// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using osu.Framework.Platform;
using osu.Game.Database;
using osu.Game.Extensions;
using osu.Game.IO.Archives;
using osu.Game.Models;
using osu.Game.Overlays.Notifications;
using Realms;

#nullable enable

namespace osu.Game.Stores
{
    /// <summary>
    /// Class which adds all the missing pieces bridging the gap between <see cref="RealmArchiveModelImporter{TModel}"/> and (legacy) ArchiveModelManager.
    /// </summary>
    public abstract class RealmArchiveModelManager<TModel> : RealmArchiveModelImporter<TModel>, IModelManager<TModel>, IModelFileManager<TModel, RealmNamedFileUsage>
        where TModel : RealmObject, IHasRealmFiles, IHasGuidPrimaryKey, ISoftDelete
    {
        private readonly RealmFileStore realmFileStore;

        protected RealmArchiveModelManager(Storage storage, RealmContextFactory contextFactory)
            : base(storage, contextFactory)
        {
            realmFileStore = new RealmFileStore(contextFactory, storage);
        }

        public void DeleteFile(TModel item, RealmNamedFileUsage file) =>
            performFileOperation(item, managed => DeleteFile(managed, managed.Files.First(f => f.Filename == file.Filename), managed.Realm));

        public void ReplaceFile(TModel item, RealmNamedFileUsage file, Stream contents) =>
            performFileOperation(item, managed => ReplaceFile(file, contents, managed.Realm));

        public void AddFile(TModel item, Stream contents, string filename) =>
            performFileOperation(item, managed => AddFile(managed, contents, filename, managed.Realm));

        private void performFileOperation(TModel item, Action<TModel> operation)
        {
            // While we are detaching so often, this seems like the easiest way to keep things in sync.
            // This method should be removed as soon as all the surrounding pieces support non-detached operations.
            if (!item.IsManaged)
            {
                var managed = ContextFactory.Context.Find<TModel>(item.ID);
                managed.Realm.Write(() => operation(managed));

                item.Files.Clear();
                item.Files.AddRange(managed.Files.Detach());
            }
            else
                operation(item);
        }

        /// <summary>
        /// Delete a file from within an ongoing realm transaction.
        /// </summary>
        protected void DeleteFile(TModel item, RealmNamedFileUsage file, Realm realm)
        {
            item.Files.Remove(file);
        }

        /// <summary>
        /// Replace a file from within an ongoing realm transaction.
        /// </summary>
        protected void ReplaceFile(RealmNamedFileUsage file, Stream contents, Realm realm)
        {
            file.File = realmFileStore.Add(contents, realm);
        }

        /// <summary>
        /// Add a file from within an ongoing realm transaction. If the file already exists, it is overwritten.
        /// </summary>
        protected void AddFile(TModel item, Stream contents, string filename, Realm realm)
        {
            var existing = item.Files.FirstOrDefault(f => string.Equals(f.Filename, filename, StringComparison.OrdinalIgnoreCase));

            if (existing != null)
            {
                ReplaceFile(existing, contents, realm);
                return;
            }

            var file = realmFileStore.Add(contents, realm);
            var namedUsage = new RealmNamedFileUsage(file, filename);

            item.Files.Add(namedUsage);
        }

        public override async Task<ILive<TModel>?> Import(TModel item, ArchiveReader? archive = null, bool lowPriority = false, CancellationToken cancellationToken = default)
        {
            return await base.Import(item, archive, lowPriority, cancellationToken).ConfigureAwait(false);
        }

        /// <summary>
        /// Delete multiple items.
        /// This will post notifications tracking progress.
        /// </summary>
        public void Delete(List<TModel> items, bool silent = false)
        {
            if (items.Count == 0) return;

            var notification = new ProgressNotification
            {
                Progress = 0,
                Text = $"Preparing to delete all {HumanisedModelName}s...",
                CompletionText = $"Deleted all {HumanisedModelName}s!",
                State = ProgressNotificationState.Active,
            };

            if (!silent)
                PostNotification?.Invoke(notification);

            int i = 0;

            foreach (var b in items)
            {
                if (notification.State == ProgressNotificationState.Cancelled)
                    // user requested abort
                    return;

                notification.Text = $"Deleting {HumanisedModelName}s ({++i} of {items.Count})";

                Delete(b);

                notification.Progress = (float)i / items.Count;
            }

            notification.State = ProgressNotificationState.Completed;
        }

        /// <summary>
        /// Restore multiple items that were previously deleted.
        /// This will post notifications tracking progress.
        /// </summary>
        public void Undelete(List<TModel> items, bool silent = false)
        {
            if (!items.Any()) return;

            var notification = new ProgressNotification
            {
                CompletionText = "Restored all deleted items!",
                Progress = 0,
                State = ProgressNotificationState.Active,
            };

            if (!silent)
                PostNotification?.Invoke(notification);

            int i = 0;

            foreach (var item in items)
            {
                if (notification.State == ProgressNotificationState.Cancelled)
                    // user requested abort
                    return;

                notification.Text = $"Restoring ({++i} of {items.Count})";

                Undelete(item);

                notification.Progress = (float)i / items.Count;
            }

            notification.State = ProgressNotificationState.Completed;
        }

        public bool Delete(TModel item)
        {
            using (var realm = ContextFactory.CreateContext())
            {
                if (!item.IsManaged)
                    item = realm.Find<TModel>(item.ID);

                if (item?.DeletePending != false)
                    return false;

                realm.Write(r => item.DeletePending = true);
                return true;
            }
        }

        public void Undelete(TModel item)
        {
            using (var realm = ContextFactory.CreateContext())
            {
                if (!item.IsManaged)
                    item = realm.Find<TModel>(item.ID);

                if (item?.DeletePending != true)
                    return;

                realm.Write(r => item.DeletePending = false);
            }
        }

        public abstract bool IsAvailableLocally(TModel model);
    }
}