package cubicchunks.util;

import java.util.function.ToDoubleFunction;
import java.util.function.ToIntFunction;

public class HashCacheDoubles<K> {
    private final double[] cache;
    private final K[] keys;
    private final ToIntFunction<K> hashFunction;
    private final ToDoubleFunction<K> source;

    @SuppressWarnings("uncecked")
    private HashCacheDoubles(int size, ToIntFunction<K> hashCode, ToDoubleFunction<K> source) {
        this.cache = new double[size];
        this.keys =  (K[]) new Object[size];
        this.hashFunction = hashCode;
        this.source = source;
    }

    public double get(K key) {
        int index = index(hashFunction.applyAsInt(key));
        if (!key.equals(keys[index])) {
            keys[index] = key;
            cache[index] = source.applyAsDouble(key);
        }
        return cache[index];
    }

    private int index(int hash) {
        return Math.floorMod(hash, cache.length);
    }

    public static <K> HashCacheDoubles<K> create(int size, ToDoubleFunction<K> source) {
        return create(size, k->k.hashCode(), source);
    }

    public static <K> HashCacheDoubles<K> create(int size, ToIntFunction<K> hashCode, ToDoubleFunction<K> source) {
        return new HashCacheDoubles<K>(size, hashCode, source);
    }
}