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Swirlds is a software platform designed to build fully-distributed applications that harness the power of the cloud without servers. Now you can develop applications with fairness in decision making, speed, trust and reliability, at a fraction of the cost of traditional server-based platforms.

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/*
 * Copyright (C) 2022-2024 Hedera Hashgraph, LLC
 *
 * 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.swirlds.common.constructable.internal;

import com.swirlds.common.constructable.ConstructableClass;
import com.swirlds.common.constructable.ConstructableIgnored;
import com.swirlds.common.constructable.NoArgsConstructor;
import com.swirlds.common.constructable.RuntimeConstructable;
import com.swirlds.common.constructable.URLClassLoaderWithLookup;
import io.github.classgraph.ClassGraph;
import io.github.classgraph.ClassInfo;
import io.github.classgraph.ScanResult;
import java.lang.reflect.Modifier;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

/**
 * Scans the classpath for {@link RuntimeConstructable} classes
 */
public final class ConstructableScanner {
    private ConstructableScanner() {}

    /**
     * Searches the classpath for all {@link RuntimeConstructable} classes.
     * 
     * The method will search the classpath for any non-abstract classes that implement {@link RuntimeConstructable} and
     * sort them by their constructor type.
     *
     * @param packagePrefix
     * 		the package prefix of classes to search for, can be an empty String to search all packages
     * @param additionalClassloader
     * 		if any classes are loaded by a non-system classloader, it must be provided to find those classes
     */
    public static Collection> getConstructableClasses(
            final String packagePrefix, final URLClassLoaderWithLookup additionalClassloader) {
        final Map, ConstructableClasses> map = new HashMap<>();
        final ClassGraph classGraph = new ClassGraph().enableClassInfo().whitelistPackages(packagePrefix);
        if (additionalClassloader != null) {
            classGraph.addClassLoader(additionalClassloader);
        }
        try (final ScanResult scanResult = classGraph.scan()) {
            for (final ClassInfo classInfo :
                    scanResult.getClassesImplementing(RuntimeConstructable.class.getCanonicalName())) {
                final Class subType = classInfo.loadClass(RuntimeConstructable.class);
                if (isSkippable(subType)) {
                    continue;
                }

                final Class constructorType = getConstructorType(subType);
                map.computeIfAbsent(constructorType, ConstructableClasses::new).addClass(subType);
            }
        }

        return map.values();
    }

    private static boolean isSkippable(final Class subType) {
        return subType.isInterface()
                || Modifier.isAbstract(subType.getModifiers())
                || subType.isAnnotationPresent(ConstructableIgnored.class);
    }

    private static Class getConstructorType(final Class subType) {
        return subType.isAnnotationPresent(ConstructableClass.class)
                ? subType.getAnnotation(ConstructableClass.class).constructorType()
                : NoArgsConstructor.class;
    }
}