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/*
* lemonad - Some functional sweetness for Java
* Copyright (C) 2019 Pacien TRAN-GIRARD
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package org.pacien.lemonad.validation;
import org.pacien.lemonad.attempt.Attempt;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.stream.Stream;
import lombok.NonNull;
import static java.util.stream.Collectors.toUnmodifiableList;
import static org.pacien.lemonad.attempt.Attempt.failure;
import static org.pacien.lemonad.attempt.Attempt.success;
/**
* Wraps the result of the validation of a subject.
*
* @param <S> the subject type,
* @param <E> the error type.
* @author pacien
*/
public interface Validation<S, E> {
/**
* @return whether no error have been reported during the validation.
*/
boolean isValid();
/**
* @return whether some error have been reported during the validation.
*/
boolean isInvalid();
/**
* @return the subject of the validation.
*/
S getSubject();
/**
* @return the potentially empty list of reported validation errors.
*/
List<E> getErrors();
/**
* @param consumer a subject consumer called if the validation is successful.
* @return the current object.
*/
default Validation<S, E> ifValid(@NonNull Consumer<? super S> consumer) {
if (isValid()) consumer.accept(getSubject());
return this;
}
/**
* @param consumer the consumer called with the validation subject and reported errors if the validation is failed.
* @return the current object.
*/
default Validation<S, E> ifInvalid(@NonNull BiConsumer<? super S, ? super List<? super E>> consumer) {
if (!isValid()) consumer.accept(getSubject(), getErrors());
return this;
}
/**
* @return an {@link Attempt} with a state corresponding to the one of the validation.
*/
default Attempt<S, List<E>> toAttempt() {
return isValid() ? success(getSubject()) : failure(getErrors());
}
/**
* @param mapper a function transforming a {@link Validation}.
* @return the transformed {@link Validation}.
*/
default <SS, EE> Validation<SS, EE> flatMap(@NonNull Function<? super Validation<? super S, ? super E>, ? extends Validation<? extends SS, ? extends EE>> mapper) {
//noinspection unchecked
return (Validation<SS, EE>) mapper.apply(this);
}
/**
* @param subject an overriding subject.
* @param validationResults a {@link Stream} of {@link Validation}s to merge.
* @return the merged {@link Validation} containing all errors from the supplied ones.
*/
static <S, E> Validation<S, E> merge(S subject, @NonNull Stream<? extends Validation<?, ? extends E>> validationResults) {
return new ValidationContainer<>(
subject,
validationResults.flatMap(res -> res.getErrors().stream()).collect(toUnmodifiableList()));
}
/**
* @param subject the suject of the validation.
* @return a successful {@link Validation}.
*/
static <S, E> Validation<S, E> valid(S subject) {
return new ValidationContainer<>(subject, List.of());
}
/**
* @param subject the suject of the validation.
* @param error a validation error.
* @param errors additional validation errors.
* @return a failed {@link Validation} for the supplied subject.
*/
@SafeVarargs static <S, E> Validation<S, E> invalid(S subject, E error, E... errors) {
return new ValidationContainer<>(
subject,
Stream.concat(Stream.of(error), Arrays.stream(errors)).map(Objects::requireNonNull).collect(toUnmodifiableList()));
}
}
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