JUnit 5.10.0 + Nahara Toolkit Pipeline a.k.a "Stream API at home"

common/attachments/build.gradle

@@ -10,7 +10,7 @@ repositories {
 }
 
 dependencies {
-    testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.10.0'
 }
 
 tasks.named('test') {

common/configurations/build.gradle

@@ -10,7 +10,7 @@ repositories {
 }
 
 dependencies {
-    testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.10.0'
 }
 
 tasks.named('test') {

common/nbtstring/build.gradle

@@ -10,7 +10,7 @@ repositories {
 }
 
 dependencies {
-    testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.10.0'
 }
 
 tasks.named('test') {

common/pipeline/build.gradle

@@ -0,0 +1,18 @@
+plugins {
+}
+
+eclipse {
+    project.name = "Nahara Toolkit - Common - Pipeline"
+}
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.10.0'
+}
+
+tasks.named('test') {
+    useJUnitPlatform()
+}

common/pipeline/src/main/java/nahara/common/pipeline/Pipeline.java

@@ -0,0 +1,42 @@
+package nahara.common.pipeline;
+
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+/**
+ * <p>Represent a pipeline that takes in inputs and yield out outputs.</p>
+ * <p>Pipelines can be used to filter and transform data, similar to {@link Stream}. I do not know why I made
+ * this (well ok to be fair I think reusing pipeline transformation could reduce memory usage), but it could
+ * be useful for someone. Only time will tell I guess?</p>
+ * @param <I> Input type.
+ * @param <O> Output type.
+ */
+public interface Pipeline<I, O> {
+	public Iterator<O> iteratorOf(Iterator<I> input);
+
+	default Iterator<O> iteratorOf(I input) {
+		return iteratorOf(Collections.singleton(input).iterator());
+	}
+
+	default Iterator<O> iteratorOf(Iterable<I> input) {
+		return iteratorOf(input.iterator());
+	}
+
+	default Optional<O> firstNonnullOf(Iterator<I> input) {
+		Iterator<O> iter = iteratorOf(input);
+
+		while (iter.hasNext()) {
+			O obj = iter.next();
+			if (obj == null) continue;
+			return Optional.of(obj);
+		}
+
+		return Optional.empty();
+	}
+
+	default Optional<O> firstNonnullOf(I input) {
+		return firstNonnullOf(Collections.singleton(input).iterator());
+	}
+}

common/pipeline/src/main/java/nahara/common/pipeline/PipelineBuilder.java

@@ -0,0 +1,19 @@
+package nahara.common.pipeline;
+
+import java.util.function.Function;
+import java.util.function.Predicate;
+
+import nahara.common.pipeline.impl.PipelineBuilderImpl;
+import nahara.common.pipeline.impl.StartOfPipelineImpl;
+
+public interface PipelineBuilder<I, O> {
+	public PipelineBuilder<I, O> filter(Predicate<O> predicate);
+	public <M> PipelineBuilder<I, M> map(Function<O, M> mapper);
+
+	// Create and build
+	public Pipeline<I, O> build();
+
+	public static <T> PipelineBuilder<T, T> create() {
+		return new PipelineBuilderImpl<>(new StartOfPipelineImpl<>());
+	}
+}

common/pipeline/src/main/java/nahara/common/pipeline/impl/FilterPipelineImpl.java

@@ -0,0 +1,56 @@
+package nahara.common.pipeline.impl;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.function.Predicate;
+
+import nahara.common.pipeline.Pipeline;
+
+public class FilterPipelineImpl<I, O> implements Pipeline<I, O> {
+	private Pipeline<I, O> previous;
+	private Predicate<O> predicate;
+
+	public FilterPipelineImpl(Pipeline<I, O> previous, Predicate<O> predicate) {
+		this.previous = previous;
+		this.predicate = predicate;
+	}
+
+	@Override
+	public Iterator<O> iteratorOf(Iterator<I> input) {
+		return new Iterator<O>() {
+			private O nextObj = null;
+			private boolean holdingNextObj = false, isEnded = false;
+			private Iterator<O> prevIter = previous.iteratorOf(input);
+
+			@Override
+			public boolean hasNext() {
+				if (isEnded) return false;
+				if (!holdingNextObj) {
+					while (prevIter.hasNext()) {
+						O obj = prevIter.next();
+						if (!predicate.test(obj)) continue;
+
+						holdingNextObj = true;
+						nextObj = obj;
+						return true;
+					}
+
+					isEnded = true;
+					return false;
+				}
+
+				return true;
+			}
+
+			@Override
+			public O next() {
+				if (!holdingNextObj) {
+					if (isEnded || !hasNext()) throw new NoSuchElementException();
+				}
+
+				holdingNextObj = false;
+				return nextObj;
+			}
+		};
+	}
+}

common/pipeline/src/main/java/nahara/common/pipeline/impl/MapPipelineImpl.java

@@ -0,0 +1,53 @@
+package nahara.common.pipeline.impl;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.function.Function;
+
+import nahara.common.pipeline.Pipeline;
+
+public class MapPipelineImpl<I, M, O> implements Pipeline<I, O> {
+	private Pipeline<I, M> previous;
+	private Function<M, O> mapper;
+
+	public MapPipelineImpl(Pipeline<I, M> previous, Function<M, O> mapper) {
+		this.previous = previous;
+		this.mapper = mapper;
+	}
+
+	@Override
+	public Iterator<O> iteratorOf(Iterator<I> input) {
+		return new Iterator<O>() {
+			private O nextObj = null;
+			private boolean holdingNextObj = false, isEnded = false;
+			private Iterator<M> prevIter = previous.iteratorOf(input);
+
+			@Override
+			public boolean hasNext() {
+				if (isEnded) return false;
+				if (!holdingNextObj) {
+					if (!prevIter.hasNext()) {
+						isEnded = true;
+						return false;
+					}
+
+					holdingNextObj = true;
+					nextObj = mapper.apply(prevIter.next());
+					return true;
+				}
+
+				return true;
+			}
+
+			@Override
+			public O next() {
+				if (!holdingNextObj) {
+					if (isEnded || !hasNext()) throw new NoSuchElementException();
+				}
+
+				holdingNextObj = false;
+				return nextObj;
+			}
+		};
+	}
+}

common/pipeline/src/main/java/nahara/common/pipeline/impl/PipelineBuilderImpl.java

@@ -0,0 +1,31 @@
+package nahara.common.pipeline.impl;
+
+import java.util.function.Function;
+import java.util.function.Predicate;
+
+import nahara.common.pipeline.Pipeline;
+import nahara.common.pipeline.PipelineBuilder;
+
+public class PipelineBuilderImpl<I, O> implements PipelineBuilder<I, O> {
+	private Pipeline<I, O> current;
+
+	public PipelineBuilderImpl(Pipeline<I, O> current) {
+		this.current = current;
+	}
+
+	@Override
+	public PipelineBuilder<I, O> filter(Predicate<O> predicate) {
+		current = new FilterPipelineImpl<>(current, predicate);
+		return this;
+	}
+
+	@Override
+	public <M> PipelineBuilder<I, M> map(Function<O, M> mapper) {
+		return new PipelineBuilderImpl<>(new MapPipelineImpl<>(current, mapper));
+	}
+
+	@Override
+	public Pipeline<I, O> build() {
+		return current;
+	}
+}

common/pipeline/src/main/java/nahara/common/pipeline/impl/StartOfPipelineImpl.java

@@ -0,0 +1,12 @@
+package nahara.common.pipeline.impl;
+
+import java.util.Iterator;
+
+import nahara.common.pipeline.Pipeline;
+
+public class StartOfPipelineImpl<I> implements Pipeline<I, I> {
+	@Override
+	public Iterator<I> iteratorOf(Iterator<I> input) {
+		return input;
+	}
+}

common/pipeline/src/test/java/nahara/common/pipeline/PipelineTest.java

@@ -0,0 +1,18 @@
+package nahara.common.pipeline;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class PipelineTest {
+	@Test
+	void testMapping() {
+		var pipeline = PipelineBuilder.<String>create()
+				.map(v -> Integer.parseInt(v))
+				.map(v -> v + 1)
+				.filter(v -> v != 0)
+				.build();
+		assertEquals(124, pipeline.firstNonnullOf("123").orElseThrow());
+		assertTrue(pipeline.firstNonnullOf("-1").isEmpty());
+	}
+}

common/structures/build.gradle

@@ -10,7 +10,7 @@ repositories {
 }
 
 dependencies {
-    testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.10.0'
 }
 
 tasks.named('test') {

common/tasks/build.gradle

@@ -10,7 +10,7 @@ repositories {
 }
 
 dependencies {
-    testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.10.0'
 }
 
 tasks.named('test') {

settings.gradle

@@ -8,6 +8,7 @@ plugins {
     'common/configurations',
     'common/localize',
     'common/nbtstring',
+    'common/pipeline',
     'common/structures',
     'common/tasks',