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Diversion Network Result type.
package net.diversionmc.error;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.stream.Collector;
import java.util.stream.Stream;
import static java.util.Collections.reverse;
import static net.diversionmc.error.Functionals.*;
import static net.diversionmc.error.Success.tryRun;
/**
* Result immutable type: Success or Error.
*
* @param Success type.
* @param Error type.
* @see Success
* @see Optional
*/
public final class Result {
//
// Factory
//
/**
* Create a success result.
*
* @param s Success value.
* @param Success type.
* @param Error type.
* @return Success result. Use {@link Optional} if you do not want error type.
*/
public static Result ok(S s) {
if (s == null) throw new IllegalArgumentException("Supplied null to result");
return new Result<>(s, null);
}
/**
* Create an error result.
*
* @param e Error value.
* @param Success type.
* @param Error type.
* @return Error result. Use {@link Success} if you do not want success type.
*/
public static Result error(E e) {
if (e == null) throw new IllegalArgumentException("Supplied null to result");
return new Result<>(null, e);
}
/**
* Convert a boolean into Result.
*
* @param test Boolean to convert.
* @param ok Object supplied if true.
* @param error Object supplied if false.
* @param Success type.
* @param Error type.
* @return Ok if true, else error.
*/
public static Result check(boolean test, Supplier ok, Supplier error) {
return test ? ok(ok.get()) : error(error.get());
}
/**
* Convert a boolean into Result.
*
* @param test Boolean to convert.
* @param ifTrue Result supplied if true.
* @param ifFalse Result supplied if false.
* @param Success type.
* @param Error type.
* @return Obvious.
*/
public static Result flatCheck(boolean test, Supplier> ifTrue, Supplier> ifFalse) {
return (test ? ifTrue : ifFalse).get();
}
/**
* Convert an optional into Result.
*
* @param ok Optional to check and turn into success result.
* @param error Object supplied if optional is empty.
* @param Success type.
* @param Error type.
* @return Ok with the optional's value if present, else error.
*/
public static Result from(Optional ok, Supplier error) {
return ok
.map(Result::ok)
.orElseGet(applyFS(Result::error, error));
}
/**
* Convert an optional into Result.
*
* @param check Optional to check and turn into success result.
* @param other Object supplied if optional is empty.
* @param Success type.
* @param Error type.
* @return Ok with the optional's value if present, else other.
*/
public static Result flatFrom(Optional check, Supplier> other) {
return check
.map(Result::ok)
.orElseGet(other);
}
//
// Boilerplate
//
private final S ok;
private final E error;
private Result(S ok, E error) {
this.ok = ok;
this.error = error;
}
/**
* Get success value.
*
* @return Success value if result is successful or empty.
*/
public Optional ok() {
return optional(ok);
}
/**
* Get success value.
*
* @return Success value if result is successful or empty.
*/
public Stream okStream() {
return stream(ok);
}
/**
* Get error value.
*
* @return Error value if result is unsuccessful or empty.
*/
public Optional error() {
return optional(error);
}
/**
* Get error value.
*
* @return Error value if result is unsuccessful or empty.
*/
public Stream errorStream() {
return stream(error);
}
/**
* Check if result is successful.
*
* @return True if success result.
*/
public boolean isOk() {
return ok != null;
}
/**
* Check if result is unsuccessful.
*
* @return True if error result.
*/
public boolean isError() {
return error != null;
}
/**
* Convert result to success (throw out success value).
*
* @return Success object.
*/
public Success success() {
return isOk()
? Success.ok()
: Success.error(error);
}
/**
* Debug representation of the result.
*
* @return Ok or error, converted to string.
*/
public String toString() {
return (isOk() ? ok : error) + "";
}
/**
* Compare to either {@link Result}, {@link Success} or {@link Optional}.
*
* @param obj Object to compare to.
* @return True if underlying objects under those 3 types match this result (ok or error) or are missing.
*/
public boolean equals(Object obj) {
return (obj instanceof Result r2 && isOk() == r2.isOk() && (isOk() ? ok.equals(r2.ok) : error.equals(r2.error)))
|| (obj instanceof Success s2 && isOk() == s2.isOk() && (isOk() || error.equals(s2.error().get())))
|| (obj instanceof Optional o2 && isOk() == o2.isPresent() && (!isOk() || ok.equals(o2.get())));
}
/**
* This hashCode method refers to either hashCode of ok or error.
*
* @return Ok hashCode if this result is successful, error hashCode otherwise.
*/
public int hashCode() {
return (isOk() ? ok : error).hashCode();
}
//
// Function
//
/**
* Convert a result into another result.
*
* @param mapper Converter.
* @param New success type.
* @param New error type.
* @return New result.
*/
public Result map(Function, Result> mapper) {
return mapper.apply(this);
}
/**
* Convert the success value.
*
* @param sMapper Success converter.
* @param eMapper Error converter.
* @param New success type.
* @param New error type.
* @return New result.
*/
public Result map(Function sMapper, Function eMapper) {
return isOk()
? ok(sMapper.apply(ok))
: error(eMapper.apply(error));
}
/**
* Convert the success value.
*
* @param mapper Converter.
* @param New success type.
* @return New result.
*/
public Result mapOk(Function mapper) {
return isOk()
? ok(mapper.apply(ok))
: error(error);
}
/**
* Convert the error value.
*
* @param mapper Converter.
* @param New error type.
* @return New result.
*/
public Result mapError(Function mapper) {
return isOk()
? ok(ok)
: error(mapper.apply(error));
}
/**
* Convert the success value to a new result.
*
* @param mapper Converter.
* @param New success type.
* @return New result.
*/
public Result flatMapResult(Function> mapper) {
return isOk()
? mapper.apply(ok)
: error(error);
}
/**
* Convert the success value to a new success.
*
* @param mapper Converter.
* @return New success.
*/
public Success flatMapSuccess(Function> mapper) {
return isOk()
? mapper.apply(ok)
: Success.error(error);
}
/**
* Peek at the result without changing it.
*
* @param peeker Peeker function.
*/
public Result peek(Consumer> peeker) {
peeker.accept(this);
return this;
}
/**
* Peek at the success value without changing it, if it is present.
*
* @param peeker Peeker function.
*/
public Result peekOk(Consumer peeker) {
if (isOk()) peeker.accept(ok);
return this;
}
/**
* Peek at the error value without changing it, if it is present.
*
* @param peeker Peeker function.
*/
public Result peekError(Consumer peeker) {
if (isError()) peeker.accept(error);
return this;
}
/**
* Filter the ok value, do an error if not passed.
*
* @param filter Filter function.
* @param error Error supplier in case ok does not pass filter.
*/
public Result filter(Predicate filter, Supplier error) {
// don't do anything if error or filter passed
// error if ok but filter not passed
return isError()
|| filter.test(ok)
? this
: error(error.get());
}
/**
* Try to receive value from another result.
*
* @param other Other result to use if this result is unsuccessful.
* @return Either this or other, but if other result fails, this error is used, ignoring other's error.
*/
public Result or(Result other) {
return isOk()
? this
: other
.mapError(ignoreS(applyS(error)));
}
/**
* Try to receive value from an optional.
*
* @param other Optional to use if this result is unsuccessful.
* @return Either this or other, but if other result is empty, this error is used, ignoring other's error.
*/
public Result or(Optional other) {
return isOk()
? this
: from(other, applyS(error));
}
/**
* Try to receive value from another result.
*
* @param other Other result to use if this result is unsuccessful.
* @return Either this or other, but if other result fails, this error is used, ignoring other's error.
*/
public Result flatOr(Supplier> other) {
return isOk()
? this
: other.get()
.mapError(ignoreS(applyS(error)));
}
//
// Static Utils
//
/**
* Catch an exception.
*
* @param ce Exception type to catch
* @param s TryS to catch
* @param Success type
* @param Error type
* @return Ok if successful, error if caught an exception
*/
@SuppressWarnings("unchecked")
public static Result tryGet(Class ce, Supplier s) {
try {
return ok(s.get());
} catch (ResultException e) {
var ex = e.exception();
if (ce.isInstance(ex))
return error((E) ex);
throw e;
}
}
private static List tryCloseAll(List resources) {
reverse(resources); // reversing a stream does not make sense, so reverse a list
return resources.stream()
.map(i -> tryRun(
Exception.class,
(TryR) i::close))
.flatMap(Success::errorStream)
.toList(); // this lets us close all resources ignoring errors until collect
}
@SuppressWarnings("unchecked")
private static Result errorCatchRethrow(Class ce, ResultException e) {
if (ce.isInstance(e.exception()))
return error((E) e);
throw e;
}
/**
* Catch an exception.
*
* @param ce Exception type to catch
* @param f TryWithResources block to catch
* @param Success type
* @param Error type
* @return Ok if successful, error if caught an exception
*/
public static Result tryGet(Class ce, TryF f) {
var resources = new ArrayList();
try {
var res = f.apply(new TryWithResources(resources)); // this may throw...
var closed = tryCloseAll(resources);
if (closed.isEmpty()) return ok(res);
var firstCloseFailure = closed.get(0);
closed.stream()
.skip(1)
.forEach(firstCloseFailure::addSuppressed);
return errorCatchRethrow(ce, new ResultException(firstCloseFailure));
} catch (ResultException e) {
var closed = tryCloseAll(resources); // ...so we need to close all resources before catchRethrow
var caught = Result.errorCatchRethrow(ce, e);
closed.forEach(caught.error::addSuppressed);
return caught;
}
}
/**
* Catch an exception.
*
* @param ce Exception type to catch
* @param f TryWithResources block to catch
* @param Success type
* @param Error type
* @return Ok if successful, error if caught an exception
*/
public static Result flatTryGet(Class ce, TryF, E> f) {
var resources = new ArrayList();
try {
var res = f.apply(new TryWithResources(resources)); // this may throw...
var closed = tryCloseAll(resources);
if (closed.isEmpty()) return res; // this res may be not ok
var firstCloseFailure = closed.get(0);
closed.stream()
.skip(1)
.forEach(firstCloseFailure::addSuppressed);
return errorCatchRethrow(ce, new ResultException(firstCloseFailure));
} catch (ResultException e) {
var closed = tryCloseAll(resources); // ...so we need to close all resources before catchRethrow
var caught = Result.errorCatchRethrow(ce, e);
closed.forEach(caught.error::addSuppressed);
return caught;
}
}
/**
* Collect all successful type to a list, if possible.
*
* @param Success type
* @param Error type
* @return Result of collected list or first error
*/
public static Collector, ?, Result, E>> toResultList() {
return Collector.of(
mapS(mapS(ArrayList::new, Result::, E>ok), AtomicReference::new),
(results, result) -> results.set(result
.flatMapResult(r -> results.get()
.peekOk(list -> list.add(r)))),
(results, result) -> {
results.set(result.get()
.flatMapResult(r -> results.get()
.peekOk(list -> list.addAll(r))));
return results;
},
AtomicReference::get);
}
}