/*
 * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.yangtools.yang.model.repo.util;

import com.google.common.base.Preconditions;

import org.opendaylight.yangtools.yang.model.repo.api.SchemaSourceRepresentation;
import org.opendaylight.yangtools.yang.model.repo.api.SourceIdentifier;
import org.opendaylight.yangtools.yang.model.repo.spi.PotentialSchemaSource;
import org.opendaylight.yangtools.yang.model.repo.spi.PotentialSchemaSource.Costs;
import org.opendaylight.yangtools.yang.model.repo.spi.SchemaSourceListener;
import org.opendaylight.yangtools.yang.model.repo.spi.SchemaSourceProvider;
import org.opendaylight.yangtools.yang.model.repo.spi.SchemaSourceRegistration;
import org.opendaylight.yangtools.yang.model.repo.spi.SchemaSourceRegistry;

/**
 * Abstract base class for cache-type SchemaSourceListeners. It needs to be
 * registered with a {@link SchemaSourceRegistry}, where it gets notifications
 * from. It performs filtering and {@link #offer(SchemaSourceRepresentation)}s
 * conforming sources to the subclass.
 *
 * @param <T> Cached schema source type.
 */
public abstract class AbstractSchemaSourceCache<T extends SchemaSourceRepresentation> implements SchemaSourceListener, SchemaSourceProvider<T> {
    private final SchemaSourceRegistry consumer;
    private final Class<T> representation;
    private final Costs cost;

    protected AbstractSchemaSourceCache(final SchemaSourceRegistry consumer, final Class<T> representation, final Costs cost) {
        this.consumer = Preconditions.checkNotNull(consumer);
        this.representation = Preconditions.checkNotNull(representation);
        this.cost = Preconditions.checkNotNull(cost);
    }

    /**
     * Offer a schema source in requested representation for caching. Subclasses
     * need to implement this method to store the schema source. Once they have
     * determined to cache the source, they should call {@link #register(SourceIdentifier)}.
     *
     * @param source schema source
     */
    protected abstract void offer(T source);

    /**
     * Register the presence of a cached schema source with the consumer. Subclasses
     * need to call this method once they have cached a schema source representation,
     * or when they have determined they have a schema source is available -- like
     * when a persistent cache reads its cache index.
     *
     * @param sourceIdentifier Source identifier
     * @return schema source registration, which the subclass needs to
     *         {@link SchemaSourceRegistration#close()} once it expunges the source
     *         from the cache.
     */
    protected final SchemaSourceRegistration<T> register(final SourceIdentifier sourceIdentifier) {
        final PotentialSchemaSource<T> src = PotentialSchemaSource.create(sourceIdentifier, representation, cost.getValue());
        return consumer.registerSchemaSource(this, src);
    }

    @Override
    public void schemaSourceEncountered(final SchemaSourceRepresentation source) {
        if (representation.isAssignableFrom(source.getType())) {
            @SuppressWarnings("unchecked")
            final T src = (T)source;
            offer(src);
        }
    }

    @Override
    public final void schemaSourceRegistered(final Iterable<PotentialSchemaSource<?>> sources) {
        // Not interesting
    }

    @Override
    public final void schemaSourceUnregistered(final PotentialSchemaSource<?> source) {
        // Not interesting
    }
}