From 94e30f7ffbafcdd188d09d8c7bf7e4794b650018 Mon Sep 17 00:00:00 2001
From: Linnea Gräf <nea@nea.moe>
Date: Wed, 13 Nov 2024 22:27:28 +0100
Subject: wip

---
 src/main/java/moe/nea/pcj/Result.java | 107 ++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 src/main/java/moe/nea/pcj/Result.java

(limited to 'src/main/java/moe/nea/pcj/Result.java')

diff --git a/src/main/java/moe/nea/pcj/Result.java b/src/main/java/moe/nea/pcj/Result.java
new file mode 100644
index 0000000..8bec96a
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/Result.java
@@ -0,0 +1,107 @@
+package moe.nea.pcj;
+
+import org.jspecify.annotations.Nullable;
+
+import java.util.Optional;
+import java.util.function.Function;
+
+public sealed interface Result<Good, Bad> permits Result.Ok, Result.Fail {
+	default boolean isOk() {
+		return error().isEmpty();
+	}
+
+	Optional<Good> value();
+
+	Optional<Good> partial();
+
+	default Optional<Good> valueOrPartial() {
+		return value().or(this::partial);
+	}
+
+	Optional<Bad> error();
+
+	default <Next> Result<Next, Bad> map(Function<Good, Next> mapper) {
+		return flatMap(mapper.andThen(Result::ok));
+	}
+
+	default <Next> Result<Next, Bad> flatMap(Function<Good, Result<Next, Bad>> mapper) {
+		return flatMapBoth(mapper, Result::fail);
+	}
+
+	<NextGood> Result<NextGood, Bad> flatMapBoth(
+			Function<Good, Result<NextGood, Bad>> mapGood,
+			Function<Bad, Result<NextGood, Bad>> mapBad);
+
+	Result<Good, Bad> appendError(Bad error);
+
+	record Ok<Good, Bad>(Good okValue) implements Result<Good, Bad> {
+		@Override
+		public Result<Good, Bad> appendError(Bad error) {
+			return Result.partial(okValue, error);
+		}
+
+		@Override
+		public Optional<Good> partial() {
+			return Optional.empty();
+		}
+
+		@Override
+		public Optional<Good> value() {
+			return Optional.of(okValue);
+		}
+
+		@Override
+		public Optional<Bad> error() {
+			return Optional.empty();
+		}
+
+		@Override
+		public <NextGood> Result<NextGood, Bad> flatMapBoth(Function<Good, Result<NextGood, Bad>> mapGood, Function<Bad, Result<NextGood, Bad>> mapBad) {
+			return mapGood.apply(okValue);
+		}
+	}
+
+	record Fail<Good, Bad>(@Nullable Good partialValue, Bad badValue) implements Result<Good, Bad> {
+
+		@Override
+		public Optional<Good> value() {
+			return Optional.empty();
+		}
+
+		@Override
+		public Optional<Good> partial() {
+			return Optional.ofNullable(partialValue);
+		}
+
+		@Override
+		public Optional<Bad> error() {
+			return Optional.of(badValue);
+		}
+
+		@Override
+		public <NextGood> Result<NextGood, Bad> flatMapBoth(Function<Good, Result<NextGood, Bad>> mapGood, Function<Bad, Result<NextGood, Bad>> mapBad) {
+			if (partialValue != null) {
+				var nextPartial = mapGood.apply(partialValue);
+				return nextPartial.appendError(badValue);
+			}
+			return mapBad.apply(badValue);
+		}
+
+		@Override
+		public Result<Good, Bad> appendError(Bad error) {
+			return Result.partial(partialValue, AppendableError.concatError(badValue, error));
+		}
+	}
+
+	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, error);
+	}
+
+	static <Good, Bad> Result.Fail<Good, Bad> partial(@Nullable Good partial, Bad error) {
+		return new Fail<>(partial, error);
+	}
+}
-- 
cgit