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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.Indexed;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.indexed.IndexedArray;
import org.javimmutable.collections.iterators.GenericIterator;

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

@Immutable
class FullBranchTrieNode
    extends TrieNode
{
    private final int shift;
    private final int valueCount;
    private final TrieNode[] entries;

    FullBranchTrieNode(int shift,
                       int valueCount,
                       TrieNode[] entries)
    {
        assert shift != ROOT_SHIFT;
        this.shift = shift;
        this.valueCount = valueCount;
        this.entries = entries;
    }

    static  FullBranchTrieNode fromSource(int index,
                                                Indexed source,
                                                int offset)
    {
        assert (source.size() - offset) >= 32;
        TrieNode[] entries = MultiBranchTrieNode.allocate(32);
        for (int i = 0; i < 32; ++i) {
            entries[i] = LeafTrieNode.of(index++, source.get(offset++));
        }
        return new FullBranchTrieNode<>(0, computeValueCount(entries), entries);
    }

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

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

    @Override
    public T getValueOr(int shift,
                        int index,
                        T defaultValue)
    {
        assert this.shift == shift;
        final int childIndex = (index >>> shift) & 0x1f;
        return entries[childIndex].getValueOr(shift - 5, index, defaultValue);
    }

    @Override
    public Holder find(int shift,
                          int index)
    {
        assert this.shift == shift;
        final int childIndex = (index >>> shift) & 0x1f;
        return entries[childIndex].find(shift - 5, index);
    }

    @Override
    public TrieNode assign(int shift,
                              int index,
                              T value)
    {
        assert this.shift == shift;
        final int childIndex = (index >>> shift) & 0x1f;
        final TrieNode child = entries[childIndex];
        final TrieNode newChild = child.assign(shift - 5, index, value);
        if (newChild == child) {
            return this;
        } else {
            return createUpdatedEntries(shift, childIndex, newChild);
        }
    }

    @Override
    public TrieNode delete(int shift,
                              int index)
    {
        assert this.shift == shift;
        final int childIndex = (index >>> shift) & 0x1f;
        final TrieNode child = entries[childIndex];
        final TrieNode newChild = child.delete(shift - 5, index);
        return createDeleteResultNode(shift, childIndex, child, newChild);
    }

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

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

    @Nullable
    @Override
    public GenericIterator.State> iterateOverRange(@Nullable GenericIterator.State> parent,
                                                                                   int offset,
                                                                                   int limit)
    {
        return GenericIterator.indexedState(parent, IndexedArray.retained(entries), offset, limit);
    }

    @Override
    public void checkInvariants()
    {
        if (shift < 0 || shift > ROOT_SHIFT) {
            throw new IllegalStateException("illegal shift value: " + shift);
        }
        if (entries.length != 32) {
            throw new IllegalStateException("unexpected entries size: expected=32 actual=" + entries.length);
        }
        if (valueCount != computeValueCount(entries)) {
            throw new IllegalStateException("unexpected valueCount: expected=" + valueCount + " actual=" + computeValueCount(entries));
        }
        for (TrieNode entry : entries) {
            entry.checkInvariants();
        }
    }

    private TrieNode createUpdatedEntries(int shift,
                                             int childIndex,
                                             TrieNode newChild)
    {
        assert newChild.isLeaf() || (newChild.getShift() == (shift - 5));
        final int newValueCount = valueCount - entries[childIndex].valueCount() + newChild.valueCount();
        TrieNode[] newEntries = entries.clone();
        newEntries[childIndex] = newChild;
        return new FullBranchTrieNode<>(shift, newValueCount, newEntries);
    }

    private TrieNode createDeleteResultNode(int shift,
                                               int childIndex,
                                               TrieNode child,
                                               TrieNode newChild)
    {
        if (newChild == child) {
            return this;
        } else if (newChild.isEmpty()) {
            final int newValueCount = valueCount - child.valueCount() + newChild.valueCount();
            return MultiBranchTrieNode.fullWithout(shift, newValueCount, entries, childIndex);
        } else {
            return createUpdatedEntries(shift, childIndex, newChild);
        }
    }
}