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Datastructures and utility classes for non-negative integers
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/*
 * Copyright (C) 2017 Tobias Meggendorfer
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */

package de.tum.in.naturals.bitset;

import com.zaxxer.sparsebits.SparseBitSet;
import de.tum.in.naturals.Indices;
import de.tum.in.naturals.set.NatBitSet;
import de.tum.in.naturals.set.NatBitSets;
import it.unimi.dsi.fastutil.ints.IntIterable;
import it.unimi.dsi.fastutil.ints.IntIterator;
import it.unimi.dsi.fastutil.ints.IntSortedSet;
import java.util.BitSet;
import java.util.PrimitiveIterator;
import java.util.Set;
import java.util.function.IntConsumer;

/**
 * Utility class to help interacting with {@link BitSet}.
 */
public final class BitSets {
    private BitSets() {}

    public static BitSet of() {
        return new BitSet(0);
    }

    public static BitSet of(int index) {
        BitSet bitSet = new BitSet(index + 1);
        bitSet.set(index);
        return bitSet;
    }

    public static BitSet of(int... indices) {
        BitSet bitSet = new BitSet();
        for (int index : indices) {
            bitSet.set(index);
        }
        return bitSet;
    }

    public static BitSet of(IntIterable iterable) {
        if (iterable instanceof NatBitSet) {
            return NatBitSets.toBitSet((NatBitSet) iterable);
        }

        BitSet bitSet;
        if (iterable instanceof IntSortedSet) {
            IntSortedSet sortedSet = (IntSortedSet) iterable;
            if (sortedSet.comparator() == null) {
                bitSet = new BitSet(sortedSet.lastInt() + 1);
            } else {
                bitSet = new BitSet();
            }
        } else {
            bitSet = new BitSet();
        }
        iterable.forEach((IntConsumer) bitSet::set);
        return bitSet;
    }

    public static BitSet of(Iterable iterable) {
        if (iterable instanceof IntIterable) {
            return of((IntIterable) iterable);
        }

        BitSet bitSet = new BitSet();
        for (Integer integer : iterable) {
            bitSet.set(integer);
        }
        return bitSet;
    }

    public static BitSet of(PrimitiveIterator.OfInt iterator) {
        BitSet bitSet = new BitSet();
        iterator.forEachRemaining((IntConsumer) bitSet::set);
        return bitSet;
    }

    public static BitSet of(boolean... indices) {
        BitSet bitSet = new BitSet(indices.length);
        Indices.forEach(indices, bitSet::set);
        return bitSet;
    }

    public static BitSet of(SparseBitSet sparseBitSet) {
        BitSet bitSet = new BitSet(sparseBitSet.length());
        SparseBitSets.forEach(sparseBitSet, bitSet::set);
        return bitSet;
    }

    public static BitSet copyOf(BitSet bitset) {
        return (BitSet) bitset.clone();
    }

    public static IntIterator complementIterator(BitSet bitSet, int length) {
        return new BitSetComplementIterator(bitSet, length);
    }

    public static void forEach(BitSet bitSet, IntConsumer consumer) {
        int length = bitSet.length();
        int cardinality = bitSet.cardinality();
        if (length < cardinality * 2) {
            // the set is rather dense, meaning there probably are a lot of blocks of 1s
            int currentBlock = bitSet.nextSetBit(0);
            while (currentBlock > -1) {
                int blockEnd = bitSet.nextClearBit(currentBlock);
                assert blockEnd > currentBlock;
                for (int i = currentBlock; i < blockEnd; i++) {
                    consumer.accept(i);
                }
                currentBlock = bitSet.nextSetBit(blockEnd);
            }
        } else {
            for (int i = bitSet.nextSetBit(0); i >= 0; i = bitSet.nextSetBit(i + 1)) {
                consumer.accept(i);
            }
        }
    }

    /**
     * Checks if {@code first} is a subset of {@code second}.
     */
    public static boolean isSubset(BitSet first, BitSet second) {
        return isSubsetConsuming(copyOf(first), second);
    }

    /**
     * Checks if {@code first} is a subset of {@code second}, potentially modifying both sets in the
     * process.
     */
    public static boolean isSubsetConsuming(BitSet first, BitSet second) {
        first.andNot(second);
        return first.isEmpty();
    }

    public static boolean isDisjoint(BitSet first, BitSet second) {
        return !first.intersects(second);
    }

    public static IntIterator iterator(BitSet bitSet) {
        return new BitSetIterator(bitSet);
    }

    /**
     * Returns the set containing all subsets of the given basis.
     * Warning: For performance reasons, the iterator of this set may modify the
     * returned elements in place.
     */
    public static Set powerSet(BitSet basis) {
        int length = basis.length();
        if (length == basis.cardinality()) {
            return powerSet(length);
        }
        return new PowerBitSet(basis);
    }

    public static Set powerSet(int i) {
        return new PowerBitSetSimple(i);
    }
}