/*_############################################################################
  _## 
  _##  SNMP4J-AgentX - BufferedMOMutableTableModel.java  
  _## 
  _##  Copyright (C) 2005-2026  Frank Fock (SNMP4J.org)
  _##  
  _##  This program is free software; you can redistribute it and/or modify
  _##  it under the terms of the GNU General Public License version 2 as 
  _##  published by the Free Software Foundation.
  _##
  _##  This program is distributed in the hope that it will be useful,
  _##  but WITHOUT ANY WARRANTY; without even the implied warranty of
  _##  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  _##  GNU General Public License for more details.
  _##
  _##  You should have received a copy of the GNU General Public License
  _##  along with this program; if not, write to the Free Software
  _##  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 
  _##  MA  02110-1301  USA
  _##  
  _##########################################################################*/

package org.snmp4j.agent.mox;

import org.snmp4j.agent.mo.*;
import org.snmp4j.smi.OID;
import org.snmp4j.smi.Variable;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * The BufferedMOMutableTableModel is a read/write/create table model that dynamically loads data from an
 * backend as needed. The internal buffer holds up to {@link #getMaxBufferSize()} rows fetched from the backend.
 * Rows are removed from the buffer either when they are older than {@link #getBufferTimeoutNanoSeconds()} or
 * if the maximum number of buffered rows is reached.
 * <p>
 * Updates, row creations and removals are directly processed by the backend. Thus, updates are not buffered
 * by this table model although the internal buffer reflects the changes.
 * </p>
 * <p>
 * IMPORTANT: The table model needs to be informed about row changes by calling the {@link #rowChanged(MOTableRowEvent)}
 * method of the implemented {@link org.snmp4j.agent.mo.MOTableRowListener} interface. This is typically done by
 * adding this model as row listener with
 * {@link org.snmp4j.agent.mo.DefaultMOTable#addMOTableRowListener(MOTableRowListener)} but it can also be called
 * manually.
 * </p>
 * <p>
 * If you need to be sure that every row change is automatically processed by the backend through this
 * BufferedMOMutableTableModel then you will have to implement and use your own {@link org.snmp4j.agent.mo.MOTableRow}
 * implementation created by your own {@link org.snmp4j.agent.mo.MOTableRowFactory}. That row implementation has then
 * to call the {@link #rowChanged(MOTableRowEvent)} of this table model after each change.
 * </p>
 *
 * @author Frank Fock
 * @since 2.2
 */
public abstract class BufferedMOMutableTableModel<R extends MOTableRow>
        extends BufferedMOTableModel<R>
        implements MOMutableTableModel<R>, MOTableRowListener<R> {

    /**
     * Creates a BufferedMOMutableTableModel with the specified {@link org.snmp4j.agent.mo.MOTableRowFactory}.
     *
     * @param rowFactory
     *         the row factory to be used to create rows from backend data.
     */
    protected BufferedMOMutableTableModel(MOTableRowFactory<R> rowFactory) {
        super(rowFactory);
    }

    @Override
    public R addRow(R row) {
        Variable[] values = new Variable[row.size()];
        for (int i = 0; i < values.length; i++) {
            values[i] = row.getValue(i);
        }
        R previous = getRow(row.getIndex());
        if (previous != null) {
            writeRow(row.getIndex(), values);
        } else {
            insertRow(row.getIndex(), values);
        }
        updateBuffer(Collections.singletonList(row), null);
        return previous;
    }

    @Override
    public synchronized void clear() {
        firstRow = null;
        lastRow = null;
        bufferedChunksList.clear();
        bufferedRows.clear();
        deleteAllRows();
    }

    @Override
    public synchronized List<R> clear(MOTableRowFilter<R> filter) {
        ArrayList<OID> deleted = new ArrayList<OID>();
        List<R> deletedRows = new ArrayList<R>();
        for (Iterator<R> rowIterator = iterator(); rowIterator.hasNext(); ) {
            R row = rowIterator.next();
            if (!filter.passesFilter(row)) {
                deleted.add(row.getIndex());
                deletedRows.add(row);
            }
        }
        bulkDeleteRows(deleted);
        BufferedMOTableRow<R> firstRowCopy = firstRow;
        if (firstRowCopy != null && deleted.contains(firstRowCopy.getIndex())) {
            firstRow = null;
        }
        BufferedMOTableRow<R> lastRowCopy = lastRow;
        if (lastRowCopy != null && deleted.contains(lastRowCopy.getIndex())) {
            lastRow = null;
        }
        for (OID index : deleted) {
            BufferedMOTableRow<R> bufferedMOMutableTableRow = bufferedRows.remove(index);
            if (bufferedMOMutableTableRow != null) {
                bufferedChunksList.remove(bufferedMOMutableTableRow);
            }
        }
        return deletedRows;
    }

    /**
     * Removes all rows in the table.
     */
    protected abstract void deleteAllRows();

    /**
     * Removes the rows with a row index that matches an entry in the supplied index list.
     *
     * @param indexList
     *         the row indexes of the rows to remove.
     */
    protected abstract void bulkDeleteRows(List<OID> indexList);

    /**
     * Inserts a non-existing row.
     *
     * @param index
     *         the row index of the new row.
     * @param values
     *         the values for the columns of the row.
     */
    protected abstract void insertRow(OID index, Variable[] values);

    /**
     * Updates/writes the content of a row.
     *
     * @param index
     *         the row index of the existing row.
     * @param values
     *         the new values for the columns in that row.
     */
    protected abstract void writeRow(OID index, Variable[] values);

    /**
     * Deletes a single row.
     *
     * @param index
     *         the row index of the deleting row.
     */
    protected abstract void deleteRow(OID index);

    @Override
    public void rowChanged(MOTableRowEvent<R> event) {
        if (event.getType() == MOTableRowEvent.UPDATED) {
            Variable[] values = new Variable[event.getRow().size()];
            for (int i = 0; i < values.length; i++) {
                values[i] = event.getRow().getValue(i);
            }
            writeRow(event.getRow().getIndex(), values);
            updateBuffer(Collections.singletonList(rowFactory.createRow(event.getRow().getIndex(), values)), null);
        }
    }

    @Override
    public R removeRow(OID index) {
        BufferedMOTableRow<R> row = getRowFromBuffer(index);
        if (row == null) {
            bufferMisses++;
            Variable[] rowValues = fetchRow(index);
            if (rowValues != null) {
                R r = rowFactory.createRow(index, rowValues);
                row = new BufferedMOTableRow<R>(null);
                deleteRow(index);
                bufferedRows.put(index, row);
                return r;
            }
        } else {
            bufferHits++;
            row.setBufferedRow(null);
            row.setLastRefresh(System.nanoTime());
            deleteRow(index);
            return row.getBufferedRow();
        }
        return null;
    }
}
