/* 
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.statistics;

import java.util.ArrayList;

import org.geogebra.common.kernel.Construction;
import org.geogebra.common.kernel.algos.AlgoElement;
import org.geogebra.common.kernel.commands.Commands;
import org.geogebra.common.kernel.geos.GeoBoolean;
import org.geogebra.common.kernel.geos.GeoElement;
import org.geogebra.common.kernel.geos.GeoList;
import org.geogebra.common.kernel.geos.GeoNumberValue;

/**
 * Sample from a list. Adapted from AlgoMode
 * 
 * @author Michael Borcherds
 */

public class AlgoSample extends AlgoElement {

	// maximum size for a sample
	private static int SAMPLE_MAXSIZE = 10000;

	private GeoList inputList; // input
	private GeoBoolean replacement;
	private GeoNumberValue num;
	private GeoList outputList; // output

	public AlgoSample(Construction cons, String label, GeoList inputList,
			GeoNumberValue num, GeoBoolean replacement) {
		super(cons);
		this.inputList = inputList;
		this.replacement = replacement;
		this.num = num;

		outputList = new GeoList(cons);

		setInputOutput();
		compute();
		outputList.setLabel(label);
	}

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

	@Override
	protected void setInputOutput() {
		input = new GeoElement[replacement == null ? 2 : 3];
		input[0] = inputList;
		input[1] = num.toGeoElement();
		if (replacement != null) {
			input[2] = replacement;
		}

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

	public GeoList getResult() {
		return outputList;
	}

	@Override
	public final void compute() {

		int size = (int) num.getDouble();
		if (!inputList.isDefined() || num.getDouble() < 1
				|| num.getDouble() > SAMPLE_MAXSIZE) {
			outputList.setUndefined();
			return;
		}

		boolean withReplacement = true;

		if (replacement != null) {
			withReplacement = replacement.getBoolean();
		}

		int inputListSize = inputList.size();

		outputList.clear();

		if (withReplacement) {
			for (int i = 0; i < size; i++) {
				GeoElement geo;

				geo = inputList.get((int) Math
						.floor(cons.getApplication().getRandomNumber()
								* inputListSize));
				setListElement(i, geo);
			}
		} else {

			// sampling without replacement

			if (size > inputListSize) {
				outputList.setUndefined();
				return;
			}

			ArrayList<GeoElement> list = new ArrayList<GeoElement>();

			// copy inputList into arraylist
			for (int i = 0; i < inputListSize; i++) {
				list.add(inputList.get(i));
			}

			// copy the geos back into a GeoList in a random order
			for (int i = 0; i < size; i++) {
				int pos = (int) Math
						.floor(cons.getApplication().getRandomNumber()
								* (inputListSize - i));
				outputList.add(list.get(pos));
				list.remove(pos);
			}

		}

		outputList.setDefined(true);

	}

	// copied from AlgoIterationList.java
	// TODO should it be centralised?
	private void setListElement(int index, GeoElement geo) {
		GeoElement listElement;
		if (index < outputList.getCacheSize()) {
			// use existing list element
			listElement = outputList.getCached(index);
			listElement.set(geo);
		} else {
			// create a new list element
			listElement = geo.copy();
			listElement.setParentAlgorithm(this);
			listElement.setConstructionDefaults();
			listElement.setUseVisualDefaults(false);
		}

		outputList.add(listElement);

	}

}