/*
    * Copyright (c) 2001-2017, Zoltan Farkas All Rights Reserved.
    *
    * This library is free software; you can redistribute it and/or
    * modify it under the terms of the GNU Lesser General Public
    * License as published by the Free Software Foundation; either
    * version 2.1 of the License, or (at your option) any later version.
    *
    * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
   *
   * Additionally licensed with:
   *
   * 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 org.spf4j.base;
  
  import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  import java.util.ArrayDeque;
  import java.util.Deque;
  import java.util.Set;
  import java.util.function.BiConsumer;
  import java.util.function.BinaryOperator;
  import java.util.function.Function;
  import java.util.function.Predicate;
  import java.util.function.Supplier;
  import java.util.stream.Collector;
  
  /**
   * @author Zoltan Farkas
   */
  public final class XCollectors {
  
    private XCollectors() {
    }
  
    public static <T> Collector<T, ?, ArrayDeque<T>> last(final int limit) {
      return Collector.of(
              ArrayDeque<T>::new,
              (l, e) -> {
                if (l.size() >= limit) {
                  l.removeFirst();
                }
                l.addLast(e);
              },
              (l1, l2) -> {
                throw new UnsupportedOperationException("Limiting collectors do not support combining");
              }
      );
    }
  
    public static <T, X extends T> Collector<T, ArrayDeque<T>,
           ArrayDeque<T>> last(final int limit, final X addIfLimited) {
      return  last(() -> new ArrayDeque<T>(), limit, addIfLimited);
    }
  
    public static <T, X extends T, D extends Deque<T>> Collector<T, D, D> last(final Supplier<D> dqSupp,
            final int limit, final X addIfLimited) {
      return Collector.of(dqSupp,
              (l, e) -> {
                l.addLast(e);
                limitDequeue(l, limit, addIfLimited);
              }, new BinaryOperator<D>() {
        @Override
        @SuppressFBWarnings("CFS_CONFUSING_FUNCTION_SEMANTICS")
        // Agree with FB here, however this confusing behavior is documented in Collector javadoc...
        public D apply(final D l1, final D l2) {
          l1.addAll(l2);
          limitDequeue(l1, limit, addIfLimited);
          return l1;
        }
      }, Collector.Characteristics.IDENTITY_FINISH);
    }
  
    public static <T> void limitDequeue(final Deque<T> l1, final int limit, final T addIfLimited) {
      int extra = l1.size() - limit;
      if (extra > 0) {
        for (int i = 0, m = extra + 1; i < m; i++) {
          l1.removeFirst();
        }
        l1.addFirst(addIfLimited);
      }
    }
 
   /**
    * THis is a backport from JDK9.
    */
   public static <T, A, R>
           Collector<T, ?, R> filtering(final Predicate<? super T> predicate,
                   final Collector<? super T, A, R> downstream) {
     BiConsumer<A, ? super T> downstreamAccumulator = downstream.accumulator();
     return new CollectorImpl<>(downstream.supplier(),
             (r, t) -> {
               if (predicate.test(t)) {
                 downstreamAccumulator.accept(r, t);
               }
             },
             downstream.combiner(), downstream.finisher(),
             downstream.characteristics());
   }
 
   @SuppressWarnings("unchecked")
   private static <I, R> Function<I, R> castingIdentity() {
     return (Function<I, R>) Function.identity();
   }
 
   static final class CollectorImpl<T, A, R> implements Collector<T, A, R> {
 
     private final Supplier<A> supplier;
     private final BiConsumer<A, T> accumulator;
     private final BinaryOperator<A> combiner;
     private final Function<A, R> finisher;
     private final Set<Collector.Characteristics> characteristics;
 
     CollectorImpl(final Supplier<A> supplier,
             final BiConsumer<A, T> accumulator,
             final BinaryOperator<A> combiner,
             final Function<A, R> finisher,
             final Set<Collector.Characteristics> characteristics) {
       this.supplier = supplier;
       this.accumulator = accumulator;
       this.combiner = combiner;
       this.finisher = finisher;
       this.characteristics = characteristics;
     }
 
     CollectorImpl(final Supplier<A> supplier,
             final BiConsumer<A, T> accumulator,
             final BinaryOperator<A> combiner,
             final Set<Collector.Characteristics> characteristics) {
       this(supplier, accumulator, combiner, castingIdentity(), characteristics);
     }
 
     @Override
     public BiConsumer<A, T> accumulator() {
       return accumulator;
     }
 
     @Override
     public Supplier<A> supplier() {
       return supplier;
     }
 
     @Override
     public BinaryOperator<A> combiner() {
       return combiner;
     }
 
     @Override
     public Function<A, R> finisher() {
       return finisher;
     }
 
     @Override
     public Set<Collector.Characteristics> characteristics() {
       return characteristics;
     }
   }
 
 }