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/*
 * Copyright (C) 2007 The Guava 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 com.google.common.eventbus;

import com.google.common.base.Objects;
import com.google.common.base.Throwables;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.reflect.TypeToken;
import com.google.common.util.concurrent.UncheckedExecutionException;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;

/**
 *  A {@link HandlerFindingStrategy} for collecting all event handler methods that are marked with
 *  the {@link Subscribe} annotation.
 *
 *  @author Cliff Biffle
 *  @author Louis Wasserman
 *
 * @deprecated The Google Guava Core Libraries are deprecated and will not be part of the AEM SDK after April 2023
 */
@Deprecated(since = "2022-12-01")
class AnnotatedHandlerFinder implements HandlerFindingStrategy {

    /**
     * A thread-safe cache that contains the mapping from each class to all methods in that class and
     * all super-classes, that are annotated with {@code @Subscribe}. The cache is shared across all
     * instances of this class; this greatly improves performance if multiple EventBus instances are
     * created and objects of the same class are registered on all of them.
     */
    private static final LoadingCache, ImmutableList> handlerMethodsCache = CacheBuilder.newBuilder().weakKeys().build(new CacheLoader, ImmutableList>() {

        @Override
        public ImmutableList load(Class concreteClass) throws Exception {
            return getAnnotatedMethodsInternal(concreteClass);
        }
    });

    /**
     * {@inheritDoc}
     *
     * This implementation finds all methods marked with a {@link Subscribe} annotation.
     */
    @Override
    public Multimap, EventHandler> findAllHandlers(Object listener) {
        Multimap, EventHandler> methodsInListener = HashMultimap.create();
        Class clazz = listener.getClass();
        for (Method method : getAnnotatedMethods(clazz)) {
            Class[] parameterTypes = method.getParameterTypes();
            Class eventType = parameterTypes[0];
            EventHandler handler = makeHandler(listener, method);
            methodsInListener.put(eventType, handler);
        }
        return methodsInListener;
    }

    private static ImmutableList getAnnotatedMethods(Class clazz) {
        try {
            return handlerMethodsCache.getUnchecked(clazz);
        } catch (UncheckedExecutionException e) {
            throw Throwables.propagate(e.getCause());
        }
    }

    // @deprecated The Google Guava Core Libraries are deprecated and will not be part of the AEM SDK after April 2023
    @Deprecated(since = "2022-12-01")
    private static final class MethodIdentifier {

        private final String name;

        private final List> parameterTypes;

        MethodIdentifier(Method method) {
            this.name = method.getName();
            this.parameterTypes = Arrays.asList(method.getParameterTypes());
        }

        @Override
        public int hashCode() {
            return Objects.hashCode(name, parameterTypes);
        }

        @Override
        public boolean equals(@Nullable Object o) {
            if (o instanceof MethodIdentifier) {
                MethodIdentifier ident = (MethodIdentifier) o;
                return name.equals(ident.name) && parameterTypes.equals(ident.parameterTypes);
            }
            return false;
        }
    }

    private static ImmutableList getAnnotatedMethodsInternal(Class clazz) {
        Set> supers = TypeToken.of(clazz).getTypes().rawTypes();
        Map identifiers = Maps.newHashMap();
        for (Class superClazz : supers) {
            for (Method superClazzMethod : superClazz.getMethods()) {
                if (superClazzMethod.isAnnotationPresent(Subscribe.class)) {
                    Class[] parameterTypes = superClazzMethod.getParameterTypes();
                    if (parameterTypes.length != 1) {
                        throw new IllegalArgumentException("Method " + superClazzMethod + " has @Subscribe annotation, but requires " + parameterTypes.length + " arguments.  Event handler methods must require a single argument.");
                    }
                    MethodIdentifier ident = new MethodIdentifier(superClazzMethod);
                    if (!identifiers.containsKey(ident)) {
                        identifiers.put(ident, superClazzMethod);
                    }
                }
            }
        }
        return ImmutableList.copyOf(identifiers.values());
    }

    /**
     * Creates an {@code EventHandler} for subsequently calling {@code method} on
     * {@code listener}.
     * Selects an EventHandler implementation based on the annotations on
     * {@code method}.
     *
     * @param listener  object bearing the event handler method.
     * @param method  the event handler method to wrap in an EventHandler.
     * @return an EventHandler that will call {@code method} on {@code listener}
     *         when invoked.
     */
    private static EventHandler makeHandler(Object listener, Method method) {
        EventHandler wrapper;
        if (methodIsDeclaredThreadSafe(method)) {
            wrapper = new EventHandler(listener, method);
        } else {
            wrapper = new SynchronizedEventHandler(listener, method);
        }
        return wrapper;
    }

    /**
     * Checks whether {@code method} is thread-safe, as indicated by the
     * {@link AllowConcurrentEvents} annotation.
     *
     * @param method  handler method to check.
     * @return {@code true} if {@code handler} is marked as thread-safe,
     *         {@code false} otherwise.
     */
    private static boolean methodIsDeclaredThreadSafe(Method method) {
        return method.getAnnotation(AllowConcurrentEvents.class) != null;
    }
}