//
// ========================================================================
// Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
//
// This program and the accompanying materials are made available under
// the terms of the Eclipse Public License 2.0 which is available at
// https://www.eclipse.org/legal/epl-2.0
//
// This Source Code may also be made available under the following
// Secondary Licenses when the conditions for such availability set
// forth in the Eclipse Public License, v. 2.0 are satisfied:
// the Apache License v2.0 which is available at
// https://www.apache.org/licenses/LICENSE-2.0
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
// ========================================================================
//

package org.eclipse.jetty.server;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;

import org.eclipse.jetty.server.handler.ContextHandler.AliasCheck;
import org.eclipse.jetty.util.resource.PathResource;
import org.eclipse.jetty.util.resource.Resource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

Alias checking for working with FileSystems that normalize access to the
File System.
 The Java Files.isSameFile(Path, Path) method is used to determine if the requested file is the same as the alias file. 

For File Systems that are case insensitive (eg: Microsoft Windows FAT32 and NTFS),
the access to the file can be in any combination or style of upper and lowercase.


For File Systems that normalize UTF-8 access (eg: Mac OSX on HFS+ or APFS,
or Linux on XFS) the the actual file could be stored using UTF-16,
but be accessed using NFD UTF-8 or NFC UTF-8 for the same file.

/**
 * Alias checking for working with FileSystems that normalize access to the
 * File System.
 * <p>
 * The Java {@link Files#isSameFile(Path, Path)} method is used to determine
 * if the requested file is the same as the alias file.
 * </p>
 * <p>
 * For File Systems that are case insensitive (eg: Microsoft Windows FAT32 and NTFS),
 * the access to the file can be in any combination or style of upper and lowercase.
 * </p>
 * <p>
 * For File Systems that normalize UTF-8 access (eg: Mac OSX on HFS+ or APFS,
 * or Linux on XFS) the the actual file could be stored using UTF-16,
 * but be accessed using NFD UTF-8 or NFC UTF-8 for the same file.
 * </p>
 */
public class SameFileAliasChecker implements AliasCheck
{
    private static final Logger LOG = LoggerFactory.getLogger(SameFileAliasChecker.class);

    @Override
    public boolean check(String uri, Resource resource)
    {
        // Only support PathResource alias checking
        if (!(resource instanceof PathResource))
            return false;

        try
        {
            PathResource pathResource = (PathResource)resource;
            Path path = pathResource.getPath();
            Path alias = pathResource.getAliasPath();

            if (Files.isSameFile(path, alias))
            {
                if (LOG.isDebugEnabled())
                    LOG.debug("Allow alias to same file {} --> {}", path, alias);
                return true;
            }
        }
        catch (IOException e)
        {
            LOG.trace("IGNORED", e);
        }
        return false;
    }
}