/* 
GeoGebra - Dynamic Mathematics for Everyone
http://www.geogebra.org

This file is part of GeoGebra.

This program is free software; you can redistribute it and/or modify it 
under the terms of the GNU General Public License as published by 
the Free Software Foundation.

 */

package org.geogebra.common.kernel.cas;

import org.geogebra.common.kernel.Construction;
import org.geogebra.common.kernel.algos.AlgoElement;
import org.geogebra.common.kernel.arithmetic.Function;
import org.geogebra.common.kernel.arithmetic.PolyFunction;
import org.geogebra.common.kernel.commands.Commands;
import org.geogebra.common.kernel.geos.GeoElement;
import org.geogebra.common.kernel.geos.GeoFunction;
import org.geogebra.common.kernel.geos.GeoList;
import org.geogebra.common.kernel.geos.GeoNumeric;
import org.geogebra.common.kernel.statistics.FitAlgo;

/**
 * returns coefficients of a Polynomial as a list
 * 
 * Uses CAS sometimes, eg Coefficients[x^n] so needs "implements UsesCAS"
 * 
 * @author Michael Borcherds
 */
public class AlgoCoefficients extends AlgoElement implements UsesCAS {

	private GeoFunction f; // input
	private GeoList g; // output

	/**
	 * @param cons
	 *            construction
	 * @param label
	 *            label for output
	 * @param f
	 *            function
	 */
	public AlgoCoefficients(Construction cons, String label, GeoFunction f) {
		this(cons, f);
		g.setLabel(label);
	}

	/**
	 * @param cons
	 *            construction
	 * @param f
	 *            function
	 */
	public AlgoCoefficients(Construction cons, GeoFunction f) {
		super(cons);
		cons.addCASAlgo(this);
		this.f = f;

		g = new GeoList(cons);
		setInputOutput(); // for AlgoElement
		compute();
	}

	@Override
	public Commands getClassName() {
		return Commands.Coefficients;
	}

	// for AlgoElement
	@Override
	protected void setInputOutput() {
		input = new GeoElement[1];
		input[0] = f;

		setOutputLength(1);
		setOutput(0, g);
		setDependencies(); // done by AlgoElement
	}

	/**
	 * @return resulting function
	 */
	public GeoList getResult() {
		return g;
	}

	@Override
	public final void compute() {
		if (!f.isDefined()) {
			g.setUndefined();
			return;
		}

		Function inFun = f.getFunction();

		if (inFun.getExpression().isSecret()) {
			g.setUndefined();
			return;
		}

		// check if it's a polynomial & get coefficients
		PolyFunction poly = inFun.expandToPolyFunction(inFun.getExpression(),
				false, false);

		if (poly != null) {

			double[] coeffs = poly.getCoeffs();

			g.clear();
			g.setDefined(true);

			for (int i = coeffs.length - 1; i >= 0; i--) {
				g.add(new GeoNumeric(cons, coeffs[i]));
			}

			return;
		} else if (f.getParentAlgorithm() instanceof FitAlgo) {

			FitAlgo fitAlgo = (FitAlgo) f.getParentAlgorithm();

			double[] coeffs = fitAlgo.getCoeffs();

			g.clear();
			g.setDefined(true);

			for (int i = coeffs.length - 1; i >= 0; i--) {
				g.add(new GeoNumeric(cons, coeffs[i]));
			}

			return;

			// Log.debug(fitAlgo.P.getEntry(0,0)+" "+fitAlgo.P.getEntry(0,1));
		}

		// not a polynomial
		g.setUndefined();
	}

}