/*
 * 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.auron.flink.arrow.writers;

import java.util.Objects;
import org.apache.arrow.vector.complex.MapVector;
import org.apache.arrow.vector.complex.StructVector;
import org.apache.flink.table.data.ArrayData;
import org.apache.flink.table.data.MapData;
import org.apache.flink.table.data.RowData;

/**
 * {@link ArrowFieldWriter} for maps ({@link MapVector}).
 *
 * <p>Arrow represents maps as {@code List<Struct{key, value}>}. This writer holds separate key and
 * value writers that operate on {@link ArrayData} (from {@link MapData#keyArray()} and {@link
 * MapData#valueArray()}).
 *
 * @param <T> the input data type
 */
public abstract class MapWriter<T> extends ArrowFieldWriter<T> {

    /** Creates a MapWriter that reads from {@link RowData}. */
    public static MapWriter<RowData> forRow(
            MapVector mapVector, ArrowFieldWriter<ArrayData> keyWriter, ArrowFieldWriter<ArrayData> valueWriter) {
        return new MapWriterForRow(mapVector, keyWriter, valueWriter);
    }

    /** Creates a MapWriter that reads from {@link ArrayData}. */
    public static MapWriter<ArrayData> forArray(
            MapVector mapVector, ArrowFieldWriter<ArrayData> keyWriter, ArrowFieldWriter<ArrayData> valueWriter) {
        return new MapWriterForArray(mapVector, keyWriter, valueWriter);
    }

    // ------------------------------------------------------------------------------------------

    private final ArrowFieldWriter<ArrayData> keyWriter;
    private final ArrowFieldWriter<ArrayData> valueWriter;

    private MapWriter(
            MapVector mapVector, ArrowFieldWriter<ArrayData> keyWriter, ArrowFieldWriter<ArrayData> valueWriter) {
        super(mapVector);
        this.keyWriter = Objects.requireNonNull(keyWriter);
        this.valueWriter = Objects.requireNonNull(valueWriter);
    }

    abstract boolean isNullAt(T in, int ordinal);

    abstract MapData readMap(T in, int ordinal);

    @Override
    public void doWrite(T in, int ordinal) {
        if (!isNullAt(in, ordinal)) {
            ((MapVector) getValueVector()).startNewValue(getCount());

            StructVector structVector = (StructVector) ((MapVector) getValueVector()).getDataVector();
            MapData map = readMap(in, ordinal);
            ArrayData keys = map.keyArray();
            ArrayData values = map.valueArray();
            for (int i = 0; i < map.size(); i++) {
                structVector.setIndexDefined(keyWriter.getCount());
                keyWriter.write(keys, i);
                valueWriter.write(values, i);
            }

            ((MapVector) getValueVector()).endValue(getCount(), map.size());
        }
    }

    @Override
    public void finish() {
        super.finish();
        keyWriter.finish();
        valueWriter.finish();
    }

    @Override
    public void reset() {
        super.reset();
        keyWriter.reset();
        valueWriter.reset();
    }

    // ---- Inner classes for RowData and ArrayData ----

    public static final class MapWriterForRow extends MapWriter<RowData> {
        private MapWriterForRow(
                MapVector mapVector, ArrowFieldWriter<ArrayData> keyWriter, ArrowFieldWriter<ArrayData> valueWriter) {
            super(mapVector, keyWriter, valueWriter);
        }

        @Override
        boolean isNullAt(RowData in, int ordinal) {
            return in.isNullAt(ordinal);
        }

        @Override
        MapData readMap(RowData in, int ordinal) {
            return in.getMap(ordinal);
        }
    }

    public static final class MapWriterForArray extends MapWriter<ArrayData> {
        private MapWriterForArray(
                MapVector mapVector, ArrowFieldWriter<ArrayData> keyWriter, ArrowFieldWriter<ArrayData> valueWriter) {
            super(mapVector, keyWriter, valueWriter);
        }

        @Override
        boolean isNullAt(ArrayData in, int ordinal) {
            return in.isNullAt(ordinal);
        }

        @Override
        MapData readMap(ArrayData in, int ordinal) {
            return in.getMap(ordinal);
        }
    }
}
