/*******************************************************************************
 * MIT License
 * 
 * Copyright (c) 2018 Antonin Delpeuch
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 ******************************************************************************/
package org.openrefine.wikidata.updates.scheduler;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.openrefine.wikidata.schema.entityvalues.ReconEntityIdValue;
import org.openrefine.wikidata.updates.EntityEdit;
import org.openrefine.wikidata.updates.ItemEdit;
import org.openrefine.wikidata.updates.ItemEditBuilder;
import org.openrefine.wikidata.updates.MediaInfoEdit;
import org.openrefine.wikidata.updates.MediaInfoEditBuilder;
import org.openrefine.wikidata.updates.StatementEdit;
import org.openrefine.wikidata.updates.TermedStatementEntityEdit;
import org.wikidata.wdtk.datamodel.interfaces.EntityIdValue;

public class QuickStatementsUpdateScheduler implements UpdateScheduler {

    private PointerExtractor extractor = new PointerExtractor();

    /**
     * This map holds for each new entity id value a list of updates that refer to
     * this id (and should hence be scheduled right after creation of that entity).
     */
    private Map<EntityIdValue, UpdateSequence> pointerUpdates;

    /**
     * This contains all updates which do not refer to any new entity apart from
     * possibly the subject, in the order that they were supplied to us.
     */
    private UpdateSequence pointerFreeUpdates;

    /**
     * Separates out the statements which refer to new entities from the rest of the
     * update. The resulting updates are stored in {@link referencingUpdates} and
     * {@link updatesWithoutReferences}.
     * 
     * @param update
     * @throws ImpossibleSchedulingException
     *             if two new entity ids are referred to in the same statement
     */
    protected void splitUpdate(EntityEdit edit)
            throws ImpossibleSchedulingException {
    	if (edit instanceof ItemEdit) {
	    	ItemEdit update = (ItemEdit) edit;
	        ItemEditBuilder remainingUpdateBuilder = new ItemEditBuilder(update.getEntityId())
	                .addLabels(update.getLabels(), true)
	                .addLabels(update.getLabelsIfNew(), false)
	                .addDescriptions(update.getDescriptions(), true)
	                .addDescriptions(update.getDescriptionsIfNew(), false)
	                .addAliases(update.getAliases());
	        Map<EntityIdValue, ItemEditBuilder> referencingUpdates = new HashMap<>();
	
	        for (StatementEdit statement : update.getStatementEdits()) {
	            Set<ReconEntityIdValue> pointers = extractor.extractPointers(statement.getStatement());
	            if (pointers.isEmpty()) {
	                remainingUpdateBuilder.addStatement(statement);
	            } else if (pointers.size() == 1 && !update.isNew()) {
	                EntityIdValue pointer = pointers.stream().findFirst().get();
	                ItemEditBuilder referencingBuilder = referencingUpdates.get(pointer);
	                if (referencingBuilder == null) {
	                    referencingBuilder = new ItemEditBuilder(update.getEntityId());
	                }
	                referencingBuilder.addStatement(statement);
	                referencingUpdates.put(pointer, referencingBuilder);
	            } else if (pointers.size() == 1 && pointers.stream().findFirst().get().equals(update.getEntityId())) {
	                remainingUpdateBuilder.addStatement(statement);
	            } else {
	                throw new ImpossibleSchedulingException("An item refers to multiple new entities, which is not supported by QuickStatements");
	            }
	        }
	
	        // Add the update that is not referring to anything to the schedule
	        ItemEdit pointerFree = remainingUpdateBuilder.build();
	        if (!pointerFree.isNull()) {
	            pointerFreeUpdates.add(pointerFree);
	        }
	        // Add the other updates to the map
	        for (Entry<EntityIdValue, ItemEditBuilder> entry : referencingUpdates.entrySet()) {
	        	TermedStatementEntityEdit pointerUpdate = entry.getValue().build();
	            UpdateSequence pointerUpdatesForKey = pointerUpdates.get(entry.getKey());
	            if (pointerUpdatesForKey == null) {
	                pointerUpdatesForKey = new UpdateSequence();
	            }
	            pointerUpdatesForKey.add(pointerUpdate);
	            pointerUpdates.put(entry.getKey(), pointerUpdatesForKey);
	        }
    	} else if (edit instanceof MediaInfoEdit){
	    	MediaInfoEdit update = (MediaInfoEdit) edit;
	        MediaInfoEditBuilder remainingUpdateBuilder = new MediaInfoEditBuilder(update.getEntityId())
	                .addLabels(update.getLabels(), true)
	                .addLabels(update.getLabelsIfNew(), false);
	        Map<EntityIdValue, MediaInfoEditBuilder> referencingUpdates = new HashMap<>();
	
	        for (StatementEdit statement : update.getStatementEdits()) {
	            Set<ReconEntityIdValue> pointers = extractor.extractPointers(statement.getStatement());
	            if (pointers.isEmpty()) {
	                remainingUpdateBuilder.addStatement(statement);
	            } else if (pointers.size() == 1 && !update.isNew()) {
	                EntityIdValue pointer = pointers.stream().findFirst().get();
	                MediaInfoEditBuilder referencingBuilder = referencingUpdates.get(pointer);
	                if (referencingBuilder == null) {
	                    referencingBuilder = new MediaInfoEditBuilder(update.getEntityId());
	                }
	                referencingBuilder.addStatement(statement);
	                referencingUpdates.put(pointer, referencingBuilder);
	            } else if (pointers.size() == 1 && pointers.stream().findFirst().get().equals(update.getEntityId())) {
	                remainingUpdateBuilder.addStatement(statement);
	            } else {
	                throw new ImpossibleSchedulingException("A mediainfo entity refers to multiple new entities, which is not supported by QuickStatements");
	            }
	        }
	
	        // Add the update that is not referring to anything to the schedule
	        MediaInfoEdit pointerFree = remainingUpdateBuilder.build();
	        if (!pointerFree.isNull()) {
	            pointerFreeUpdates.add(pointerFree);
	        }
	        // Add the other updates to the map
	        for (Entry<EntityIdValue, MediaInfoEditBuilder> entry : referencingUpdates.entrySet()) {
	        	MediaInfoEdit pointerUpdate = entry.getValue().build();
	            UpdateSequence pointerUpdatesForKey = pointerUpdates.get(entry.getKey());
	            if (pointerUpdatesForKey == null) {
	                pointerUpdatesForKey = new UpdateSequence();
	            }
	            pointerUpdatesForKey.add(pointerUpdate);
	            pointerUpdates.put(entry.getKey(), pointerUpdatesForKey);
	        }
    	}
    }

    @Override
    public List<EntityEdit> schedule(List<EntityEdit> updates)
            throws ImpossibleSchedulingException {
        pointerUpdates = new HashMap<>();
        pointerFreeUpdates = new UpdateSequence();

        for (EntityEdit update : updates) {
            splitUpdate(update);
        }

        // Reconstruct
        List<EntityEdit> fullSchedule = new ArrayList<>();
        Set<EntityIdValue> mentionedNewEntities = new HashSet<>(pointerUpdates.keySet());
        for (EntityEdit update : pointerFreeUpdates.getUpdates()) {
            fullSchedule.add(update);
            UpdateSequence backPointers = pointerUpdates.get(update.getEntityId());
            if (backPointers != null) {
                fullSchedule.addAll(backPointers.getUpdates());
            }
            mentionedNewEntities.remove(update.getEntityId());
        }

        // Create any entity that was referred to but untouched
        // (this is just for the sake of correctness, it would be bad to do that
        // as the entities would remain blank in this batch).
        for (EntityIdValue missingId : mentionedNewEntities) {
            fullSchedule.add(new ItemEditBuilder(missingId).build());
            fullSchedule.addAll(pointerUpdates.get(missingId).getUpdates());
        }
        return fullSchedule;
    }

}
