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package Torello.HTML.Tools.NewsSite;

import Torello.Java.*;
import Torello.Java.Additional.Ret4;

import java.io.*;
import java.util.Vector;

/**
 * When the main iteration-loop for downloading news-articles is running, the loop-variables are
 * kept current to this class; so if (while watching the downloader), the programmer has decided
 * to go take a break (and presses {@code Control-^C}), 'download progress' won't be lost and
 * starting over with articles that have already been saved won't be necessary.
 * 
 * <BR /><BR /><EMBED CLASS='external-html' DATA-FILE-ID=PAUSE>
 */
public interface Pause extends Serializable
{
    /** <EMBED CLASS='external-html' DATA-FILE-ID=SVUID> */
    public static final long serialVersionUID = 1;

    /**
     * This method needs to save the current download state.  The three integers provided are all
     * that the download logic needs in order to identify which newspaper article {@code URL's}
     * have already downloaded - <I>and, therefore, where to begin the download process after a
     * pause or break.</I>  The instance of {@code Vector} that is required by this method's 
     * parameter list contain the "Download Results" for each news-{@code Article} in the
     * {@code URL} list.
     * 
     * @param results  This is the two dimensional {@code Vector} that contains instances of
     * {@code 'DownloadResult'}.  Each news-{@code Article} in each section of a newspaper
     * website has a specific location in this two dimensional {@code Vector}.  As the downloader
     * retrieves (or fails) to scrape news-{@code Article's}, the result of the scrape (or 
     * scrape-attempt) are inserted into this 2-D {@code Vector}.
     * 
     * @param outerCounter This is the outer-{@code Vector} index of the last {@code URL}
     * downloaded.
     * 
     * @param innerCounter This is the inner-{@code Vector} index of the last {@code URL}
     * downloaded.
     * 
     * @param successCounter This is how many of the {@code URL's} that were downloaded without
     * throwing any exceptions.
     */
    public void saveState(
            Vector<Vector<DownloadResult>> results,
            int outerCounter, int innerCounter, int successCounter
        ) throws PauseException;

    /**
     * This method loads the state of the downloader.  This can be helpful if the user wishes to 
     * "pause" the download when long-lists of article {@code URL's} are being retrieved.  Also, if
     * the downloader exits due to an exception, the state of download is maintained.
     * @return An instance of {@code Ret4<Vector<Vector<DownloadResult>>, Integer, Integer, Integer>}
     * <BR /><BR /><UL CLASS=JDUL>
     * <LI>{@code Ret4.a} - The current state of the "Return {@code Vector}".  This two dimensional
     *                      {@code Vector} fills up with instances of enumerated-type
     *                      {@code DownloadResult}.
     * </LI>
     * <LI>{@code Ret2.b} - The outer-{@code Vector} index of the last attempted newspaper article
     *                      {@code URL} download.
     * </LI>
     * <LI>{@code Ret2.c} - The inner-{@code Vector} index of the last attempted newspaper article
     *                      {@code URL} download.
     * </LI>
     * <LI>{@code Ret2.d} - The number of article {@code URL's} that have successfully downloaded.
     * </LI>
     * </UL>
     */
    public Ret4<Vector<Vector<DownloadResult>>, Integer, Integer, Integer> loadState()
        throws PauseException;

    /**
     * If the {@code Pause} implementation needs initialization, it ought to implement this method.
     * <BR /><BR /><B><SPAN STYLE="color: red;">IMPORTANT:</B></SPAN>
     * The initialize process should ensure that a call to {@code loadState()} will return a
     * {@code Ret4} data-structure whose integer fields are all equal to zero.  These fields are
     * counters, and when download begins, if they are not-zero, then many news-articles will not
     * be scraped.
     * <BR /><BR /><B><SPAN STYLE="color: red;">ALSO:</B></SPAN>
     * On initialization, the value for the 2-D {@code Vector} in the {@code Ret4} data-structure
     * need only be present - <B><I>it does not matter what values have been inserted into it, nor
     * the sizes of the sub-{@code Vector's}.</I></B>  Do note that it's values will be clobbered by
     * the downloader if / when the downloader determines that the download process is starting at
     * the beginning.
     * @throws PauseException This exception is thrown if the implementation of this {@code interface}
     * fails to init or load.
     */
    public void initialize() throws PauseException;

    /**
     * This method is a {@code static}-factory method that returns an instance of this
     * {@code interface Pause} that uses the file-system for saving the state to a user-specified
     * file-name.
     * @param saveFileName This is just the name of the data-file where state shall be saved.
     * This state contains only two integers, and is, therefore, an extremely small data-file.
     * @return A functioning instance of this interface - one that uses a flat file for saving state.
     */
    public static Pause getFSInstance(String saveFileName)
        throws PauseException
    { return new PauseFS(saveFileName); }
}