Extract separate classes from RefasterTemplateProcessor

src/main/java/org/openrewrite/java/template/processor/Precondition.java

@@ -24,7 +24,7 @@
 import static java.util.stream.Collectors.joining;
 import static org.openrewrite.java.template.internal.StringUtils.indent;
 
-public abstract class Precondition {
+abstract class Precondition {
     private static final Comparator<String> BY_USES_TYPE_METHOD_FIRST = Comparator
             .comparing((String s) -> {
                 if (s.startsWith("new UsesType")) return 0;

src/main/java/org/openrewrite/java/template/processor/RuleDescriptor.java

@@ -0,0 +1,124 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.template.processor;
+
+import com.sun.tools.javac.processing.JavacProcessingEnvironment;
+import com.sun.tools.javac.tree.JCTree;
+import com.sun.tools.javac.util.Name;
+import org.jspecify.annotations.Nullable;
+
+import javax.tools.Diagnostic;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+
+import static org.openrewrite.java.template.processor.RefasterTemplateProcessor.AFTER_TEMPLATE;
+import static org.openrewrite.java.template.processor.RefasterTemplateProcessor.BEFORE_TEMPLATE;
+
+class RuleDescriptor {
+
+    public final JCTree.JCClassDecl classDecl;
+    public final List<TemplateDescriptor> beforeTemplates;
+    public final @Nullable TemplateDescriptor afterTemplate;
+
+    private RuleDescriptor(
+            JCTree.JCClassDecl classDecl,
+            List<TemplateDescriptor> beforeTemplates,
+            @Nullable TemplateDescriptor afterTemplate) {
+        this.classDecl = classDecl;
+        this.beforeTemplates = beforeTemplates;
+        this.afterTemplate = afterTemplate;
+    }
+
+    public static @Nullable RuleDescriptor create(
+            JavacProcessingEnvironment processingEnv,
+            JCTree.JCCompilationUnit cu, JCTree.JCClassDecl classDecl) {
+        List<TemplateDescriptor> beforeTemplates = new ArrayList<>();
+        TemplateDescriptor afterTemplate = null;
+        for (JCTree member : classDecl.getMembers()) {
+            if (member instanceof JCTree.JCMethodDecl) {
+                JCTree.JCMethodDecl method = (JCTree.JCMethodDecl) member;
+                List<JCTree.JCAnnotation> annotations = RefasterTemplateProcessor.getTemplateAnnotations(method, BEFORE_TEMPLATE::equals);
+                if (!annotations.isEmpty()) {
+                    beforeTemplates.add(new TemplateDescriptor(processingEnv, cu, classDecl, method));
+                }
+                annotations = RefasterTemplateProcessor.getTemplateAnnotations(method, AFTER_TEMPLATE::equals);
+                if (!annotations.isEmpty()) {
+                    afterTemplate = new TemplateDescriptor(processingEnv, cu, classDecl, method);
+                }
+            }
+        }
+        return new RuleDescriptor(classDecl, beforeTemplates, afterTemplate)
+                .validate(processingEnv, classDecl);
+    }
+
+    private @Nullable RuleDescriptor validate(JavacProcessingEnvironment processingEnv, JCTree.JCClassDecl classDecl) {
+        if (beforeTemplates.isEmpty()) {
+            return null;
+        }
+
+        for (JCTree member : classDecl.getMembers()) {
+            if (member instanceof JCTree.JCMethodDecl && beforeTemplates.stream().noneMatch(t -> t.method == member) &&
+                    (afterTemplate == null || member != afterTemplate.method)) {
+                for (JCTree.JCAnnotation annotation : RefasterTemplateProcessor.getTemplateAnnotations(((JCTree.JCMethodDecl) member), RefasterTemplateProcessor.UNSUPPORTED_ANNOTATIONS::contains)) {
+                    RefasterTemplateProcessor.printNoteOnce(processingEnv, "@" + annotation.annotationType + " is currently not supported", classDecl.sym);
+                    return null;
+                }
+            }
+        }
+
+        // resolve so that we can inspect the template body
+        boolean valid = resolve(processingEnv);
+        if (valid) {
+            for (TemplateDescriptor template : beforeTemplates) {
+                valid &= template.validate();
+            }
+            if (afterTemplate != null) {
+                valid &= afterTemplate.validate();
+            }
+        }
+
+        if (valid && afterTemplate != null) {
+            Set<Name> requiredParameters = RefasterTemplateProcessor.findParameterOrder(afterTemplate.method, 0).keySet();
+            for (TemplateDescriptor beforeTemplate : beforeTemplates) {
+                for (int i = 0; i < beforeTemplate.getArity(); i++) {
+                    Set<Name> providedParameters = RefasterTemplateProcessor.findParameterOrder(beforeTemplate.method, i).keySet();
+                    if (!providedParameters.containsAll(requiredParameters)) {
+                        RefasterTemplateProcessor.printNoteOnce(processingEnv, "@AfterTemplate defines arguments that are not present in all @BeforeTemplate methods", classDecl.sym);
+                        return null;
+                    }
+                }
+            }
+        }
+        return valid ? this : null;
+    }
+
+    private boolean resolve(JavacProcessingEnvironment processingEnv) {
+        boolean valid = true;
+        try {
+            for (TemplateDescriptor beforeTemplate : beforeTemplates) {
+                valid &= beforeTemplate.resolve();
+            }
+            if (afterTemplate != null) {
+                valid &= afterTemplate.resolve();
+            }
+        } catch (Throwable t) {
+            processingEnv.getMessager().printMessage(Diagnostic.Kind.WARNING, "Had trouble type attributing the template.");
+            valid = false;
+        }
+        return valid;
+    }
+}