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

using System.Linq;
using System.Threading.Tasks;
using Squidex.Domain.Apps.Core.Contents;
using Squidex.Domain.Apps.Entities.Contents;
using Squidex.Domain.Apps.Entities.Contents.Commands;
using Squidex.Infrastructure;
using Squidex.Infrastructure.Commands;
using Squidex.Infrastructure.Json.Objects;

namespace Squidex.Extensions.Samples.Middleware
{
    public sealed class DoubleLinkedContentMiddleware : ICustomCommandMiddleware
    {
        private readonly IContentLoader contentLoader;

        public DoubleLinkedContentMiddleware(IContentLoader contentLoader)
        {
            this.contentLoader = contentLoader;
        }

        public async Task HandleAsync(CommandContext context, NextDelegate next)
        {
            await next(context);

            if (context.Command is UpdateContent update && context.IsCompleted && update.SchemaId.Name == "source")
            {
                // After a change is made, the content is put to the command context.
                var content = context.Result<IContentEntity>();

                var contentPrevious =
                    await contentLoader.GetAsync(
                        content.AppId.Id,
                        content.Id,
                        content.Version - 1);

                // The data might have been changed within the domain object. Therefore we do not use the data fro mthe command.
                var oldReferenceId = GetReference(contentPrevious?.Data);
                var newReferenceId = GetReference(content.Data);

                // If nothing has been changed we can just stop here.
                if (newReferenceId == oldReferenceId)
                {
                    return;
                }

                if (oldReferenceId != null)
                {
                    var oldReferenced = await contentLoader.GetAsync(content.AppId.Id, DomainId.Create(oldReferenceId));

                    if (oldReferenced != null)
                    {
                        var data = oldReferenced.Data.Clone();

                        // Remove the reference from the old referenced content.
                        data.Remove("referencing");

                        await UpdateReferencing(context, oldReferenced, data);
                    }
                }

                if (newReferenceId != null)
                {
                    var newReferenced = await contentLoader.GetAsync(content.AppId.Id, DomainId.Create(newReferenceId));

                    if (newReferenced != null)
                    {
                        var data = newReferenced.Data.Clone();

                        // Add the reference to the new referenced content.
                        data["referencing"] = new ContentFieldData
                        {
                            ["iv"] = JsonValue.Array(content.Id)
                        };

                        await UpdateReferencing(context, newReferenced, data);
                    }
                }
            }
        }

        private static async Task UpdateReferencing(CommandContext context, IContentEntity reference, ContentData data)
        {
            await context.CommandBus.PublishAsync(new UpdateContent
            {
                AppId = reference.AppId,
                SchemaId = reference.SchemaId,
                ContentId = reference.Id,
                DoNotScript = true,
                DoNotValidate = true,
                Data = data,
                // Also set the expected version, otherwise it will be overriden with the version from the request.
                ExpectedVersion = reference.Version
            });
        }

        private static string GetReference(ContentData data)
        {
            if (data != null && data.TryGetValue("reference", out ContentFieldData fieldData))
            {
                return fieldData.Values.OfType<JsonArray>().SelectMany(x => x).SingleOrDefault()?.ToString();
            }

            return null;
        }
    }
}