/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.webresources;

import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import org.apache.catalina.LifecycleException;
import org.apache.tomcat.util.compat.JrePlatform;
import org.apache.tomcat.util.http.RequestUtil;

public abstract class AbstractFileResourceSet extends AbstractResourceSet {

    protected static final String[] EMPTY_STRING_ARRAY = new String[0];

    private File fileBase;
    private String absoluteBase;
    private String canonicalBase;
    private boolean readOnly = false;

    protected AbstractFileResourceSet(String internalPath) {
        setInternalPath(internalPath);
    }

    protected final File getFileBase() {
        return fileBase;
    }

    @Override
    public void setReadOnly(boolean readOnly) {
        this.readOnly = readOnly;
    }

    @Override
    public boolean isReadOnly() {
        return readOnly;
    }

    protected final File file(String name, boolean mustExist) {

        if (name.equals("/")) {
            name = "";
        }
        File file = new File(fileBase, name);

        // If the requested names ends in '/', the Java File API will return a
        // matching file if one exists. This isn't what we want as it is not
        // consistent with the Servlet spec rules for request mapping.
        if (name.endsWith("/") && file.isFile()) {
            return null;
        }

        // If the file/dir must exist but the identified file/dir can't be read
        // then signal that the resource was not found
        if (mustExist && !file.canRead()) {
            return null;
        }

        // If allow linking is enabled, files are not limited to being located
        // under the fileBase so all further checks are disabled.
        if (getRoot().getAllowLinking()) {
            return file;
        }

        // Additional Windows specific checks to handle known problems with
        // File.getCanonicalPath()
        if (JrePlatform.IS_WINDOWS && isInvalidWindowsFilename(name)) {
            return null;
        }

        // Check that this file is located under the WebResourceSet's base
        String canPath = null;
        try {
            canPath = file.getCanonicalPath();
        } catch (IOException e) {
            // Ignore
        }
        if (canPath == null || !canPath.startsWith(canonicalBase)) {
            return null;
        }

        // Ensure that the file is not outside the fileBase. This should not be
        // possible for standard requests (the request is normalized early in
        // the request processing) but might be possible for some access via the
        // Servlet API (RequestDispatcher, HTTP/2 push etc.) therefore these
        // checks are retained as an additional safety measure
        // absoluteBase has been normalized so absPath needs to be normalized as
        // well.
        String absPath = normalize(file.getAbsolutePath());
        if (absoluteBase.length() > absPath.length()) {
            return null;
        }

        // Remove the fileBase location from the start of the paths since that
        // was not part of the requested path and the remaining check only
        // applies to the request path
        absPath = absPath.substring(absoluteBase.length());
        canPath = canPath.substring(canonicalBase.length());

        // Case sensitivity check
        // The normalized requested path should be an exact match the equivalent
        // canonical path. If it is not, possible reasons include:
        // - case differences on case insensitive file systems
        // - Windows removing a trailing ' ' or '.' from the file name
        //
        // In all cases, a mis-match here results in the resource not being
        // found
        //
        // absPath is normalized so canPath needs to be normalized as well
        // Can't normalize canPath earlier as canonicalBase is not normalized
        if (canPath.length() > 0) {
            canPath = normalize(canPath);
        }
        if (!canPath.equals(absPath)) {
            return null;
        }

        return file;
    }


    private boolean isInvalidWindowsFilename(String name) {
        final int len = name.length();
        if (len == 0) {
            return false;
        }
        // This consistently ~10 times faster than the equivalent regular
        // expression irrespective of input length.
        for (int i = 0; i < len; i++) {
            char c = name.charAt(i);
            if (c == '\"' || c == '<' || c == '>') {
                // These characters are disallowed in Windows file names and
                // there are known problems for file names with these characters
                // when using File#getCanonicalPath().
                // Note: There are additional characters that are disallowed in
                //       Windows file names but these are not known to cause
                //       problems when using File#getCanonicalPath().
                return true;
            }
        }
        // Windows does not allow file names to end in ' ' unless specific low
        // level APIs are used to create the files that bypass various checks.
        // File names that end in ' ' are known to cause problems when using
        // File#getCanonicalPath().
        if (name.charAt(len -1) == ' ') {
            return true;
        }
        return false;
    }


    
Return a context-relative path, beginning with a "/", that represents
the canonical version of the specified path after ".." and "." elements
are resolved out.  If the specified path attempts to go outside the
boundaries of the current context (i.e. too many ".." path elements
are present), return null instead.
Params:
path – Path to be normalized/**
     * Return a context-relative path, beginning with a "/", that represents
     * the canonical version of the specified path after ".." and "." elements
     * are resolved out.  If the specified path attempts to go outside the
     * boundaries of the current context (i.e. too many ".." path elements
     * are present), return <code>null</code> instead.
     *
     * @param path Path to be normalized
     */
    private String normalize(String path) {
        return RequestUtil.normalize(path, File.separatorChar == '\\');
    }

    @Override
    public URL getBaseUrl() {
        try {
            return getFileBase().toURI().toURL();
        } catch (MalformedURLException e) {
            return null;
        }
    }

    
{@inheritDoc}

This is a NO-OP by default for File based resource sets.
/**
     * {@inheritDoc}
     * <p>
     * This is a NO-OP by default for File based resource sets.
     */
    @Override
    public void gc() {
        // NO-OP
    }


    //-------------------------------------------------------- Lifecycle methods

    @Override
    protected void initInternal() throws LifecycleException {
        fileBase = new File(getBase(), getInternalPath());
        checkType(fileBase);

        this.absoluteBase = normalize(fileBase.getAbsolutePath());

        try {
            this.canonicalBase = fileBase.getCanonicalPath();
        } catch (IOException e) {
            throw new IllegalArgumentException(e);
        }
    }


    protected abstract void checkType(File file);
}