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/*
 * Copyright (C) 2012 United States Government as represented by the Administrator of the
 * National Aeronautics and Space Administration.
 * All Rights Reserved.
 */

package gov.nasa.worldwind.ogc.collada;

import gov.nasa.worldwind.util.WWUtil;
import gov.nasa.worldwind.util.xml.XMLEventParserContext;

import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.*;
import java.util.*;

/**
 * Represents the COLLADA accessor element and provides access to its contents.
 *
 * @author pabercrombie
 * @version $Id: ColladaAccessor.java 654 2012-06-25 04:15:52Z pabercrombie $
 */
public class ColladaAccessor extends ColladaAbstractObject
{
    /** Parameters used by this accessor. */
    protected List params = new ArrayList();

    /**
     * Create a new accessor.
     *
     * @param ns Namespace.
     */
    public ColladaAccessor(String ns)
    {
        super(ns);
    }

    /**
     * Get the identifier of this accessor's source.
     *
     * @return Accessor source.
     */
    public String getSource()
    {
        return (String) this.getField("source");
    }

    /**
     * Indicates the number of elements that this accessor can read. An element is a tuple whose length depends on the
     * number of accessor parameters. For example, if the accessor has three float parameters, than an element is three
     * floats, and this method returns the number of float triplets.
     *
     * @return Number of elements that the accessor can read.
     */
    public int getCount()
    {
        Integer count = (Integer) this.getField("count");
        return count != null ? count : 0;
    }

    /**
     * Indicates the offset into the source data at which the accessor starts reading. Returns zero if this attribute
     * has not been set.
     *
     * @return Offset at which the accessor starts reading.
     */
    public int getOffset()
    {
        Integer offset = (Integer) this.getField("offset");
        return offset != null ? offset : 0;
    }

    /**
     * Indicates the number of tokens in the source data to advance between elements.
     *
     * @return Offset at which the accessor starts reading.
     */
    public int getStride()
    {
        Integer stride = (Integer) this.getField("stride");
        return stride != null ? stride : 1;
    }

    /**
     * Indicates the number of tokens that the accessor can read. For example, if the accessor reads floats, then this
     * method returns the number of floats that the accessor can read.
     *
     * @return Number of tokens that the accessor can read.
     */
    public int size()
    {
        int count = 0;
        for (ColladaParam param : this.params)
        {
            if (!WWUtil.isEmpty(param.getName()))
                count += 1;
        }
        return count * this.getCount();
    }

    /**
     * Copies this accessor's content to a buffer. This method begins writing data at the buffer's current position, and
     * continues until the accessor is out of data.
     *
     * @return Array of floats. May return null if the data source is not available.
     */
    public float[] getFloats()
    {
        String source = this.getSource();
        if (source == null)
            return null;

        Object o = this.getRoot().resolveReference(source);
        if (o == null)
            return null; // Source not available

        // TODO: COLLADA spec says source can be a non-COLLADA document (pg 5-5)
        if (!(o instanceof ColladaFloatArray))
            return null;

        float[] floats = ((ColladaFloatArray) o).getFloats();
        if (floats == null)
            return null;

        // Skip values before the start offset
        int index = this.getOffset();

        int strideSkip = 0;
        int stride = this.getStride();
        if (stride > this.params.size())
            strideSkip = stride - this.params.size();

        float[] result = new float[this.size()];
        int ri = 0;

        for (int i = 0; i < this.getCount() && index < floats.length; i++)
        {
            for (ColladaParam param : this.params)
            {
                if (index >= floats.length)
                    break;

                // Parse the next value and add to the buffer. Skip unnamed parameters.
                // See COLLADA spec pg 5-5.
                if (!WWUtil.isEmpty(param.getName()))
                    result[ri++] = floats[index];

                index += 1;
            }

            // Skip elements up to the stride.
            index += strideSkip;
        }

        return result;
    }

    /** {@inheritDoc} */
    @Override
    public void setField(String keyName, Object value)
    {
        if (keyName.equals("param"))
            this.params.add((ColladaParam) value);
        else
            super.setField(keyName, value);
    }

    /** {@inheritDoc} */
    @Override
    protected void doAddEventAttribute(Attribute attr, XMLEventParserContext ctx, XMLEvent event, Object... args)
        throws XMLStreamException
    {
        String localName = attr.getName().getLocalPart();
        boolean isIntField = "count".equals(localName) || "offset".equals(localName) || "stride".equals(localName);

        if (isIntField)
            this.setField(localName, WWUtil.makeInteger(attr.getValue()));
        else
            super.doAddEventAttribute(attr, ctx, event, args);
    }
}