/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.cassandra.db;

import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import java.util.NavigableSet;

import org.apache.cassandra.config.ColumnDefinition;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.btree.BTreeSet;

/**
 * Builder that allow to build multiple Clustering/Slice.Bound at the same time.
 */
public class MultiCBuilder
{
    /**
     * The table comparator.
     */
    private final ClusteringComparator comparator;

    /**
     * The elements of the clusterings
     */
    private final List<List<ByteBuffer>> elementsList = new ArrayList<>();

    /**
     * The number of elements that have been added.
     */
    private int size;

    /**
     * <code>true</code> if the clusterings have been build, <code>false</code> otherwise.
     */
    private boolean built;

    /**
     * <code>true</code> if the clusterings contains some <code>null</code> elements.
     */
    private boolean containsNull;

    /**
     * <code>true</code> if the composites contains some <code>unset</code> elements.
     */
    private boolean containsUnset;

    /**
     * <code>true</code> if some empty collection have been added.
     */
    private boolean hasMissingElements;

    private MultiCBuilder(ClusteringComparator comparator)
    {
        this.comparator = comparator;
    }

    /**
     * Creates a new empty {@code MultiCBuilder}.
     */
    public static MultiCBuilder create(ClusteringComparator comparator)
    {
        return new MultiCBuilder(comparator);
    }

    /**
     * Checks if this builder is empty.
     *
     * @return <code>true</code> if this builder is empty, <code>false</code> otherwise.
     */
    private boolean isEmpty()
    {
        return elementsList.isEmpty();
    }

    /**
     * Adds the specified element to all the clusterings.
     * <p>
     * If this builder contains 2 clustering: A-B and A-C a call to this method to add D will result in the clusterings:
     * A-B-D and A-C-D.
     * </p>
     *
     * @param value the value of the next element
     * @return this <code>MulitCBuilder</code>
     */
    public MultiCBuilder addElementToAll(ByteBuffer value)
    {
        checkUpdateable();

        if (isEmpty())
            elementsList.add(new ArrayList<ByteBuffer>());

        for (int i = 0, m = elementsList.size(); i < m; i++)
        {
            if (value == null)
                containsNull = true;
            if (value == ByteBufferUtil.UNSET_BYTE_BUFFER)
                containsUnset = true;

            elementsList.get(i).add(value);
        }
        size++;
        return this;
    }

    /**
     * Adds individually each of the specified elements to the end of all of the existing clusterings.
     * <p>
     * If this builder contains 2 clusterings: A-B and A-C a call to this method to add D and E will result in the 4
     * clusterings: A-B-D, A-B-E, A-C-D and A-C-E.
     * </p>
     *
     * @param values the elements to add
     * @return this <code>CompositeBuilder</code>
     */
    public MultiCBuilder addEachElementToAll(List<ByteBuffer> values)
    {
        checkUpdateable();

        if (isEmpty())
            elementsList.add(new ArrayList<ByteBuffer>());

        if (values.isEmpty())
        {
            hasMissingElements = true;
        }
        else
        {
            for (int i = 0, m = elementsList.size(); i < m; i++)
            {
                List<ByteBuffer> oldComposite = elementsList.remove(0);

                for (int j = 0, n = values.size(); j < n; j++)
                {
                    List<ByteBuffer> newComposite = new ArrayList<>(oldComposite);
                    elementsList.add(newComposite);

                    ByteBuffer value = values.get(j);

                    if (value == null)
                        containsNull = true;
                    if (value == ByteBufferUtil.UNSET_BYTE_BUFFER)
                        containsUnset = true;

                    newComposite.add(values.get(j));
                }
            }
        }
        size++;
        return this;
    }

    /**
     * Adds individually each of the specified list of elements to the end of all of the existing composites.
     * <p>
     * If this builder contains 2 composites: A-B and A-C a call to this method to add [[D, E], [F, G]] will result in the 4
     * composites: A-B-D-E, A-B-F-G, A-C-D-E and A-C-F-G.
     * </p>
     *
     * @param values the elements to add
     * @return this <code>CompositeBuilder</code>
     */
    public MultiCBuilder addAllElementsToAll(List<List<ByteBuffer>> values)
    {
        checkUpdateable();

        if (isEmpty())
            elementsList.add(new ArrayList<ByteBuffer>());

        if (values.isEmpty())
        {
            hasMissingElements = true;
        }
        else
        {
            for (int i = 0, m = elementsList.size(); i < m; i++)
            {
                List<ByteBuffer> oldComposite = elementsList.remove(0);

                for (int j = 0, n = values.size(); j < n; j++)
                {
                    List<ByteBuffer> newComposite = new ArrayList<>(oldComposite);
                    elementsList.add(newComposite);

                    List<ByteBuffer> value = values.get(j);

                    if (value.contains(null))
                        containsNull = true;
                    if (value.contains(ByteBufferUtil.UNSET_BYTE_BUFFER))
                        containsUnset = true;

                    newComposite.addAll(value);
                }
            }
            size += values.get(0).size();
        }
        return this;
    }

    /**
     * Returns the number of elements that can be added to the clusterings.
     *
     * @return the number of elements that can be added to the clusterings.
     */
    public int remainingCount()
    {
        return comparator.size() - size;
    }

    /**
     * Checks if the clusterings contains null elements.
     *
     * @return <code>true</code> if the clusterings contains <code>null</code> elements, <code>false</code> otherwise.
     */
    public boolean containsNull()
    {
        return containsNull;
    }

    /**
     * Checks if the clusterings contains unset elements.
     *
     * @return <code>true</code> if the clusterings contains <code>unset</code> elements, <code>false</code> otherwise.
     */
    public boolean containsUnset()
    {
        return containsUnset;
    }

    /**
     * Checks if some empty list of values have been added
     * @return <code>true</code> if the clusterings have some missing elements, <code>false</code> otherwise.
     */
    public boolean hasMissingElements()
    {
        return hasMissingElements;
    }

    /**
     * Builds the <code>clusterings</code>.
     *
     * @return the clusterings
     */
    public NavigableSet<Clustering> build()
    {
        built = true;

        if (hasMissingElements)
            return BTreeSet.empty(comparator);

        CBuilder builder = CBuilder.create(comparator);

        if (elementsList.isEmpty())
            return BTreeSet.of(builder.comparator(), builder.build());

        BTreeSet.Builder<Clustering> set = BTreeSet.builder(builder.comparator());
        for (int i = 0, m = elementsList.size(); i < m; i++)
        {
            List<ByteBuffer> elements = elementsList.get(i);
            set.add(builder.buildWith(elements));
        }
        return set.build();
    }

    /**
     * Builds the <code>Slice.Bound</code>s for slice restrictions.
     *
     * @param isStart specify if the bound is a start one
     * @param isInclusive specify if the bound is inclusive or not
     * @param isOtherBoundInclusive specify if the other bound is inclusive or not
     * @param columnDefs the columns of the slice restriction
     * @return the <code>Slice.Bound</code>s
     */
    public NavigableSet<Slice.Bound> buildBoundForSlice(boolean isStart,
                                                        boolean isInclusive,
                                                        boolean isOtherBoundInclusive,
                                                        List<ColumnDefinition> columnDefs)
    {
        built = true;

        if (hasMissingElements)
            return BTreeSet.empty(comparator);

        CBuilder builder = CBuilder.create(comparator);

        if (elementsList.isEmpty())
            return BTreeSet.of(comparator, builder.buildBound(isStart, isInclusive));

        // Use a TreeSet to sort and eliminate duplicates
        BTreeSet.Builder<Slice.Bound> set = BTreeSet.builder(comparator);

        // The first column of the slice might not be the first clustering column (e.g. clustering_0 = ? AND (clustering_1, clustering_2) >= (?, ?)
        int offset = columnDefs.get(0).position();

        for (int i = 0, m = elementsList.size(); i < m; i++)
        {
            List<ByteBuffer> elements = elementsList.get(i);

            // Handle the no bound case
            if (elements.size() == offset)
            {
                set.add(builder.buildBoundWith(elements, isStart, true));
                continue;
            }

            // In the case of mixed order columns, we will have some extra slices where the columns change directions.
            // For example: if we have clustering_0 DESC and clustering_1 ASC a slice like (clustering_0, clustering_1) > (1, 2)
            // will produce 2 slices: [BOTTOM, 1) and (1.2, 1]
            // So, the END bound will return 2 bounds with the same values 1
            ColumnDefinition lastColumn = columnDefs.get(columnDefs.size() - 1);
            if (elements.size() <= lastColumn.position() && i < m - 1 && elements.equals(elementsList.get(i + 1)))
            {
                set.add(builder.buildBoundWith(elements, isStart, false));
                set.add(builder.buildBoundWith(elementsList.get(i++), isStart, true));
                continue;
            }

            // Handle the normal bounds
            ColumnDefinition column = columnDefs.get(elements.size() - 1 - offset);
            set.add(builder.buildBoundWith(elements, isStart, column.isReversedType() ? isOtherBoundInclusive : isInclusive));
        }
        return set.build();
    }

    public NavigableSet<Slice.Bound> buildBound(boolean isStart, boolean isInclusive)
    {
        built = true;

        if (hasMissingElements)
            return BTreeSet.empty(comparator);

        CBuilder builder = CBuilder.create(comparator);

        if (elementsList.isEmpty())
            return BTreeSet.of(comparator, builder.buildBound(isStart, isInclusive));

        // Use a TreeSet to sort and eliminate duplicates
        BTreeSet.Builder<Slice.Bound> set = BTreeSet.builder(comparator);

        for (int i = 0, m = elementsList.size(); i < m; i++)
        {
            List<ByteBuffer> elements = elementsList.get(i);
            set.add(builder.buildBoundWith(elements, isStart, isInclusive));
        }
        return set.build();
    }

    /**
     * Checks if some elements can still be added to the clusterings.
     *
     * @return <code>true</code> if it is possible to add more elements to the clusterings, <code>false</code> otherwise.
     */
    public boolean hasRemaining()
    {
        return remainingCount() > 0;
    }

    private void checkUpdateable()
    {
        if (!hasRemaining() || built)
            throw new IllegalStateException("this builder cannot be updated anymore");
    }
}