WeightedRandomSpaceGen.java

package matteroverdrive.starmap;

import matteroverdrive.starmap.data.SpaceBody;
import matteroverdrive.starmap.gen.ISpaceBodyGen;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Random;

/**
 * Created by Simeon on 6/21/2015.
 */
public class WeightedRandomSpaceGen<T extends SpaceBody>
{
    Random random;
    List<ISpaceBodyGen<T>> collection;

    public WeightedRandomSpaceGen(Random random)
    {
        collection = new ArrayList<ISpaceBodyGen<T>>();
        this.random = random;
    }

    public ISpaceBodyGen<T> getRandomGen(T spaceBody)
    {
        return getRandomGen(collection,spaceBody,random);
    }

    public ISpaceBodyGen<T> getRandomGen(T spaceBody,Random random)
    {
        return getRandomGen(collection,spaceBody,random);
    }

    public ISpaceBodyGen<T> getRandomGen(Collection<ISpaceBodyGen<T>> collection,T spaceBody,Random rangomGen)
    {
        // Compute the total weight of all items together
        double totalWeight = 0.0d;
        for (ISpaceBodyGen<T> i : collection)
        {
            totalWeight += i.getWeight(spaceBody);
        }
        // Now choose a random item
        ISpaceBodyGen gen = null;
        double random = rangomGen.nextDouble() * totalWeight;
        for (ISpaceBodyGen<T> i : collection)
        {
            random -= i.getWeight(spaceBody);
            if (random <= 0.0d)
            {
                gen = i;
                break;
            }
        }
        return gen;
    }

    public ISpaceBodyGen<T> getGenAt(int index)
    {
        return collection.get(index);
    }

    public void addGen(ISpaceBodyGen<T> gen)
    {
        collection.add(gen);
    }

    public <K extends ISpaceBodyGen<T>> void addGens(Collection<K> gens)
    {
        collection.addAll(gens);
    }

    public List<ISpaceBodyGen<T>> getGens(){return collection;}
}