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package moe.nea.pcj;
import org.jspecify.annotations.Nullable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Consumer;
import java.util.function.Function;
public sealed interface Result<Good, Bad> permits Result.Ok, Result.Fail {
default boolean isOk() {
return errors().isEmpty();
}
Optional<Good> value();
Optional<Good> partial();
default Optional<Good> valueOrPartial() {
return value().or(this::partial);
}
List<Bad> errors();
default <Next> Result<Next, Bad> map(Function<Good, Next> mapper) {
return flatMap(mapper.andThen(Result::ok));
}
<Next> Result<Next, Bad> flatMap(Function<Good, Result<? extends Next, ? extends Bad>> mapper);
default <NextBad> Result<Good, NextBad> mapError(Function<Bad, NextBad> mapper) {
return mapErrors(it -> it.stream().map(mapper).toList());
}
<NextBad> Result<Good, NextBad> mapErrors(Function<List<Bad>, List<NextBad>> mapper);
Result<Good, Bad> appendErrors(List<Bad> error);
record Ok<Good, Bad>(Good okValue) implements Result<Good, Bad> {
@Override
public Result<Good, Bad> appendErrors(List<Bad> errors) {
if (errors.isEmpty()) return new Ok<>(okValue);
return new Fail<>(okValue, errors);
}
@Override
public <NextBad> Result<Good, NextBad> mapErrors(Function<List<Bad>, List<NextBad>> mapper) {
return new Ok<>(okValue);
}
@Override
public Optional<Good> partial() {
return Optional.empty();
}
@Override
public List<Bad> errors() {
return List.of();
}
@Override
public <Next> Result<Next, Bad> flatMap(Function<Good, Result<? extends Next, ? extends Bad>> mapper) {
return Result.cast(mapper.apply(okValue));
}
@Override
public Optional<Good> value() {
return Optional.of(okValue);
}
@Override
public int hashCode() {
return Objects.hash(okValue);
}
@Override
public boolean equals(Object obj) {
if (obj == this) return true;
if (obj instanceof Result.Ok<?, ?> ok) {
return Objects.equals(ok.okValue, this.okValue);
}
return false;
}
}
record Fail<Good, Bad>(@Nullable Good partialValue, List<Bad> badValue) implements Result<Good, Bad> {
public Fail {
if (badValue.isEmpty())
throw new IllegalArgumentException("Cannot create failure without any error values");
}
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj instanceof Result.Fail<?, ?> fail) {
return Objects.equals(partialValue, fail.partialValue) && badValue.equals(fail.badValue);
}
return false;
}
@Override
public int hashCode() {
return Objects.hash(partialValue, badValue);
}
@Override
public Optional<Good> value() {
return Optional.empty();
}
@Override
public Optional<Good> partial() {
return Optional.ofNullable(partialValue);
}
@Override
public List<Bad> errors() {
return Collections.unmodifiableList(badValue);
}
@Override
public <Next> Result<Next, Bad> flatMap(Function<Good, Result<? extends Next, ? extends Bad>> mapper) {
if (partialValue != null) {
return Result.<Next, Bad>cast(mapper.apply(partialValue)).appendErrors(badValue);
}
return new Fail<>(null, badValue);
}
@Override
public <NextBad> Result<Good, NextBad> mapErrors(Function<List<Bad>, List<NextBad>> mapper) {
return new Fail<>(partialValue, mapper.apply(badValue));
}
@Override
public Result<Good, Bad> appendErrors(List<Bad> errors) {
var nextErrors = new ArrayList<>(badValue);
nextErrors.addAll(errors);
return new Fail<>(partialValue, nextErrors);
}
}
static <Good, Bad> Result<Good, Bad> ok(Good value) {
return new Ok<>(value);
}
static <Good, Bad> Result.Fail<Good, Bad> fail(Bad error) {
return new Fail<>(null, List.of(error));
}
static <Good, Bad> Result<Good, Bad> cast(Result<? extends Good, ? extends Bad> c) {
//noinspection unchecked
return (Result<Good, Bad>) c;
}
static <Good, Bad> Result.Fail<Good, Bad> partial(@Nullable Good partial, Bad error) {
return new Fail<>(partial, List.of(error));
}
}
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