/*******************************************************************************
 * Copyright (c) 2007, 2011 Association for Decentralized Information Management
 * in Industry THTH ry.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.db.layer0.util;

import java.util.function.Consumer;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.NullProgressMonitor;
import org.simantics.db.ReadGraph;
import org.simantics.db.Session;
import org.simantics.db.WriteGraph;
import org.simantics.db.common.request.WriteRequest;
import org.simantics.db.common.utils.Logger;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.service.ClusterControl;
import org.simantics.db.service.LifecycleSupport;
import org.simantics.db.service.QueryControl;
import org.simantics.utils.DataContainer;

/**
 * @author Tuukka Lehtonen
 */
public class SessionGarbageCollection {
    /**
     * collect everything possible, default target is 0 queries.
     */
    private static int DEFAULT_ALLOWED_TIME = 300;
    public static int getDefaultQueryTarget() {
        return DEFAULT_ALLOWED_TIME;
    }
    public static void setDefaultAllowedTime(int a) {
        DEFAULT_ALLOWED_TIME = a;
    }
    /**
     * Default maximum cluster memory consumption target is 32MB.
     */
    private static int DEFAULT_CLUSTER_TARGET = -1;
    public static int getDefaultClusterTarget() {
        return DEFAULT_CLUSTER_TARGET;
    }
    public static void setDefaultClusterTarget(int a) {
        DEFAULT_CLUSTER_TARGET = a;
    }
    /**
     * @param monitor <code>null</code> if progress monitor not available
     * @param session the session to GC
     * @param sync <code>true</code> to block until gc is completed
     * @param errorCallback callback for any errors occuring during the
     *        operation or <code>null</code> to ignore errors
     */
    public static boolean gc(IProgressMonitor monitor, Session session, boolean sync,
            final Consumer<DatabaseException> errorCallback) {
    	long took = gc(monitor, session, sync, errorCallback, DEFAULT_ALLOWED_TIME, DEFAULT_CLUSTER_TARGET);
        return ((16*took) / DEFAULT_ALLOWED_TIME) > 15;
    }

    public static void gc(ReadGraph graph, final int allowedTimeInMs, final int clusterTarget) throws DatabaseException {
        doIt(null, graph, allowedTimeInMs, clusterTarget);
    }

    public static void gc(IProgressMonitor monitor, ReadGraph graph, final int allowedTimeInMs, final int clusterTarget) throws DatabaseException {
        doIt(monitor, graph, allowedTimeInMs, clusterTarget);
    }

    private static void doIt(IProgressMonitor _monitor, ReadGraph graph, final int allowedTimeInMs, final int clusterTarget) {
        if(_monitor == null) _monitor = new NullProgressMonitor();
        QueryControl qc = graph.getService(QueryControl.class);
        ClusterControl cc = graph.getService(ClusterControl.class);
        _monitor.beginTask("Collect clusters", IProgressMonitor.UNKNOWN);
        //cc.gc(graph, clusterTarget);
        if(clusterTarget == -1) {
            int used = cc.used();
            //System.err.println("session gc, cluster use = " + used);
            int baseline = 32*(1<<20);
            if(used > baseline) {
                int dynamicTarget = (int)(0.95 * (used-baseline)) + baseline;
                cc.gc(graph, dynamicTarget);
            }
        } else {
            cc.gc(graph, clusterTarget);
        }
        _monitor.beginTask("Collect queries", IProgressMonitor.UNKNOWN);
        qc.gc(graph, allowedTimeInMs);
    }

    /**
     * @param monitor
     * @param session
     * @param sync
     * @param errorCallback
     */
    /**
     * @param monitor <code>null</code> if progress monitor not available
     * @param session the session to GC
     * @param sync <code>true</code> to block until gc is completed
     * @param errorCallback callback for any errors occuring during the
     *        operation or <code>null</code> to ignore errors
     * @param allowedTimeInMs the time allowed for query collection in ms
     * @param clusterTarget target for the maximum amount of memory in bytes to
     *        be consumed by cluster caches after collection.
     */
    public static long gc(IProgressMonitor monitor, Session session, boolean sync,
            final Consumer<DatabaseException> errorCallback, final int allowedTimeInMs, final int clusterTarget) {
        if (monitor == null)
            monitor = new NullProgressMonitor();
        final IProgressMonitor _monitor = monitor;
        if (session == null)
            throw new NullPointerException("null session");

        final DataContainer<Long> took = new DataContainer<Long>(0L);
        
        WriteRequest request = new WriteRequest() {
            @Override
            public void perform(WriteGraph graph) throws DatabaseException {
            	long start = System.nanoTime();
            	doIt(_monitor, graph, allowedTimeInMs, clusterTarget);
            	long duration = System.nanoTime()-start;
            	took.set((long)(duration*1e-6));
            }
        };
        
        LifecycleSupport lfs = session.peekService(LifecycleSupport.class);
        if (lfs == null || lfs.isClosed() || lfs.isClosing())
            return 0L;
        
        if (sync) {
            try {
                session.syncRequest(request);
            } catch (DatabaseException e) {
                if (errorCallback != null)
                    errorCallback.accept(e);
                else
                    Logger.defaultLogError(e);
            }
        } else {
            session.asyncRequest(request, e -> {
                if (e != null) {
                    if (errorCallback != null)
                        errorCallback.accept(e);
                    else
                        Logger.defaultLogError(e);
                }
            });
        }
        
        return took.get();
        
    }

}