/*

 * Copyright (c) 2017, 2017, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package org.graalvm.util;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collection;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

import java.util.Objects;

import java.util.function.Function;

import java.util.function.IntFunction;

import java.util.function.Predicate;

import java.util.function.Supplier;

/**

 * This class contains utility methods for commonly used functional patterns for collections.

 */

    /**

     * Concatenates two iterables into a single iterable. The iterator exposed by the returned

     * iterable does not support {@link Iterator#remove()} even if the input iterables do.

     *

     * @throws NullPointerException if {@code a} or {@code b} is {@code null}

     */

    public static <T> Iterable<T> concat(Iterable<T> a, Iterable<T> b) {

        List<Iterable<T>> l = Arrays.asList(a, b);

        return concat(l);

    }

    /**

     * Concatenates multiple iterables into a single iterable. The iterator exposed by the returned

     * iterable does not support {@link Iterator#remove()} even if the input iterables do.

     *

     * @throws NullPointerException if {@code iterables} or any of its elements are {@code null}

     */

    public static <T> Iterable<T> concat(List<Iterable<T>> iterables) {

        for (Iterable<T> iterable : iterables) {

            Objects.requireNonNull(iterable);

        }

        return new Iterable<T>() {

            @Override

            public Iterator<T> iterator() {

                if (iterables.size() == 0) {

                    return Collections.emptyIterator();

                }

                return new Iterator<T>() {

                    Iterator<Iterable<T>> cursor = iterables.iterator();

                    Iterator<T> currentIterator = cursor.next().iterator();

                    private void advance() {

                        while (!currentIterator.hasNext() && cursor.hasNext()) {

                            currentIterator = cursor.next().iterator();

                        }

                    }

                    @Override

                    public boolean hasNext() {

                        advance();

                        return currentIterator.hasNext();

                    }

                    @Override

                    public T next() {

                        advance();

                        return currentIterator.next();

                    }

                };

            }

        };

    }

    public static <T> boolean allMatch(T[] inputs, Predicate<T> predicate) {

        return allMatch(Arrays.asList(inputs), predicate);

    }

    public static <T> boolean allMatch(Iterable<T> inputs, Predicate<T> predicate) {

        for (T t : inputs) {

            if (!predicate.test(t)) {

                return false;

            }

        }

        return true;

    }

    public static <T> boolean anyMatch(T[] inputs, Predicate<T> predicate) {

        return anyMatch(Arrays.asList(inputs), predicate);

    }

    public static <T> boolean anyMatch(Iterable<T> inputs, Predicate<T> predicate) {

        for (T t : inputs) {

            if (predicate.test(t)) {

                return true;

            }

        }

        return false;

    }

    public static <T> List<T> filterToList(List<T> inputs, Predicate<? super T> predicate) {

        return filterToList(inputs, predicate, ArrayList::new);

    }

    public static <T> List<T> filterToList(List<T> inputs, Predicate<? super T> predicate, Supplier<List<T>> listGenerator) {

        List<T> resultList = listGenerator.get();

        for (T t : inputs) {

            if (predicate.test(t)) {

                resultList.add(t);

            }

        }

        return resultList;

    }

    /**

     */

    public static <T, R> R[] filterAndMapToArray(T[] inputs, Predicate<? super T> predicate, Function<? super T, ? extends R> mapper, IntFunction<R[]> arrayGenerator) {

        List<R> resultList = new ArrayList<>();

        for (T t : inputs) {

            if (predicate.test(t)) {

                resultList.add(mapper.apply(t));

            }

        }

        return resultList.toArray(arrayGenerator.apply(resultList.size()));

    }

    /**

     */

    public static <T, R> R[] mapToArray(T[] inputs, Function<? super T, ? extends R> mapper, IntFunction<R[]> arrayGenerator) {

        return mapToArray(Arrays.asList(inputs), mapper, arrayGenerator);

    }

    public static <T, R> R[] mapToArray(Collection<T> inputs, Function<? super T, ? extends R> mapper, IntFunction<R[]> arrayGenerator) {

        R[] result = arrayGenerator.apply(inputs.size());

        int idx = 0;

        for (T t : inputs) {

            result[idx++] = mapper.apply(t);

        }

        return result;

    }

    public static <T, R> String mapAndJoin(T[] inputs, Function<? super T, ? extends R> mapper, String delimiter) {

        return mapAndJoin(Arrays.asList(inputs), mapper, delimiter, "", "");

    }

    public static <T, R> String mapAndJoin(T[] inputs, Function<? super T, ? extends R> mapper, String delimiter, String prefix) {

        return mapAndJoin(Arrays.asList(inputs), mapper, delimiter, prefix, "");

    }

    public static <T, R> String mapAndJoin(T[] inputs, Function<? super T, ? extends R> mapper, String delimiter, String prefix, String suffix) {

        return mapAndJoin(Arrays.asList(inputs), mapper, delimiter, prefix, suffix);

    }

    public static <T, R> String mapAndJoin(Iterable<T> inputs, Function<? super T, ? extends R> mapper, String delimiter) {

        return mapAndJoin(inputs, mapper, delimiter, "", "");

    }

    public static <T, R> String mapAndJoin(Iterable<T> inputs, Function<? super T, ? extends R> mapper, String delimiter, String prefix) {

        return mapAndJoin(inputs, mapper, delimiter, prefix, "");

    }

    public static <T, R> String mapAndJoin(Iterable<T> inputs, Function<? super T, ? extends R> mapper, String delimiter, String prefix, String suffix) {

        StringBuilder strb = new StringBuilder();

        String sep = "";

        for (T t : inputs) {

            strb.append(sep).append(prefix).append(mapper.apply(t)).append(suffix);

            sep = delimiter;

        }

        return strb.toString();

    }

}