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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.set;

import it.unimi.dsi.fastutil.ints.IntIterator;
import it.unimi.dsi.fastutil.ints.IntIterators;
import java.util.NoSuchElementException;
import javax.annotation.Nonnegative;

class BoundedMutableSingletonNatBitSet extends AbstractBoundedNatBitSet {
    private static final int EMPTY = Integer.MIN_VALUE;
    private final boolean complement;
    private final BoundedMutableSingletonNatBitSet complementView;
    private final int[] store;

    private BoundedMutableSingletonNatBitSet(int element, @Nonnegative int domainSize, boolean complement) {
        super(domainSize);
        this.store = new int[] {element};
        this.complement = complement;
        this.complementView = new BoundedMutableSingletonNatBitSet(this);
    }

    private BoundedMutableSingletonNatBitSet(BoundedMutableSingletonNatBitSet other) {
        super(other.domainSize());
        this.complementView = other;
        this.complement = !other.complement;
        this.store = other.store;
    }

    BoundedMutableSingletonNatBitSet(@Nonnegative int element, @Nonnegative int domainSize) {
        this(element, domainSize, false);
        NatBitSetsUtil.checkNonNegative(element);
    }

    BoundedMutableSingletonNatBitSet(@Nonnegative int domainSize) {
        this(EMPTY, domainSize, false);
    }

    private static UnsupportedOperationException unsupportedOperation() {
        return new UnsupportedOperationException("Singleton can hold at most one value");
    }

    @Override
    public void clear(int index) {
        checkInDomain(index);

        if (complement) {
            if (isStoreEmpty()) {
                setStoreValue(index);
            } else if (index != store[0]) {
                throw unsupportedOperation();
            }
        } else {
            assert index != EMPTY;
            if (index == store[0]) {
                setStoreEmpty();
            }
        }
    }

    @Override
    public void clear(int from, int to) {
        checkInDomain(from, to);
        if (from == to) {
            return;
        }
        if (isEmpty()) {
            return;
        }

        if (complement) {
            if (from + 1 != to) {
                throw unsupportedOperation();
            }
            if (isStoreEmpty()) {
                setStoreValue(from);
            } else if (from != store[0]) {
                throw unsupportedOperation();
            }
        } else if (from <= store[0] && store[0] < to) {
            setStoreEmpty();
        }
    }

    @Override
    public void clear() {
        if (complement) {
            if (domainSize() > 1) {
                throw unsupportedOperation();
            }
            setStoreValue(0);
        } else {
            setStoreEmpty();
        }
    }

    @Override
    public BoundedMutableSingletonNatBitSet clone() {
        return (BoundedMutableSingletonNatBitSet) super.clone();
    }

    @SuppressWarnings("AssignmentOrReturnOfFieldWithMutableType")
    @Override
    public BoundedNatBitSet complement() {
        return complementView;
    }

    @Override
    public boolean contains(int index) {
        return index >= 0 && (complement == (store[0] != index));
    }

    @Override
    public int firstInt() {
        if (isEmpty()) {
            throw new NoSuchElementException();
        }
        if (complement) {
            return store[0] == 0 ? 1 : 0;
        }
        return store[0];
    }

    @Override
    public void flip(int index) {
        checkInDomain(index);
        if (index == store[0]) {
            setStoreEmpty();
        } else if (isStoreEmpty()) {
            setStoreValue(index);
        } else {
            throw unsupportedOperation();
        }
    }

    @Override
    public void flip(int from, int to) {
        checkInDomain(from, to);
        if (from == to) {
            return;
        }
        if (from + 1 != to) {
            throw unsupportedOperation();
        }
        flip(from);
    }

    @Override
    boolean isComplement() {
        return complement;
    }

    @Override
    public boolean isEmpty() {
        return complement ? (domainSize() == 1 && !isStoreEmpty()) : isStoreEmpty();
    }

    private boolean isStoreEmpty() {
        return store[0] == EMPTY;
    }

    @Override
    public IntIterator iterator() {
        if (isStoreEmpty()) {
            return complement ? IntIterators.fromTo(0, domainSize()) : IntIterators.EMPTY_ITERATOR;
        }
        if (complement) {
            IntIterator first = IntIterators.fromTo(0, store[0]);
            IntIterator second = IntIterators.fromTo(store[0] + 1, domainSize());
            return IntIterators.concat(first, second);
        }
        return IntIterators.singleton(store[0]);
    }

    @Override
    public int lastInt() {
        if (isEmpty()) {
            throw new NoSuchElementException();
        }
        if (complement) {
            int domainSize = domainSize();
            return domainSize - (store[0] == domainSize - 1 ? 2 : 1);
        }
        return store[0];
    }

    @Override
    public int nextAbsentIndex(int index) {
        NatBitSetsUtil.checkNonNegative(index);
        if (complement) {
            return index <= store[0] ? store[0] : domainSize();
        }
        return (!isEmpty() && index == store[0]) ? store[0] + 1 : index;
    }

    @Override
    public int nextPresentIndex(int index) {
        NatBitSetsUtil.checkNonNegative(index);
        if (isEmpty()) {
            return -1;
        }
        if (domainSize() <= index) {
            return -1;
        }

        if (complement) {
            return index == store[0] ? index + 1 : index;
        }
        return index <= store[0] ? store[0] : -1;
    }

    @Override
    public int previousAbsentIndex(int index) {
        NatBitSetsUtil.checkNonNegative(index);
        if (isEmpty()) {
            return index;
        }
        if (complement) {
            return index >= store[0] ? store[0] : -1;
        }
        return index == store[0] ? store[0] - 1 : index;
    }

    @Override
    public int previousPresentIndex(int index) {
        NatBitSetsUtil.checkNonNegative(index);
        if (isEmpty()) {
            return -1;
        }
        if (complement) {
            return index == store[0] ? store[0] - 1 : index;
        }
        return index >= store[0] ? store[0] : -1;
    }

    @Override
    public IntIterator reverseIterator() {
        if (isStoreEmpty()) {
            return complement ? new ReverseRangeIterator(0, domainSize()) : IntIterators.EMPTY_ITERATOR;
        }
        if (complement) {
            IntIterator first = new ReverseRangeIterator(store[0] + 1, domainSize());
            IntIterator second = new ReverseRangeIterator(0, store[0]);
            return IntIterators.concat(first, second);
        }
        return IntIterators.singleton(store[0]);
    }

    @Override
    public void set(int index) {
        checkInDomain(index);

        if (complement) {
            if (index == store[0]) {
                setStoreEmpty();
            }
        } else {
            if (isStoreEmpty()) {
                store[0] = index;
            } else if (index != store[0]) {
                throw unsupportedOperation();
            }
        }
    }

    @Override
    public void set(int index, boolean value) {
        if (value) {
            set(index);
        } else {
            clear(index);
        }
    }

    @Override
    public void set(int from, int to) {
        checkInDomain(from, to);
        if (from == to) {
            return;
        }
        if (from + 1 != to) {
            throw unsupportedOperation();
        }
        set(from);
    }

    private void setStoreEmpty() {
        store[0] = EMPTY;
    }

    private void setStoreValue(int value) {
        assert value >= 0 && isEmpty();
        store[0] = value;
    }

    @Override
    public int size() {
        if (complement) {
            return isStoreEmpty() ? domainSize() : domainSize() - 1;
        }
        return isStoreEmpty() ? 0 : 1;
    }
}