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A library for unit-tests to check the dependencies between classes.
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package de.spricom.dessert.resolve;

/*-
 * #%L
 * Dessert Dependency Assertion Library for Java
 * %%
 * Copyright (C) 2017 - 2023 Hans Jörg Heßmann
 * %%
 * 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.
 * #L%
 */

import de.spricom.dessert.util.Assertions;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.jar.Manifest;

final class JarRoot extends ClassRoot {
    private JarFile jarFileArchive;

    public JarRoot(File jarFile) {
        super(jarFile);
    }

    @Override
    protected void scan(ClassCollector collector) throws IOException {
        Map packages = new HashMap();
        packages.put("", this);
        collector.addPackage(this);

        JarFile jarFile = getJarFileArchive();
        Enumeration entries = jarFile.entries();
        while (entries.hasMoreElements()) {
            JarEntry entry = entries.nextElement();
            if (!entry.isDirectory()
                    && entry.getName().endsWith(".class")) {
                addClass(collector, packages, jarFile, entry);
            }
        }
        // JarFile must not be closed to be able to access the content of each JarEntry.
    }

    private JarFile getJarFileArchive() throws IOException {
        if (jarFileArchive == null) {
            jarFileArchive = new JarFile(getRootFile());
        }
        return jarFileArchive;
    }

    private void addClass(ClassCollector collector, Map packages, JarFile jarFile, JarEntry entry) {
        ClassPackage pckg = ensurePackage(collector, packages, packageName(entry));
        ClassEntry ce = new JarClassEntry(pckg, jarFile, entry);
        pckg.addClass(ce);
        collector.addClass(ce);
    }

    private String packageName(JarEntry entry) {
        String path = VersionsHelper.removeVersionPrefix(entry.getName());
        return packageName(path, '/').replace('/', '.');
    }

    private ClassPackage ensurePackage(ClassCollector collector, Map packages, String packageName) {
        ClassPackage pckg = packages.get(packageName);
        if (pckg != null) {
            return pckg;
        }
        ClassPackage parent = ensurePackage(collector, packages, parentPackageName(packageName));
        pckg = new ClassPackage(parent, packageName);
        collector.addPackage(pckg);
        packages.put(packageName, pckg);
        return pckg;
    }

    private String parentPackageName(String packageName) {
        return packageName(packageName, '.');
    }

    private String packageName(String name, char separator) {
        int index = name.lastIndexOf(separator);
        if (index == -1) {
            return "";
        }
        String packageName = name.substring(0, index);
        return packageName;
    }

    @Override
    public URL getResource(String name) {
        JarEntry jarEntry = getJarEntry(name);
        if (jarEntry == null) {
            return null;
        }
        try {
            return new URL("jar:" + getRootFile().toURI().toURL() + "!/" + jarEntry.getName());
        } catch (MalformedURLException ex) {
            throw new IllegalArgumentException("Unable to convert " + getRootFile().toURI() + " to an URL: " + ex, ex);
        }
    }

    @Override
    public InputStream getResourceAsStream(String name) {
        JarEntry jarEntry = getJarEntry(name);
        if (jarEntry == null) {
            return null;
        }
        try {
            return jarFileArchive.getInputStream(jarEntry);
        } catch (IOException ex) {
            throw new IllegalArgumentException("Unable to read " + jarEntry.getName()
                    + " from jar-archive " + getRootFile().getPath() + ": " + ex, ex);
        }
    }

    public JarEntry getJarEntry(String name) {
        Assertions.notNull(name, "name");
        try {
            if (name.startsWith("/")) {
                name = name.substring(1);
            }
            JarEntry jarEntry = getJarFileArchive().getJarEntry(name);
            return jarEntry;
        } catch (IOException ex) {
            throw new IllegalStateException("Unable to read jar-archive " + getRootFile().getPath() + ": " + ex, ex);
        }
    }

    public Manifest getManifest() throws IOException {
        JarFile jarFile = getJarFileArchive();
        Manifest manifest = jarFile.getManifest();
        return manifest;
    }
}