// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschraenkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

using GraphQL.DataLoader;
using Squidex.Domain.Apps.Entities.Assets;
using Squidex.Domain.Apps.Entities.Contents.Queries;
using Squidex.Infrastructure;
using Squidex.Infrastructure.Json.Objects;
using Squidex.Shared.Users;

namespace Squidex.Domain.Apps.Entities.Contents.GraphQL
{
    public sealed class GraphQLExecutionContext : QueryExecutionContext
    {
        private static readonly List<IEnrichedAssetEntity> EmptyAssets = new List<IEnrichedAssetEntity>();
        private static readonly List<IEnrichedContentEntity> EmptyContents = new List<IEnrichedContentEntity>();
        private readonly IDataLoaderContextAccessor dataLoaders;

        public override Context Context { get; }

        public GraphQLExecutionContext(
            IDataLoaderContextAccessor dataLoaders,
            IAssetQueryService assetQuery,
            IAssetCache assetCache,
            IContentQueryService contentQuery,
            IContentCache contentCache,
            IServiceProvider serviceProvider,
            Context context)
            : base(assetQuery, assetCache, contentQuery, contentCache, serviceProvider)
        {
            this.dataLoaders = dataLoaders;

            Context = context.Clone(b => b
                .WithoutCleanup()
                .WithoutContentEnrichment());
        }

        public async ValueTask<IUser?> FindUserAsync(RefToken refToken,
            CancellationToken ct)
        {
            if (refToken.IsClient)
            {
                return new ClientUser(refToken);
            }
            else
            {
                var dataLoader = GetUserLoader();

                return await dataLoader.LoadAsync(refToken.Identifier).GetResultAsync(ct);
            }
        }

        public async Task<IEnrichedAssetEntity?> FindAssetAsync(DomainId id,
            CancellationToken ct)
        {
            var dataLoader = GetAssetsLoader();

            return await dataLoader.LoadAsync(id).GetResultAsync(ct);
        }

        public async Task<IContentEntity?> FindContentAsync(DomainId schemaId, DomainId id,
            CancellationToken ct)
        {
            var dataLoader = GetContentsLoader();

            var content = await dataLoader.LoadAsync(id).GetResultAsync(ct);

            if (content?.SchemaId.Id != schemaId)
            {
                content = null;
            }

            return content;
        }

        public Task<IReadOnlyList<IEnrichedAssetEntity>> GetReferencedAssetsAsync(JsonValue value, TimeSpan cacheDuration,
            CancellationToken ct)
        {
            var ids = ParseIds(value);

            return GetAssetsAsync(ids, cacheDuration, ct);
        }

        public async Task<IReadOnlyList<IEnrichedAssetEntity>> GetAssetsAsync(List<DomainId>? ids, TimeSpan cacheDuration,
            CancellationToken ct)
        {
            if (ids == null || ids.Count == 0)
            {
                return EmptyAssets;
            }

            async Task<IReadOnlyList<IEnrichedAssetEntity>> LoadAsync(IEnumerable<DomainId> ids)
            {
                var result = await GetAssetsLoader().LoadAsync(ids).GetResultAsync(ct);

                return result?.NotNull().ToList() ?? EmptyAssets;
            }

            if (cacheDuration > TimeSpan.Zero)
            {
                var assets = await AssetCache.CacheOrQueryAsync(ids, async pendingIds =>
                {
                    return await LoadAsync(pendingIds);
                }, cacheDuration);

                return assets;
            }

            return await LoadAsync(ids);
        }

        public Task<IReadOnlyList<IEnrichedContentEntity>> GetReferencedContentsAsync(JsonValue value, TimeSpan cacheDuration,
            CancellationToken ct)
        {
            var ids = ParseIds(value);

            return GetContentsAsync(ids, cacheDuration, ct);
        }

        public async Task<IReadOnlyList<IEnrichedContentEntity>> GetContentsAsync(List<DomainId>? ids, TimeSpan cacheDuration,
            CancellationToken ct)
        {
            if (ids == null || ids.Count == 0)
            {
                return EmptyContents;
            }

            async Task<IReadOnlyList<IEnrichedContentEntity>> LoadAsync(IEnumerable<DomainId> ids)
            {
                var result = await GetContentsLoader().LoadAsync(ids).GetResultAsync(ct);

                return result?.NotNull().ToList() ?? EmptyContents;
            }

            if (cacheDuration > TimeSpan.Zero)
            {
                var contents = await ContentCache.CacheOrQueryAsync(ids, async pendingIds =>
                {
                    return await LoadAsync(pendingIds);
                }, cacheDuration);

                return contents.ToList();
            }

            return await LoadAsync(ids);
        }

        private IDataLoader<DomainId, IEnrichedAssetEntity> GetAssetsLoader()
        {
            return dataLoaders.Context!.GetOrAddBatchLoader<DomainId, IEnrichedAssetEntity>(nameof(GetAssetsLoader),
                async (batch, ct) =>
                {
                    var result = await GetReferencedAssetsAsync(new List<DomainId>(batch), ct);

                    return result.ToDictionary(x => x.Id);
                });
        }

        private IDataLoader<DomainId, IEnrichedContentEntity> GetContentsLoader()
        {
            return dataLoaders.Context!.GetOrAddBatchLoader<DomainId, IEnrichedContentEntity>(nameof(GetContentsLoader),
                async (batch, ct) =>
                {
                    var result = await GetReferencedContentsAsync(new List<DomainId>(batch), ct);

                    return result.ToDictionary(x => x.Id);
                });
        }

        private IDataLoader<string, IUser> GetUserLoader()
        {
            return dataLoaders.Context!.GetOrAddBatchLoader<string, IUser>(nameof(GetUserLoader),
                async (batch, ct) =>
                {
                    var result = await Resolve<IUserResolver>().QueryManyAsync(batch.ToArray(), ct);

                    return result;
                });
        }

        private static List<DomainId>? ParseIds(JsonValue value)
        {
            try
            {
                List<DomainId>? result = null;

                if (value.Value is JsonArray a)
                {
                    foreach (var item in a)
                    {
                        if (item.Value is string id)
                        {
                            result ??= new List<DomainId>();
                            result.Add(DomainId.Create(id));
                        }
                    }
                }

                return result;
            }
            catch
            {
                return null;
            }
        }
    }
}