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/*
 * Licensed 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 io.trino.operator.unnest;

import io.trino.spi.block.Block;

/**
 * This is a layer of abstraction between {@link UnnestOperator} and {@link UnnestBlockBuilder} to enable
 * translation of indices from input nested blocks to underlying element blocks.
 */
public interface Unnester
{
    int getChannelCount();

    void resetInput(Block block);

    /**
     * Return a vector with the number of entries for each position of the block to be unnested.
     */
    int[] getOutputEntriesPerPosition();

    /**
     * Build the output blocks for the current batch for this unnester.
     *
     * @param outputEntriesPerPosition A vector that holds the max unnested row count for each position of all blocks to be unnested.
     * @param startPosition The start input position of this batch.
     * @param batchSize The number of input rows to be processed in this batch.
     * @param outputRowCount The total output row count for this batch after the unnest is done.
     */
    Block[] buildOutputBlocks(int[] outputEntriesPerPosition, int startPosition, int batchSize, int outputRowCount);

    long getRetainedSizeInBytes();
}