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//
// Burton Computer Corporation
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// Copyright (c) 2019, Burton Computer Corporation
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package org.javimmutable.collections.array;

import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.MapEntry;
import org.javimmutable.collections.iterators.GenericIterator;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

@Immutable
class LeafTrieNode
    extends TrieNode
    implements JImmutableMap.Entry,
               Holders.Filled
{
    private final int index;
    private final T value;
    private final int shift;

    private LeafTrieNode(int index,
                         T value,
                         int shift)
    {
        this.index = index;
        this.value = value;
        this.shift = shift;
    }

    static  LeafTrieNode of(int index,
                                  @Nonnull T value)
    {
        return new LeafTrieNode<>(index, value, shiftForIndex(index));
    }

    @Override
    public int valueCount()
    {
        return 1;
    }

    @Override
    public boolean isEmpty()
    {
        return false;
    }

    @Override
    public boolean isNonEmpty()
    {
        return true;
    }

    @Nonnull
    @Override
    public Integer getKey()
    {
        return index;
    }

    @Override
    public T getValue()
    {
        return value;
    }

    @Override
    public T getValueOr(int shift,
                        int index,
                        T defaultValue)
    {
        assert shift >= -5;
        return (this.index == index) ? value : defaultValue;
    }

    @Override
    public Holder find(int shift,
                          int index)
    {
        assert shift >= -5;
        return (this.index == index) ? this : Holders.of();
    }

    @Override
    public TrieNode assign(int shift,
                              int index,
                              T value)
    {
        assert shift >= -5;
        if (this.index == index) {
            if (this.value == value) {
                return this;
            } else {
                return withValue(value);
            }
        } else {
            assert shift >= 0;
            return SingleBranchTrieNode.forIndex(shift, this.index, this).assign(shift, index, value);
        }
    }

    @Override
    public TrieNode delete(int shift,
                              int index)
    {
        assert shift >= -5;
        if (this.index == index) {
            return of();
        } else {
            return this;
        }
    }

    @Override
    public int getShift()
    {
        return shift;
    }

    @Override
    public boolean isLeaf()
    {
        return true;
    }

    @Override
    public TrieNode paddedToMinimumDepthForShift(int shift)
    {
        if (this.shift >= shift) {
            return this;
        } else {
            return SingleBranchTrieNode.forIndex(shift, index, this);
        }
    }

    @Nullable
    @Override
    public GenericIterator.State> iterateOverRange(@Nullable GenericIterator.State> parent,
                                                                                   int offset,
                                                                                   int limit)
    {
        return GenericIterator.valueState(parent, this);
    }

    @Override
    public void checkInvariants()
    {
        if (shift < -5 || shift > ROOT_SHIFT) {
            throw new IllegalStateException("illegal shift value: " + shift);
        }
    }

    @Override
    public boolean equals(Object o)
    {
        if (this == o) {
            return true;
        }
        if ((o == null) || (getClass() != o.getClass())) {
            return false;
        }

        LeafTrieNode that = (LeafTrieNode)o;

        if (index != that.index) {
            return false;
        }
        if (shift != that.shift) {
            return false;
        }
        //noinspection RedundantIfStatement
        if (!value.equals(that.value)) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode()
    {
        int result = index;
        result = 31 * result + value.hashCode();
        result = 31 * result + shift;
        return result;
    }

    @Override
    public String toString()
    {
        return MapEntry.makeToString(this);
    }

    private TrieNode withValue(T newValue)
    {
        return new LeafTrieNode<>(index, newValue, shift);
    }
}