/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.clerezza.platform.typerendering;


import java.util.*;
import javax.ws.rs.core.MediaType;
import org.apache.clerezza.rdf.utils.graphnodeprovider.GraphNodeProvider;
import org.apache.clerezza.platform.typepriority.TypePrioritizer;
import org.apache.clerezza.platform.typerendering.utils.MediaTypeMap;
import org.apache.clerezza.platform.typerendering.utils.RegexMap;
import org.apache.clerezza.rdf.core.TypedLiteral;
import org.apache.clerezza.rdf.core.UriRef;
import org.apache.clerezza.rdf.ontologies.RDF;
import org.apache.clerezza.rdf.ontologies.RDFS;
import org.apache.clerezza.rdf.utils.GraphNode;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.ReferencePolicy;
import org.apache.felix.scr.annotations.Service;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.service.component.ComponentContext;
import org.osgi.service.startlevel.StartLevel;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Creates a <code>Renderer</code> which can used to render a <code>GraphNode</code>.
 *
 * @author mir, reto
 */
@Component
@Service(RendererFactory.class)
@Reference(name = "typeRenderlet",
cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE,
policy = ReferencePolicy.DYNAMIC,
referenceInterface = TypeRenderlet.class)
public class RendererFactory {

    private Logger logger = LoggerFactory.getLogger(RendererFactory.class);
    
    @Reference
    private TypePrioritizer typePrioritizer;

    @Reference
    private StartLevel startLevelService;

    @Reference
    private GraphNodeProvider graphNodeProvider;

    /**
     * A Tuple Type-Renderler Startlevel, for identity only the renderlet is relevan
     */
    private static class TypeRenderletStartLevel {
        TypeRenderlet renderlet;
        int startLevel;

        private TypeRenderletStartLevel(TypeRenderlet renderlet, int startLevel) {
            this.startLevel = startLevel;
            this.renderlet = renderlet;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            TypeRenderletStartLevel that = (TypeRenderletStartLevel) o;
            return renderlet.equals(that.renderlet);
        }

        @Override
        public int hashCode() {
            return renderlet.hashCode();
        }
    }

    private Map<UriRef, RegexMap<MediaTypeMap<TypeRenderletStartLevel>>> typeRenderletMap =
            Collections.synchronizedMap(new HashMap<UriRef, RegexMap<MediaTypeMap<TypeRenderletStartLevel>>>());

    private BundleContext bundleContext;

    private Set<ServiceReference> pendingRenderletRegistrations = new HashSet<ServiceReference>();

    protected void activate(ComponentContext componentContext) {
        bundleContext = componentContext.getBundleContext();
        for (ServiceReference r : pendingRenderletRegistrations) {
            registerTypeRenderlet(r);
        }
    }

    protected void deactivate(ComponentContext componentContext) {
        bundleContext = null;
    }

    /**
     * Creates a <code>Renderer</code> for the specified mode, acceptable 
     * media-types as well as the types of <code>GraphNode</code>.
     * The <code>acceptableMediaTypes</code> list represent the media
     * types that are acceptable for the rendered output. The list has a
     * order where the most desirable media type is a the beginning of the list.
     * The media type of the rendered output will be compatible to at least one
     * media type in the list.
     *
     * @param resource The <code>GraphNode</code> to be rendered
     * @param mode mode
     * @param acceptableMediaTypes acceptable media types for the rendered output
     * @return the Renderer or null if no renderer could be created for the specified parameters
     */
    public Renderer createRenderer(GraphNode resource, String mode,
            List<MediaType> acceptableMediaTypes) {
        Set<UriRef> types = new HashSet<UriRef>();
        if (resource.getNode() instanceof TypedLiteral) {
            types.add(((TypedLiteral) resource.getNode()).getDataType());
        } else {
            // extract rdf types
            Iterator<UriRef> it = resource.getUriRefObjects(RDF.type);
            while (it.hasNext()) {
                final UriRef rdfType = it.next();
                types.add(rdfType);
            }
            types.add(RDFS.Resource);
        }
        return getRenderer(types, mode, acceptableMediaTypes);
    }

    private Renderer getRenderer(Set<UriRef> types, String mode,
            List<MediaType> acceptableMediaTypes) {
        Iterator<UriRef> sortedTypes = typePrioritizer.iterate(types);
        while (sortedTypes.hasNext()) {
            final UriRef currentType = sortedTypes.next();
            final RegexMap<MediaTypeMap<TypeRenderletStartLevel>> regexMap = typeRenderletMap.get(currentType);
            if (regexMap != null) {
                Iterator<MediaTypeMap<TypeRenderletStartLevel>> mediaTypeMapIter = regexMap.getMatching(mode);
                while (mediaTypeMapIter.hasNext()) {
                    MediaTypeMap<TypeRenderletStartLevel> mediaTypeMap = mediaTypeMapIter.next();
                    for (MediaType acceptableType : acceptableMediaTypes) {
                        Iterator<TypeRenderletStartLevel> renderlets = mediaTypeMap.getMatching(acceptableType);
                        if (renderlets.hasNext()) {
                            TypeRenderlet bestRenderlet = null;
                            int highestStartLevel = 0;
                            while (renderlets.hasNext()) {
                                TypeRenderletStartLevel typeRenderletStartLevel = renderlets.next();
                                if (typeRenderletStartLevel.startLevel > highestStartLevel) {
                                    highestStartLevel = typeRenderletStartLevel.startLevel;
                                    bestRenderlet = typeRenderletStartLevel.renderlet;
                                }
                            }
                            return new TypeRenderletRendererImpl(
                                bestRenderlet,
                                acceptableType,
                                this, graphNodeProvider,
                                bundleContext);
                        }
                    }
                }
            }
        }
        return null;
    }

    protected void bindTypeRenderlet(ServiceReference serviceReference) {
        if (bundleContext == null) {
            pendingRenderletRegistrations.add(serviceReference);
        } else {
            registerTypeRenderlet(serviceReference);
        }
    }

    private void registerTypeRenderlet(ServiceReference serviceReference) {
        int startLevel = startLevelService.getBundleStartLevel(serviceReference.getBundle());
        TypeRenderlet renderlet = (TypeRenderlet) bundleContext.getService(serviceReference);
        registerRenderlet(renderlet, startLevel);
    }

    private void registerRenderlet(TypeRenderlet typeRenderlet, int startLevel) {
        final UriRef rdfType = typeRenderlet.getRdfType();
        RegexMap<MediaTypeMap<TypeRenderletStartLevel>> regexMap = typeRenderletMap.get(rdfType);
        if (regexMap == null) {
            regexMap = new RegexMap<MediaTypeMap<TypeRenderletStartLevel>>();
            typeRenderletMap.put(rdfType, regexMap);
        }
        final String modePattern = typeRenderlet.getModePattern();
        MediaTypeMap<TypeRenderletStartLevel> mediaTypeMap = regexMap.getFirstExactMatch(modePattern);
        if (mediaTypeMap == null) {
            mediaTypeMap = new MediaTypeMap<TypeRenderletStartLevel>();
            regexMap.addEntry(modePattern, mediaTypeMap);
        }
        final MediaType mediaType = typeRenderlet.getMediaType();
        mediaTypeMap.addEntry(mediaType, new TypeRenderletStartLevel(typeRenderlet, startLevel));
    }

    protected void unbindTypeRenderlet(TypeRenderlet typeRenderlet) {
        TypeRenderletStartLevel typeRenderletStartLevel = new TypeRenderletStartLevel(typeRenderlet, 0);
        for (Map.Entry<UriRef, RegexMap<MediaTypeMap<TypeRenderletStartLevel>>> typeEntry: typeRenderletMap.entrySet()) {
            final RegexMap<MediaTypeMap<TypeRenderletStartLevel>> regexMap = typeEntry.getValue();
            for (Map.Entry<String, MediaTypeMap<TypeRenderletStartLevel>> regexEntry: regexMap.entrySet()) {
                final MediaTypeMap<TypeRenderletStartLevel> mediaTypeMap = regexEntry.getValue();
                if (mediaTypeMap.remove(typeRenderletStartLevel)) {
                    //for now we just leave the potentially empty mediaTypeMap there
                    //IMPROVEMENT remove without entries
                    return;
                }
            }
        }
    }

}
