/*
 * 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.tsfile.external.commons.lang3.stream;

import java.util.Collections;
import java.util.Set;
import java.util.StringJoiner;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;
import java.util.stream.Collectors;

public class LangCollectors {

  private static final Set<Collector.Characteristics> CH_NOID = Collections.emptySet();

  /**
   * Simple implementation class for {@code Collector}.
   *
   * @param <T> the type of elements to be collected
   * @param <R> the type of the result
   */
  private static final class SimpleCollector<T, A, R> implements Collector<T, A, R> {

    private final BiConsumer<A, T> accumulator;
    private final Set<Characteristics> characteristics;
    private final BinaryOperator<A> combiner;
    private final Function<A, R> finisher;
    private final Supplier<A> supplier;

    private SimpleCollector(
        final Supplier<A> supplier,
        final BiConsumer<A, T> accumulator,
        final BinaryOperator<A> combiner,
        final Function<A, R> finisher,
        final Set<Characteristics> characteristics) {
      this.supplier = supplier;
      this.accumulator = accumulator;
      this.combiner = combiner;
      this.finisher = finisher;
      this.characteristics = characteristics;
    }

    @Override
    public BiConsumer<A, T> accumulator() {
      return accumulator;
    }

    @Override
    public Set<Characteristics> characteristics() {
      return characteristics;
    }

    @Override
    public BinaryOperator<A> combiner() {
      return combiner;
    }

    @Override
    public Function<A, R> finisher() {
      return finisher;
    }

    @Override
    public Supplier<A> supplier() {
      return supplier;
    }
  }

  /**
   * Returns a {@code Collector} that concatenates the input elements, separated by the specified
   * delimiter, with the specified prefix and suffix, in encounter order.
   *
   * <p>This is a variation of {@link Collectors#joining(CharSequence, CharSequence, CharSequence)}
   * that works with any element class, not just {@code CharSequence}.
   *
   * @param delimiter the delimiter to be used between each element
   * @param prefix the sequence of characters to be used at the beginning of the joined result
   * @param suffix the sequence of characters to be used at the end of the joined result
   * @param toString A function that takes an Object and returns a non-null String.
   * @return A {@code Collector} which concatenates CharSequence elements, separated by the
   *     specified delimiter, in encounter order
   */
  public static Collector<Object, ?, String> joining(
      final CharSequence delimiter,
      final CharSequence prefix,
      final CharSequence suffix,
      final Function<Object, String> toString) {
    return new SimpleCollector<>(
        () -> new StringJoiner(delimiter, prefix, suffix),
        (a, t) -> a.add(toString.apply(t)),
        StringJoiner::merge,
        StringJoiner::toString,
        CH_NOID);
  }
}
