/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.nlpcraft.model.tools.cmdline;

import org.apache.nlpcraft.model.NCModel;

import java.io.*;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.*;
import java.util.jar.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * Completer for model classes from classpath. Currently only JAR files are supported.
 */
class NCCliModelClassCompleter {
    /**
     *
     * @param jarPath Path of the JAR file.
     * @return Set of class names from the given JAR file.
     * @throws IOException Thrown in case of any I/O errors.
     */
    private Set<String> getClassNamesFromJar(File jarPath) throws IOException {
        assert jarPath != null;

        Set<String> classNames = new HashSet<>();

        if (jarPath.getAbsolutePath().toLowerCase().endsWith(".jar"))
            try (JarFile jarFile = new JarFile(jarPath)) {
                Enumeration<JarEntry> entries = jarFile.entries();

                while (entries.hasMoreElements()) {
                    JarEntry entry = entries.nextElement();

                    if (entry.getName().endsWith(".class"))
                        classNames.add(entry.getName()
                            .replace("/", ".")
                            .replace(".class", "")
                        );
                }
            }

        return classNames;
    }

    /**
     *
     * @param dirPath Path of the directory.
     * @return Set of class names from the given JAR file.
     * @throws IOException Thrown in case of any I/O errors.
     */
    private Set<String> getClassNameFromDirectory(File dirPath) throws IOException {
        assert dirPath != null;

        int dirPathLen = dirPath.getAbsolutePath().length();
        Set<String> classNames = new HashSet<>();

        try (Stream<Path> pathTree = Files.walk(dirPath.toPath())) {
            pathTree.forEach(path -> {
                File file = path.toFile();

                if (file.isFile() && !file.isHidden() && file.getName().toLowerCase().endsWith(".class")) {
                    String clsName = file.getAbsolutePath().substring(dirPathLen)
                        .replace(File.separator, ".")
                        .replace(".class", "");

                    if (clsName.startsWith("."))
                        clsName = clsName.substring(1);

                    classNames.add(clsName);
                }
            });
        }

        return classNames;
    }

    /**
     *
     * @param path Path to test.
     */
    private boolean isJar(String path) {
        return path.toLowerCase().endsWith(".jar");
    }

    /**
     *
     * @param cp List of classpath entries.
     * @return Set of model class name for the given classpath.
     * @throws IOException Thrown in case of any I/O errors.
     */
    public Set<String> getModelClassNamesFromClasspath(List<String> cp) throws IOException {
        Set<URL> urls = cp.stream().map(entry -> {
            try {
                if (isJar(entry))
                    return new URL("jar:file:" + entry + "!/");
                else {
                    boolean trailingSlash = entry.endsWith("/");

                    return new URL("file:" + entry + (trailingSlash ? "" : "/"));
                }
            }
            catch (MalformedURLException e) {
                e.printStackTrace();
                return null;
            }
        }).filter(Objects::nonNull).collect(Collectors.toSet());

        URL[] urlsArr = new URL[urls.size()];

        urls.toArray(urlsArr);

        Set<String> mdlClasses = new HashSet<>();

        try (URLClassLoader clsLdr = URLClassLoader.newInstance(urlsArr)) {
            for (String cpEntry : cp) {
                try {
                    File file = new File(cpEntry);

                    Set<String> classNames = isJar(cpEntry) ? getClassNamesFromJar(file) : getClassNameFromDirectory(file);

                    for (String name : classNames) {
                        try {
                            Class<?> clazz = clsLdr.loadClass(name);

                            if (NCModel.class.isAssignableFrom(clazz))
                                mdlClasses.add(clazz.getName());
                        }
                        catch (Throwable e) {
                            // Ignoring.
                        }
                    }
                }
                catch (Exception e) {
                    // Ignore.
                }
            }
        }

        return mdlClasses;
    }
}