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package org.nuiton.math.matrix;

/*
 * #%L
 * Nuiton Matrix :: API
 * %%
 * Copyright (C) 2004 - 2014 CodeLutin
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */


import java.util.concurrent.atomic.AtomicInteger;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 *
 * Cette classe encapsule un Vector et permet de l'initialiser reellement que
 * lorsqu'on souhaite modifier une valeur. Cela permet de ne pas initialise
 * d'enorme tableau s'il n'y en a pas besoin. Chaque lazy est initialisé avec
 * un Vector non initialise, lorsque l'on fait un paste, si le vector a partir
 * duquel on fait le paste est aussi un lazy, alors on partage le backend
 * jusqu'a ce qu'un des deux vector veuille modifier une de ses valeurs.
 *
 * @author poussin
 * @version $Revision$
 *
 * Last update: $Date$
 * by : $Author$
 */
public class LazyVector implements Vector {

    /** to use log facility, just put in your code: log.info(\"...\"); */
    static private Log log = LogFactory.getLog(LazyVector.class);

    protected boolean isInitBackend = false;
    /** reel backend, not initialized since not necessary */
    protected Vector backend;
    protected AtomicInteger users = new AtomicInteger();

    protected long capacity;

    /**
     * Create new lazy, with initialized backend
     * @param backend
     */
    public LazyVector(Vector backend) {
        this.isInitBackend = true;
        this.backend = backend;
        this.capacity = backend.size();
    }

    /**
     * Create new lazy with not initialized backend
     *
     * @param backend
     * @param capacity
     */
    public LazyVector(Vector backend, long capacity) {
        this.backend = backend;
        this.capacity = capacity;
    }

    @Override
    public void init(long capacity) {
    }

    @Override
    public String getInfo() {
        return "Lazy vector: " + (isInitBackend?backend.getInfo():"no backend");
    }

    @Override
    public long getNumberOfAssignedValue() {
        return isInitBackend?backend.getNumberOfAssignedValue():0;
    }

    @Override
    public double getMaxOccurence() {
        return getMaxOccurrence();
    }

    @Override
    public double getMaxOccurrence() {
        double result = 0;
        if (isInitBackend) {
            result = backend.getMaxOccurrence();
        }
        return result;
    }

    @Override
    public double getValue(long pos) {
        double result = 0;
        if (isInitBackend) {
            result = backend.getValue(pos);
        }
        return result;
    }

    @Override
    public void setValue(long pos, double value) {
        prepareBackendForModification();
        backend.setValue(pos, value);
    }

    @Override
    public long size() {
        return capacity;
    }

    @Override
    public boolean isImplementedPaste(Vector v) {
        return true;
    }

    @Override
    public boolean isImplementedAdd(Vector v) {
        return backend.isImplementedAdd(v);
    }

    @Override
    public boolean isImplementedMinus(Vector v) {
        return backend.isImplementedMinus(v);
    }

    @Override
    public boolean isImplementedMap() {
        return backend.isImplementedMap();
    }

    @Override
    public void paste(Vector source) {
        if (!isInitBackend && source instanceof LazyVector && ((LazyVector)source).size() == size()) {
            LazyVector l = ((LazyVector)source);

            l.users.incrementAndGet();
            users = l.users;
            isInitBackend = l.isInitBackend;
            backend = l.backend;
        } else {
            // initialized or already has copy, we need to paste, and not just
            // reassign copy variable, in case of source Vector is smaller than copy
            prepareBackendForModification();
            pasteToBackend(backend, source);
        }
    }

    @Override
    public void add(Vector v) {
        prepareBackendForModification();
        backend.add(v);
    }

    @Override
    public void minus(Vector v) {
        prepareBackendForModification();
        backend.minus(v);
    }

    @Override
    public void map(MapFunction f) {
        prepareBackendForModification();
        backend.map(f);
    }

    @Override
    public boolean equals(Object o) {
        boolean result = false;
        if (o instanceof Vector) {
            Vector v = (Vector)o;
            if (size() == v.size()) {
                if (isInitBackend) {
                    result = v.equals(backend);
                } else if (v instanceof LazyVector && !((LazyVector)v).isInitBackend) {
                    result = true;
                } else {
                    result = v.equals(this);
                }
            }
        }
        return result;
    }

    @Override
    public int hashCode() {
        return Long.hashCode(size());
    }

    protected void prepareBackendForModification() {
        if (users.get() > 0) {
            try {
                // others LazyVector use this backend, create new backend copy
                Vector copy = backend.getClass().newInstance();
                if (isInitBackend) {
                    copy.init(capacity);
                    pasteToBackend(copy, backend);
                }
                backend = copy;
                users.decrementAndGet();
                users = new AtomicInteger();
            } catch (Exception eee) {
                throw new MatrixException("Can't create new backend Vector", eee);
            }
        }
        
        if (!isInitBackend) {
            backend.init(capacity);
            isInitBackend = true;
        }
    }

    /**
     * Before call this method backend, must be initialized
     * @param target
     * @param copy
     */
    protected void pasteToBackend(Vector target, Vector copy) {
        if (target.isImplementedPaste(copy)) {
            target.paste(copy);
        } else {
            for (long i=0, max=Math.min(size(), copy.size()); i