Set<String> getClassNames(Collection<TransformInput> inputs) {
    Set<String> classNames = new HashSet<>();

    for (TransformInput input : inputs) {
        classNames.addAll(getDirectoryInputs(input.getDirectoryInputs()));
        classNames.addAll(getJarInputs(input.getJarInputs()));
    }
    return classNames;
}

Set<String> getDirectoryInputs(Collection<DirectoryInput> directoryInputs) {
    Set<String> classNames = new HashSet<>();
    for (DirectoryInput input : directoryInputs) {
        try {
            classNames.addAll(processDirectoryInput(input));
        } catch (IOException e) {
            throw new GradleException(e.getMessage());
        }
    }
    return classNames;
}

Set<String> processDirectoryInput(DirectoryInput input) throws IOException {
    String dirPath = input.getFile().getAbsolutePath();

    return Files.walk(input.getFile().toPath())
            .map(file -> file.toAbsolutePath().toString())
            .filter(path -> path.endsWith(SdkConstants.DOT_CLASS))
            .map(path -> path.substring(dirPath.length() + 1,
                    path.length() - SdkConstants.DOT_CLASS.length()))
            .map(path -> path.replaceAll(File.separator, "."))
            .collect(Collectors.toSet());
}

Set<String> getJarInputs(Collection<JarInput> jarInputs) {
    return jarInputs.stream().map(QualifiedContent::getFile)
            .map(this::toJar)
            .map(JarFile::entries)
            .flatMap(this::toStream)
            .filter(entry -> !entry.isDirectory() && entry.getName().endsWith(SdkConstants.DOT_CLASS))
            .map(ZipEntry::getName)
            .map(name -> name.substring(0, name.length() - SdkConstants.DOT_CLASS.length()))
            .map(name -> name.replaceAll(File.separator, "."))
            .collect(Collectors.toSet());
}

ClassPool createClassPool(Collection<TransformInput> inputs,
                          Collection<TransformInput> referencedInputs) {
    ClassPool classPool = new ClassPool();
    classPool.appendSystemPath();
    classPool.appendClassPath(new LoaderClassPath(getClass().getClassLoader()));

    Stream.concat(inputs.stream(), referencedInputs.stream())
            .flatMap(input -> Stream.concat(input.getDirectoryInputs().stream(),
                    input.getJarInputs().stream()))
            .map(input -> input.getFile().getAbsolutePath())
            .forEach(entry -> {
                try {
                    classPool.appendClassPath(entry);
                } catch (NotFoundException e) {
                    throw new GradleException(e.getMessage());
                }
            });

    return classPool;
}