source: main/trunk/greenstone3/src/java/org/greenstone/gsdl3/build/CollectionConstructor.java@ 31671

package org.greenstone.gsdl3.build;

import java.io.File;

import org.greenstone.gsdl3.util.*;
//import java.util.Thread
import java.util.concurrent.CopyOnWriteArrayList;
import org.w3c.dom.Element;

/** base class for collection construction */
public abstract class CollectionConstructor extends Thread
{

    /** the site in which building is to take place */
    protected String site_home = null;
    /** the name of the site */
    protected String site_name = null;
    /** the name of the collection */
    protected String collection_name = null;
    /** the stage of construction */
    protected int process_type = -1;
    /** other arguments/parameters for the construction process - in a paramList */
    protected Element process_params = null;
    /** the list of listeners for the process. We need it to be threadsafe. 
     * see http://stackoverflow.com/questions/8259479/should-i-synchronize-listener-notifications-or-not
     * https://docs.oracle.com/javase/6/docs/api/java/util/concurrent/CopyOnWriteArrayList.html
     * "A thread-safe variant of ArrayList in which all mutative operations (add, set, and so on) are
     * implemented by making a fresh copy of the underlying array.
     * This is ordinarily too costly, but may be more efficient than alternatives when traversal operations
     * vastly outnumber mutations, and is useful when you cannot or don't want to synchronize traversals,
     * yet need to preclude interference among concurrent threads."
     */
    protected final CopyOnWriteArrayList<ConstructionListener> listeners;
    /** A flag used to determine if this process has been asked to cancel. */
    protected boolean cancel = false; // Not really used (in any way that works)
    /** Stores the name of the manifest file (if one is needed) */
    protected String manifest_file = null;
    /** The URL params constructed as a query string, representing the CGI QUERY_STRING to the process */
    protected String query_string = null;

    public CollectionConstructor(String name)
    {
        super(name);
        this.listeners = new CopyOnWriteArrayList<ConstructionListener>();
    }

    /**
     * carry out any set up stuff - returns false if couldn't set up properly
     */
    public boolean configure()
    {
        return true;
    }

    // this method never gets called. And, the way subclass GS2PerlConstructor.runPerlCommand() was originally
    // coded, setting cancel to true never had any effect anyway in stopping any perl command that was run.
    public void stopAction()
    {
        this.cancel = true;
    }

    public void setActionType(int type)
    {
        this.process_type = type;
    }

    public void setSiteHome(String site_home)
    {
        this.site_home = site_home;

        File siteHomeFile = new File(site_home);
        this.site_name = siteHomeFile.getName();
    }

    public void setCollectionName(String coll_name)
    {
        this.collection_name = coll_name;
    }

        public void setQueryString(String querystring)
    {
        this.query_string = querystring;
    }

    public void setProcessParams(Element params)
    {
        this.process_params = params;
    }
    
    public void setManifestFile(String manifestFile)
    {
        this.manifest_file = manifestFile;
    }

    public boolean addListener(ConstructionListener listener)
    {
        this.listeners.add(listener);
        return true;
    }

    // We never call removeListener. If we do start calling removeListener() change the listeners list
    // over to type ConcurrentLinkedQueue, for reasons explained at
    // http://stackoverflow.com/questions/8259479/should-i-synchronize-listener-notifications-or-not
    // The current listeners list type is CopyOnWriteArrayList, which provides thread safety. But it
    // can still send off events to listeners just as they're being unregistered, and that could be a
    // problem if we were specifically removing the listener because we wanted to cease it from
    // listening and responding to subsequent events.
    public boolean removeListener(ConstructionListener listener)
    {       
        this.listeners.remove(listener);
        return true;
    }

    protected void sendProcessBegun(ConstructionEvent evt)
    {
        // See http://stackoverflow.com/questions/8259479/should-i-synchronize-listener-notifications-or-not
        for (ConstructionListener l: this.listeners) {
        l.processBegun(evt);
        }
    }

    protected void sendProcessComplete(ConstructionEvent evt)
    {
        for (ConstructionListener l: this.listeners) {
        l.processComplete(evt);
        }
    }

    // Method doesn't need to be synchronized any more, since it uses the ThreadSafe CopyOnWriteArrayList
    // for listeners list.
    // See http://stackoverflow.com/questions/8259479/should-i-synchronize-listener-notifications-or-not
    // See http://stackoverflow.com/questions/574240/is-there-an-advantage-to-use-a-synchronized-method-instead-of-a-synchronized-blo
    protected void sendProcessStatus(ConstructionEvent evt)
    {
        for (ConstructionListener l: this.listeners) {
        l.processStatus(evt);
        }
    }

    protected void sendMessage(ConstructionEvent evt)
    {
        for (ConstructionListener l: this.listeners) {
        l.message(evt);
        }
    }

    abstract public void run();
}