using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Umbraco.Cms.Core.Cache;

namespace Umbraco.Cms.Core.PublishedCache
{

    /// <summary>
    /// Creates and manages <see cref="IPublishedSnapshot"/> instances.
    /// </summary>
    public interface IPublishedSnapshotService : IDisposable
    {
        /* Various places (such as Node) want to access the XML content, today as an XmlDocument
         * but to migrate to a new cache, they're migrating to an XPathNavigator. Still, they need
         * to find out how to get that navigator.
         *
         * Because a cache such as NuCache is contextual i.e. it has a "snapshot" thing and remains
         * consistent over the snapshot, the navigator has to come from the "current" snapshot.
         *
         * So although everything should be injected... we also need a notion of "the current published
         * snapshot". This is provided by the IPublishedSnapshotAccessor.
         *
         */

        /// <summary>
        /// Creates a published snapshot.
        /// </summary>
        /// <param name="previewToken">A preview token, or <c>null</c> if not previewing.</param>
        /// <returns>A published snapshot.</returns>
        /// <remarks>If <paramref name="previewToken"/> is null, the snapshot is not previewing, else it
        /// is previewing, and what is or is not visible in preview depends on the content of the token,
        /// which is not specified and depends on the actual published snapshot service implementation.</remarks>
        IPublishedSnapshot CreatePublishedSnapshot(string? previewToken);

        /// <summary>
        /// Rebuilds internal database caches (but does not reload).
        /// </summary>
        /// <param name="contentTypeIds">If not null will process content for the matching content types, if empty will process all content</param>
        /// <param name="mediaTypeIds">If not null will process content for the matching media types, if empty will process all media</param>
        /// <param name="memberTypeIds">If not null will process content for the matching members types, if empty will process all members</param>
        /// <remarks>
        /// <para>Forces the snapshot service to rebuild its internal database caches. For instance, some caches
        /// may rely on a database table to store pre-serialized version of documents.</para>
        /// <para>This does *not* reload the caches. Caches need to be reloaded, for instance via
        /// <see cref="DistributedCache" /> RefreshAllPublishedSnapshot method.</para>
        /// </remarks>
        void Rebuild(
            IReadOnlyCollection<int>? contentTypeIds = null,
            IReadOnlyCollection<int>? mediaTypeIds = null,
            IReadOnlyCollection<int>? memberTypeIds = null);

        /* An IPublishedCachesService implementation can rely on transaction-level events to update
         * its internal, database-level data, as these events are purely internal. However, it cannot
         * rely on cache refreshers CacheUpdated events to update itself, as these events are external
         * and the order-of-execution of the handlers cannot be guaranteed, which means that some
         * user code may run before Umbraco is finished updating itself. Instead, the cache refreshers
         * explicitly notify the service of changes.
         *
         */

        /// <summary>
        /// Notifies of content cache refresher changes.
        /// </summary>
        /// <param name="payloads">The changes.</param>
        /// <param name="draftChanged">A value indicating whether draft contents have been changed in the cache.</param>
        /// <param name="publishedChanged">A value indicating whether published contents have been changed in the cache.</param>
        void Notify(ContentCacheRefresher.JsonPayload[] payloads, out bool draftChanged, out bool publishedChanged);

        /// <summary>
        /// Notifies of media cache refresher changes.
        /// </summary>
        /// <param name="payloads">The changes.</param>
        /// <param name="anythingChanged">A value indicating whether medias have been changed in the cache.</param>
        void Notify(MediaCacheRefresher.JsonPayload[] payloads, out bool anythingChanged);

        // there is no NotifyChanges for MemberCacheRefresher because we're not caching members.

        /// <summary>
        /// Notifies of content type refresher changes.
        /// </summary>
        /// <param name="payloads">The changes.</param>
        void Notify(ContentTypeCacheRefresher.JsonPayload[] payloads);

        /// <summary>
        /// Notifies of data type refresher changes.
        /// </summary>
        /// <param name="payloads">The changes.</param>
        void Notify(DataTypeCacheRefresher.JsonPayload[] payloads);

        /// <summary>
        /// Notifies of domain refresher changes.
        /// </summary>
        /// <param name="payloads">The changes.</param>
        void Notify(DomainCacheRefresher.JsonPayload[] payloads);

        /// <summary>
        /// Cleans up unused snapshots
        /// </summary>
        Task CollectAsync();
    }
}
