package org.djutils.reflection;
   
   import java.io.Serializable;
   import java.lang.reflect.Constructor;
   import java.lang.reflect.Method;
   import java.util.ArrayList;
   import java.util.List;
   
   /**
   * A method descriptor represents the parameters that the method takes and the value that it returns. It is a series of
   * characters generated by the grammar described at
   * <a href = "https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.3"> The Java Virtual Machine
   * Specification: Method Descriptors </a>.
   * <p>
   * Copyright (c) 2002-2021 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See
   * for project information <a href="https://djutils.org" target="_blank"> https://djutils.org</a>. The DJUTILS project is
   * distributed under a three-clause BSD-style license, which can be found at
   * <a href="https://djutils.org/docs/license.html" target="_blank"> https://djutils.org/docs/license.html</a>.
   * </p>
   * @author Peter Jacobs, Niels Lang, Alexander Verbraeck
   */
  public class MethodSignature implements Serializable
  {
      /** The default serial version UID for serializable classes. */
      private static final long serialVersionUID = 20191230L;
  
      /** the value of the methodDescriptor. */
      private String value = null;
  
      /**
       * constructs a new MethodSignature.
       * @param value String; the descriptor
       */
      public MethodSignature(final String value)
      {
          this.value = value;
      }
  
      /**
       * constructs a new MethodSignature.
       * @param method Method; the method
       */
      public MethodSignature(final Method method)
      {
          Class<?>[] parameterTypes = new Class<?>[0];
          if (method.getParameterTypes() != null)
          {
              parameterTypes = method.getParameterTypes();
          }
          this.value = "(";
          for (int i = 0; i < parameterTypes.length; i++)
          {
              this.value = this.value + FieldSignature.toDescriptor(parameterTypes[i]);
          }
          this.value = this.value + ")" + FieldSignature.toDescriptor(method.getReturnType());
      }
  
      /**
       * constructs a new MethodSignature.
       * @param constructor Constructor&lt;?&gt;; the constructor
       */
      public MethodSignature(final Constructor<?> constructor)
      {
          Class<?>[] parameterTypes = new Class<?>[0];
          if (constructor.getParameterTypes() != null)
          {
              parameterTypes = constructor.getParameterTypes();
          }
  
          this.value = "(";
          for (int i = 0; i < parameterTypes.length; i++)
          {
              this.value = this.value + FieldSignature.toDescriptor(parameterTypes[i]);
          }
          this.value = this.value + ")" + FieldSignature.toDescriptor(constructor.getDeclaringClass());
      }
  
      /**
       * @return Returns the parameterDescriptor
       */
      public String getParameterDescriptor()
      {
          return MethodSignature.getParameterDescriptor(this.value);
      }
  
      /**
       * returns the parameterTypes.
       * @return ClassDescriptor[] the result
       * @throws ClassNotFoundException on incomplete classPath
       */
      public Class<?>[] getParameterTypes() throws ClassNotFoundException
      {
          return MethodSignature.getParameterTypes(this.value);
      }
  
      /**
       * @return Returns the returnDescriptor.
       */
      public String getReturnDescriptor()
     {
         return MethodSignature.getReturnDescriptor(this.value);
     }
 
     /**
      * returns the returnType of this methodDescriptor.
      * @return Returns the returnType
      * @throws ClassNotFoundException on incomplete classPath
      */
     public Class<?> getReturnType() throws ClassNotFoundException
     {
         return MethodSignature.getReturnType(this.value);
     }
 
     /** {@inheritDoc} */
     @Override
     public String toString()
     {
         return this.value;
     }
 
     /**
      * @return Returns the parameterDescriptor
      * @param methodDescriptor String; the methodDescriptor
      */
     public static String getParameterDescriptor(final String methodDescriptor)
     {
         return methodDescriptor.substring(1, methodDescriptor.indexOf(')'));
     }
 
     /**
      * returns the parameterTypes.
      * @param methodDescriptor String; the string
      * @return ClassDescriptor[] the result
      * @throws ClassNotFoundException on incomplete classPath
      */
     public static Class<?>[] getParameterTypes(final String methodDescriptor) throws ClassNotFoundException
     {
         String parameterDescriptor = MethodSignature.getParameterDescriptor(methodDescriptor);
         List<Class<?>> result = new ArrayList<Class<?>>();
         int length = 0;
         while (length < parameterDescriptor.length())
         {
             String array = "";
             while (parameterDescriptor.charAt(length) == '[')
             {
                 array = array + "[";
                 length++;
             }
             if (parameterDescriptor.charAt(length) == 'L')
             {
                 String argument = parameterDescriptor.substring(length);
                 argument = array + argument.substring(0, argument.indexOf(';') + 1);
                 result.add(FieldSignature.toClass(argument));
                 length = length + argument.length() - array.length();
             }
             else
             {
                 result.add(FieldSignature.toClass(array + parameterDescriptor.charAt(length)));
                 length++;
             }
         }
         return result.toArray(new Class<?>[result.size()]);
     }
 
     /**
      * @return Returns the returnDescriptor
      * @param methodDescriptor String; the methodDescriptor
      */
     public static String getReturnDescriptor(final String methodDescriptor)
     {
         return methodDescriptor.substring(methodDescriptor.indexOf(')') + 1);
     }
 
     /**
      * returns the returnType of this methodDescriptor.
      * @param methodDescriptor String; the returnDescriptor
      * @return Returns the returnType
      * @throws ClassNotFoundException on incomplete classPath
      */
     public static Class<?> getReturnType(final String methodDescriptor) throws ClassNotFoundException
     {
         return FieldSignature.toClass(MethodSignature.getReturnDescriptor(methodDescriptor));
     }
 }