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/*
 * Copyright (C) 2018  Sun.Hao
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */

package lodsve.core.utils;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.HashSet;
import java.util.Set;

/**
 * 泛型工具类.
 *
 * @author sunhao([email protected])
 * @date 2015-1-6 16:20
 */
public class GenericUtils {
    private GenericUtils() {

    }

    public static  Class getGenericParameter(Class clazz, int index) {
        Type genType = clazz.isInterface() ? clazz.getGenericInterfaces()[0] : clazz.getGenericSuperclass();
        if (genType instanceof ParameterizedType) {
            return getGenericParameter((ParameterizedType) genType, index);
        }
        return null;
    }

    public static  Class getGenericParameter0(Class clazz) {
        return getGenericParameter(clazz, 0);
    }

    public static  Class getGenericParameter(Field field, int index) {
        Type genType = field.getGenericType();
        if (genType instanceof ParameterizedType) {
            return getGenericParameter((ParameterizedType) genType, index);
        }
        return null;
    }

    public static  Class getGenericParameter0(Field field) {
        return getGenericParameter(field, 0);
    }

    public static  Class getGenericParameter(Method method, int index) {
        Type genType = method.getGenericReturnType();
        if (genType instanceof ParameterizedType) {
            return getGenericParameter((ParameterizedType) genType, index);
        }
        return null;
    }

    public static  Class getGenericParameter0(Method method) {
        return getGenericParameter(method, 0);
    }

    @SuppressWarnings("unchecked")
    private static  Class getGenericParameter(ParameterizedType type, int index) {
        Type param = type.getActualTypeArguments()[index];
        if (param instanceof Class) {
            return (Class) param;
        }
        return null;
    }

    @SafeVarargs
    public static Set getAnnotatedFields(Class clazz, Class... annotations) {
        return doInAnnotatedFields(clazz, new SetFieldExtractor(), annotations);
    }

    @SafeVarargs
    public static Field getAnnotatedField(Class clazz, Class... annotations) {
        return doInAnnotatedFields(clazz, new SingleFieldExtractor(), annotations);
    }

    @SafeVarargs
    public static  T doInAnnotatedFields(Class clazz, FieldExtractor extractor, Class... annotations) {
        for (Field field : clazz.getDeclaredFields()) {
            int hit = 0;
            for (Class annotation : annotations) {
                if (field.isAnnotationPresent(annotation)) {
                    hit++;
                } else {
                    break;
                }
            }
            if (hit == annotations.length) {
                if (!extractor.extractNext(field)) {
                    return extractor.getReturn();
                }
            }
        }
        Class parent = clazz.getSuperclass();
        if (parent != null) {
            return doInAnnotatedFields(parent, extractor, annotations);
        }
        return extractor.getReturn();
    }

    private static class SetFieldExtractor implements FieldExtractor> {
        Set result = new HashSet<>();

        @Override
        public boolean extractNext(Field field) {
            result.add(field);
            return true;
        }

        @Override
        public Set getReturn() {
            return result;
        }
    }

    private static class SingleFieldExtractor implements FieldExtractor {
        Field field = null;

        @Override
        public boolean extractNext(Field field) {
            this.field = field;
            return false;
        }

        @Override
        public Field getReturn() {
            return field;
        }
    }

    public interface FieldExtractor {
        boolean extractNext(Field field);

        T getReturn();
    }
}