/*
 * [RSSFeedExport.java]
 *
 * Summary: Convert the rss/temprss.bin binary log of items into RSS2 feeds of form rss/jgloss.xml.
 *
 * Copyright: (c) 2009-2017 Roedy Green, Canadian Mind Products, http://mindprod.com
 *
 * Licence: This software may be copied and used freely for any purpose but military.
 *          http://mindprod.com/contact/nonmil.html
 *
 * Requires: JDK 1.8+
 *
 * Created with: JetBrains IntelliJ IDEA IDE http://www.jetbrains.com/idea/
 *
 * Version History:
 *  1.8 2009-02-06 include go package in ZIP bundle.
 *                 prepends the rss/prelude/jgloss.xml prelude header.
 */
package com.mindprod.htmlmacros.support;

import com.mindprod.common18.EIO;
import com.mindprod.fastcat.FastCat;
import com.mindprod.hunkio.HunkIO;

import java.io.DataInputStream;
import java.io.EOFException;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

import static com.mindprod.htmlmacros.macro.Global.configuration;
import static java.lang.System.*;

/**
 * Convert the rss/temprss.bin binary log of items into RSS2 feeds of form rss/jgloss.xml.
 *
 * @author Roedy Green, Canadian Mind Products
 * @version 1.8 2009-02-06 include go package in ZIP bundle.
 * prepends the rss/prelude/jgloss.xml prelude header.
 * @since 2009
 */
final class RSSFeedExport
    {
    /**
     * mask for:  "Fri, 08 Aug 2008 12:27:08 UTC" must be in English.
     */
    @SuppressWarnings( { "StringWithMistakes" } )
    /**
     format for build date  of entire feed */
    private static final SimpleDateFormat BUILD_DATE_SDF;

    private static PrintWriter emit;

    static
        {
        BUILD_DATE_SDF =
                new SimpleDateFormat( "EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US );
        BUILD_DATE_SDF.setTimeZone( TimeZone.getTimeZone( "GMT" ) );// standard does not support UTC
        }

    /**
     * emit xml need for one item
     *
     * @param feedItem rss item to export as XML to the corresponding feed file.
     */
    private static void doFeedItem( RSSSortableItem feedItem )
        {
        emit.println( feedItem.asRSSxml() );
        }

    /**
     * emit xml needed for end of a feed
     */
    private static void endFeed()
        {
        // close off previous group
        emit.println( postlude() );
        emit.close();
        }

    /**
     * Prepare the various feeds from the combined binary RSS feed log.
     */
    @SuppressWarnings( { "StringEquality" } )
    static void exportAllFeeds()
        {
        // if whatsnew.html was bypassed by cache mechanism
        // it will have no items processed.
        // if it has no items, we will have no items
        // if processed some subset of the files that did not include
        // whatsnew.html, we will have no items.
        // SO, if items we don't export anything. Leave existing XML files
        // as is.
        if ( RSSFeedLog.count == 0 )
            {
            return;
            }
        try
            {
            if ( configuration.isVerbose() )
                {
                out.println( "preparing " + RSSFeedLog.count + " RSS items" );
                }
            ArrayList<RSSSortableItem> sortableRSSFeedItems = new ArrayList<>( RSSFeedLog.count );
            readAllFeeds( sortableRSSFeedItems );
            // sort items by feed/descending date.
            Collections.sort( sortableRSSFeedItems, new RSSSortableItem.ByFeedByDate() );
            emit = null;
            String prevKey = null;
            // code works even if no items.
            for ( RSSSortableItem feedItem : sortableRSSFeedItems )
                {
                // exporting to xml, several different RSS feeds.
                // feedName is interned so can directly compare with != instead of .equals
                String thisKey = feedItem.getFeedName();
                if ( thisKey != prevKey )
                    {
                    // starting a new group
                    if ( prevKey != null )
                        {
                        endFeed();
                        }
                    startFeed( feedItem );
                    }
                // always emit the item itself.
                doFeedItem( feedItem );
                prevKey = thisKey;
                } // end for
            // finish off the very last group.
            if ( prevKey != null )
                {
                endFeed();
                }
            }
        catch ( IOException e )
            {
            throw new IllegalArgumentException( "Problems preparing the RSS feed files from the binary log. : "
                                                + e.getMessage() );
            }
        }

    /**
     * get XML to tack on end  of XML feed file
     *
     * @return xml tail for an RSS feed file
     */
    @SuppressWarnings( { "SameReturnValue" } )
    private static String postlude()
        {
        return "</channel></rss>";
        }

    /**
     * get XML to tack on front of XML feed file.
     *
     * @param feedName name of feed
     *
     * @return xml prelude to an RSS feed.
     */
    private static String prelude( String feedName )
        {
        /**
         * fetch from prelude file.
         * we need to insert build date with current time between
         * <lastBuildDate></lastBuildDate> tags.
         */
        final File preludeFile = new File( configuration.getLocalWebrootWithSlashes() + "/rss/prelude/" + feedName +
                                           ".xml" );
        try
            {
            String preludeText = HunkIO.readEntireFile( preludeFile, EIO.UTF8 );
            int fix = preludeText.indexOf( "<lastBuildDate></lastBuildDate>" );
            if ( fix < 0 )
                {
                throw new IllegalArgumentException( "Missing <lastBuildDate></lastBuildDate> in RSS preludeText file" +
                                                    " " + preludeFile.toString() );
                }
            // get current time in form <lastBuildDate>Fri, 08 Aug 2008 12:27:08 UTC</lastBuildDate>
            String buildDate = BUILD_DATE_SDF.format( new Date() );// current time
            final FastCat sb = new FastCat( 3 );
            sb.append( preludeText.substring( 0, fix + "<lastBuildDate>".length() ) );
            sb.append( buildDate );
            sb.append( preludeText.substring( fix + "<lastBuildDate>".length() ) );
            return sb.toString();
            }
        catch ( IOException e )
            {
            throw new IllegalArgumentException( "Trouble reading RSS prelude file " + preludeFile.toString() + " : "
                                                + e.getMessage() );
            }
        }

    /**
     * read the binary RSS feed item log into an ArrayList
     *
     * @param sortableRSSFeedItems ArrayList to add items to.
     *
     * @throws IOException if problem reading binary log file.
     */
    @SuppressWarnings( { "InfiniteLoopStatement" } )
    private static void readAllFeeds( ArrayList<RSSSortableItem> sortableRSSFeedItems ) throws IOException
        {
        DataInputStream instream = null;
        try
            {
            instream = EIO.getDataInputStream( RSSFeedLog.rssBinaryLogFile, 1024 * 10 );
            while ( true )
                {
                sortableRSSFeedItems.add( RSSSortableItem.read( instream ) );
                }
            }
        catch ( EOFException e )
            {
            // normal eof
            }
        finally
            {
            if ( instream != null )
                {
                instream.close();
                // no longer need the binary log file.
                //noinspection ResultOfMethodCallIgnored
                RSSFeedLog.rssBinaryLogFile.delete();
                }
            }
        }

    /**
     * emit xml needed for start of feed  export
     *
     * @param feedItem first rss item of a feed.
     *
     * @throws java.io.FileNotFoundException        if trouble finding the corresponding prelude file.
     * @throws java.io.UnsupportedEncodingException if ISO-8859-1 not supported.
     */
    private static void startFeed( RSSSortableItem feedItem )
            throws UnsupportedEncodingException, FileNotFoundException
        {
        // first item in group.
        final File emitFile = new File( configuration.getLocalWebrootWithSlashes() + "/rss/" + feedItem.getFeedName()
                                        + ".xml" );
        emit = EIO.getPrintWriter( emitFile, 4 * 1024, EIO.UTF8 );
        emit.println( prelude( feedItem.getFeedName() ) );
        }
    }