/*
 
* Copyright (c) 2016, Metron, Inc.
 
* All rights reserved.
 
*
 
* Redistribution and use in source and binary forms, with or without
 
* modification, are permitted provided that the following conditions are met:
 
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* Redistributions of source code must retain the above copyright
 
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notice, this list of conditions and the following disclaimer.
 
*
     
* Redistributions in binary form must reproduce the above copyright
 
*
       
notice, this list of conditions and the following disclaimer in the
 
*
       
documentation and/or other materials provided with the distribution.
 
*
     
* Neither the name of Metron, Inc. nor the
 
*
       
names of its contributors may be used to endorse or promote products
 
*
       
derived from this software without specific prior written permission.
 
*
 
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 
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package com.metsci.glimpse.dnc;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.function.Supplier;

import com.google.common.collect.ImmutableList;
import com.metsci.glimpse.dnc.DncChunks.DncChunkKey;
import com.metsci.glimpse.util.geo.LatLonGeo;

public class DncAreaFeature extends DncFeature
{

    
protected final Supplier<List<List<LatLonGeo>>> ringsLoader;
    
protected final Object ringsMutex;
    
protected volatile ImmutableList<ImmutableList<LatLonGeo>> rings;


    
public DncAreaFeature( DncChunkKey chunkKey, int featureNum, String fcode, Supplier<Map<String,Object>> attrsLoader, Supplier<List<List<LatLonGeo>>> ringsLoader )
    
{
        
super( chunkKey, featureNum, fcode, attrsLoader );

        
this.ringsLoader = ringsLoader;
        
this.ringsMutex = new Object( );
        
this.rings = null;
    
}

    
public ImmutableList<ImmutableList<LatLonGeo>> getRings( )
    
{
        
// Field is volatile, and only assigned once
        
if ( rings != null )
        
{
            
return rings;
        
}
        
else
        
{
            
synchronized ( ringsMutex )
            
{
                
if ( rings == null )
                
{
                    
rings = immutableCopy( ringsLoader.get( ) );
                
}
                
return rings;
            
}
        
}
    
}

    
protected static <V> ImmutableList<ImmutableList<V>> immutableCopy( List<List<V>> lists )
    
{
        
List<ImmutableList<V>> listsCopy = new ArrayList<>( );
        
for ( List<V> list : lists )
        
{
            
listsCopy.add( ImmutableList.copyOf( list ) );
        
}
        
return ImmutableList.copyOf( listsCopy );
    
}

}