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

using System;
using System.Collections.Concurrent;
using System.Threading.Tasks;
using System.Threading.Tasks.Dataflow;
using Squidex.Domain.Apps.Entities.Assets.Commands;
using Squidex.Domain.Apps.Entities.Contents;
using Squidex.Infrastructure;
using Squidex.Infrastructure.Commands;
using Squidex.Infrastructure.Reflection;
using Squidex.Shared;

#pragma warning disable SA1313 // Parameter names should begin with lower-case letter
#pragma warning disable RECS0082 // Parameter has the same name as a member and hides it

namespace Squidex.Domain.Apps.Entities.Assets.DomainObject
{
    public sealed class AssetsBulkUpdateCommandMiddleware : ICommandMiddleware
    {
        private readonly IContextProvider contextProvider;

        private sealed record BulkTaskCommand(BulkTask Task, DomainId Id, ICommand Command)
        {
        }

        private sealed record BulkTask(
            ICommandBus Bus,
            int JobIndex,
            BulkUpdateJob Job,
            BulkUpdateAssets Command,
            ConcurrentBag<BulkUpdateResultItem> Results
        )
        {
        }

        public AssetsBulkUpdateCommandMiddleware(IContextProvider contextProvider)
        {
            Guard.NotNull(contextProvider, nameof(contextProvider));

            this.contextProvider = contextProvider;
        }

        public async Task HandleAsync(CommandContext context, NextDelegate next)
        {
            if (context.Command is BulkUpdateAssets bulkUpdates)
            {
                if (bulkUpdates.Jobs?.Length > 0)
                {
                    var executionOptions = new ExecutionDataflowBlockOptions
                    {
                        MaxDegreeOfParallelism = Math.Max(1, Environment.ProcessorCount / 2)
                    };

                    var createCommandsBlock = new TransformBlock<BulkTask, BulkTaskCommand?>(task =>
                    {
                        return CreateCommand(task);
                    }, executionOptions);

                    var executeCommandBlock = new ActionBlock<BulkTaskCommand?>(async command =>
                    {
                        if (command != null)
                        {
                            await ExecuteCommandAsync(command);
                        }
                    }, executionOptions);

                    createCommandsBlock.LinkTo(executeCommandBlock, new DataflowLinkOptions
                    {
                        PropagateCompletion = true
                    });

                    contextProvider.Context.Change(b => b
                        .WithoutAssetEnrichment()
                        .WithoutCleanup()
                        .WithUnpublished(true)
                        .WithoutTotal());

                    var results = new ConcurrentBag<BulkUpdateResultItem>();

                    for (var i = 0; i < bulkUpdates.Jobs.Length; i++)
                    {
                        var task = new BulkTask(
                            context.CommandBus,
                            i,
                            bulkUpdates.Jobs[i],
                            bulkUpdates,
                            results);

                        await createCommandsBlock.SendAsync(task);
                    }

                    createCommandsBlock.Complete();

                    await executeCommandBlock.Completion;

                    context.Complete(new BulkUpdateResult(results));
                }
                else
                {
                    context.Complete(new BulkUpdateResult());
                }
            }
            else
            {
                await next(context);
            }
        }

        private static async Task ExecuteCommandAsync(BulkTaskCommand bulkCommand)
        {
            var (task, id, command) = bulkCommand;

            Exception? exception = null;
            try
            {
                await task.Bus.PublishAsync(command);
            }
            catch (Exception ex)
            {
                exception = ex;
            }

            task.Results.Add(new BulkUpdateResultItem
            {
                Id = id,
                JobIndex = task.JobIndex,
                Exception = exception
            });
        }

        private BulkTaskCommand? CreateCommand(BulkTask task)
        {
            var id = task.Job.Id;

            try
            {
                var command = CreateCommandCore(task);

                command.AssetId = id;

                return new BulkTaskCommand(task, id, command);
            }
            catch (Exception ex)
            {
                task.Results.Add(new BulkUpdateResultItem
                {
                    Id = id,
                    JobIndex = task.JobIndex,
                    Exception = ex
                });

                return null;
            }
        }

        private AssetCommand CreateCommandCore(BulkTask task)
        {
            var job = task.Job;

            switch (job.Type)
            {
                case BulkUpdateAssetType.Annotate:
                    {
                        var command = new AnnotateAsset();

                        EnrichAndCheckPermission(task, command, Permissions.AppAssetsUpdate);
                        return command;
                    }

                case BulkUpdateAssetType.Move:
                    {
                        var command = new MoveAsset();

                        EnrichAndCheckPermission(task, command, Permissions.AppAssetsUpdate);
                        return command;
                    }

                case BulkUpdateAssetType.Delete:
                    {
                        var command = new DeleteAsset();

                        EnrichAndCheckPermission(task, command, Permissions.AppAssetsDelete);
                        return command;
                    }

                default:
                    throw new NotSupportedException();
            }
        }

        private void EnrichAndCheckPermission<T>(BulkTask task, T command, string permissionId) where T : AssetCommand
        {
            SimpleMapper.Map(task.Command, command);
            SimpleMapper.Map(task.Job, command);

            if (!contextProvider.Context.Allows(permissionId))
            {
                throw new DomainForbiddenException("Forbidden");
            }

            command.ExpectedVersion = task.Command.ExpectedVersion;
        }
    }
}