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/*
 * Copyright 2013-2018 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
 *
 *      https://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.springblade.core.cloud.sentinel;
 
import com.alibaba.cloud.sentinel.feign.SentinelContractHolder;
import feign.Contract;
import feign.Feign;
import feign.InvocationHandlerFactory;
import feign.Target;
import org.springframework.cloud.openfeign.FallbackFactory;
import lombok.SneakyThrows;
import org.springblade.core.cloud.feign.BladeFallbackFactory;
import org.springframework.beans.BeansException;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.cloud.openfeign.FeignContext;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.util.StringUtils;
 
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.Map;
 
/**
 * feign集成sentinel自动配置
 * 重写 {@link com.alibaba.cloud.sentinel.feign.SentinelFeign} 适配最新API
 *
 * @author Chill
 */
public class BladeFeignSentinel {
 
    public static Builder builder() {
        return new Builder();
    }
 
    public static final class Builder extends Feign.Builder implements ApplicationContextAware {
        private Contract contract = new Contract.Default();
        private ApplicationContext applicationContext;
        private FeignContext feignContext;
 
        @Override
        public Feign.Builder invocationHandlerFactory(
            InvocationHandlerFactory invocationHandlerFactory) {
            throw new UnsupportedOperationException();
        }
 
        @Override
        public Builder contract(Contract contract) {
            this.contract = contract;
            return this;
        }
 
        @Override
        public Feign build() {
            super.invocationHandlerFactory(new InvocationHandlerFactory() {
                @SneakyThrows
                @Override
                public InvocationHandler create(Target target, Map<Method, MethodHandler> dispatch) {
                    // 注解取值以避免循环依赖的问题
                    FeignClient feignClient = AnnotationUtils.findAnnotation(target.type(), FeignClient.class);
                    Class fallback = feignClient.fallback();
                    Class fallbackFactory = feignClient.fallbackFactory();
                    String contextId = feignClient.contextId();
 
                    if (!StringUtils.hasText(contextId)) {
                        contextId = feignClient.name();
                    }
 
                    Object fallbackInstance;
                    FallbackFactory fallbackFactoryInstance;
                    // 判断fallback类型
                    if (void.class != fallback) {
                        fallbackInstance = getFromContext(contextId, "fallback", fallback, target.type());
                        return new BladeSentinelInvocationHandler(target, dispatch, new FallbackFactory.Default(fallbackInstance));
                    }
                    if (void.class != fallbackFactory) {
                        fallbackFactoryInstance = (FallbackFactory) getFromContext(contextId, "fallbackFactory", fallbackFactory, FallbackFactory.class);
                        return new BladeSentinelInvocationHandler(target, dispatch, fallbackFactoryInstance);
                    }
                    // 默认fallbackFactory
                    BladeFallbackFactory bladeFallbackFactory = new BladeFallbackFactory(target);
                    return new BladeSentinelInvocationHandler(target, dispatch, bladeFallbackFactory);
                }
 
                private Object getFromContext(String name, String type, Class fallbackType, Class targetType) {
                    Object fallbackInstance = feignContext.getInstance(name, fallbackType);
                    if (fallbackInstance == null) {
                        throw new IllegalStateException(
                            String.format("No %s instance of type %s found for feign client %s",
                                type, fallbackType, name)
                        );
                    }
 
                    if (!targetType.isAssignableFrom(fallbackType)) {
                        throw new IllegalStateException(
                            String.format("Incompatible %s instance. Fallback/fallbackFactory of type %s is not assignable to %s for feign client %s",
                                type, fallbackType, targetType, name)
                        );
                    }
                    return fallbackInstance;
                }
            });
            super.contract(new SentinelContractHolder(contract));
            return super.build();
        }
 
        @Override
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
            this.applicationContext = applicationContext;
            feignContext = this.applicationContext.getBean(FeignContext.class);
        }
    }
 
}