/*
 * Copyright (c) 2015 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.mdsal.binding.dom.adapter;

import static java.util.Objects.requireNonNull;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import java.time.Instant;
import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.mdsal.binding.dom.codec.api.BindingNormalizedNodeSerializer;
import org.opendaylight.mdsal.binding.spec.reflect.BindingReflections;
import org.opendaylight.mdsal.dom.api.DOMEvent;
import org.opendaylight.mdsal.dom.api.DOMNotification;
import org.opendaylight.yangtools.yang.binding.Notification;
import org.opendaylight.yangtools.yang.data.api.schema.ContainerNode;
import org.opendaylight.yangtools.yang.model.api.stmt.SchemaNodeIdentifier.Absolute;

/**
 * Lazy serialized implementation of DOM Notification.
 *
 * <p>
 * This implementation performs serialization of data, only if receiver of notification actually accessed data from
 * notification.
 */
final class LazySerializedDOMNotification implements DOMNotification, DOMEvent {
    private static final LoadingCache<Class<?>, Absolute> PATHS = CacheBuilder.newBuilder().weakKeys()
        .build(new CacheLoader<Class<?>, Absolute>() {
            @Override
            public Absolute load(final Class<?> key) {
                // TODO: for nested (YANG 1.1) notifications we will need the SchemaNodeIdentifier where the
                //       notification is being invoked and use that instead of ROOT. How Binding users will refer to
                //       it is TBD (but probably InstanceIdentifier, which means we will need to do some lifting to
                //       find the SchemaNodeIdentifier), as we will need to deal with the same multiplicies we need
                //       for data due to grouping-based reuse.
                return Absolute.of(BindingReflections.findQName(key)).intern();
            }
        });

    private final @NonNull BindingNormalizedNodeSerializer codec;
    private final @NonNull Notification data;
    private final @NonNull Absolute type;
    private final @NonNull Instant eventInstant;

    private volatile ContainerNode domBody;

    LazySerializedDOMNotification(final BindingNormalizedNodeSerializer codec, final Notification data,
            final Absolute type, final Instant eventInstant) {
        this.codec = requireNonNull(codec);
        this.data = requireNonNull(data);
        this.type = requireNonNull(type);
        this.eventInstant = requireNonNull(eventInstant);
    }

    static @NonNull DOMNotification create(final BindingNormalizedNodeSerializer codec, final Notification data,
            final Instant eventInstant) {
        final Absolute type = PATHS.getUnchecked(data.implementedInterface());
        return new LazySerializedDOMNotification(codec, data, type, eventInstant);
    }

    @Override
    public Absolute getType() {
        return type;
    }

    @Override
    public ContainerNode getBody() {
        ContainerNode local = domBody;
        if (local == null) {
            domBody = local = codec.toNormalizedNodeNotification(data);
        }
        return local;
    }

    @Override
    public Instant getEventInstant() {
        return eventInstant;
    }

    @NonNull Notification getBindingData() {
        return data;
    }
}