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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2020-2030 郑庚伟 ZHENGGENGWEI (码匠君),  Licensed under the AGPL License
 *
 * This file is part of Herodotus Engine.
 *
 * Herodotus Engine is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Herodotus Engine 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see .
 */

package cn.herodotus.engine.facility.alibaba.autoconfigure.sentinel.enhance;

import com.alibaba.cloud.sentinel.feign.SentinelContractHolder;
import com.alibaba.csp.sentinel.Entry;
import com.alibaba.csp.sentinel.EntryType;
import com.alibaba.csp.sentinel.SphU;
import com.alibaba.csp.sentinel.Tracer;
import com.alibaba.csp.sentinel.context.ContextUtil;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import feign.Feign;
import feign.InvocationHandlerFactory.MethodHandler;
import feign.MethodMetadata;
import feign.Target;
import org.springframework.cloud.openfeign.FallbackFactory;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.LinkedHashMap;
import java.util.Map;

import static feign.Util.checkNotNull;

/**
 * {@link InvocationHandler} handle invocation that protected by Sentinel.
 *
 * @author Jim
 */
public class HerodotusSentinelInvocationHandler implements InvocationHandler {

    private final Target target;

    private final Map dispatch;

    private FallbackFactory fallbackFactory;

    private Map fallbackMethodMap;

    HerodotusSentinelInvocationHandler(Target target, Map dispatch, FallbackFactory fallbackFactory) {
        this.target = checkNotNull(target, "target");
        this.dispatch = checkNotNull(dispatch, "dispatch");
        this.fallbackFactory = fallbackFactory;
        this.fallbackMethodMap = toFallbackMethod(dispatch);
    }

    HerodotusSentinelInvocationHandler(Target target, Map dispatch) {
        this.target = checkNotNull(target, "target");
        this.dispatch = checkNotNull(dispatch, "dispatch");
    }

    static Map toFallbackMethod(Map dispatch) {
        Map result = new LinkedHashMap<>();
        for (Method method : dispatch.keySet()) {
            method.setAccessible(true);
            result.put(method, method);
        }
        return result;
    }

    @Override
    public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable {
        switch (method.getName()) {
            case "equals" -> {
                try {
                    Object otherHandler = args.length > 0 && args[0] != null
                            ? Proxy.getInvocationHandler(args[0])
                            : null;
                    return equals(otherHandler);
                } catch (IllegalArgumentException e) {
                    return false;
                }
            }
            case "hashCode" -> {
                return hashCode();
            }
            case "toString" -> {
                return toString();
            }
        }

        Object result;
        MethodHandler methodHandler = this.dispatch.get(method);
        // only handle by HardCodedTarget
        if (target instanceof Target.HardCodedTarget hardCodedTarget) {
            MethodMetadata methodMetadata = SentinelContractHolder.METADATA_MAP
                    .get(hardCodedTarget.type().getName()
                            + Feign.configKey(hardCodedTarget.type(), method));
            // resource default is HttpMethod:protocol://url
            if (methodMetadata == null) {
                result = methodHandler.invoke(args);
            } else {
                String resourceName = methodMetadata.template().method().toUpperCase()
                        + ":" + hardCodedTarget.url() + methodMetadata.template().path();
                Entry entry = null;
                try {
                    ContextUtil.enter(resourceName);
                    entry = SphU.entry(resourceName, EntryType.OUT, 1, args);
                    result = methodHandler.invoke(args);
                } catch (Throwable ex) {
                    // fallback handle
                    if (!BlockException.isBlockException(ex)) {
                        Tracer.traceEntry(ex, entry);
                    }
                    if (fallbackFactory != null) {
                        try {
                            return fallbackMethodMap.get(method).invoke(fallbackFactory.create(ex), args);
                        } catch (IllegalAccessException e) {
                            // shouldn't happen as method is public due to being an
                            // interface
                            throw new AssertionError(e);
                        } catch (InvocationTargetException e) {
                            throw new AssertionError(e.getCause());
                        }
                    } else {
                        // throw exception if fallbackFactory is null
                        throw ex;
                    }
                } finally {
                    if (entry != null) {
                        entry.exit(1, args);
                    }
                    ContextUtil.exit();
                }
            }
        } else {
            // other target type using default strategy
            result = methodHandler.invoke(args);
        }

        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof HerodotusSentinelInvocationHandler sentinelInvocationHandler) {
            return target.equals(sentinelInvocationHandler.target);
        }
        return false;
    }

    @Override
    public int hashCode() {
        return target.hashCode();
    }

    @Override
    public String toString() {
        return target.toString();
    }

}