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The core HTTP and composition mechanisms of Ratpack

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/*
 * Copyright 2014 the original author or authors.
 *
 * 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
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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 ratpack.handling.internal;

import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import javassist.ClassPool;
import javassist.CtBehavior;
import javassist.CtClass;
import javassist.NotFoundException;
import javassist.bytecode.ClassFile;
import ratpack.handling.Handler;

import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;

public class DescribingHandlers {

  public static void describeTo(Handler handler, StringBuilder stringBuilder) {
    Class clazz = handler.getClass();
    if (clazz.isAnonymousClass()) {
      ClassPool pool = ClassPool.getDefault();

      CtClass ctClass;
      try {
        ctClass = pool.get(clazz.getName());
        CtBehavior[] behaviors = ctClass.getDeclaredBehaviors();
        Iterable withLineNumberIterable = Iterables.filter(Arrays.asList(behaviors), input -> input.getMethodInfo().getLineNumber(0) > 0);

        LinkedList withLineNumber = Lists.newLinkedList(withLineNumberIterable);
        Collections.sort(withLineNumber, (o1, o2) -> Integer.valueOf(o1.getMethodInfo().getLineNumber(0)).compareTo(o2.getMethodInfo().getLineNumber(0)));

        if (!withLineNumber.isEmpty()) {
          CtBehavior method = withLineNumber.get(0);
          int lineNumber = method.getMethodInfo().getLineNumber(0);

          ClassFile classFile = ctClass.getClassFile();
          String sourceFile = classFile.getSourceFile();

          if (lineNumber != -1 && sourceFile != null) {
            stringBuilder
              .append("anonymous class ")
              .append(clazz.getName())
              .append(" at approximately line ")
              .append(lineNumber)
              .append(" of ")
              .append(sourceFile);
            return;
          }
        }
      } catch (NotFoundException ignore) {
        // fall through
      }
    }

    stringBuilder.append(clazz.getName());
  }

}