package net.minecraft.util.random;

import java.util.List;
import java.util.Optional;
import java.util.function.ToIntFunction;
import net.minecraft.util.RandomSource;
import net.minecraft.util.Util;

public class WeightedRandom {
	private WeightedRandom() {
	}

	public static <T> int getTotalWeight(final List<T> items, final ToIntFunction<T> weightGetter) {
		long totalWeight = 0L;

		for (T item : items) {
			totalWeight += weightGetter.applyAsInt(item);
		}

		if (totalWeight > 2147483647L) {
			throw new IllegalArgumentException("Sum of weights must be <= 2147483647");
		} else {
			return (int)totalWeight;
		}
	}

	public static <T> Optional<T> getRandomItem(final RandomSource random, final List<T> items, final int totalWeight, final ToIntFunction<T> weightGetter) {
		if (totalWeight < 0) {
			throw (IllegalArgumentException)Util.pauseInIde((T)(new IllegalArgumentException("Negative total weight in getRandomItem")));
		} else if (totalWeight == 0) {
			return Optional.empty();
		} else {
			int selection = random.nextInt(totalWeight);
			return getWeightedItem(items, selection, weightGetter);
		}
	}

	public static <T> Optional<T> getWeightedItem(final List<T> items, int index, final ToIntFunction<T> weightGetter) {
		for (T item : items) {
			index -= weightGetter.applyAsInt(item);
			if (index < 0) {
				return Optional.of(item);
			}
		}

		return Optional.empty();
	}

	public static <T> Optional<T> getRandomItem(final RandomSource random, final List<T> items, final ToIntFunction<T> weightGetter) {
		return getRandomItem(random, items, getTotalWeight(items, weightGetter), weightGetter);
	}
}