CC-Tweaked/src/main/java/dan200/computercraft/core/filesystem/FileMount.java

/*
 * This file is part of ComputerCraft - http://www.computercraft.info
 * Copyright Daniel Ratcliffe, 2011-2017. Do not distribute without permission.
 * Send enquiries to dratcliffe@gmail.com
 */

package dan200.computercraft.core.filesystem;

import dan200.computercraft.api.filesystem.IWritableMount;

import javax.annotation.Nonnull;
import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.nio.file.Files;
import java.nio.file.StandardOpenOption;
import java.util.List;

public class FileMount implements IWritableMount
{
    private static final int MINIMUM_FILE_SIZE = 500;

    private class WritableCountingChannel implements WritableByteChannel
    {

        private final WritableByteChannel m_inner;
        long m_ignoredBytesLeft;

        WritableCountingChannel( WritableByteChannel inner, long bytesToIgnore )
        {
            m_inner = inner;
            m_ignoredBytesLeft = bytesToIgnore;
        }

        @Override
        public int write( @Nonnull ByteBuffer b ) throws IOException
        {
            count( b.remaining() );
            return m_inner.write( b );
        }

        void count( long n ) throws IOException
        {
            m_ignoredBytesLeft -= n;
            if( m_ignoredBytesLeft < 0 )
            {
                long newBytes = -m_ignoredBytesLeft;
                m_ignoredBytesLeft = 0;

                long bytesLeft = m_capacity - m_usedSpace;
                if( newBytes > bytesLeft )
                {
                    throw new IOException( "Out of space" );
                }
                else
                {
                    m_usedSpace += newBytes;
                }
            }
        }

        @Override
        public boolean isOpen()
        {
            return m_inner.isOpen();
        }

        @Override
        public void close() throws IOException
        {
            m_inner.close();
        }
    }

    private class SeekableCountingChannel extends WritableCountingChannel implements SeekableByteChannel
    {
        private final SeekableByteChannel m_inner;

        SeekableCountingChannel( SeekableByteChannel inner, long bytesToIgnore )
        {
            super( inner, bytesToIgnore );
            this.m_inner = inner;
        }

        @Override
        public SeekableByteChannel position( long newPosition ) throws IOException
        {
            if( !isOpen() ) throw new ClosedChannelException();
            if( newPosition < 0 ) throw new IllegalArgumentException();

            long delta = newPosition - m_inner.position();
            if( delta < 0 )
            {
                m_ignoredBytesLeft -= delta;
            }
            else
            {
                count( delta );
            }

            return m_inner.position( newPosition );
        }

        @Override
        public SeekableByteChannel truncate( long size ) throws IOException
        {
            throw new IOException( "Not yet implemented" );
        }

        @Override
        public int read( ByteBuffer dst ) throws IOException
        {
            if( !m_inner.isOpen() ) throw new ClosedChannelException();
            throw new NonReadableChannelException();
        }

        @Override
        public long position() throws IOException
        {
            return m_inner.position();
        }

        @Override
        public long size() throws IOException
        {
            return m_inner.size();
        }
    }

    private File m_rootPath;
    private long m_capacity;
    private long m_usedSpace;

    public FileMount( File rootPath, long capacity )
    {
        m_rootPath = rootPath;
        m_capacity = capacity + MINIMUM_FILE_SIZE;
        m_usedSpace = created() ? measureUsedSpace( m_rootPath ) : MINIMUM_FILE_SIZE;
    }

    // IMount implementation

    @Override
    public boolean exists( @Nonnull String path )
    {
        if( !created() )
        {
            return path.length() == 0;
        }
        else
        {
            File file = getRealPath( path );
            return file.exists();
        }
    }

    @Override
    public boolean isDirectory( @Nonnull String path )
    {
        if( !created() )
        {
            return path.length() == 0;
        }
        else
        {
            File file = getRealPath( path );
            return file.exists() && file.isDirectory();
        }
    }

    @Override
    public void list( @Nonnull String path, @Nonnull List<String> contents ) throws IOException
    {
        if( !created() )
        {
            if( path.length() != 0 )
            {
                throw new IOException( "/" + path + ": Not a directory" );
            }
        }
        else
        {
            File file = getRealPath( path );
            if( file.exists() && file.isDirectory() )
            {
                String[] paths = file.list();
                for( String subPath : paths )
                {
                    if( new File( file, subPath ).exists() )
                    {
                        contents.add( subPath );
                    }
                }
            }
            else
            {
                throw new IOException( "/" + path + ": Not a directory" );
            }
        }
    }

    @Override
    public long getSize( @Nonnull String path ) throws IOException
    {
        if( !created() )
        {
            if( path.length() == 0 )
            {
                return 0;
            }
        }
        else
        {
            File file = getRealPath( path );
            if( file.exists() )
            {
                if( file.isDirectory() )
                {
                    return 0;
                }
                else
                {
                    return file.length();
                }
            }
        }
        throw new IOException( "/" + path + ": No such file" );
    }

    @Nonnull
    @Override
    @Deprecated
    public InputStream openForRead( @Nonnull String path ) throws IOException
    {
        if( created() )
        {
            File file = getRealPath( path );
            if( file.exists() && !file.isDirectory() )
            {
                return new FileInputStream( file );
            }
        }
        throw new IOException( "/" + path + ": No such file" );
    }

    @Nonnull
    @Override
    public ReadableByteChannel openChannelForRead( @Nonnull String path ) throws IOException
    {
        if( created() )
        {
            File file = getRealPath( path );
            if( file.exists() && !file.isDirectory() )
            {
                return FileChannel.open( file.toPath(), StandardOpenOption.READ );
            }
        }
        throw new IOException( "/" + path + ": No such file" );
    }

    // IWritableMount implementation

    @Override
    public void makeDirectory( @Nonnull String path ) throws IOException
    {
        create();
        File file = getRealPath( path );
        if( file.exists() )
        {
            if( !file.isDirectory() )
            {
                throw new IOException( "/" + path + ": File exists" );
            }
        }
        else
        {
            int dirsToCreate = 1;
            File parent = file.getParentFile();
            while( !parent.exists() )
            {
                ++dirsToCreate;
                parent = parent.getParentFile();
            }

            if( getRemainingSpace() < dirsToCreate * MINIMUM_FILE_SIZE )
            {
                throw new IOException( "/" + path + ": Out of space" );
            }

            boolean success = file.mkdirs();
            if( success )
            {
                m_usedSpace += dirsToCreate * MINIMUM_FILE_SIZE;
            }
            else
            {
                throw new IOException( "/" + path + ": Access denied" );
            }
        }
    }

    @Override
    public void delete( @Nonnull String path ) throws IOException
    {
        if( path.length() == 0 )
        {
            throw new IOException( "/" + path + ": Access denied" );
        }

        if( created() )
        {
            File file = getRealPath( path );
            if( file.exists() )
            {
                deleteRecursively( file );
            }
        }
    }

    private void deleteRecursively( File file ) throws IOException
    {
        // Empty directories first
        if( file.isDirectory() )
        {
            String[] children = file.list();
            for( String aChildren : children )
            {
                deleteRecursively( new File( file, aChildren ) );
            }
        }

        // Then delete
        long fileSize = file.isDirectory() ? 0 : file.length();
        boolean success = file.delete();
        if( success )
        {
            m_usedSpace -= Math.max( MINIMUM_FILE_SIZE, fileSize );
        }
        else
        {
            throw new IOException( "Access denied" );
        }
    }

    @Nonnull
    @Override
    @Deprecated
    public OutputStream openForWrite( @Nonnull String path ) throws IOException
    {
        return Channels.newOutputStream( openStreamForWrite( path ) );
    }

    @Nonnull
    @Override
    @Deprecated
    public OutputStream openForAppend( @Nonnull String path ) throws IOException
    {
        return Channels.newOutputStream( openStreamForAppend( path ) );
    }

    @Nonnull
    @Override
    public WritableByteChannel openStreamForWrite( @Nonnull String path ) throws IOException
    {
        create();
        File file = getRealPath( path );
        if( file.exists() && file.isDirectory() )
        {
            throw new IOException( "/" + path + ": Cannot write to directory" );
        }
        else
        {
            if( !file.exists() )
            {
                if( getRemainingSpace() < MINIMUM_FILE_SIZE )
                {
                    throw new IOException( "/" + path + ": Out of space" );
                }
                else
                {
                    m_usedSpace += MINIMUM_FILE_SIZE;
                }
            }
            else
            {
                m_usedSpace -= Math.max( file.length(), MINIMUM_FILE_SIZE );
                m_usedSpace += MINIMUM_FILE_SIZE;
            }
            return new SeekableCountingChannel( Files.newByteChannel( file.toPath(), StandardOpenOption.WRITE, StandardOpenOption.CREATE ),
                MINIMUM_FILE_SIZE );
        }
    }

    @Nonnull
    @Override
    public WritableByteChannel openStreamForAppend( @Nonnull String path ) throws IOException
    {
        if( created() )
        {
            File file = getRealPath( path );
            if( !file.exists() )
            {
                throw new IOException( "/" + path + ": No such file" );
            }
            else if( file.isDirectory() )
            {
                throw new IOException( "/" + path + ": Cannot write to directory" );
            }
            else
            {
                // Allowing seeking when appending is not recommended, so we use a separate channel.
                return new WritableCountingChannel( Files.newByteChannel( file.toPath(), StandardOpenOption.WRITE, StandardOpenOption.CREATE, StandardOpenOption.APPEND ),
                    Math.max( MINIMUM_FILE_SIZE - file.length(), 0 ) );
            }
        }
        else
        {
            throw new IOException( "/" + path + ": No such file" );
        }
    }

    @Override
    public long getRemainingSpace()
    {
        return Math.max( m_capacity - m_usedSpace, 0 );
    }

    public File getRealPath( String path )
    {
        return new File( m_rootPath, path );
    }

    private boolean created()
    {
        return m_rootPath.exists();
    }

    private void create() throws IOException
    {
        if( !m_rootPath.exists() )
        {
            boolean success = m_rootPath.mkdirs();
            if( !success )
            {
                throw new IOException( "Access denied" );
            }
        }
    }

    private long measureUsedSpace( File file )
    {
        if( !file.exists() )
        {
            return 0;
        }
        if( file.isDirectory() )
        {
            long size = MINIMUM_FILE_SIZE;
            String[] contents = file.list();
            for( String content : contents )
            {
                size += measureUsedSpace( new File( file, content ) );
            }
            return size;
        }
        else
        {
            return Math.max( file.length(), MINIMUM_FILE_SIZE );
        }
    }
}