package org.simantics.db.common.utils;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.simantics.databoard.Bindings;
import org.simantics.db.ReadGraph;
import org.simantics.db.Resource;
import org.simantics.db.Statement;
import org.simantics.db.WriteGraph;
import org.simantics.db.common.procedure.adapter.DirectStatementProcedure;
import org.simantics.db.common.request.IsParent;
import org.simantics.db.common.request.ObjectsWithType;
import org.simantics.db.common.request.PossibleObjectWithType;
import org.simantics.db.common.request.PossibleOwner;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.exception.InvalidResourceReferenceException;
import org.simantics.db.service.ClusterUID;
import org.simantics.db.service.ClusteringSupport;
import org.simantics.db.service.DirectQuerySupport;
import org.simantics.db.service.SerialisationSupport;
import org.simantics.db.service.XSupport;
import org.simantics.layer0.Layer0;
import org.simantics.utils.datastructures.collections.CollectionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import gnu.trove.list.array.TIntArrayList;
import gnu.trove.procedure.TIntProcedure;
import gnu.trove.set.hash.TIntHashSet;

public class CommonDBUtils {

	private static final Logger LOGGER = LoggerFactory.getLogger(CommonDBUtils.class);

	public static boolean isParent(ReadGraph graph, Resource possibleParent, Resource possibleChild) throws DatabaseException {
		return graph.sync(new IsParent(possibleParent, possibleChild));
	}
	
	public static Resource parent(ReadGraph graph, Resource child) throws DatabaseException {
		return graph.getSingleObject(child, Layer0.getInstance(graph).PartOf);
	}
	
	public static String possibleRelatedString(ReadGraph graph, Resource subject, Resource relation) throws DatabaseException {
		return graph.getPossibleRelatedValue(subject, relation, Bindings.STRING);
	}

	public static Integer possibleRelatedInteger(ReadGraph graph, Resource subject, Resource relation) throws DatabaseException {
		return graph.getPossibleRelatedValue(subject, relation, Bindings.INTEGER);
	}

    public static Resource getPossibleOwner(ReadGraph graph, Resource resource) throws DatabaseException {
        return graph.syncRequest(new PossibleOwner(resource));
    }
    
    public static Resource commonAncestor(ReadGraph graph, Resource r1, Resource r2) throws DatabaseException {
        Layer0 L0 = Layer0.getInstance(graph);
    	if(r1.equals(r2)) return r1;
    	HashSet<Resource> visited = new HashSet<Resource>();
    	visited.add(r1);
    	visited.add(r2);
    	while(true) {
    		if(r1 != null) {
    			r1 = graph.getPossibleObject(r1, L0.IsOwnedBy);
    			if(r1 != null)
    				if(!visited.add(r1)) return r1;
    		}
    		else if(r2 == null) return null;
    		if(r2 != null) {
    			r2 = graph.getPossibleObject(r2, L0.IsOwnedBy);
    			if(r2 != null)
    				if(!visited.add(r2)) return r2;
    		}
    	}
    }
	
    public static Resource getNearestOwner(ReadGraph graph, Collection<Resource> resources) throws DatabaseException {

        Layer0 L0 = Layer0.getInstance(graph);
        
        
        Set<Resource> direct = new HashSet<Resource>();
        Set<Resource> owners = new HashSet<Resource>();
        
        for(Resource r : resources) {
            
            Collection<Resource> objects = graph.getObjects(r, L0.IsOwnedBy);
            // FIXME: 
            // TODO: getObjects returns duplicate entries (https://www.simantics.org/redmine/issues/4885) and therefore direct is Set<Resource>. Fix getObjects to not return duplicate entries
            if (objects.size() > 1) objects = new HashSet<Resource>(objects);
            
            if (objects.size() == 1)
                direct.addAll(objects);
            else if (objects.isEmpty()) {
                for(Statement stm : graph.getStatements(r, L0.IsWeaklyRelatedTo)) {
                    Resource inverse = graph.getPossibleInverse(stm.getPredicate());
                    if(inverse != null) {
                        if(graph.isSubrelationOf(inverse, L0.IsRelatedTo)) {
                            // Filter away tags
                            if(!r.equals(stm.getObject()))
                                owners.add(stm.getObject());
                        }
                    }
                }
            } else {
                System.err.println("Multiple owners for " + graph.getPossibleURI(r) + " id : " + r);
                for (Resource r2 : objects)
                    System.err.println("owner : " + graph.getPossibleURI(r2) + " id " + r2);
                return null;
            }
        }
        
        if(!direct.isEmpty()) {
            Iterator<Resource> iter = direct.iterator();
            Resource common = iter.next();
            while (iter.hasNext()) {
                Resource other = iter.next();
                common = commonAncestor(graph, common, other);
                if (common == null) break;
            }
        	if(common != null)
        		owners.add(common);
        }
        
        if(!Collections.disjoint(owners, resources)) {
            System.err.println("Overlapping owners:");
            for(Resource r : resources)
                System.err.println("-resource " + NameUtils.getSafeName(graph, r, true));
            for(Resource r : owners)
                System.err.println("-owner " + NameUtils.getSafeName(graph, r, true));
            return null;
        }
        
        if(owners.size() == 1) return owners.iterator().next();
        if(owners.size() == 0) return null;
        
        return getNearestOwner(graph, owners);
        
    }
    
    public static Resource getClusterSetForNewResource(ReadGraph graph, Resource ... resources) throws DatabaseException {

    	if(resources.length == 1) return getClusterSetForNewResource(graph, resources[0]);
    	
        Resource owner = getNearestOwner(graph, CollectionUtils.toList(resources));
        if(owner == null) return null;
        return getClusterSetForNewResource(graph, owner, new HashSet<Resource>());
        
    }
    
    public static Resource getClusterSetForNewResource(ReadGraph graph, Collection<Resource> resources) throws DatabaseException {

    	if(resources.size() == 1) return getClusterSetForNewResource(graph, resources.iterator().next());

        Resource owner = getNearestOwner(graph, resources);
        return getClusterSetForNewResource(graph, owner, new HashSet<Resource>());
        
    }
    
    public static Resource getClusterSetForNewResource(ReadGraph graph, Resource resource, Set<Resource> visited) throws DatabaseException {
        
        ClusteringSupport cs = graph.getService(ClusteringSupport.class);
        if(cs.isClusterSet(resource)) return resource;
        
        Resource owner = getPossibleOwner(graph, resource);
        
        if(owner == null || owner == resource) return null;
        if(!visited.add(owner)) return null;

        return getClusterSetForNewResource(graph, owner, visited);
        
    }

    public static Resource getClusterSetForNewResource(ReadGraph graph, Resource r) throws DatabaseException {
        return getClusterSetForNewResource(graph, r, new HashSet<Resource>());
    }


    public static void selectClusterSet(WriteGraph graph, Collection<Resource> resources) throws DatabaseException {
        Resource clusterSet = getClusterSetForNewResource(graph, resources);
        if(clusterSet == null) clusterSet = graph.getRootLibrary();
        graph.setClusterSet4NewResource(clusterSet);
    }

    public static void selectClusterSet(WriteGraph graph, Resource ... resources) throws DatabaseException {
        Resource clusterSet = getClusterSetForNewResource(graph, resources);
        if(clusterSet == null) clusterSet = graph.getRootLibrary();
        graph.setClusterSet4NewResource(clusterSet);
    }
    
    public static void selectClusterSet(WriteGraph graph, Resource resource) throws DatabaseException {
        Resource clusterSet = getClusterSetForNewResource(graph, resource);
        if(clusterSet == null) clusterSet = graph.getRootLibrary();
        graph.setClusterSet4NewResource(clusterSet);
    }
    
    public static List<Resource> objectsWithType(ReadGraph graph, Resource subject, Resource relation, Resource type) throws DatabaseException {
    	return new ArrayList<Resource>(graph.syncRequest(new ObjectsWithType(subject, relation, type)));
    }

    public static Resource possibleObjectWithType(ReadGraph graph, Resource subject, Resource relation, Resource type) throws DatabaseException {
    	return graph.syncRequest(new PossibleObjectWithType(subject, relation, type));
    }

	public static List<ClusterUID> listClusters(ReadGraph graph) throws DatabaseException {
    	XSupport xs = graph.getService(XSupport.class);
    	ClusterUID uids[] = xs.listClusters();
    	ArrayList<ClusterUID> result = new ArrayList<>(uids.length);
    	for(ClusterUID uid : uids) result.add(uid);
    	return result;
    }
	
	public static List<Resource> resourcesByCluster(ReadGraph graph, ClusterUID uid) throws DatabaseException {
    	SerialisationSupport ss = graph.getService(SerialisationSupport.class);
    	ArrayList<Resource> result = new ArrayList<Resource>();
    	// Index 0 is illegal
		for(int i=1;i<1<<12;i++) {
			try {
				result.add(ss.getResource(uid.toRID(i)));
			} catch (InvalidResourceReferenceException e) {
			}
		}
		return result;
	}
	
	public static List<Statement> directStatements(ReadGraph graph, Resource resource, boolean ignoreVirtual) throws DatabaseException {
		
		DirectQuerySupport dqs = graph.getService(DirectQuerySupport.class);
		DirectStatementProcedure proc = new DirectStatementProcedure();

		if (ignoreVirtual) {
			dqs.forEachDirectPersistentStatement(graph, resource, proc);
		} else {
			dqs.forEachDirectStatement(graph, resource, proc);
		}
		
		return proc.getOrThrow();

	}
	
    public static List<Resource> garbageResources(ReadGraph graph) throws DatabaseException {
    	
    	SerialisationSupport ss = graph.getService(SerialisationSupport.class);
    	
    	TIntArrayList refs = new TIntArrayList();
    	TIntArrayList res = new TIntArrayList();
    	
    	// Find all statements in the database
    	for(ClusterUID uid : listClusters(graph)) {
    		for(Resource r : resourcesByCluster(graph, uid)) {
        		int sid = ss.getTransientId(r);
        		for(Statement stm : directStatements(graph, r, true)) {
        			int oid = ss.getTransientId(stm.getObject());
        			refs.add(sid);
        			refs.add(oid);
        		}
        		res.add(sid);
    		}
    	}

    	TIntHashSet reached = new TIntHashSet();
    	
    	// Initialize root
    	int root = ss.getTransientId(graph.getRootLibrary());
    	reached.add(root);
    	
    	int[] refArray = refs.toArray();
    	
    	boolean changes = true;
    	
    	while(changes) {
    		changes = false;
    		for(int i=0;i<refArray.length;i+=2) {
    			int s = refArray[i];
    			int o = refArray[i+1];
    			if(reached.contains(s)) {
    				if(reached.add(o)) {
        				changes = true;
    				}
    			}
    		}
    		
    		System.err.println("Reachability iteration, changes = " + changes);
    	}
    	
    	ArrayList<Resource> result = new ArrayList<>();
		for(int i=0;i<refArray.length;i+=2) {
			int s = refArray[i];
			if(reached.contains(s)) {
				if(reached.add(refArray[i+1]))
					changes = true;
			}
		}

		res.forEach(new TIntProcedure() {
			
			@Override
			public boolean execute(int r) {
				if(!reached.contains(r)) {
					try {
						result.add(ss.getResource(r));
					} catch (DatabaseException e) {
						LOGGER.error("Unexpected error while resolving garbage resources.", e);
					}
				}
				return true;
			}
			
		});
		
    	return result;
    	
    }

    public static ClusterUID clusterUIDOfResource(ReadGraph graph, Resource resource) throws DatabaseException {
    	SerialisationSupport ss = graph.getService(SerialisationSupport.class);
    	return ss.getUID(resource).asCID();
    }
    
    public static boolean isClusterLoaded(ReadGraph graph, ClusterUID clusterUID) throws DatabaseException {
    	XSupport xs = graph.getService(XSupport.class);
    	return xs.isClusterLoaded(clusterUID);
    }
    
    
}