/*
    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.wiki.providers;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.Enumeration;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.TreeSet;

import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;
import org.apache.wiki.InternalWikiException;
import org.apache.wiki.WikiEngine;
import org.apache.wiki.WikiPage;
import org.apache.wiki.WikiProvider;
import org.apache.wiki.api.exceptions.NoRequiredPropertyException;
import org.apache.wiki.api.exceptions.ProviderException;
import org.apache.wiki.search.QueryItem;
import org.apache.wiki.search.SearchMatcher;
import org.apache.wiki.search.SearchResult;
import org.apache.wiki.search.SearchResultComparator;
import org.apache.wiki.util.FileUtil;
import org.apache.wiki.util.TextUtil;


/**
 *  Provides a simple directory based repository for Wiki pages.
 *  <P>
 *  All files have ".txt" appended to make life easier for those
 *  who insist on using Windows or other software which makes assumptions
 *  on the files contents based on its name.
 *  <p>
 *  This class functions as a superclass to all file based providers.
 *
 *  @since 2.1.21.
 *
 */
public abstract class AbstractFileProvider
    implements WikiPageProvider
{
    private static final Logger   log = Logger.getLogger(AbstractFileProvider.class);
    private String m_pageDirectory = "/tmp/";

    protected String m_encoding;

    protected WikiEngine m_engine;

    public static final String PROP_CUSTOMPROP_MAXLIMIT = "custom.pageproperty.max.allowed";
    public static final String PROP_CUSTOMPROP_MAXKEYLENGTH = "custom.pageproperty.key.length";
    public static final String PROP_CUSTOMPROP_MAXVALUELENGTH = "custom.pageproperty.value.length";

    public static final int DEFAULT_MAX_PROPLIMIT = 200;
    public static final int DEFAULT_MAX_PROPKEYLENGTH = 255;
    public static final int DEFAULT_MAX_PROPVALUELENGTH = 4096;

    /**
     * This parameter limits the number of custom page properties allowed on a page
     */
    public static int MAX_PROPLIMIT = DEFAULT_MAX_PROPLIMIT;
    /**
     * This number limits the length of a custom page property key length
     * The default value here designed with future JDBC providers in mind.
     */
    public static int MAX_PROPKEYLENGTH = DEFAULT_MAX_PROPKEYLENGTH;
    /**
     * This number limits the length of a custom page property value length
     * The default value here designed with future JDBC providers in mind.
     */
    public static int MAX_PROPVALUELENGTH = DEFAULT_MAX_PROPVALUELENGTH;

    /**
     *  Name of the property that defines where page directories are.
     */
    public static final String PROP_PAGEDIR = "jspwiki.fileSystemProvider.pageDir";

    /**
     *  All files should have this extension to be recognized as JSPWiki files.
     *  We default to .txt, because that is probably easiest for Windows users,
     *  and guarantees correct handling.
     */
    public static final String FILE_EXT = ".txt";

    /** The default encoding. */
    public static final String DEFAULT_ENCODING = StandardCharsets.ISO_8859_1.toString();

    private boolean m_windowsHackNeeded = false;

    /**
     *  {@inheritDoc}
     *  @throws FileNotFoundException If the specified page directory does not exist.
     *  @throws IOException In case the specified page directory is a file, not a directory.
     */
    @Override
    public void initialize( WikiEngine engine, Properties properties ) throws NoRequiredPropertyException, IOException, FileNotFoundException
    {
        log.debug("Initing FileSystemProvider");
        m_pageDirectory = TextUtil.getCanonicalFilePathProperty(properties, PROP_PAGEDIR,
                System.getProperty("user.home") + File.separator + "jspwiki-files");

        File f = new File(m_pageDirectory);

        if( !f.exists() )
        {
            if( !f.mkdirs() )
            {
                throw new IOException( "Failed to create page directory " + f.getAbsolutePath() + " , please check property "
                                       + PROP_PAGEDIR );
            }
        }
        else
        {
            if( !f.isDirectory() )
            {
                throw new IOException( "Page directory is not a directory: " + f.getAbsolutePath() );
            }
            if( !f.canWrite() )
            {
                throw new IOException( "Page directory is not writable: " + f.getAbsolutePath() );
            }
        }

        m_engine = engine;

        m_encoding = properties.getProperty( WikiEngine.PROP_ENCODING, DEFAULT_ENCODING );

        String os = System.getProperty( "os.name" ).toLowerCase();

        if( os.startsWith("windows") || os.equals("nt") )
        {
            m_windowsHackNeeded = true;
        }

        if (properties != null) {
            MAX_PROPLIMIT = TextUtil.getIntegerProperty(properties,PROP_CUSTOMPROP_MAXLIMIT,DEFAULT_MAX_PROPLIMIT);
            MAX_PROPKEYLENGTH = TextUtil.getIntegerProperty(properties,PROP_CUSTOMPROP_MAXKEYLENGTH,DEFAULT_MAX_PROPKEYLENGTH);
            MAX_PROPVALUELENGTH = TextUtil.getIntegerProperty(properties,PROP_CUSTOMPROP_MAXVALUELENGTH,DEFAULT_MAX_PROPVALUELENGTH);
        }

        log.info( "Wikipages are read from '" + m_pageDirectory + "'" );
    }


    String getPageDirectory()
    {
        return m_pageDirectory;
    }

    private static final String[] WINDOWS_DEVICE_NAMES =
    {
        "con", "prn", "nul", "aux", "lpt1", "lpt2", "lpt3", "lpt4", "lpt5", "lpt6", "lpt7", "lpt8", "lpt9",
        "com1", "com2", "com3", "com4", "com5", "com6", "com7", "com8", "com9"
    };

    /**
     *  This makes sure that the queried page name
     *  is still readable by the file system.  For example, all XML entities
     *  and slashes are encoded with the percent notation.
     *
     *  @param pagename The name to mangle
     *  @return The mangled name.
     */
    protected String mangleName( String pagename )
    {
        pagename = TextUtil.urlEncode( pagename, m_encoding );

        pagename = TextUtil.replaceString( pagename, "/", "%2F" );

        //
        //  Names which start with a dot must be escaped to prevent problems.
        //  Since we use URL encoding, this is invisible in our unescaping.
        //
        if( pagename.startsWith( "." ) )
        {
            pagename = "%2E" + pagename.substring( 1 );
        }

        if( m_windowsHackNeeded )
        {
            String pn = pagename.toLowerCase();
            for( int i = 0; i < WINDOWS_DEVICE_NAMES.length; i++ )
            {
                if( WINDOWS_DEVICE_NAMES[i].equals(pn) )
                {
                    pagename = "$$$" + pagename;
                }
            }
        }

        return pagename;
    }

    /**
     *  This makes the reverse of mangleName.
     *
     *  @param filename The filename to unmangle
     *  @return The unmangled name.
     */
    protected String unmangleName( String filename )
    {
        // The exception should never happen.
        if( m_windowsHackNeeded && filename.startsWith( "$$$") && filename.length() > 3 )
        {
            filename = filename.substring(3);
        }

        return TextUtil.urlDecode( filename, m_encoding );
    }

    /**
     *  Finds a Wiki page from the page repository.
     *
     *  @param page The name of the page.
     *  @return A File to the page.  May be null.
     */
    protected File findPage( String page )
    {
        return new File( m_pageDirectory, mangleName(page)+FILE_EXT );
    }

    /**
     *  {@inheritDoc}
     */
    @Override
    public boolean pageExists( String page )
    {
        File pagefile = findPage( page );

        return pagefile.exists();
    }

    /**
     *  {@inheritDoc}
     */
    @Override
    public boolean pageExists( String page, int version )
    {
        return pageExists (page);
    }

    /**
     *  This implementation just returns the current version, as filesystem
     *  does not provide versioning information for now.
     *
     *  @param page {@inheritDoc}
     *  @param version {@inheritDoc}
     *  @throws {@inheritDoc}
     */
    @Override
    public String getPageText( String page, int version )
        throws ProviderException
    {
        return getPageText( page );
    }

    /**
     *  Read the text directly from the correct file.
     */
    private String getPageText( String page )
    {
        String result  = null;

        File pagedata = findPage( page );

        if( pagedata.exists() ) {
            if( pagedata.canRead() ) {
                try( InputStream in = new FileInputStream( pagedata ) ) {
                    result = FileUtil.readContents( in, m_encoding );
                } catch( IOException e ) {
                    log.error("Failed to read", e);
                }
            }
            else
            {
                log.warn("Failed to read page '"+page+"' from '"+pagedata.getAbsolutePath()+"', possibly a permissions problem");
            }
        }
        else
        {
            // This is okay.
            log.info("New page '"+page+"'");
        }

        return result;
    }

    /**
     *  {@inheritDoc}
     */
    @Override
    public void putPageText( WikiPage page, String text ) throws ProviderException {
        File file = findPage( page.getName() );

        try( PrintWriter out = new PrintWriter( new OutputStreamWriter( new FileOutputStream( file ), m_encoding ) ) ) {
            out.print( text );
        } catch( IOException e ) {
            log.error( "Saving failed", e );
        }
    }

    /**
     *  {@inheritDoc}
     */
    @Override
    public Collection< WikiPage > getAllPages()
        throws ProviderException
    {
        log.debug("Getting all pages...");

        ArrayList<WikiPage> set = new ArrayList<>();

        File wikipagedir = new File( m_pageDirectory );

        File[] wikipages = wikipagedir.listFiles( new WikiFileFilter() );

        if( wikipages == null )
        {
            log.error("Wikipages directory '" + m_pageDirectory + "' does not exist! Please check " + PROP_PAGEDIR + " in jspwiki.properties.");
            throw new InternalWikiException("Page directory does not exist");
        }

        for( int i = 0; i < wikipages.length; i++ )
        {
            String wikiname = wikipages[i].getName();
            int cutpoint = wikiname.lastIndexOf( FILE_EXT );

            WikiPage page = getPageInfo( unmangleName(wikiname.substring(0,cutpoint)),
                                         WikiPageProvider.LATEST_VERSION );
            if( page == null )
            {
                // This should not really happen.
                // FIXME: Should we throw an exception here?
                log.error("Page "+wikiname+" was found in directory listing, but could not be located individually.");
                continue;
            }

            set.add( page );
        }

        return set;
    }

    /**
     *  Does not work.
     *
     *  @param date {@inheritDoc}
     *  @return {@inheritDoc}
     */
    @Override
    public Collection< WikiPage > getAllChangedSince( Date date )
    {
        return new ArrayList<>(); // FIXME
    }

    /**
     *  {@inheritDoc}
     */
    @Override
    public int getPageCount()
    {
        File wikipagedir = new File( m_pageDirectory );

        File[] wikipages = wikipagedir.listFiles( new WikiFileFilter() );

        return wikipages.length;
    }

    /**
     * Iterates through all WikiPages, matches them against the given query,
     * and returns a Collection of SearchResult objects.
     *
     * @param query {@inheritDoc}
     * @return {@inheritDoc}
     */
    @Override
    public Collection< SearchResult > findPages( QueryItem[] query )
    {
        File wikipagedir = new File( m_pageDirectory );
        TreeSet<SearchResult> res = new TreeSet<>( new SearchResultComparator() );
        SearchMatcher matcher = new SearchMatcher( m_engine, query );

        File[] wikipages = wikipagedir.listFiles( new WikiFileFilter() );

        for( int i = 0; i < wikipages.length; i++ )
        {
            // log.debug("Searching page "+wikipages[i].getPath() );

            String filename = wikipages[i].getName();
            int cutpoint    = filename.lastIndexOf( FILE_EXT );
            String wikiname = filename.substring( 0, cutpoint );

            wikiname = unmangleName( wikiname );

            try( FileInputStream input = new FileInputStream( wikipages[i] ) ) {
                String pagetext = FileUtil.readContents( input, m_encoding );
                SearchResult comparison = matcher.matchPageContent( wikiname, pagetext );
                if( comparison != null ) {
                    res.add( comparison );
                }
            } catch( IOException e ) {
                log.error( "Failed to read " + filename, e );
            }
        }

        return res;
    }

    /**
     *  Always returns the latest version, since FileSystemProvider
     *  does not support versioning.
     *
     *  @param page {@inheritDoc}
     *  @param version {@inheritDoc}
     *  @return {@inheritDoc}
     *  @throws {@inheritDoc}
     */
    @Override
    public WikiPage getPageInfo( String page, int version ) throws ProviderException {
        File file = findPage( page );

        if( !file.exists() )
        {
            return null;
        }

        WikiPage p = new WikiPage( m_engine, page );
        p.setLastModified( new Date(file.lastModified()) );

        return p;
    }

    /**
     *  The FileSystemProvider provides only one version.
     *
     *  @param page {@inheritDoc}
     *  @throws {@inheritDoc}
     *  @return {@inheritDoc}
     */
    @Override
    public List<WikiPage> getVersionHistory( String page ) throws ProviderException
    {
        ArrayList<WikiPage> list = new ArrayList<>();

        list.add( getPageInfo( page, WikiPageProvider.LATEST_VERSION ) );

        return list;
    }

    /**
     *  {@inheritDoc}
     */
    @Override
    public String getProviderInfo()
    {
        return "";
    }

    /**
     *  {@inheritDoc}
     */
    @Override
    public void deleteVersion( String pageName, int version )
        throws ProviderException
    {
        if( version == WikiProvider.LATEST_VERSION )
        {
            File f = findPage( pageName );

            f.delete();
        }
    }

    /**
     *  {@inheritDoc}
     */
    @Override
    public void deletePage( String pageName )
        throws ProviderException
    {
        File f = findPage( pageName );

        f.delete();
    }

    /**
     * Set the custom properties provided into the given page.
     *
     * @since 2.10.2
     */
    protected void setCustomProperties(WikiPage page, Properties properties) {
        Enumeration< ? > propertyNames = properties.propertyNames();
        while (propertyNames.hasMoreElements()) {
            String key = (String) propertyNames.nextElement();
            if (!key.equals(WikiPage.AUTHOR) && !key.equals(WikiPage.CHANGENOTE) && !key.equals(WikiPage.VIEWCOUNT)) {
                page.setAttribute(key, properties.get(key));
            }
        }
    }

    /**
     * Get custom properties using {@link #addCustomProperties(WikiPage, Properties)}, validate them using {@link #validateCustomPageProperties(Properties)}
     * and add them to default properties provided
     *
     * @since 2.10.2
     */
    protected void getCustomProperties(WikiPage page, Properties defaultProperties) throws IOException {
        Properties customPageProperties = addCustomProperties(page,defaultProperties);
        validateCustomPageProperties(customPageProperties);
        defaultProperties.putAll(customPageProperties);
    }

    /**
     * By default all page attributes that start with "@" are returned as custom properties.
     * This can be overwritten by custom FileSystemProviders to save additional properties.
     * CustomPageProperties are validated by {@link #validateCustomPageProperties(Properties)}
     *
     * @since 2.10.2
     * @param page the current page
     * @param props the default properties of this page
     * @return default implementation returns empty Properties.
     */
    protected Properties addCustomProperties(WikiPage page, Properties props) {
        Properties customProperties = new Properties();
        if (page != null) {
            Map<String,Object> atts = page.getAttributes();
            for (String key : atts.keySet()) {
                Object value = atts.get(key);
                if (key.startsWith("@") && value != null) {
                    customProperties.put(key,value.toString());
                }
            }

        }
        return customProperties;
    }

    /**
     * Default validation, validates that key and value is ASCII <code>StringUtils.isAsciiPrintable()</code> and within lengths set up in jspwiki-custom.properties.
     * This can be overwritten by custom FileSystemProviders to validate additional properties
     * See https://issues.apache.org/jira/browse/JSPWIKI-856
     * @since 2.10.2
     * @param customProperties the custom page properties being added
     */
    protected void validateCustomPageProperties(Properties customProperties) throws IOException {
        // Default validation rules
        if (customProperties != null && !customProperties.isEmpty()) {
            if (customProperties.size()>MAX_PROPLIMIT) {
                throw new IOException("Too many custom properties. You are adding "+customProperties.size()+", but max limit is "+MAX_PROPLIMIT);
            }
            Enumeration< ? > propertyNames = customProperties.propertyNames();
            while (propertyNames.hasMoreElements()) {
                String key = (String) propertyNames.nextElement();
                String value = (String)customProperties.get(key);
                if (key != null) {
                    if (key.length()>MAX_PROPKEYLENGTH) {
                        throw new IOException("Custom property key "+key+" is too long. Max allowed length is "+MAX_PROPKEYLENGTH);
                    }
                    if (!StringUtils.isAsciiPrintable(key)) {
                        throw new IOException("Custom property key "+key+" is not simple ASCII!");
                    }
                }
                if (value != null) {
                    if (value.length()>MAX_PROPVALUELENGTH) {
                        throw new IOException("Custom property key "+key+" has value that is too long. Value="+value+". Max allowed length is "+MAX_PROPVALUELENGTH);
                    }
                    if (!StringUtils.isAsciiPrintable(value)) {
                        throw new IOException("Custom property key "+key+" has value that is not simple ASCII! Value="+value);
                    }
                }
            }
        }
    }

    /**
     *  A simple filter which filters only those filenames which correspond to the
     *  file extension used.
     */
    public static class WikiFileFilter implements FilenameFilter {
        /**
         *  {@inheritDoc}
         */
        @Override
        public boolean accept( File dir, String name ) {
            return name.endsWith( FILE_EXT );
        }
    }

}