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Streams Utils is a set of operations written on Java 8 Streams. It allows several basic operations that are not available in the the Java 8, and that have proven to be very useful in some cases.

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/*
 * Copyright (C) 2015 José Paumard
 *
 * 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.paumard.spliterators;

import org.paumard.streams.StreamsUtils;

import java.util.Objects;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;

/**
 * See the documentation and patterns to be used in this class in the {@link StreamsUtils} factory class.
 *
 * @author José
 */
public class ValidatingSpliterator implements Spliterator {

    private final Spliterator spliterator;
    private final Function transformIfValid, transformIfNotValid;
    private final Predicate validator;

    public static class Builder {

        private Spliterator spliterator;
        private Function transformIfValid, transformIfNotValid;
        private Predicate validator;

        public Builder() {
        }

        public Builder with(Spliterator spliterator) {
            this.spliterator = Objects.requireNonNull(spliterator);
            return this;
        }

        public Builder validatedBy(Predicate validator) {
            this.validator = Objects.requireNonNull(validator);
            return this;
        }

        public Builder withValidFunction(Function validFunction) {
            this.transformIfValid = Objects.requireNonNull(validFunction);
            return this;
        }

        public Builder withNotValidFunction(Function notValidFunction) {
            this.transformIfNotValid = Objects.requireNonNull(notValidFunction);
            return this;
        }

        public ValidatingSpliterator build() {
            return new ValidatingSpliterator<>(spliterator, validator, transformIfValid, transformIfNotValid);
        }
    }

    ValidatingSpliterator(
            Spliterator spliterator, Predicate validator,
            Function transformIfValid, Function transformIfNotValid) {
        this.spliterator = Objects.requireNonNull(spliterator, "spliterator");
        this.validator = Objects.requireNonNull(validator, "validator");
        this.transformIfValid = Objects.requireNonNull(transformIfValid, "validFunction");
        this.transformIfNotValid = Objects.requireNonNull(transformIfNotValid, "notValidFunction");
    }

    @Override
    public boolean tryAdvance(Consumer action) {

        return this.spliterator.tryAdvance(
               e -> {
                   if (validator.test(e)) {
                       action.accept(transformIfValid.apply(e));
                   } else {
                       action.accept(transformIfNotValid.apply(e));
                   }
               }
        );
    }

    @Override
    public Spliterator trySplit() {
        Spliterator split = this.spliterator.trySplit();
        return split == null ? null : new ValidatingSpliterator<>(split, validator, transformIfValid, transformIfNotValid);
    }

    @Override
    public long estimateSize() {
        return spliterator.estimateSize();
    }

    @Override
    public int characteristics() {
        return this.spliterator.characteristics();
    }
}