/*
 *  Copyright 2021 Anyware Services
 *
 *  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.ametys.workspaces.repository.maintenance;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.jcr.Credentials;
import javax.jcr.NodeIterator;
import javax.jcr.RepositoryException;
import javax.jcr.Session;
import javax.jcr.SimpleCredentials;
import javax.jcr.query.Query;
import javax.jcr.version.Version;
import javax.jcr.version.VersionHistory;
import javax.jcr.version.VersionIterator;

import org.apache.jackrabbit.core.NodeImpl;
import org.apache.jackrabbit.core.RepositoryImpl;
import org.slf4j.LoggerFactory;

/**
 * Remove unused object from jcr history
 */
public class RemoveUnusedHistoryTask extends AbstractMaintenanceTask
{
    /** The JackRabbit RepositoryImpl */
    protected RepositoryImpl _repository;

    @Override
    public boolean requiresOffline()
    {
        return false;
    }
    
    @Override
    protected void setLogger()
    {
        setLogger(LoggerFactory.getLogger(RemoveUnusedHistoryTask.class));
    }

    @Override
    protected void apply() throws RepositoryException
    {
        Map<String, Session> sessions = null;
        Credentials credentials = new SimpleCredentials("ametys", new char[]{});
       
        try
        {
            _repository = getOrCreateRepository();

            String[] accessibleWorkspaceNames = _getWorkspaces(credentials);
            sessions = _loadSessions(accessibleWorkspaceNames);
            
            @SuppressWarnings("deprecation")
            Query q = sessions.get("default").getWorkspace().getQueryManager().createQuery("//element(*, nt:versionHistory)", Query.XPATH);
            NodeIterator nodes = q.execute().getNodes();
            long size = nodes.getSize();
            
            _progress = new TaskProgress(size * 2);
            _progress.setRunning();

            List<VersionHistory> vhs = _getVersionHistoryToRemove(sessions, accessibleWorkspaceNames, nodes);
            _progress.progress(size - vhs.size());
            
            _logger.info("Going to remove " + vhs.size() + " history nodes on " + size + " existing nodes");
            
            _removeUnusedHistory(vhs, sessions);
        }
        catch (RepositoryException e)
        {
            if (_progress != null)
            {
                _progress.setInErrorState(e);
            }
            
            throw e;
        }
        catch (Exception e)
        {
            if (_progress != null)
            {
                _progress.setInErrorState(e);
            }
            
            throw new RuntimeException(e);
        }
        finally
        {
            _logout(sessions);
            
            if (_progress != null)
            {
                _progress.setFinished();
            }
            
        }
    }
    
    private void _logout(Map<String, Session> sessions)
    {
        if (sessions != null)
        {
            for (Session session : sessions.values())
            {
                session.logout();
            }
        }
    }
    
    private String[] _getWorkspaces(Credentials credentials) throws RepositoryException
    {
        Session session = null;
        try
        {
            session = _repository.login(credentials, "default");
            return session.getWorkspace().getAccessibleWorkspaceNames();
        }
        finally 
        {
            if (session != null)
            {
                session.logout();
            }
        }
    }
    
    private Map<String, Session> _loadSessions(String[] accessibleWorkspaceNames) throws RepositoryException
    {
        Map<String, Session> sessions = new HashMap<>();
        Credentials credentials = new SimpleCredentials("ametys", new char[]{});
       
        for (String workspaceName: accessibleWorkspaceNames)
        {
            sessions.put(workspaceName, _repository.login(credentials, workspaceName));
        }
        
        return sessions;
    }
    
    private void _removeUnusedHistory(List<VersionHistory> versionHistories, Map<String, Session> sessions) throws RepositoryException
    {
        int errors = 0;
        int done = 0;
        int empty = 0;
        int fixed = 0;

        for (VersionHistory versionHistory : versionHistories)
        {
            VersionIterator it = versionHistory.getAllVersions();

            boolean hasError = false;
            int childNodesSize = 0;
            
            while (it.hasNext())
            {
                Version version = it.nextVersion();
                if (!"jcr:rootVersion".equals(version.getName()))
                {
                    childNodesSize++;

                    try
                    {
                        versionHistory.removeVersion(version.getName());
                    }
                    catch (RepositoryException e)
                    {
                        hasError = true;
                        _logger.error("Error with version " + version.getName() + " of " + versionHistory.getIdentifier() + "... " + e);
                    }
                }
            }
            
            if (childNodesSize == 0)
            {
                _removeEmptyHistory(versionHistory, sessions.get("default"));
                try
                {
                    sessions.get("default").getNodeByIdentifier(versionHistory.getIdentifier());
                    
                    _logger.debug("Empty history node is " + versionHistory.getIdentifier());
                    empty++;            
                }
                catch (RepositoryException e)
                {
                    fixed++;
                }
            }
            else if (hasError)
            {
                errors++;
            }
            else
            {
                done++;
            }
            
            _progress.progress();
        }

        _logger.info(done + " normal history nodes removed\n"
                    + fixed + " empty history nodes fixed and removed\n"
                    + empty + " empty history nodes that are unfixable\n"
                    + errors + " unconsistents history nodes that cannot be removed");
    }
    
    private void _removeEmptyHistory(VersionHistory vh, Session session) throws RepositoryException
    {
        var node = ((NodeImpl) session.getNode("/ametys:root")).addNodeWithUuid("historyrepair", "nt:unstructured", vh.getProperty("jcr:versionableUuid").getString());
        node.addMixin("mix:versionable");
        session.save();
        session.getWorkspace().getVersionManager().checkin(node.getPath());
        session.getWorkspace().getVersionManager().checkout(node.getPath());
        session.removeItem("/ametys:root/historyrepair");
        session.save();
        vh.removeVersion("1.0");
    }
    
    private List<VersionHistory> _getVersionHistoryToRemove(Map<String, Session> sessions, String[] accessibleWorkspaceNames, NodeIterator nodes) throws RepositoryException
    {
        List<VersionHistory> vhs = new ArrayList<>();
        
        while (nodes.hasNext())
        {
            VersionHistory versionHistory = (VersionHistory) nodes.nextNode();
            String versionableIdentifier = versionHistory.getVersionableIdentifier();
            
            var foundOne = false;
            for (var i = 0; i < accessibleWorkspaceNames.length; i++)
            {
                var workspaceName = accessibleWorkspaceNames[i];
            
                try
                {
                    sessions.get(workspaceName).getNodeByIdentifier(versionableIdentifier);
                    foundOne = true;
                    break;
                }
                catch (RepositoryException e)
                {
                    // nothing
                }
            }
        
            if (!foundOne)
            {
                vhs.add(versionHistory);
            }                
            _progress.progress();
        }
        
        return vhs;
    }

}