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/*
 * Copyright (C) 2017 Julien Viet
 *
 * 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.vertx.sqlclient.impl;

import io.vertx.sqlclient.Row;
import io.vertx.sqlclient.RowIterator;
import io.vertx.sqlclient.RowSet;
import io.vertx.sqlclient.impl.accumulator.ArrayListRowAccumulator;
import io.vertx.sqlclient.impl.accumulator.RowAccumulator;

import java.util.NoSuchElementException;
import java.util.function.Function;
import java.util.stream.Collector;

class RowSetImpl extends SqlResultBase> implements RowSet {

  static Collector, RowSet> COLLECTOR = Collector.of(
    RowSetImpl::new,
    RowSetImpl::add,
    (set1, set2) -> null, // Shall not be invoked as this is sequential
    (set) -> set
  );

  static  Collector, RowSet> collector(Function mapper) {
    return Collector.of(
      RowSetImpl::new,
      (set, row) -> {
        set.add(mapper.apply(row));
      },
      (set1, set2) -> null, // Shall not be invoked as this is sequential
      (set) -> set
    );
  }

  static Function, RowSetImpl> FACTORY = rs -> (RowSetImpl) rs;

  static  Function, RowSetImpl> factory() {
    return rs -> (RowSetImpl) rs;
  }

  private R firstRow;
  private RowAccumulator rowAccumulator;

  @Override
  public RowSet value() {
    return this;
  }

  private void add(R row) {
    if (rowAccumulator != null) {
      rowAccumulator.accept(row);
    } else if (firstRow != null) {
      rowAccumulator = new ArrayListRowAccumulator<>();
      rowAccumulator.accept(firstRow);
      rowAccumulator.accept(row);
      firstRow = null;
    } else {
      firstRow = row;
    }
  }

  @Override
  public RowIterator iterator() {
    return rowAccumulator != null ? rowAccumulator.iterator() : SingletonRowIterator.createFor(firstRow);
  }

  @Override
  public RowSetImpl next() {
    return (RowSetImpl) super.next();
  }

  private static final class SingletonRowIterator implements RowIterator {

    static final SingletonRowIterator