/*_############################################################################
  _## 
  _##  SNMP4J-Agent 3 - MOTableSizeLimit.java  
  _## 
  _##  Copyright (C) 2005-2025  Frank Fock (SNMP4J.org)
  _##  
  _##  Licensed 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.snmp4j.agent.mo.util;

import org.snmp4j.agent.mo.*;

import java.util.Properties;
import java.util.SortedMap;
import java.util.Iterator;
import java.util.Map.Entry;
import java.util.TreeMap;

import org.snmp4j.smi.OID;
import org.snmp4j.PDU;
// for JavaDoc
import org.snmp4j.agent.DefaultMOServer;

/**
 * This class implements a size limit on the number of rows in a table.
 * If the limit is reached or exceeded, no more additional rows can be
 * added by SNMP means.
 * <p>
 * Use the {@link DefaultMOServer#registerTableRowListener} method to
 * register this table row listener for all tables in your agent, in order
 * to be able to control the table sizes of all the tables in a server.
 *
 * @param <R> the {@link MOTableRow} type of the rows of the size limited table.
 * @author Frank Fock
 * @version 1.4
 * @since 1.1.5
 */
public class MOTableSizeLimit<R extends MOTableRow> implements MOTableRowListener<R> {

    /**
     * The property prefix each size limit definition has to start with.
     * The OID subtree for which the definition is effective is then appended
     * as follows:
     * {@code
     * snmp4j.MOTableSizeLimit.&lt;OID&gt;=&lt;limit&gt;
     * }
     * where {@code limit} is a positive number or zero.
     */
    public static final String PROPERTY_PREFIX = "snmp4j.tableSizeLimit.";

    private int maxNumRows = 0;
    private SortedMap<OID, Integer> limits;

    public MOTableSizeLimit(int maxNumRows) {
        this.maxNumRows = maxNumRows;
    }

    public MOTableSizeLimit(Properties limits) {
        setLimits(limits);
    }

    /**
     * A column or a complete row is changed/has been changed.
     *
     * @param event
     *         a {@code MOTableRowEvent} describing the event. To veto
     *         the event the {@link MOTableRowEvent#setVetoStatus} and optionally also
     *         the {@link MOTableRowEvent#setVetoColumn} can be called.
     */
    public void rowChanged(MOTableRowEvent<R> event) {
        if (event.getType() == MOTableRowEvent.ADD) {
            if (!checkLimits(event)) {
                event.setVetoStatus(PDU.resourceUnavailable);
            }
        }
    }

    private boolean checkLimits(MOTableRowEvent<R> event) {
        int limit = maxNumRows;
        if ((limits != null) && (!limits.isEmpty())) {
            OID search = new OID(event.getTable().getOID());
            while (search.size() > 0) {
                Integer l = limits.get(search);
                if (l != null) {
                    limit = l;
                    break;
                } else {
                    search.trim(1);
                }
            }
        }
        int currentSize = 0;
        if (limit > 0) {
            currentSize = event.getTable().getModel().getRowCount();
            if (currentSize >= limit) {
                // remove eldest
                return removeEldest(event, (currentSize - limit) + 1);
            }
            return true;
        }
        return true;
    }

    /**
     * Remove try to remove a given number of eldest rows of the table referred
     * to in the triggering event object.
     *
     * @param triggeringEvent
     *         the MOTableRowEvent object that describes the table with exceeding
     *         row limit.
     * @param numRows
     *         the number of rows to remove (if possible).
     *
     * @return {@code true} if one or more rows could be removed and
     * {@code false} if the causing event should be denied/rejected.
     * The default implementation returns {@code false} always.
     */
    protected boolean removeEldest(MOTableRowEvent<R> triggeringEvent, int numRows) {
        return false;
    }

    public void setMaxNumRows(int maxNumRows) {
        this.maxNumRows = maxNumRows;
    }

    public int getMaxNumRows() {
        return maxNumRows;
    }

    public SortedMap<OID, Integer> getLimits() {
        return limits;
    }

    public void setLimits(Properties limits) {
        this.limits = new TreeMap<OID, Integer>();
        for (Entry<Object, Object> entry : limits.entrySet()) {
            String key = (String) entry.getKey();
            if (key.startsWith(PROPERTY_PREFIX)) {
                this.limits.put(new OID(key.substring(PROPERTY_PREFIX.length())),
                        Integer.valueOf(entry.getValue().toString()));
            }
        }
    }
}
