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/*
 * 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 io.edurt.gcm.common.jdk;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLDecoder;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;

import static java.lang.String.format;

public class Classs
{
    private static final Logger LOGGER = LoggerFactory.getLogger(Classs.class);
    public static final String TYPE_FILE = "file";
    public static final String PACKAGE_SCANNER = ".";
    public static final String ENCODE = "UTF-8";

    private Classs()
    {}

    /**
     * Scan all class files under the specified package
     *
     * @param scanPackage scan package
     * @return Specify all class files under the package
     */
    public static Set> scanClassInPackage(String scanPackage)
    {
        Set> classes = new HashSet<>();
        try {
            Enumeration urls = Thread.currentThread().getContextClassLoader().getResources(scanPackage.replace(PACKAGE_SCANNER, "/"));
            if (!urls.hasMoreElements()) {
                LOGGER.error("Scan package {} not exists!", scanPackage);
                throw new RuntimeException(format("Scan package %s not exists", scanPackage));
            }
            while (urls.hasMoreElements()) {
                URL url = urls.nextElement();
                String protocol = url.getProtocol();
                // If it is a file, scan all the files under the package
                if (protocol.equalsIgnoreCase(TYPE_FILE)) {
                    scanClassesInFilePackage(scanPackage, URLDecoder.decode(url.getFile(), ENCODE), classes);
                }
                else {
                    // TODO: If it is jar, scan and parse all the files in jar
                }
            }
        }
        catch (IOException e) {
            LOGGER.error(format("Scan package %s has error!", scanPackage), e);
        }
        return classes;
    }

    /**
     * Scan all class files in the package path
     *
     * @param packageName scan package name
     * @param packagePath Specific scan packet path
     * @param classes Specify all class files under the package
     */
    private static void scanClassesInFilePackage(String packageName, String packagePath, Set> classes)
    {
        // Get the directory of this package and create a file
        File directory = new File(packagePath);
        if (!directory.exists() || !directory.isDirectory()) {
            LOGGER.error("Scan package {} not exists!", directory);
            return;
        }
        // If it exists, get all the. Class files and subdirectories under the package
        File[] directoryFiles = directory.listFiles(file -> file.isDirectory() || file.getName().endsWith(".class"));
        if (directoryFiles == null) {
            LOGGER.info("Scan class file from {} is empty!", directory);
            return;
        }
        // Loop to get all class files
        Arrays.asList(directoryFiles).forEach(v -> {
            // If it is a directory, scan recursively
            if (v.isDirectory()) {
                scanClassesInFilePackage(String.join(".", packageName, v.getName()), v.getAbsolutePath(), classes);
            }
            else {
                // If it is a Java class file, remove the following. Class and leave only the class name
                String className = v.getName().substring(0, v.getName().length() - 6);
                try {
                    classes.add(Thread.currentThread().getContextClassLoader().loadClass(packageName + '.' + className));
                }
                catch (ClassNotFoundException e) {
                    LOGGER.error("Load class {} error", className);
                }
            }
        });
    }
}