/**
 * 
 */
package de.mpiwg.itgroup.annotations.neo4j;

import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;

import org.apache.log4j.Logger;
import org.neo4j.graphdb.Direction;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Relationship;
import org.neo4j.graphdb.RelationshipType;
import org.neo4j.graphdb.Transaction;
import org.neo4j.graphdb.index.Index;
import org.neo4j.graphdb.index.IndexHits;

import de.mpiwg.itgroup.annotations.Annotation;
import de.mpiwg.itgroup.annotations.Annotation.FragmentTypes;

/**
 * @author casties
 * 
 */
public class AnnotationStore {

	protected static Logger logger = Logger.getLogger(AnnotationStore.class);

	protected GraphDatabaseService graphDb;
	
	public static enum NodeTypes {
		ANNOTATION, PERSON, TARGET
	}

	protected List<Index<Node>> nodeIndexes;
	
	public static enum RelationTypes implements RelationshipType {
		ANNOTATES, CREATED, PERMITS
	}

	public static String ANNOTATION_URI_BASE = "http://entities.mpiwg-berlin.mpg.de/annotations/";

	public AnnotationStore(GraphDatabaseService graphDb) {
		super();
		this.graphDb = graphDb;
		nodeIndexes = new ArrayList<Index<Node>>(3);
		// List.set(enum.ordinal(), val) seems not to work.
		nodeIndexes.add(NodeTypes.ANNOTATION.ordinal(), graphDb.index().forNodes("annotations"));
		nodeIndexes.add(NodeTypes.PERSON.ordinal(), graphDb.index().forNodes("persons"));
		nodeIndexes.add(NodeTypes.TARGET.ordinal(), graphDb.index().forNodes("targets"));
	}

	protected Index<Node> getNodeIndex(NodeTypes type) {
		return nodeIndexes.get(type.ordinal());
	}
	
	/**
	 * Returns the Annotation with the given id.
	 * 
	 * @param id
	 * @return
	 */
	public Annotation getAnnotationById(String id) {
		Node annotNode = getNodeIndex(NodeTypes.ANNOTATION).get("id", id).getSingle();
		Annotation annot = createAnnotationFromNode(annotNode);
		return annot;
	}

	/**
	 * Returns an Annotation object from an annotation-Node.
	 * 
	 * @param annotNode
	 * @return
	 */
	public Annotation createAnnotationFromNode(Node annotNode) {
		Annotation annot = new Annotation();
		annot.setUri((String) annotNode.getProperty("id", null));
		annot.setBodyText((String) annotNode.getProperty("bodyText", null));
		annot.setBodyUri((String) annotNode.getProperty("bodyUri", null));
		// get annotation target from relation
		Iterable<Relationship> targetRels = annotNode
				.getRelationships(RelationTypes.ANNOTATES);
		for (Relationship targetRel : targetRels) {
			Node target = targetRel.getEndNode();
			annot.setTargetBaseUri((String) target.getProperty("uri", null));
			// just the first one
			break;
		}
		annot.setTargetFragment((String) annotNode.getProperty(
				"targetFragment", null));
		String ft = (String) annotNode.getProperty("fragmentType", null);
		if (ft != null) {
			annot.setFragmentType(FragmentTypes.valueOf(ft));
		}
		// get creator form relation
		Iterable<Relationship> creatorRels = annotNode
				.getRelationships(RelationTypes.CREATED);
		for (Relationship creatorRel : creatorRels) {
			Node creator = creatorRel.getStartNode();
			annot.setCreatorUri((String) creator.getProperty("uri", null));
			annot.setCreatorName((String) creator.getProperty("name", null));
			// just the first one
			break;
		}
		annot.setCreated((String) annotNode.getProperty("created", null));
		return annot;
	}

	/**
	 * Store a new annotation in the store or update an existing one. Returns
	 * the stored annotation.
	 * 
	 * @param annot
	 * @return
	 */
	public Annotation storeAnnotation(Annotation annot) {
		Node annotNode = null;
		Transaction tx = graphDb.beginTx();
		try {
			/*
			 * create or get the annotation
			 */
			String id = annot.getUri();
			if (id == null) {
				id = createRessourceURI("annot:");
			}
			annotNode = getOrCreateAnnotationNode(id);

			/*
			 * the annotation body
			 */
			String bodyText = annot.getBodyText();
			if (bodyText != null) {
				annotNode.setProperty("bodyText", bodyText);
			}
			String bodyUri = annot.getBodyUri();
			if (bodyUri != null) {
				annotNode.setProperty("bodyUri", bodyUri);
			}

			/*
			 * the annotation target
			 */
			String targetBaseUri = annot.getTargetBaseUri();
			if (targetBaseUri != null) {
				Node target = getOrCreateTargetNode(targetBaseUri);
				getOrCreateRelation(annotNode, RelationTypes.ANNOTATES, target);
			}

			/*
			 * The fragment part of the annotation target.
			 */
			String targetFragment = annot.getTargetFragment();
			FragmentTypes fragmentType = annot.getFragmentType();
			if (targetFragment != null) {
				annotNode.setProperty("targetFragment", targetFragment);
				annotNode.setProperty("fragmentType", fragmentType.name());
			}

			/*
			 * The name of the creator of this annotation.
			 */
			String creatorName = annot.getCreatorName();

			/*
			 * The URI of the creator of this annotation.
			 */
			String creatorUri = annot.getCreatorUri();
			if (creatorUri != null) {
				Node creator = getOrCreatePersonNode(creatorUri, creatorName);
				getOrCreateRelation(creator, RelationTypes.CREATED, annotNode);
			}

			/*
			 * The creation date of this annotation.
			 */
			String created = annot.getCreated();
			if (created != null) {
				annotNode.setProperty("created", created);
			}

			tx.success();
		} finally {
			tx.finish();
		}

		// re-read and return annotation
		Annotation storedAnnot = createAnnotationFromNode(annotNode);
		return storedAnnot;
	}

	/**
	 * Deletes the annotation with the given id.
	 * 
	 * @param id
	 */
	public void deleteById(String id) {
		Node annotNode = getNodeIndex(NodeTypes.ANNOTATION).get("id", id).getSingle();
		if (annotNode != null) {
			// delete related objects
			Transaction tx = graphDb.beginTx();
			try {
				for (Relationship rel : annotNode.getRelationships()) {
					// delete relation and the related node if it has no other relations
					Node other = rel.getOtherNode(annotNode);					
					rel.delete();
					if (! other.hasRelationship()) {
						deleteNode(other);
					}
				}
				if (! annotNode.hasRelationship()) {
					deleteNode(annotNode);
				} else {
					logger.error("deleteById: unable to delete: Node still has relations.");
				}
				tx.success();
			} finally {
				tx.finish();
			}
		}
	}

	/**
	 * Returns all annotations with the given uri and/or user.
	 * 
	 * @param uri
	 * @param userUri
	 * @param limit
	 * @param offset
	 * @return
	 */
	public List<Annotation> searchByUriUser(String targetUri, String userUri,
			String limit, String offset) {
		List<Annotation> annotations = new ArrayList<Annotation>();
		if (targetUri != null) {
			// there should be only one
			Node target = getNodeIndex(NodeTypes.TARGET).get("uri", targetUri).getSingle();
			if (target != null) {
				Iterable<Relationship> relations = target
						.getRelationships(RelationTypes.ANNOTATES);
				for (Relationship relation : relations) {
					Node ann = relation.getStartNode();
					if (ann.getProperty("TYPE", "").equals("ANNOTATION")) {
						Annotation annot = createAnnotationFromNode(ann);
						annotations.add(annot);
					} else {
						logger.error("ANNOTATES relation does not start with ANNOTATION: "
								+ ann);
					}
				}
			}
		}
		if (userUri != null) {
			// there should be only one
			Node person = getNodeIndex(NodeTypes.PERSON).get("uri", userUri).getSingle();
			if (person != null) {
				Iterable<Relationship> relations = person
						.getRelationships(RelationTypes.CREATED);
				for (Relationship relation : relations) {
					Node ann = relation.getEndNode();
					if (ann.getProperty("TYPE", "").equals("ANNOTATION")) {
						Annotation annot = createAnnotationFromNode(ann);
						annotations.add(annot);
					} else {
						logger.error("CREATED relation does not end with ANNOTATION: "
								+ ann);
					}
				}
			}
		}
		return annotations;
	}

	protected Relationship getOrCreateRelation(Node start,
			RelationshipType type, Node end) {
		if (start.hasRelationship()) {
			// there are relations
			Iterable<Relationship> rels = start.getRelationships(type,
					Direction.OUTGOING);
			for (Relationship rel : rels) {
				if (rel.getEndNode().equals(end)) {
					// relation exists
					return rel;
				}
			}
		}
		// create new one
		Relationship rel;
		Transaction tx = graphDb.beginTx();
		try {
			rel = start.createRelationshipTo(end, type);
			tx.success();
		} finally {
			tx.finish();
		}
		return rel;
	}

	protected Node getOrCreateAnnotationNode(String id) {
		Index<Node> idx = getNodeIndex(NodeTypes.ANNOTATION);
		IndexHits<Node> annotations = idx.get("id", id);
		Node annotation = annotations.getSingle();
		if (annotation == null) {
			// does not exist yet
			Transaction tx = graphDb.beginTx();
			try {
				annotation = graphDb.createNode();
				annotation.setProperty("TYPE", NodeTypes.ANNOTATION.name());
				annotation.setProperty("id", id);
				idx.add(annotation, "id", id);
				tx.success();
			} finally {
				tx.finish();
			}
		}
		return annotation;
	}

	protected Node getOrCreateTargetNode(String uri) {
		Index<Node> idx = getNodeIndex(NodeTypes.TARGET);
		IndexHits<Node> targets = idx.get("uri", uri);
		Node target = targets.getSingle();
		if (target == null) {
			// does not exist yet
			Transaction tx = graphDb.beginTx();
			try {
				target = graphDb.createNode();
				target.setProperty("TYPE", NodeTypes.TARGET.name());
				target.setProperty("uri", uri);
				idx.add(target, "uri", uri);
				tx.success();
			} finally {
				tx.finish();
			}
		}
		return target;
	}

	protected Node getOrCreatePersonNode(String uri, String name) {
		// Person is identified by URI
		Index<Node> idx = getNodeIndex(NodeTypes.PERSON);
		IndexHits<Node> persons = idx.get("uri", uri);
		Node person = persons.getSingle();
		if (person == null) {
			// does not exist yet
			Transaction tx = graphDb.beginTx();
			try {
				person = graphDb.createNode();
				person.setProperty("TYPE", NodeTypes.PERSON.name());
				person.setProperty("uri", uri);
				idx.add(person, "uri", uri);
				if (name != null) {
					person.setProperty("name", name);
				}
				tx.success();
			} finally {
				tx.finish();
			}
		}
		return person;
	}

	/**
	 * Unindexes and deletes given Node if it has no relations.
	 * @param node
	 */
	protected void deleteNode(Node node) {
		Transaction tx = graphDb.beginTx();
		try {
			if (node.hasRelationship()) {
				logger.error("deleteNode: unable to delete: Node still has relations.");
			} else {
				String ts = (String) node.getProperty("TYPE", null);
				try {
					NodeTypes type = NodeTypes.valueOf(ts);
					getNodeIndex(type).remove(node);
				} catch (Exception e) {
					logger.error("deleteNode: unable to get TYPE of node: "+node);
				}
				node.delete();
			}
			tx.success();
		} finally {
			tx.finish();
		}
	}
	
	/**
	 * Erzeuge eine urn aus der aktuellen Zeit in millis
	 * 
	 * @return
	 */
	private String createRessourceURI(String prefix) {

		Calendar cal = Calendar.getInstance();

		long time = cal.getTimeInMillis();

		return String.format("%s%s%s", ANNOTATION_URI_BASE, prefix, time);

	}

}