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package space.chensheng.wsmessenger.common.util;

import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;

public class ReflectUtil {
	
	public static Class findGenericType(Object object, Class parameterizedSuperclass, String typeParamName) {
		if (object == null) {
			return null;
		}
	
		Class thisClass = object.getClass();
        Class currentClass = thisClass;
        for (;;) {
            if (currentClass.getSuperclass() == parameterizedSuperclass) {
                int typeParamIndex = -1;
                TypeVariable[] typeParams = currentClass.getSuperclass().getTypeParameters();
                for (int i = 0; i < typeParams.length; i ++) {
                    if (typeParamName.equals(typeParams[i].getName())) {
                        typeParamIndex = i;
                        break;
                    }
                }

                if (typeParamIndex < 0) {
                    throw new IllegalStateException(
                            "unknown type parameter '" + typeParamName + "': " + parameterizedSuperclass);
                }

                Type genericSuperType = currentClass.getGenericSuperclass();
                if (!(genericSuperType instanceof ParameterizedType)) {
                    return Object.class;
                }

                Type[] actualTypeParams = ((ParameterizedType) genericSuperType).getActualTypeArguments();

                Type actualTypeParam = actualTypeParams[typeParamIndex];
                if (actualTypeParam instanceof ParameterizedType) {
                    actualTypeParam = ((ParameterizedType) actualTypeParam).getRawType();
                }
                if (actualTypeParam instanceof Class) {
                    return (Class) actualTypeParam;
                }
                if (actualTypeParam instanceof GenericArrayType) {
                    Type componentType = ((GenericArrayType) actualTypeParam).getGenericComponentType();
                    if (componentType instanceof ParameterizedType) {
                        componentType = ((ParameterizedType) componentType).getRawType();
                    }
                    if (componentType instanceof Class) {
                        return Array.newInstance((Class) componentType, 0).getClass();
                    }
                }
                if (actualTypeParam instanceof TypeVariable) {
                    // Resolved type parameter points to another type parameter.
                    TypeVariable v = (TypeVariable) actualTypeParam;
                    currentClass = thisClass;
                    if (!(v.getGenericDeclaration() instanceof Class)) {
                        return Object.class;
                    }

                    parameterizedSuperclass = (Class) v.getGenericDeclaration();
                    typeParamName = v.getName();
                    if (parameterizedSuperclass.isAssignableFrom(thisClass)) {
                        continue;
                    } else {
                        return Object.class;
                    }
                }

                return null;
            }
            currentClass = currentClass.getSuperclass();
            if (currentClass == null) {
                return null;
            }
        }
    }
}