SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package cc.squirreljme.runtime.cldc.full;

import cc.squirreljme.runtime.cldc.debug.Debugging;
import java.io.IOException;
import java.nio.file.FileStore;
import java.nio.file.FileSystem;
import java.nio.file.InvalidPathException;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

/**
 * This is a file system which is completely nullary.
 *
 * @since 2019/12/22
 */
public final class NullFileSystem
    extends FileSystem
{
    /** The instance of this filesystem. */
    public static final NullFileSystem INSTANCE =
        new NullFileSystem();
    
    /**
     * {@inheritDoc}
     * @since 2019/12/22
     */
    @Override
    public final void close()
        throws IOException
    {
        // Has no effect
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/12/22
     */
    @Override
    public final Iterable<FileStore> getFileStores()
    {
        throw Debugging.todo();
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/12/22
     */
    @Override
    public final Path getPath(String __base, String... __more)
        throws NullPointerException
    {
        if (__base == null)
            throw new NullPointerException("NARG");
        
        /* {@squirreljme.error ZY01 The null filesystem only supports a single
        path element.} */
        if (!__base.equals(NullPath.ONLY_PATH_STRING))
            throw new InvalidPathException(__base, "ZY01");
        
        /* {@squirreljme.error ZY02 Additional null path elements must be
        blank or null.} */
        if (__more != null)
            for (String m : __more)
                if (m != null && !m.isEmpty())
                    throw new InvalidPathException(m, "ZY02");
        
        return NullPath.INSTANCE;
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/12/22
     */
    @Override
    public final Iterable<Path> getRootDirectories()
    {
        // There is only a single null root
        return Arrays.<Path>asList(this.getPath("null:$"));
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/12/22
     */
    @Override
    public final String getSeparator()
    {
        // Null file system uses dollar signs as paths
        return "$";
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/12/22
     */
    @Override
    public final boolean isOpen()
    {
        // Always is open
        return true;
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/12/22
     */
    @Override
    public final boolean isReadOnly()
    {
        // File system is always read-only
        return true;
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/12/22
     */
    @Override
    public final Set<String> supportedFileAttributeViews()
    {
        // No attributes are supported
        return new HashSet<>();
    }
}