/*
    *    Copyright 2009-2021 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 org.apache.ibatis.reflection;
  
  import java.lang.reflect.Array;
  import java.lang.reflect.Field;
  import java.lang.reflect.GenericArrayType;
  import java.lang.reflect.Method;
  import java.lang.reflect.ParameterizedType;
  import java.lang.reflect.Type;
  import java.lang.reflect.TypeVariable;
  import java.lang.reflect.WildcardType;
  import java.util.Arrays;
  
  /**
   * @author Iwao AVE!
   */
  public class TypeParameterResolver {
  
    /**
     * Resolve field type.
     *
     * @param field
     *          the field
     * @param srcType
     *          the src type
     * @return The field type as {@link Type}. If it has type parameters in the declaration,<br>
     *         they will be resolved to the actual runtime {@link Type}s.
     */
    public static Type resolveFieldType(Field field, Type srcType) {
      Type fieldType = field.getGenericType();
      Class<?> declaringClass = field.getDeclaringClass();
      return resolveType(fieldType, srcType, declaringClass);
    }
  
    /**
     * Resolve return type.
     *
     * @param method
     *          the method
     * @param srcType
     *          the src type
     * @return The return type of the method as {@link Type}. If it has type parameters in the declaration,<br>
     *         they will be resolved to the actual runtime {@link Type}s.
     */
    public static Type resolveReturnType(Method method, Type srcType) {
      Type returnType = method.getGenericReturnType();
      Class<?> declaringClass = method.getDeclaringClass();
      return resolveType(returnType, srcType, declaringClass);
    }
  
    /**
     * Resolve param types.
     *
     * @param method
     *          the method
     * @param srcType
     *          the src type
     * @return The parameter types of the method as an array of {@link Type}s. If they have type parameters in the
     *         declaration,<br>
     *         they will be resolved to the actual runtime {@link Type}s.
     */
    public static Type[] resolveParamTypes(Method method, Type srcType) {
      Type[] paramTypes = method.getGenericParameterTypes();
      Class<?> declaringClass = method.getDeclaringClass();
      Type[] result = new Type[paramTypes.length];
      for (int i = 0; i < paramTypes.length; i++) {
        result[i] = resolveType(paramTypes[i], srcType, declaringClass);
      }
      return result;
    }
  
    private static Type resolveType(Type type, Type srcType, Class<?> declaringClass) {
      if (type instanceof TypeVariable) {
        return resolveTypeVar((TypeVariable<?>) type, srcType, declaringClass);
      } else if (type instanceof ParameterizedType) {
        return resolveParameterizedType((ParameterizedType) type, srcType, declaringClass);
      } else if (type instanceof GenericArrayType) {
        return resolveGenericArrayType((GenericArrayType) type, srcType, declaringClass);
      } else {
        return type;
      }
    }
  
    private static Type resolveGenericArrayType(GenericArrayType genericArrayType, Type srcType, Class<?> declaringClass) {
      Type componentType = genericArrayType.getGenericComponentType();
     Type resolvedComponentType = null;
     if (componentType instanceof TypeVariable) {
       resolvedComponentType = resolveTypeVar((TypeVariable<?>) componentType, srcType, declaringClass);
     } else if (componentType instanceof GenericArrayType) {
       resolvedComponentType = resolveGenericArrayType((GenericArrayType) componentType, srcType, declaringClass);
     } else if (componentType instanceof ParameterizedType) {
       resolvedComponentType = resolveParameterizedType((ParameterizedType) componentType, srcType, declaringClass);
     }
     if (resolvedComponentType instanceof Class) {
       return Array.newInstance((Class<?>) resolvedComponentType, 0).getClass();
     } else {
       return new GenericArrayTypeImpl(resolvedComponentType);
     }
   }
 
   private static ParameterizedType resolveParameterizedType(ParameterizedType parameterizedType, Type srcType, Class<?> declaringClass) {
     Class<?> rawType = (Class<?>) parameterizedType.getRawType();
     Type[] typeArgs = parameterizedType.getActualTypeArguments();
     Type[] args = new Type[typeArgs.length];
     for (int i = 0; i < typeArgs.length; i++) {
       if (typeArgs[i] instanceof TypeVariable) {
         args[i] = resolveTypeVar((TypeVariable<?>) typeArgs[i], srcType, declaringClass);
       } else if (typeArgs[i] instanceof ParameterizedType) {
         args[i] = resolveParameterizedType((ParameterizedType) typeArgs[i], srcType, declaringClass);
       } else if (typeArgs[i] instanceof WildcardType) {
         args[i] = resolveWildcardType((WildcardType) typeArgs[i], srcType, declaringClass);
       } else {
         args[i] = typeArgs[i];
       }
     }
     return new ParameterizedTypeImpl(rawType, null, args);
   }
 
   private static Type resolveWildcardType(WildcardType wildcardType, Type srcType, Class<?> declaringClass) {
     Type[] lowerBounds = resolveWildcardTypeBounds(wildcardType.getLowerBounds(), srcType, declaringClass);
     Type[] upperBounds = resolveWildcardTypeBounds(wildcardType.getUpperBounds(), srcType, declaringClass);
     return new WildcardTypeImpl(lowerBounds, upperBounds);
   }
 
   private static Type[] resolveWildcardTypeBounds(Type[] bounds, Type srcType, Class<?> declaringClass) {
     Type[] result = new Type[bounds.length];
     for (int i = 0; i < bounds.length; i++) {
       if (bounds[i] instanceof TypeVariable) {
         result[i] = resolveTypeVar((TypeVariable<?>) bounds[i], srcType, declaringClass);
       } else if (bounds[i] instanceof ParameterizedType) {
         result[i] = resolveParameterizedType((ParameterizedType) bounds[i], srcType, declaringClass);
       } else if (bounds[i] instanceof WildcardType) {
         result[i] = resolveWildcardType((WildcardType) bounds[i], srcType, declaringClass);
       } else {
         result[i] = bounds[i];
       }
     }
     return result;
   }
 
   private static Type resolveTypeVar(TypeVariable<?> typeVar, Type srcType, Class<?> declaringClass) {
     Type result;
     Class<?> clazz;
     if (srcType instanceof Class) {
       clazz = (Class<?>) srcType;
     } else if (srcType instanceof ParameterizedType) {
       ParameterizedType parameterizedType = (ParameterizedType) srcType;
       clazz = (Class<?>) parameterizedType.getRawType();
     } else {
       throw new IllegalArgumentException("The 2nd arg must be Class or ParameterizedType, but was: " + srcType.getClass());
     }
 
     if (clazz == declaringClass) {
       Type[] bounds = typeVar.getBounds();
       if (bounds.length > 0) {
         return bounds[0];
       }
       return Object.class;
     }
 
     Type superclass = clazz.getGenericSuperclass();
     result = scanSuperTypes(typeVar, srcType, declaringClass, clazz, superclass);
     if (result != null) {
       return result;
     }
 
     Type[] superInterfaces = clazz.getGenericInterfaces();
     for (Type superInterface : superInterfaces) {
       result = scanSuperTypes(typeVar, srcType, declaringClass, clazz, superInterface);
       if (result != null) {
         return result;
       }
     }
     return Object.class;
   }
 
   private static Type scanSuperTypes(TypeVariable<?> typeVar, Type srcType, Class<?> declaringClass, Class<?> clazz, Type superclass) {
     if (superclass instanceof ParameterizedType) {
       ParameterizedType parentAsType = (ParameterizedType) superclass;
       Class<?> parentAsClass = (Class<?>) parentAsType.getRawType();
       TypeVariable<?>[] parentTypeVars = parentAsClass.getTypeParameters();
       if (srcType instanceof ParameterizedType) {
         parentAsType = translateParentTypeVars((ParameterizedType) srcType, clazz, parentAsType);
       }
       if (declaringClass == parentAsClass) {
         for (int i = 0; i < parentTypeVars.length; i++) {
           if (typeVar.equals(parentTypeVars[i])) {
             return parentAsType.getActualTypeArguments()[i];
           }
         }
       }
       if (declaringClass.isAssignableFrom(parentAsClass)) {
         return resolveTypeVar(typeVar, parentAsType, declaringClass);
       }
     } else if (superclass instanceof Class && declaringClass.isAssignableFrom((Class<?>) superclass)) {
       return resolveTypeVar(typeVar, superclass, declaringClass);
     }
     return null;
   }
 
   private static ParameterizedType translateParentTypeVars(ParameterizedType srcType, Class<?> srcClass, ParameterizedType parentType) {
     Type[] parentTypeArgs = parentType.getActualTypeArguments();
     Type[] srcTypeArgs = srcType.getActualTypeArguments();
     TypeVariable<?>[] srcTypeVars = srcClass.getTypeParameters();
     Type[] newParentArgs = new Type[parentTypeArgs.length];
     boolean noChange = true;
     for (int i = 0; i < parentTypeArgs.length; i++) {
       if (parentTypeArgs[i] instanceof TypeVariable) {
         for (int j = 0; j < srcTypeVars.length; j++) {
           if (srcTypeVars[j].equals(parentTypeArgs[i])) {
             noChange = false;
             newParentArgs[i] = srcTypeArgs[j];
           }
         }
       } else {
         newParentArgs[i] = parentTypeArgs[i];
       }
     }
     return noChange ? parentType : new ParameterizedTypeImpl((Class<?>)parentType.getRawType(), null, newParentArgs);
   }
 
   private TypeParameterResolver() {
     super();
   }
 
   static class ParameterizedTypeImpl implements ParameterizedType {
     private Class<?> rawType;
 
     private Type ownerType;
 
     private Type[] actualTypeArguments;
 
     public ParameterizedTypeImpl(Class<?> rawType, Type ownerType, Type[] actualTypeArguments) {
       super();
       this.rawType = rawType;
       this.ownerType = ownerType;
       this.actualTypeArguments = actualTypeArguments;
     }
 
     @Override
     public Type[] getActualTypeArguments() {
       return actualTypeArguments;
     }
 
     @Override
     public Type getOwnerType() {
       return ownerType;
     }
 
     @Override
     public Type getRawType() {
       return rawType;
     }
 
     @Override
     public String toString() {
       return "ParameterizedTypeImpl [rawType=" + rawType + ", ownerType=" + ownerType + ", actualTypeArguments=" + Arrays.toString(actualTypeArguments) + "]";
     }
   }
 
   static class WildcardTypeImpl implements WildcardType {
     private Type[] lowerBounds;
 
     private Type[] upperBounds;
 
     WildcardTypeImpl(Type[] lowerBounds, Type[] upperBounds) {
       super();
       this.lowerBounds = lowerBounds;
       this.upperBounds = upperBounds;
     }
 
     @Override
     public Type[] getLowerBounds() {
       return lowerBounds;
     }
 
     @Override
     public Type[] getUpperBounds() {
       return upperBounds;
     }
   }
 
   static class GenericArrayTypeImpl implements GenericArrayType {
     private Type genericComponentType;
 
     GenericArrayTypeImpl(Type genericComponentType) {
       super();
       this.genericComponentType = genericComponentType;
     }
 
     @Override
     public Type getGenericComponentType() {
       return genericComponentType;
     }
   }
 }