/*
    * 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.commons.lang3;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.Set;
  import java.util.function.BiConsumer;
  import java.util.function.BinaryOperator;
  import java.util.function.Consumer;
  import java.util.function.Function;
  import java.util.function.Predicate;
  import java.util.function.Supplier;
  import java.util.stream.Collector;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import org.apache.commons.lang3.Functions.FailableConsumer;
  import org.apache.commons.lang3.Functions.FailableFunction;
  import org.apache.commons.lang3.Functions.FailablePredicate;
  
  /**
   * Provides utility functions, and classes for working with the
   * {@code java.util.stream} package, or more generally, with Java 8 lambdas. More
   * specifically, it attempts to address the fact that lambdas are supposed
   * not to throw Exceptions, at least not checked Exceptions, AKA instances
   * of {@link Exception}. This enforces the use of constructs like
   * <pre>{@code
   *     Consumer<java.lang.reflect.Method> consumer = m -> {
   *         try {
   *             m.invoke(o, args);
   *         } catch (Throwable t) {
   *             throw Functions.rethrow(t);
   *         }
   *    };
   *    stream.forEach(consumer);
   * }</pre>
   * Using a {@link FailableStream}, this can be rewritten as follows:
   * <pre>{@code
   *     Streams.failable(stream).forEach(m -> m.invoke(o, args));
   * }</pre>
   * Obviously, the second version is much more concise and the spirit of
   * Lambda expressions is met better than in the first version.
   *
   * @see Stream
   * @see Functions
   * @since 3.10
   * @deprecated Use {@link org.apache.commons.lang3.stream.Streams}.
   */
  @Deprecated
  public class Streams {
  
      /**
       * A Collector type for arrays.
       *
       * @param <O> The array type.
       * @deprecated Use {@link org.apache.commons.lang3.stream.Streams.ArrayCollector}.
       */
      @Deprecated
      public static class ArrayCollector<O> implements Collector<O, List<O>, O[]> {
          private static final Set<Characteristics> characteristics = Collections.emptySet();
          private final Class<O> elementType;
  
          /**
           * Constructs a new instance for the given element type.
           *
           * @param elementType The element type.
           */
          public ArrayCollector(final Class<O> elementType) {
              this.elementType = elementType;
          }
  
          @Override
          public BiConsumer<List<O>, O> accumulator() {
              return List::add;
          }
  
          @Override
          public Set<Characteristics> characteristics() {
              return characteristics;
          }
  
          @Override
         public BinaryOperator<List<O>> combiner() {
             return (left, right) -> {
                 left.addAll(right);
                 return left;
             };
         }
 
         @Override
         public Function<List<O>, O[]> finisher() {
             return list -> list.toArray(ArrayUtils.newInstance(elementType, list.size()));
         }
 
         @Override
         public Supplier<List<O>> supplier() {
             return ArrayList::new;
         }
     }
 
     /**
      * A reduced, and simplified version of a {@link Stream} with
      * failable method signatures.
      * @param <O> The streams element type.
      * @deprecated Use {@link org.apache.commons.lang3.stream.Streams.FailableStream}.
      */
     @Deprecated
     public static class FailableStream<O> {
 
         private Stream<O> stream;
         private boolean terminated;
 
         /**
          * Constructs a new instance with the given {@code stream}.
          * @param stream The stream.
          */
         public FailableStream(final Stream<O> stream) {
             this.stream = stream;
         }
 
         /**
          * Returns whether all elements of this stream match the provided predicate.
          * May not evaluate the predicate on all elements if not necessary for
          * determining the result.  If the stream is empty then {@code true} is
          * returned and the predicate is not evaluated.
          *
          * <p>
          * This is a short-circuiting terminal operation.
          * </p>
          *
          * <p>
          * Note
          * This method evaluates the <em>universal quantification</em> of the
          * predicate over the elements of the stream (for all x P(x)).  If the
          * stream is empty, the quantification is said to be <em>vacuously
          * satisfied</em> and is always {@code true} (regardless of P(x)).
          * </p>
          *
          * @param predicate A non-interfering, stateless predicate to apply to
          * elements of this stream
          * @return {@code true} If either all elements of the stream match the
          * provided predicate or the stream is empty, otherwise {@code false}.
          */
         public boolean allMatch(final FailablePredicate<O, ?> predicate) {
             assertNotTerminated();
             return stream().allMatch(Functions.asPredicate(predicate));
         }
 
         /**
          * Returns whether any elements of this stream match the provided
          * predicate.  May not evaluate the predicate on all elements if not
          * necessary for determining the result.  If the stream is empty then
          * {@code false} is returned and the predicate is not evaluated.
          *
          * <p>
          * This is a short-circuiting terminal operation.
          * </p>
          *
          * Note
          * This method evaluates the <em>existential quantification</em> of the
          * predicate over the elements of the stream (for some x P(x)).
          *
          * @param predicate A non-interfering, stateless predicate to apply to
          * elements of this stream
          * @return {@code true} if any elements of the stream match the provided
          * predicate, otherwise {@code false}
          */
         public boolean anyMatch(final FailablePredicate<O, ?> predicate) {
             assertNotTerminated();
             return stream().anyMatch(Functions.asPredicate(predicate));
         }
 
         /**
          * Throws IllegalStateException if this stream is already terminated.
          *
          * @throws IllegalStateException if this stream is already terminated.
          */
         protected void assertNotTerminated() {
             if (terminated) {
                 throw new IllegalStateException("This stream is already terminated.");
             }
         }
 
         /**
          * Performs a mutable reduction operation on the elements of this stream using a
          * {@link Collector}.  A {@link Collector}
          * encapsulates the functions used as arguments to
          * {@link #collect(Supplier, BiConsumer, BiConsumer)}, allowing for reuse of
          * collection strategies and composition of collect operations such as
          * multiple-level grouping or partitioning.
          *
          * <p>
          * If the underlying stream is parallel, and the {@link Collector}
          * is concurrent, and either the stream is unordered or the collector is
          * unordered, then a concurrent reduction will be performed
          * (see {@link Collector} for details on concurrent reduction.)
          * </p>
          *
          * <p>
          * This is an intermediate operation.
          * </p>
          *
          * <p>
          * When executed in parallel, multiple intermediate results may be
          * instantiated, populated, and merged so as to maintain isolation of
          * mutable data structures.  Therefore, even when executed in parallel
          * with non-thread-safe data structures (such as {@link ArrayList}), no
          * additional synchronization is needed for a parallel reduction.
          * </p>
          * <p>
          * Note
          * The following will accumulate strings into an ArrayList:
          * </p>
          * <pre>{@code
          *     List<String> asList = stringStream.collect(Collectors.toList());
          * }</pre>
          *
          * <p>
          * The following will classify {@code Person} objects by city:
          * </p>
          * <pre>{@code
          *     Map<String, List<Person>> peopleByCity
          *         = personStream.collect(Collectors.groupingBy(Person::getCity));
          * }</pre>
          *
          * <p>
          * The following will classify {@code Person} objects by state and city,
          * cascading two {@link Collector}s together:
          * </p>
          * <pre>{@code
          *     Map<String, Map<String, List<Person>>> peopleByStateAndCity
          *         = personStream.collect(Collectors.groupingBy(Person::getState,
          *                                                      Collectors.groupingBy(Person::getCity)));
          * }</pre>
          *
          * @param <R> the type of the result
          * @param <A> the intermediate accumulation type of the {@link Collector}
          * @param collector the {@link Collector} describing the reduction
          * @return the result of the reduction
          * @see #collect(Supplier, BiConsumer, BiConsumer)
          * @see Collectors
          */
         public <A, R> R collect(final Collector<? super O, A, R> collector) {
             makeTerminated();
             return stream().collect(collector);
         }
 
         /**
          * Performs a mutable reduction operation on the elements of this FailableStream.
          * A mutable reduction is one in which the reduced value is a mutable result
          * container, such as an {@link ArrayList}, and elements are incorporated by updating
          * the state of the result rather than by replacing the result. This produces a result equivalent to:
          * <pre>{@code
          *     R result = supplier.get();
          *     for (T element : this stream)
          *         accumulator.accept(result, element);
          *     return result;
          * }</pre>
          *
          * <p>
          * Like {@link #reduce(Object, BinaryOperator)}, {@code collect} operations
          * can be parallelized without requiring additional synchronization.
          * </p>
          *
          * <p>
          * This is an intermediate operation.
          * </p>
          *
          * <p>
          * Note There are many existing classes in the JDK whose signatures are
          * well-suited for use with method references as arguments to {@code collect()}.
          * For example, the following will accumulate strings into an {@link ArrayList}:
          * </p>
          * <pre>{@code
          *     List<String> asList = stringStream.collect(ArrayList::new, ArrayList::add,
          *                                                ArrayList::addAll);
          * }</pre>
          *
          * <p>
          * The following will take a stream of strings and concatenates them into a
          * single string:
          * </p>
          * <pre>{@code
          *     String concat = stringStream.collect(StringBuilder::new, StringBuilder::append,
          *                                          StringBuilder::append)
          *                                 .toString();
          * }</pre>
          *
          * @param <R> type of the result
          * @param <A> Type of the accumulator.
          * @param supplier a function that creates a new result container. For a
          *                 parallel execution, this function may be called
          *                 multiple times and must return a fresh value each time.
          * @param accumulator An associative, non-interfering, stateless function for
          *   incorporating an additional element into a result
          * @param combiner An associative, non-interfering, stateless
          *   function for combining two values, which must be compatible with the
          *   accumulator function
          * @return The result of the reduction
          */
         public <A, R> R collect(final Supplier<R> supplier, final BiConsumer<R, ? super O> accumulator, final BiConsumer<R, R> combiner) {
             makeTerminated();
             return stream().collect(supplier, accumulator, combiner);
         }
 
         /**
          * Returns a FailableStream consisting of the elements of this stream that match
          * the given FailablePredicate.
          *
          * <p>
          * This is an intermediate operation.
          * </p>
          *
          * @param predicate a non-interfering, stateless predicate to apply to each
          * element to determine if it should be included.
          * @return the new stream
          */
         public FailableStream<O> filter(final FailablePredicate<O, ?> predicate) {
             assertNotTerminated();
             stream = stream.filter(Functions.asPredicate(predicate));
             return this;
         }
 
         /**
          * Performs an action for each element of this stream.
          *
          * <p>
          * This is an intermediate operation.
          * </p>
          *
          * <p>
          * The behavior of this operation is explicitly nondeterministic.
          * For parallel stream pipelines, this operation does <em>not</em>
          * guarantee to respect the encounter order of the stream, as doing so
          * would sacrifice the benefit of parallelism.  For any given element, the
          * action may be performed at whatever time and in whatever thread the
          * library chooses.  If the action accesses shared state, it is
          * responsible for providing the required synchronization.
          * </p>
          *
          * @param action a non-interfering action to perform on the elements
          */
         public void forEach(final FailableConsumer<O, ?> action) {
             makeTerminated();
             stream().forEach(Functions.asConsumer(action));
         }
 
         /**
          * Marks this stream as terminated.
          *
          * @throws IllegalStateException if this stream is already terminated.
          */
         protected void makeTerminated() {
             assertNotTerminated();
             terminated = true;
         }
 
         /**
          * Returns a stream consisting of the results of applying the given
          * function to the elements of this stream.
          *
          * <p>
          * This is an intermediate operation.
          * </p>
          *
          * @param <R> The element type of the new stream
          * @param mapper A non-interfering, stateless function to apply to each element
          * @return the new stream
          */
         public <R> FailableStream<R> map(final FailableFunction<O, R, ?> mapper) {
             assertNotTerminated();
             return new FailableStream<>(stream.map(Functions.asFunction(mapper)));
         }
 
         /**
          * Performs a reduction on the elements of this stream, using the provided
          * identity value and an associative accumulation function, and returns
          * the reduced value.  This is equivalent to:
          * <pre>{@code
          *     T result = identity;
          *     for (T element : this stream)
          *         result = accumulator.apply(result, element)
          *     return result;
          * }</pre>
          *
          * but is not constrained to execute sequentially.
          *
          * <p>
          * The {@code identity} value must be an identity for the accumulator
          * function. This means that for all {@code t},
          * {@code accumulator.apply(identity, t)} is equal to {@code t}.
          * The {@code accumulator} function must be an associative function.
          * </p>
          *
          * <p>
          * This is an intermediate operation.
          * </p>
          *
          * Note Sum, min, max, average, and string concatenation are all special
          * cases of reduction. Summing a stream of numbers can be expressed as:
          *
          * <pre>{@code
          *     Integer sum = integers.reduce(0, (a, b) -> a+b);
          * }</pre>
          *
          * or:
          *
          * <pre>{@code
          *     Integer sum = integers.reduce(0, Integer::sum);
          * }</pre>
          *
          * <p>
          * While this may seem a more roundabout way to perform an aggregation
          * compared to simply mutating a running total in a loop, reduction
          * operations parallelize more gracefully, without needing additional
          * synchronization and with greatly reduced risk of data races.
          * </p>
          *
          * @param identity the identity value for the accumulating function
          * @param accumulator an associative, non-interfering, stateless
          *                    function for combining two values
          * @return the result of the reduction
          */
         public O reduce(final O identity, final BinaryOperator<O> accumulator) {
             makeTerminated();
             return stream().reduce(identity, accumulator);
         }
 
         /**
          * Converts the FailableStream into an equivalent stream.
          * @return A stream, which will return the same elements, which this FailableStream would return.
          */
         public Stream<O> stream() {
             return stream;
         }
     }
 
     /**
      * Converts the given {@link Collection} into a {@link FailableStream}.
      * This is basically a simplified, reduced version of the {@link Stream}
      * class, with the same underlying element stream, except that failable
      * objects, like {@link FailablePredicate}, {@link FailableFunction}, or
      * {@link FailableConsumer} may be applied, instead of
      * {@link Predicate}, {@link Function}, or {@link Consumer}. The idea is
      * to rewrite a code snippet like this:
      * <pre>{@code
      *     final List<O> list;
      *     final Method m;
      *     final Function<O,String> mapper = (o) -> {
      *         try {
      *             return (String) m.invoke(o);
      *         } catch (Throwable t) {
      *             throw Functions.rethrow(t);
      *         }
      *     };
      *     final List<String> strList = list.stream()
      *         .map(mapper).collect(Collectors.toList());
      *  }</pre>
      *  as follows:
      *  <pre>{@code
      *     final List<O> list;
      *     final Method m;
      *     final List<String> strList = Functions.stream(list.stream())
      *         .map((o) -> (String) m.invoke(o)).collect(Collectors.toList());
      *  }</pre>
      *  While the second version may not be <em>quite</em> as
      *  efficient (because it depends on the creation of additional,
      *  intermediate objects, of type FailableStream), it is much more
      *  concise, and readable, and meets the spirit of Lambdas better
      *  than the first version.
      * @param <O> The streams element type.
      * @param stream The stream, which is being converted.
      * @return The {@link FailableStream}, which has been created by
      *   converting the stream.
      */
     public static <O> FailableStream<O> stream(final Collection<O> stream) {
         return stream(stream.stream());
     }
 
     /**
      * Converts the given {@link Stream stream} into a {@link FailableStream}.
      * This is basically a simplified, reduced version of the {@link Stream}
      * class, with the same underlying element stream, except that failable
      * objects, like {@link FailablePredicate}, {@link FailableFunction}, or
      * {@link FailableConsumer} may be applied, instead of
      * {@link Predicate}, {@link Function}, or {@link Consumer}. The idea is
      * to rewrite a code snippet like this:
      * <pre>{@code
      *     final List<O> list;
      *     final Method m;
      *     final Function<O,String> mapper = (o) -> {
      *         try {
      *             return (String) m.invoke(o);
      *         } catch (Throwable t) {
      *             throw Functions.rethrow(t);
      *         }
      *     };
      *     final List<String> strList = list.stream()
      *         .map(mapper).collect(Collectors.toList());
      *  }</pre>
      *  as follows:
      *  <pre>{@code
      *     final List<O> list;
      *     final Method m;
      *     final List<String> strList = Functions.stream(list.stream())
      *         .map((o) -> (String) m.invoke(o)).collect(Collectors.toList());
      *  }</pre>
      *  While the second version may not be <em>quite</em> as
      *  efficient (because it depends on the creation of additional,
      *  intermediate objects, of type FailableStream), it is much more
      *  concise, and readable, and meets the spirit of Lambdas better
      *  than the first version.
      * @param <O> The streams element type.
      * @param stream The stream, which is being converted.
      * @return The {@link FailableStream}, which has been created by
      *   converting the stream.
      */
     public static <O> FailableStream<O> stream(final Stream<O> stream) {
         return new FailableStream<>(stream);
     }
 
     /**
      * Returns a {@link Collector} that accumulates the input elements into a
      * new array.
      *
      * @param pElementType Type of an element in the array.
      * @param <O> the type of the input elements
      * @return a {@link Collector} which collects all the input elements into an
      * array, in encounter order
      */
     public static <O> Collector<O, ?, O[]> toArray(final Class<O> pElementType) {
         return new ArrayCollector<>(pElementType);
     }
 
     /**
      * Constructs a new instance.
      */
     public Streams() {
         // empty
     }
 }