2 files changed, 149 insertions, 0 deletions
diff --git a/src/main/java/foo/zaaarf/routecompass/Route.java b/src/main/java/foo/zaaarf/routecompass/Route.java
new file mode 100644
index 0000000..2b61571
--- /dev/null
+++ b/src/main/java/foo/zaaarf/routecompass/Route.java
@@ -0,0 +1,29 @@
+package foo.zaaarf.routecompass;
+
+import org.springframework.web.bind.annotation.RequestMethod;
+
+/**
+ * Internal representation of a REST route.
+ */
+public class Route {
+	public final String classFqn;
+	public final String route;
+	public final String method;
+	public final boolean deprecated;
+
+
+	public Route(String classFqn, String route, RequestMethod[] methods, boolean deprecated) {
+		this.classFqn = classFqn;
+		this.route = route;
+		StringBuilder methodStringBuilder = new StringBuilder("[");
+		for(RequestMethod m : methods)
+			methodStringBuilder
+				.append(m.name())
+				.append("|");
+		methodStringBuilder
+			.deleteCharAt(methodStringBuilder.length() - 1)
+			.append("]");
+		this.method = methodStringBuilder.toString();
+		this.deprecated = deprecated;
+	}
+}
diff --git a/src/main/java/foo/zaaarf/routecompass/RouteCompass.java b/src/main/java/foo/zaaarf/routecompass/RouteCompass.java
new file mode 100644
index 0000000..a3e9667
--- /dev/null
+++ b/src/main/java/foo/zaaarf/routecompass/RouteCompass.java
@@ -0,0 +1,120 @@
+package foo.zaaarf.routecompass;
+
+import org.springframework.web.bind.annotation.*;
+
+import javax.annotation.processing.AbstractProcessor;
+import javax.annotation.processing.RoundEnvironment;
+import javax.annotation.processing.SupportedSourceVersion;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.ExecutableElement;
+import javax.lang.model.element.TypeElement;
+import javax.tools.Diagnostic;
+import java.lang.annotation.Annotation;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.function.BiFunction;
+import java.util.stream.Collectors;
+
+@SupportedSourceVersion(SourceVersion.RELEASE_8)
+public class RouteCompass extends AbstractProcessor {
+
+	private final HashSet<Route> foundRoutes = new HashSet<>();
+	private final HashSet<Class<? extends Annotation>> annotationClasses = new HashSet<>();
+
+	public RouteCompass() {
+		annotationClasses.add(RequestMapping.class);
+		annotationClasses.add(GetMapping.class);
+		annotationClasses.add(PostMapping.class);
+		annotationClasses.add(PutMapping.class);
+		annotationClasses.add(DeleteMapping.class);
+		annotationClasses.add(PatchMapping.class);
+	}
+
+	@Override
+	public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment env) {
+		for(TypeElement annotationType : annotations) {
+			env.getElementsAnnotatedWith(annotationType)
+				.stream()
+				.filter(elem -> elem instanceof ExecutableElement)
+				.map(elem -> (ExecutableElement) elem)
+				.forEach(elem -> this.foundRoutes.add(new Route(
+					elem.getEnclosingElement().asType().toString(),
+					this.getFullRoute(annotationType, elem),
+					this.getRequestMethods(annotationType, elem),
+					this.isDeprecated(elem)
+				)));
+		}
+
+		//TODO print
+
+		return false; //don't claim them, let spring do its job
+	}
+
+	private String getFullRoute(TypeElement annotationType, Element element) {
+		@SuppressWarnings("OptionalGetWithoutIsPresent") //find matching annotation class
+		Class<? extends Annotation> annClass = this.annotationClasses.stream()
+			.filter(c -> annotationType.getQualifiedName().contentEquals(c.getName()))
+			.findFirst()
+			.get(); //should never fail
+
+		try {
+			//it can be both path and value
+			String pathValue = (String) annClass.getField("path").get(element.getAnnotation(annClass));
+			String route = pathValue == null
+				? (String) annClass.getField("value").get(element.getAnnotation(annClass))
+				: pathValue;
+
+			return this.parentOrFallback(element, route, (a, e) -> {
+				String parent = this.getFullRoute(a, e);
+				StringBuilder sb = new StringBuilder(parent);
+				if(!parent.endsWith("/")) sb.append("/");
+				sb.append(route);
+				return sb.toString();
+			});
+		} catch (ReflectiveOperationException ex) {
+			throw new RuntimeException(ex); //if it fails something went very wrong
+		}
+	}
+
+	private RequestMethod[] getRequestMethods(TypeElement annotationType, Element element) {
+		RequestMethod[] methods = annotationType.getQualifiedName().contentEquals(RequestMapping.class.getName())
+			? element.getAnnotation(RequestMapping.class).method()
+			: annotationType.getAnnotation(RequestMapping.class).method();
+		return methods.length == 0
+			? this.parentOrFallback(element, methods, this::getRequestMethods)
+			: methods;
+	}
+
+	private boolean isDeprecated(Element elem) {
+		return elem.getAnnotation(Deprecated.class) != null
+			|| elem.getEnclosingElement().getAnnotation(Deprecated.class) != null;
+	}
+
+	private <T> T parentOrFallback(Element element, T fallback, BiFunction<TypeElement, Element, T> fun) {
+		List<Class<? extends Annotation>> found = this.annotationClasses.stream()
+			.filter(annClass -> element.getEnclosingElement().getAnnotation(annClass) != null)
+			.collect(Collectors.toList());
+
+		if(found.isEmpty()) return fallback;
+
+		if(found.size() > 1) this.processingEnv.getMessager().printMessage(
+			Diagnostic.Kind.WARNING,
+			"Found multiple mapping annotations on "
+				+ element.getSimpleName().toString()
+				+ ", only one of the will be considered!"
+		);
+
+		return fun.apply(
+			this.processingEnv.getElementUtils()
+				.getTypeElement(found.get(0).getName()),
+			element
+		);
+	}
+
+	@Override
+	public Set<String> getSupportedAnnotationTypes() {
+		return annotationClasses.stream().map(Class::getCanonicalName).collect(Collectors.toSet());
+	}
+}