From d6c2f86eb00a05d92542c2f01292d1461ff2142b Mon Sep 17 00:00:00 2001
From: MartinWitt <wittlinger.martin@gmail.com>
Date: Fri, 21 Jan 2022 06:07:09 +0100
Subject: [PATCH] feat: LambdaToExecutableReference (#39)

---
 .../code_solver/TransformationEngine.java     |  2 +
 .../self/LambdaToExecutableReference.java     | 80 +++++++++++++++++++
 2 files changed, 82 insertions(+)
 create mode 100644 code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/transformations/self/LambdaToExecutableReference.java

diff --git a/code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/TransformationEngine.java b/code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/TransformationEngine.java
index 5b0181ed6..ac238a6d5 100644
--- a/code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/TransformationEngine.java
+++ b/code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/TransformationEngine.java
@@ -39,6 +39,7 @@
 import xyz.keksdose.spoon.code_solver.transformations.junit.simplification.TempoaryFolderAsParameter;
 import xyz.keksdose.spoon.code_solver.transformations.qodana.ArraysToString;
 import xyz.keksdose.spoon.code_solver.transformations.qodana.EmptyStringCheck;
+import xyz.keksdose.spoon.code_solver.transformations.self.LambdaToExecutableReference;
 import xyz.keksdose.spoon.code_solver.transformations.self.StringBuilderDirectUse;
 import xyz.keksdose.spoon.code_solver.transformations.self.ThreadLocalWithInitial;
 
@@ -82,6 +83,7 @@ protected void addProcessors(ProcessingManager pm, ChangeListener listener) {
 		pm.addProcessor(new EmptyStringCheck(listener));
 		pm.addProcessor(new StringBuilderDirectUse(listener));
 		pm.addProcessor(new ThreadLocalWithInitial(listener));
+		pm.addProcessor(new LambdaToExecutableReference(listener));
 		// pm.addProcessor(new AssertTrueEqualsCheck(listener));
 		// pm.addProcessor(new AssertFalseEqualsCheck(listener));
 		// pm.addProcessor(new AssertNullTransformation(listener));
diff --git a/code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/transformations/self/LambdaToExecutableReference.java b/code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/transformations/self/LambdaToExecutableReference.java
new file mode 100644
index 000000000..167d376eb
--- /dev/null
+++ b/code-transformation/src/main/java/xyz/keksdose/spoon/code_solver/transformations/self/LambdaToExecutableReference.java
@@ -0,0 +1,80 @@
+
+package xyz.keksdose.spoon.code_solver.transformations.self;
+
+import java.util.List;
+
+import spoon.reflect.code.CtConstructorCall;
+import spoon.reflect.code.CtExecutableReferenceExpression;
+import spoon.reflect.code.CtExpression;
+import spoon.reflect.code.CtInvocation;
+import spoon.reflect.code.CtLambda;
+import spoon.reflect.code.CtTypeAccess;
+import spoon.reflect.declaration.CtType;
+import spoon.reflect.declaration.CtTypedElement;
+import spoon.reflect.reference.CtExecutableReference;
+import spoon.reflect.reference.CtTypeReference;
+import xyz.keksdose.spoon.code_solver.history.Change;
+import xyz.keksdose.spoon.code_solver.history.ChangeListener;
+import xyz.keksdose.spoon.code_solver.history.Link;
+import xyz.keksdose.spoon.code_solver.history.MarkdownString;
+import xyz.keksdose.spoon.code_solver.transformations.BadSmell;
+import xyz.keksdose.spoon.code_solver.transformations.TransformationProcessor;
+
+public class LambdaToExecutableReference extends TransformationProcessor<CtLambda<?>> {
+
+	private static final BadSmell lambdaInsteadOfExecutableReference = new BadSmell() {
+		@Override
+		public MarkdownString getName() {
+			return MarkdownString.fromRaw("LambdaInsteadOfExecutableReference");
+		}
+
+		@Override
+		public MarkdownString getDescription() {
+			return MarkdownString.fromRaw("Lambda is used instead of executable reference");
+		}
+
+		@Override
+		public List<Link> getLinks() {
+			return List.of(new Link("https://rules.sonarsource.com/java/RSPEC-1612"));
+		}
+	};
+	public LambdaToExecutableReference(ChangeListener listener) {
+		super(listener);
+	}
+
+	@Override
+	public void process(CtLambda<?> lambda) {
+		if (lambda.getBody() == null) {
+			CtExpression<?> expression = lambda.getExpression();
+			if (expression instanceof CtInvocation) {
+				//TODO: handle this
+			}
+			if (expression instanceof CtConstructorCall) {
+				refactorConstructorCall(lambda, expression);
+			}
+		}
+	}
+
+	private void refactorConstructorCall(CtLambda<?> lambda, CtExpression<?> expression) {
+		CtConstructorCall<?> invocation = (CtConstructorCall<?>) expression;
+		if (invocation.getArguments().isEmpty()) {
+			CtExecutableReferenceExpression<?, CtTypeAccess<?>> exec = getFactory().Core()
+					.createExecutableReferenceExpression();
+			exec.setExecutable((CtExecutableReference) invocation.getExecutable());
+			exec.setType(getType(invocation));
+			exec.setTarget(getFactory().createTypeAccess(invocation.getType()));
+			lambda.replace(exec);
+			String raw = String.format("Replaced lambda %s with executable ref %s", lambda, exec);
+			String markdown = String.format("Replaced lambda `%s` with executable ref `%s`", lambda, exec);
+			CtType<Object> topLevelType = lambda.getParent(CtType.class).getTopLevelType();
+			setChanged(topLevelType, new Change(lambdaInsteadOfExecutableReference,
+				MarkdownString.fromMarkdown(raw, markdown), topLevelType));
+		}
+	}
+
+	@SuppressWarnings("unchecked")
+	private <T> CtTypeReference<T> getType(CtTypedElement<?> typedElement) {
+		return (CtTypeReference<T>) typedElement.getType();
+	}
+
+}