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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.attempt;
import java.util.function.Consumer;
import java.util.function.Function;
import lombok.NonNull;
/**
* Wraps either a value from a success or an error from a failure.
*
* @param <R> the potential wrapped result type.
* @param <E> the potential error type.
* @author pacien
*/
public interface Attempt<R, E> {
/**
* @return whether the {@link Attempt} is successful.
*/
boolean isSuccess();
/**
* @return whether the {@link Attempt} is failed.
*/
boolean isFailure();
/**
* @return the result if this {@link Attempt} is a success.
* @throws java.util.NoSuchElementException if this {@link Attempt} is a failure.
*/
R getResult();
/**
* @return the error if this {@link Attempt} is a failure.
* @throws java.util.NoSuchElementException if this {@link Attempt} is a success.
*/
E getError();
/**
* @param resultConsumer a {@link Consumer} of result called if the {@link Attempt} is a success.
* @return the current {@link Attempt}
*/
default Attempt<R, E> ifSuccess(@NonNull Consumer<? super R> resultConsumer) {
if (isSuccess()) resultConsumer.accept(getResult());
return this;
}
/**
* @param errorConsumer a {@link Consumer} of error called if the {@link Attempt} is a failure.
* @return the current {@link Attempt}
*/
default Attempt<R, E> ifFailure(@NonNull Consumer<? super E> errorConsumer) {
if (isFailure()) errorConsumer.accept(getError());
return this;
}
/**
* @param mapper a function producing an {@link Attempt}, called with the current result if this {@link Attempt} is a success.
* @return this {@link Attempt} if it is a failure, or the produced one otherwise.
*/
default <RR> Attempt<RR, E> mapResult(@NonNull Function<? super R, ? extends Attempt<? extends RR, ? extends E>> mapper) {
//noinspection unchecked
return (Attempt<RR, E>) (isSuccess() ? mapper.apply(getResult()) : this);
}
/**
* @param mapper a function producing an {@link Attempt}, called with the current error if this {@link Attempt} is a failure.
* @return this {@link Attempt} if it is a success, or the alternative {@link Attempt} retrieved from the supplier otherwise.
*/
default <EE> Attempt<R, EE> mapError(@NonNull Function<? super E, ? extends Attempt<? extends R, ? extends EE>> mapper) {
//noinspection unchecked
return (Attempt<R, EE>) (isFailure() ? mapper.apply(getError()) : this);
}
/**
* @param mapper a function transforming an {@link Attempt}.
* @return the transformed {@link Attempt}
*/
default <RR, EE> Attempt<RR, EE> flatMap(@NonNull Function<? super Attempt<? super R, ? super E>, ? extends Attempt<? extends RR, ? extends EE>> mapper) {
//noinspection unchecked
return (Attempt<RR, EE>) mapper.apply(this);
}
/**
* @param result the result of the {@link Attempt}.
* @return a successful {@link Attempt} wrapping the supplied result.
*/
static <R, E> Attempt<R, E> success(R result) {
return new Success<>(result);
}
/**
* @param error the cause of the failure of the {@link Attempt}.
* @return a failed {@link Attempt} with the supplied error.
*/
static <R, E> Attempt<R, E> failure(E error) {
return new Failure<>(error);
}
/**
* @param supplier a {@code Supplier} that may throw an {@link Throwable}.
* @return an {@link Attempt} wrapping either the result of the execution of the supplier or any thrown {@link Throwable}.
*/
static <R, E extends Throwable> Attempt<R, E> attempt(@NonNull ThrowingSupplier<? extends R, ? extends E> supplier) {
try {
return success(supplier.get());
} catch (Throwable throwable) {
//noinspection unchecked
return (Attempt<R, E>) failure(throwable);
}
}
}
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