//
//  ========================================================================
//  Copyright (c) 1995-2019 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.util.resource;

import java.io.Closeable;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.nio.channels.ReadableByteChannel;
import java.nio.file.Path;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Base64;
import java.util.Collection;
import java.util.Date;
import java.util.List;

import org.eclipse.jetty.util.IO;
import org.eclipse.jetty.util.Loader;
import org.eclipse.jetty.util.MultiMap;
import org.eclipse.jetty.util.StringUtil;
import org.eclipse.jetty.util.URIUtil;
import org.eclipse.jetty.util.UrlEncoded;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;

import static java.nio.charset.StandardCharsets.UTF_8;

Abstract resource class.

This class provides a resource abstraction, where a resource may be
a file, a URL or an entry in a jar file.

/**
 * Abstract resource class.
 * <p>
 * This class provides a resource abstraction, where a resource may be
 * a file, a URL or an entry in a jar file.
 * </p>
 */
public abstract class Resource implements ResourceFactory, Closeable
{
    private static final Logger LOG = Log.getLogger(Resource.class);
    public static boolean __defaultUseCaches = true;
    volatile Object _associate;

    
Change the default setting for url connection caches.
Subsequent URLConnections will use this default.
Params:
useCaches – true to enable URL connection caches, false otherwise./**
     * Change the default setting for url connection caches.
     * Subsequent URLConnections will use this default.
     *
     * @param useCaches true to enable URL connection caches, false otherwise.
     */
    public static void setDefaultUseCaches(boolean useCaches)
    {
        __defaultUseCaches = useCaches;
    }

    public static boolean getDefaultUseCaches()
    {
        return __defaultUseCaches;
    }

    
Construct a resource from a uri.
Params:
uri – A URI.
Throws:
MalformedURLException – Problem accessing URI
Returns:
A Resource object./**
     * Construct a resource from a uri.
     *
     * @param uri A URI.
     * @return A Resource object.
     * @throws MalformedURLException Problem accessing URI
     */
    public static Resource newResource(URI uri)
        throws MalformedURLException
    {
        return newResource(uri.toURL());
    }

    
Construct a resource from a url.
Params:
url – A URL.
Returns:
A Resource object./**
     * Construct a resource from a url.
     *
     * @param url A URL.
     * @return A Resource object.
     */
    public static Resource newResource(URL url)
    {
        return newResource(url, __defaultUseCaches);
    }

    
Construct a resource from a url.
Params:
url – the url for which to make the resource
useCaches – true enables URLConnection caching if applicable to the type of resource
Returns:
a new resource from the given URL/**
     * Construct a resource from a url.
     *
     * @param url the url for which to make the resource
     * @param useCaches true enables URLConnection caching if applicable to the type of resource
     * @return a new resource from the given URL
     */
    static Resource newResource(URL url, boolean useCaches)
    {
        if (url == null)
            return null;

        String urlString = url.toExternalForm();
        if (urlString.startsWith("file:"))
        {
            try
            {
                return new PathResource(url);
            }
            catch (Exception e)
            {
                LOG.warn(e.toString());
                LOG.debug(Log.EXCEPTION, e);
                return new BadResource(url, e.toString());
            }
        }
        else if (urlString.startsWith("jar:file:"))
        {
            return new JarFileResource(url, useCaches);
        }
        else if (urlString.startsWith("jar:"))
        {
            return new JarResource(url, useCaches);
        }

        return new URLResource(url, null, useCaches);
    }

    
Construct a resource from a string.
Params:
resource – A URL or filename.
Throws:
MalformedURLException – Problem accessing URI
Returns:
A Resource object./**
     * Construct a resource from a string.
     *
     * @param resource A URL or filename.
     * @return A Resource object.
     * @throws MalformedURLException Problem accessing URI
     */
    public static Resource newResource(String resource) throws IOException
    {
        return newResource(resource, __defaultUseCaches);
    }

    
Construct a resource from a string.
Params:
resource – A URL or filename.
useCaches – controls URLConnection caching
Throws:
MalformedURLException – Problem accessing URI
Returns:
A Resource object./**
     * Construct a resource from a string.
     *
     * @param resource A URL or filename.
     * @param useCaches controls URLConnection caching
     * @return A Resource object.
     * @throws MalformedURLException Problem accessing URI
     */
    public static Resource newResource(String resource, boolean useCaches) throws IOException
    {
        URL url;
        try
        {
            // Try to format as a URL?
            url = new URL(resource);
        }
        catch (MalformedURLException e)
        {
            if (!resource.startsWith("ftp:") &&
                !resource.startsWith("file:") &&
                !resource.startsWith("jar:"))
            {
                try
                {
                    // It's a file.
                    if (resource.startsWith("./"))
                        resource = resource.substring(2);
                    File file = new File(resource).getCanonicalFile();
                    return new PathResource(file);
                }
                catch (IOException e2)
                {
                    e2.addSuppressed(e);
                    throw e2;
                }
            }
            else
            {
                LOG.warn("Bad Resource: " + resource);
                throw e;
            }
        }

        return newResource(url, useCaches);
    }

    public static Resource newResource(File file)
    {
        return new PathResource(file.toPath());
    }

    
Construct a Resource from provided path
Params:
path – the path
Returns:
the Resource for the provided path
Since:
9.4.10/**
     * Construct a Resource from provided path
     *
     * @param path the path
     * @return the Resource for the provided path
     * @since 9.4.10
     */
    public static Resource newResource(Path path)
    {
        return new PathResource(path);
    }

    
Construct a system resource from a string.
The resource is tried as classloader resource before being
treated as a normal resource.
Params:
resource – Resource as string representation
Throws:
IOException – Problem accessing resource.
Returns:
The new Resource/**
     * Construct a system resource from a string.
     * The resource is tried as classloader resource before being
     * treated as a normal resource.
     *
     * @param resource Resource as string representation
     * @return The new Resource
     * @throws IOException Problem accessing resource.
     */
    public static Resource newSystemResource(String resource) throws IOException
    {
        URL url = null;
        // Try to format as a URL?
        ClassLoader loader = Thread.currentThread().getContextClassLoader();
        if (loader != null)
        {
            try
            {
                url = loader.getResource(resource);
                if (url == null && resource.startsWith("/"))
                    url = loader.getResource(resource.substring(1));
            }
            catch (IllegalArgumentException e)
            {
                LOG.ignore(e);
                // Catches scenario where a bad Windows path like "C:\dev" is
                // improperly escaped, which various downstream classloaders
                // tend to have a problem with
                url = null;
            }
        }
        if (url == null)
        {
            loader = Resource.class.getClassLoader();
            if (loader != null)
            {
                url = loader.getResource(resource);
                if (url == null && resource.startsWith("/"))
                    url = loader.getResource(resource.substring(1));
            }
        }

        if (url == null)
        {
            url = ClassLoader.getSystemResource(resource);
            if (url == null && resource.startsWith("/"))
                url = ClassLoader.getSystemResource(resource.substring(1));
        }

        if (url == null)
            return null;

        return newResource(url);
    }

    
Find a classpath resource.
Params:
resource – the relative name of the resource
Returns:
Resource or null/**
     * Find a classpath resource.
     *
     * @param resource the relative name of the resource
     * @return Resource or null
     */
    public static Resource newClassPathResource(String resource)
    {
        return newClassPathResource(resource, true, false);
    }

    
Find a classpath resource. The Class.getResource(String) method is used to lookup the resource. If it is not found, then the Loader.getResource(String) method is used. If it is still not found, then ClassLoader.getSystemResource(String) is used. Unlike ClassLoader.getSystemResource(String) this method does not check for normal resources. 
Params:
name – The relative name of the resource
useCaches – True if URL caches are to be used.
checkParents – True if forced searching of parent Classloaders is performed to work around
loaders with inverted priorities
Returns:
Resource or null/**
     * Find a classpath resource.
     * The {@link java.lang.Class#getResource(String)} method is used to lookup the resource. If it is not
     * found, then the {@link Loader#getResource(String)} method is used.
     * If it is still not found, then {@link ClassLoader#getSystemResource(String)} is used.
     * Unlike {@link ClassLoader#getSystemResource(String)} this method does not check for normal resources.
     *
     * @param name The relative name of the resource
     * @param useCaches True if URL caches are to be used.
     * @param checkParents True if forced searching of parent Classloaders is performed to work around
     * loaders with inverted priorities
     * @return Resource or null
     */
    public static Resource newClassPathResource(String name, boolean useCaches, boolean checkParents)
    {
        URL url = Resource.class.getResource(name);

        if (url == null)
            url = Loader.getResource(name);
        if (url == null)
            return null;
        return newResource(url, useCaches);
    }

    public static boolean isContainedIn(Resource r, Resource containingResource) throws MalformedURLException
    {
        return r.isContainedIn(containingResource);
    }

    public abstract boolean isContainedIn(Resource r) throws MalformedURLException;

    
Release any temporary resources held by the resource.
/**
     * Release any temporary resources held by the resource.
     */
    @Override
    public abstract void close();

    
Returns:
true if the represented resource exists./**
     * @return true if the represented resource exists.
     */
    public abstract boolean exists();

    
Returns:
true if the represented resource is a container/directory.
if the resource is not a file, resources ending with "/" are
considered directories./**
     * @return true if the represented resource is a container/directory.
     * if the resource is not a file, resources ending with "/" are
     * considered directories.
     */
    public abstract boolean isDirectory();

    
Time resource was last modified.
Returns:
the last modified time as milliseconds since unix epoch/**
     * Time resource was last modified.
     *
     * @return the last modified time as milliseconds since unix epoch
     */
    public abstract long lastModified();

    
Length of the resource.
Returns:
the length of the resource/**
     * Length of the resource.
     *
     * @return the length of the resource
     */
    public abstract long length();

    
URI representing the resource.
Returns:
an URI representing the given resource/**
     * URI representing the resource.
     *
     * @return an URI representing the given resource
     */
    public abstract URI getURI();

    
File representing the given resource.
Throws:
IOException – if unable to get the resource due to permissions
Returns:
an File representing the given resource or NULL if this
is not possible./**
     * File representing the given resource.
     *
     * @return an File representing the given resource or NULL if this
     * is not possible.
     * @throws IOException if unable to get the resource due to permissions
     */
    public abstract File getFile()
        throws IOException;

    
The name of the resource.
Returns:
the name of the resource/**
     * The name of the resource.
     *
     * @return the name of the resource
     */
    public abstract String getName();

    
Input stream to the resource
Throws:
IOException – if unable to open the input stream
Returns:
an input stream to the resource/**
     * Input stream to the resource
     *
     * @return an input stream to the resource
     * @throws IOException if unable to open the input stream
     */
    public abstract InputStream getInputStream()
        throws IOException;

    
Readable ByteChannel for the resource.
Throws:
IOException – if unable to open the readable bytechannel for the resource.
Returns:
an readable bytechannel to the resource or null if one is not available./**
     * Readable ByteChannel for the resource.
     *
     * @return an readable bytechannel to the resource or null if one is not available.
     * @throws IOException if unable to open the readable bytechannel for the resource.
     */
    public abstract ReadableByteChannel getReadableByteChannel()
        throws IOException;

    
Deletes the given resource
Throws:
SecurityException – if unable to delete due to permissions
Returns:
true if resource was found and successfully deleted, false if resource didn't exist or was unable to
be deleted./**
     * Deletes the given resource
     *
     * @return true if resource was found and successfully deleted, false if resource didn't exist or was unable to
     * be deleted.
     * @throws SecurityException if unable to delete due to permissions
     */
    public abstract boolean delete()
        throws SecurityException;

    
Rename the given resource
Params:
dest – the destination name for the resource
Throws:
SecurityException – if unable to rename due to permissions
Returns:
true if the resource was renamed, false if the resource didn't exist or was unable to be renamed./**
     * Rename the given resource
     *
     * @param dest the destination name for the resource
     * @return true if the resource was renamed, false if the resource didn't exist or was unable to be renamed.
     * @throws SecurityException if unable to rename due to permissions
     */
    public abstract boolean renameTo(Resource dest)
        throws SecurityException;

    
list of resource names contained in the given resource.
Ordering is unspecified, so callers may wish to sort the return value to ensure deterministic behavior.
Returns:
a list of resource names contained in the given resource, or null.
Note: The resource names are not URL encoded./**
     * list of resource names contained in the given resource.
     * Ordering is unspecified, so callers may wish to sort the return value to ensure deterministic behavior.
     *
     * @return a list of resource names contained in the given resource, or null.
     * Note: The resource names are not URL encoded.
     */
    public abstract String[] list();

    
Returns the resource contained inside the current resource with the
given name.
Params:
path – The path segment to add, which is not encoded
Throws:
IOException – if unable to resolve the path
MalformedURLException – if the resolution of the path fails because the input path parameter is malformed.
Returns:
the Resource for the resolved path within this Resource./**
     * Returns the resource contained inside the current resource with the
     * given name.
     *
     * @param path The path segment to add, which is not encoded
     * @return the Resource for the resolved path within this Resource.
     * @throws IOException if unable to resolve the path
     * @throws MalformedURLException if the resolution of the path fails because the input path parameter is malformed.
     */
    public abstract Resource addPath(String path)
        throws IOException, MalformedURLException;

    
Get a resource from within this resource.
 This method is essentially an alias for addPath(String), but without checked exceptions. This method satisfied the ResourceFactory interface. /**
     * Get a resource from within this resource.
     * <p>
     * This method is essentially an alias for {@link #addPath(String)}, but without checked exceptions.
     * This method satisfied the {@link ResourceFactory} interface.
     */
    @Override
    public Resource getResource(String path)
    {
        try
        {
            return addPath(path);
        }
        catch (Exception e)
        {
            LOG.debug(e);
            return null;
        }
    }

    // FIXME: this appears to not be used
    @SuppressWarnings("javadoc")
    public Object getAssociate()
    {
        return _associate;
    }

    // FIXME: this appear to not be used
    @SuppressWarnings("javadoc")
    public void setAssociate(Object o)
    {
        _associate = o;
    }

    
Returns:
true if this Resource is an alias to another real Resource/**
     * @return true if this Resource is an alias to another real Resource
     */
    public boolean isAlias()
    {
        return getAlias() != null;
    }

    
Returns:
The canonical Alias of this resource or null if none./**
     * @return The canonical Alias of this resource or null if none.
     */
    public URI getAlias()
    {
        return null;
    }

    
Get the resource list as a HTML directory listing.
Params:
base – The base URL
parent – True if the parent directory should be included
query – query params
Returns:
String of HTML/**
     * Get the resource list as a HTML directory listing.
     *
     * @param base The base URL
     * @param parent True if the parent directory should be included
     * @param query query params
     * @return String of HTML
     */
    public String getListHTML(String base, boolean parent, String query) throws IOException
    {
        base = URIUtil.canonicalPath(base);
        if (base == null || !isDirectory())
            return null;

        String[] rawListing = list();
        if (rawListing == null)
        {
            return null;
        }

        boolean sortOrderAscending = true;
        String sortColumn = "N"; // name (or "M" for Last Modified, or "S" for Size)

        // check for query
        if (query != null)
        {
            MultiMap<String> params = new MultiMap<>();
            UrlEncoded.decodeUtf8To(query, 0, query.length(), params);

            String paramO = params.getString("O");
            String paramC = params.getString("C");
            if (StringUtil.isNotBlank(paramO))
            {
                if (paramO.equals("A"))
                {
                    sortOrderAscending = true;
                }
                else if (paramO.equals("D"))
                {
                    sortOrderAscending = false;
                }
            }
            if (StringUtil.isNotBlank(paramC))
            {
                if (paramC.equals("N") || paramC.equals("M") || paramC.equals("S"))
                {
                    sortColumn = paramC;
                }
            }
        }

        // Gather up entries
        List<Resource> items = new ArrayList<>();
        for (String l : rawListing)
        {
            Resource item = addPath(l);
            items.add(item);
        }

        // Perform sort
        if (sortColumn.equals("M"))
        {
            items.sort(ResourceCollators.byLastModified(sortOrderAscending));
        }
        else if (sortColumn.equals("S"))
        {
            items.sort(ResourceCollators.bySize(sortOrderAscending));
        }
        else
        {
            items.sort(ResourceCollators.byName(sortOrderAscending));
        }

        String decodedBase = URIUtil.decodePath(base);
        String title = "Directory: " + deTag(decodedBase);

        StringBuilder buf = new StringBuilder(4096);

        // Doctype Declaration (HTML5)
        buf.append("<!DOCTYPE html>\n");
        buf.append("<html lang=\"en\">\n");

        // HTML Header
        buf.append("<head>\n");
        buf.append("<meta charset=\"utf-8\">\n");
        buf.append("<link href=\"jetty-dir.css\" rel=\"stylesheet\" />\n");
        buf.append("<title>");
        buf.append(title);
        buf.append("</title>\n");
        buf.append("</head>\n");

        // HTML Body
        buf.append("<body>\n");
        buf.append("<h1 class=\"title\">").append(title).append("</h1>\n");

        // HTML Table
        final String ARROW_DOWN = "&nbsp; &#8681;";
        final String ARROW_UP = "&nbsp; &#8679;";

        buf.append("<table class=\"listing\">\n");
        buf.append("<thead>\n");

        String arrow = "";
        String order = "A";
        if (sortColumn.equals("N"))
        {
            if (sortOrderAscending)
            {
                order = "D";
                arrow = ARROW_UP;
            }
            else
            {
                order = "A";
                arrow = ARROW_DOWN;
            }
        }

        buf.append("<tr><th class=\"name\"><a href=\"?C=N&O=").append(order).append("\">");
        buf.append("Name").append(arrow);
        buf.append("</a></th>");

        arrow = "";
        order = "A";
        if (sortColumn.equals("M"))
        {
            if (sortOrderAscending)
            {
                order = "D";
                arrow = ARROW_UP;
            }
            else
            {
                order = "A";
                arrow = ARROW_DOWN;
            }
        }

        buf.append("<th class=\"lastmodified\"><a href=\"?C=M&O=").append(order).append("\">");
        buf.append("Last Modified").append(arrow);
        buf.append("</a></th>");

        arrow = "";
        order = "A";
        if (sortColumn.equals("S"))
        {
            if (sortOrderAscending)
            {
                order = "D";
                arrow = ARROW_UP;
            }
            else
            {
                order = "A";
                arrow = ARROW_DOWN;
            }
        }
        buf.append("<th class=\"size\"><a href=\"?C=S&O=").append(order).append("\">");
        buf.append("Size").append(arrow);
        buf.append("</a></th></tr>\n");
        buf.append("</thead>\n");

        buf.append("<tbody>\n");

        String encodedBase = hrefEncodeURI(base);

        if (parent)
        {
            // Name
            buf.append("<tr><td class=\"name\"><a href=\"");
            buf.append(URIUtil.addPaths(encodedBase, "../"));
            buf.append("\">Parent Directory</a></td>");
            // Last Modified
            buf.append("<td class=\"lastmodified\">-</td>");
            // Size
            buf.append("<td>-</td>");
            buf.append("</tr>\n");
        }

        DateFormat dfmt = DateFormat.getDateTimeInstance(DateFormat.MEDIUM,
            DateFormat.MEDIUM);
        for (Resource item : items)
        {
            String name = item.getFileName();
            if (StringUtil.isBlank(name))
            {
                continue; // skip
            }

            if (item.isDirectory() && !name.endsWith("/"))
            {
                name += URIUtil.SLASH;
            }

            // Name
            buf.append("<tr><td class=\"name\"><a href=\"");
            String path = URIUtil.addEncodedPaths(encodedBase, URIUtil.encodePath(name));
            buf.append(path);
            buf.append("\">");
            buf.append(deTag(name));
            buf.append("&nbsp;");
            buf.append("</a></td>");

            // Last Modified
            buf.append("<td class=\"lastmodified\">");
            long lastModified = item.lastModified();
            if (lastModified > 0)
            {
                buf.append(dfmt.format(new Date(item.lastModified())));
            }
            buf.append("&nbsp;</td>");

            // Size
            buf.append("<td class=\"size\">");
            long length = item.length();
            if (length >= 0)
            {
                buf.append(String.format("%,d bytes", item.length()));
            }
            buf.append("&nbsp;</td></tr>\n");
        }
        buf.append("</tbody>\n");
        buf.append("</table>\n");
        buf.append("</body></html>\n");

        return buf.toString();
    }

    
Get the raw (decoded if possible) Filename for this Resource.
This is the last segment of the path.
Returns:
the raw / decoded filename for this resource/**
     * Get the raw (decoded if possible) Filename for this Resource.
     * This is the last segment of the path.
     *
     * @return the raw / decoded filename for this resource
     */
    private String getFileName()
    {
        try
        {
            // if a Resource supports File
            File file = getFile();
            if (file != null)
            {
                return file.getName();
            }
        }
        catch (Throwable ignored)
        {
        }

        // All others use raw getName
        try
        {
            String rawName = getName(); // gets long name "/foo/bar/xxx"
            int idx = rawName.lastIndexOf('/');
            if (idx == rawName.length() - 1)
            {
                // hit a tail slash, aka a name for a directory "/foo/bar/"
                idx = rawName.lastIndexOf('/', idx - 1);
            }

            String encodedFileName;
            if (idx >= 0)
            {
                encodedFileName = rawName.substring(idx + 1);
            }
            else
            {
                encodedFileName = rawName; // entire name
            }
            return UrlEncoded.decodeString(encodedFileName, 0, encodedFileName.length(), UTF_8);
        }
        catch (Throwable ignored)
        {
        }

        return null;
    }

    
Encode any characters that could break the URI string in an HREF.
Such as ">Link
The above example would parse incorrectly on various browsers as the "<" or '"' characters
would end the href attribute value string prematurely.
Params:
raw – the raw text to encode.
Returns:
the defanged text./**
     * Encode any characters that could break the URI string in an HREF.
     * Such as <a href="/path/to;<script>Window.alert("XSS"+'%20'+"here");</script>">Link</a>
     *
     * The above example would parse incorrectly on various browsers as the "<" or '"' characters
     * would end the href attribute value string prematurely.
     *
     * @param raw the raw text to encode.
     * @return the defanged text.
     */
    private static String hrefEncodeURI(String raw)
    {
        StringBuffer buf = null;

        loop:
        for (int i = 0; i < raw.length(); i++)
        {
            char c = raw.charAt(i);
            switch (c)
            {
                case '\'':
                case '"':
                case '<':
                case '>':
                    buf = new StringBuffer(raw.length() << 1);
                    break loop;
                default:
                    break;
            }
        }
        if (buf == null)
            return raw;

        for (int i = 0; i < raw.length(); i++)
        {
            char c = raw.charAt(i);
            switch (c)
            {
                case '"':
                    buf.append("%22");
                    break;
                case '\'':
                    buf.append("%27");
                    break;
                case '<':
                    buf.append("%3C");
                    break;
                case '>':
                    buf.append("%3E");
                    break;
                default:
                    buf.append(c);
                    break;
            }
        }

        return buf.toString();
    }

    private static String deTag(String raw)
    {
        return StringUtil.sanitizeXmlString(raw);
    }

    
Params:
out – the output stream to write to
start – First byte to write
count – Bytes to write or -1 for all of them.
Throws:
IOException – if unable to copy the Resource to the output/**
     * @param out the output stream to write to
     * @param start First byte to write
     * @param count Bytes to write or -1 for all of them.
     * @throws IOException if unable to copy the Resource to the output
     */
    public void writeTo(OutputStream out, long start, long count)
        throws IOException
    {
        try (InputStream in = getInputStream())
        {
            in.skip(start);
            if (count < 0)
                IO.copy(in, out);
            else
                IO.copy(in, out, count);
        }
    }

    
Copy the Resource to the new destination file.

Will not replace existing destination file.
Params:
destination – the destination file to create
Throws:
IOException – if unable to copy the resource/**
     * Copy the Resource to the new destination file.
     * <p>
     * Will not replace existing destination file.
     *
     * @param destination the destination file to create
     * @throws IOException if unable to copy the resource
     */
    public void copyTo(File destination)
        throws IOException
    {
        if (destination.exists())
            throw new IllegalArgumentException(destination + " exists");

        try (OutputStream out = new FileOutputStream(destination))
        {
            writeTo(out, 0, -1);
        }
    }

    
Generate a weak ETag reference for this Resource.
Returns:
the weak ETag reference for this resource./**
     * Generate a weak ETag reference for this Resource.
     *
     * @return the weak ETag reference for this resource.
     */
    public String getWeakETag()
    {
        return getWeakETag("");
    }

    public String getWeakETag(String suffix)
    {
        StringBuilder b = new StringBuilder(32);
        b.append("W/\"");

        String name = getName();
        int length = name.length();
        long lhash = 0;
        for (int i = 0; i < length; i++)
        {
            lhash = 31 * lhash + name.charAt(i);
        }

        Base64.Encoder encoder = Base64.getEncoder().withoutPadding();
        b.append(encoder.encodeToString(longToBytes(lastModified() ^ lhash)));
        b.append(encoder.encodeToString(longToBytes(length() ^ lhash)));
        b.append(suffix);
        b.append('"');
        return b.toString();
    }

    private static byte[] longToBytes(long value)
    {
        byte[] result = new byte[Long.BYTES];
        for (int i = Long.BYTES - 1; i >= 0; i--)
        {
            result[i] = (byte)(value & 0xFF);
            value >>= 8;
        }
        return result;
    }

    public Collection<Resource> getAllResources()
    {
        try
        {
            ArrayList<Resource> deep = new ArrayList<>();
            {
                String[] list = list();
                if (list != null)
                {
                    for (String i : list)
                    {
                        Resource r = addPath(i);
                        if (r.isDirectory())
                            deep.addAll(r.getAllResources());
                        else
                            deep.add(r);
                    }
                }
            }
            return deep;
        }
        catch (Exception e)
        {
            throw new IllegalStateException(e);
        }
    }

    
Generate a properly encoded URL from a File instance. 
Params:
file – Target file.
Throws:
MalformedURLException – if unable to convert File to URL
Returns:
URL of the target file./**
     * Generate a properly encoded URL from a {@link File} instance.
     *
     * @param file Target file.
     * @return URL of the target file.
     * @throws MalformedURLException if unable to convert File to URL
     */
    public static URL toURL(File file) throws MalformedURLException
    {
        return file.toURI().toURL();
    }
}