinedParameter(int i) {
		switch (i) {
			case 0:
				return "f(i)";
			case 1:
				return "i";
			case 2:
				return "from";
			case 3:
				return "to";
			default:
				return super.formatUndefinedParameter(i);
		}
	}

	public void toMathML(MathML element, Object data) {
		int exponent = data instanceof Integer ? ((Integer) data).intValue() : 1;
		if (exponent == 1) bodyToMathML(element);
		else {
			MathML e1 = element.element("msup");
			MathML e2 = element.element("mfenced");
			bodyToMathML(e2);
			e1.appendChild(e2);
			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 Product(parameters);
	}

	void bodyToMathML(MathML element) {
		MathML e1 = element.element("mrow");
		MathML e2 = element.element("munderover");
		MathML e3 = element.element("mo");
		e3.appendChild(element.text("\u220F"));
		e2.appendChild(e3);
		e3 = element.element("mrow");
		parameters[1].toMathML(e3, null);
		MathML e4 = element.element("mo");
		e4.appendChild(element.text("="));
		e3.appendChild(e4);
		parameters[2].toMathML(e3, null);
		e2.appendChild(e3);
		parameters[3].toMathML(e2, null);
		e1.appendChild(e2);
		parameters[0].toMathML(e1, null);
		element.appendChild(e1);
	}

	@Nonnull
	public Variable newInstance() {
		return new Product(null, null, null, null);
	}
}