using Data.SeaHavenIndustries;
using Microsoft.EntityFrameworkCore;
using SeaHaven.DataServices.Interfaces;

namespace SeaHaven.DataServices.Implementation
{
    public sealed class WorkOrderWebhookDataService : IWorkOrderWebhookDataService
    {
        private static readonly SemaphoreSlim InMemoryNumberLock = new(1, 1);
        private readonly ApplicationDbContext _context;

        public WorkOrderWebhookDataService(ApplicationDbContext context)
        {
            _context = context;
        }

        public async Task<WorkOrderWebhookPersistenceResult> ApplyAsync(
            WorkOrderWebhookMutation mutation,
            CancellationToken cancellationToken)
        {
            var prior = await _context.WorkOrderWebhookDeliveries
                .AsNoTracking()
                .SingleOrDefaultAsync(d => d.DeliveryId == mutation.DeliveryId, cancellationToken);

            if (prior != null)
                return ExistingDeliveryResult(prior, mutation.BodySha256);

            var workOrder = await _context.workOrders
                .SingleOrDefaultAsync(
                    w => w.ExternalWorkOrderId == mutation.ExternalWorkOrderId,
                    cancellationToken);

            if (workOrder == null)
            {
                var internalNumber = await AllocateInternalNumberAsync(cancellationToken);
                workOrder = new WorkOrder
                {
                    ExternalWorkOrderId = mutation.ExternalWorkOrderId,
                    ExternalSource = mutation.Source,
                    WorkerOrderNumber = mutation.WorkerOrderNumber,
                    InternalWONumber = internalNumber.ToString("D11"),
                    WorkerOrderTitle = mutation.Title ?? mutation.Description
                        ?? $"Imported work order {mutation.ExternalWorkOrderId}",
                    Description = mutation.Description,
                    Source = mutation.Source,
                    istemplate = false,
                    CreatedDate = mutation.CreatedAt ?? mutation.ProcessedAt.UtcDateTime
                };
                _context.workOrders.Add(workOrder);
            }

            var staleState = mutation.IsStateEvent
                && !IsNewer(
                    mutation.UpdatedAt,
                    mutation.VersionHash,
                    workOrder.ExternalUpdatedAt,
                    workOrder.ExternalVersionHash);

            if (mutation.IsStateEvent && !staleState)
            {
                var locationKey = mutation.SiteCode ?? mutation.Building;
                if (!string.IsNullOrWhiteSpace(locationKey))
                {
                    var locationIsNewer = await UpsertReceiptAsync(
                        mutation.Source,
                        "location",
                        locationKey,
                        mutation.UpdatedAt,
                        mutation.VersionHash,
                        mutation.ProcessedAt,
                        cancellationToken);
                    var location = await _context.Locations
                        .FirstOrDefaultAsync(
                            l => l.ExternalSource == mutation.Source
                                && l.ExternalLocationId == locationKey,
                            cancellationToken);
                    if (location == null)
                    {
                        location = new Locations
                        {
                            ExternalSource = mutation.Source,
                            ExternalLocationId = locationKey,
                            Name = locationKey,
                            Title = mutation.Building,
                            Address1 = mutation.Address,
                            Status = "Active"
                        };
                        _context.Locations.Add(location);
                    }
                    else if (locationIsNewer)
                    {
                        location.Name = locationKey;
                        location.Title = mutation.Building;
                        location.Address1 = mutation.Address;
                        location.Status = "Active";
                    }

                    workOrder.Locations = location;
                }

                workOrder.WorkerOrderNumber = mutation.WorkerOrderNumber;
                workOrder.WorkerOrderTitle = mutation.Title ?? mutation.Description;
                workOrder.Description = mutation.Description;
                workOrder.Status = mutation.IsCancelled ? "Cancelled" : mutation.Status;
                if (mutation.LifecycleStatus.HasValue)
                    workOrder.LifecycleStatus = mutation.LifecycleStatus.Value;
                workOrder.Severity = mutation.Severity;
                workOrder.Priority = mutation.Priority;
                workOrder.ExternalAssignedTo = mutation.AssignedTo;
                workOrder.ExternalRecordType = mutation.RecordType;
                workOrder.Customer = mutation.Customer;
                workOrder.SiteCode = mutation.SiteCode;
                workOrder.Building = mutation.Building;
                workOrder.DueDate = mutation.DueDate;
                workOrder.DateReported = mutation.DateReported;
                workOrder.ScheduledStart = mutation.ScheduledStart;
                workOrder.Source = mutation.Source;
                workOrder.SourceEmailS3Key = mutation.SourceEmailS3Key;
                workOrder.ExternalSource = mutation.Source;
                workOrder.istemplate = false;
                workOrder.ExternalLastOccurredAt = mutation.OccurredAt;
                workOrder.ExternalUpdatedAt = mutation.UpdatedAt;
                workOrder.ExternalVersionHash = mutation.VersionHash;
            }

            if (mutation.CommentId != null)
            {
                var receiptIsNewer = await UpsertReceiptAsync(
                    mutation.Source,
                    "comment",
                    mutation.CommentId,
                    mutation.UpdatedAt,
                    mutation.VersionHash,
                    mutation.ProcessedAt,
                    cancellationToken);
                var comment = await _context.Comments
                    .SingleOrDefaultAsync(
                        c => c.ExternalSource == mutation.Source
                            && c.ExternalCommentId == mutation.CommentId,
                        cancellationToken);

                if (comment == null)
                {
                    comment = new Comments
                    {
                        ExternalSource = mutation.Source,
                        ExternalCommentId = mutation.CommentId,
                        RecordType = "WorkOrder",
                        WorkOrder = workOrder,
                        CreatedDate = mutation.OccurredAt.UtcDateTime,
                    };
                    _context.Comments.Add(comment);
                }

                if (receiptIsNewer)
                {
                    comment.Commenttext = mutation.CommentText;
                    comment.Commenter = mutation.Commenter;
                    comment.CommentType = mutation.CommentType;
                    comment.ExternalUpdatedAt = mutation.UpdatedAt;
                    comment.ExternalVersionHash = mutation.VersionHash;
                    comment.ExternalSourceEmailS3Key = mutation.SourceEmailS3Key;
                }
            }

            _context.WorkOrderWebhookDeliveries.Add(new WorkOrderWebhookDelivery
            {
                DeliveryId = mutation.DeliveryId,
                EventType = mutation.EventType,
                OccurredAt = mutation.OccurredAt,
                ProcessedAt = mutation.ProcessedAt,
                BodySha256 = mutation.BodySha256
            });

            try
            {
                await _context.SaveChangesAsync(cancellationToken);
                return new WorkOrderWebhookPersistenceResult(
                    WorkOrderWebhookPersistenceStatus.Applied,
                    staleState);
            }
            catch (DbUpdateException)
            {
                _context.ChangeTracker.Clear();
                var concurrent = await _context.WorkOrderWebhookDeliveries
                    .AsNoTracking()
                    .SingleOrDefaultAsync(d => d.DeliveryId == mutation.DeliveryId, cancellationToken);

                if (concurrent == null)
                    throw;

                return ExistingDeliveryResult(concurrent, mutation.BodySha256);
            }
        }

        private async Task<long> AllocateInternalNumberAsync(CancellationToken cancellationToken)
        {
            if (_context.Database.IsSqlServer())
            {
                return await _context.Database
                    .SqlQueryRaw<long>(
                        "SELECT NEXT VALUE FOR dbo.WorkOrderInternalNumberSequence AS [Value]")
                    .SingleAsync(cancellationToken);
            }

            await InMemoryNumberLock.WaitAsync(cancellationToken);
            try
            {
                var values = await _context.workOrders
                    .AsNoTracking()
                    .Where(w => w.InternalWONumber != null)
                    .Select(w => w.InternalWONumber!)
                    .ToListAsync(cancellationToken);
                return values
                    .Select(v => long.TryParse(v, out var parsed) ? parsed : 0L)
                    .DefaultIfEmpty()
                    .Max() + 1;
            }
            finally
            {
                InMemoryNumberLock.Release();
            }
        }

        private async Task<bool> UpsertReceiptAsync(
            string source,
            string kind,
            string externalId,
            DateTimeOffset updatedAt,
            string versionHash,
            DateTimeOffset processedAt,
            CancellationToken cancellationToken)
        {
            var receipt = await _context.WorkOrderExternalReceipts.SingleOrDefaultAsync(
                r => r.Source == source && r.Kind == kind && r.ExternalId == externalId,
                cancellationToken);
            if (receipt == null)
            {
                _context.WorkOrderExternalReceipts.Add(new WorkOrderExternalReceipt
                {
                    Source = source,
                    Kind = kind,
                    ExternalId = externalId,
                    UpdatedAt = updatedAt,
                    VersionHash = versionHash,
                    ProcessedAt = processedAt
                });
                return true;
            }

            if (!IsNewer(updatedAt, versionHash, receipt.UpdatedAt, receipt.VersionHash))
                return false;

            receipt.UpdatedAt = updatedAt;
            receipt.VersionHash = versionHash;
            receipt.ProcessedAt = processedAt;
            return true;
        }

        private static bool IsNewer(
            DateTimeOffset candidateUpdatedAt,
            string candidateHash,
            DateTimeOffset? currentUpdatedAt,
            string? currentHash)
        {
            if (!currentUpdatedAt.HasValue)
                return true;

            var timestampComparison = candidateUpdatedAt.CompareTo(currentUpdatedAt.Value);
            return timestampComparison > 0
                || (timestampComparison == 0
                    && string.CompareOrdinal(candidateHash, currentHash ?? string.Empty) > 0);
        }

        private static WorkOrderWebhookPersistenceResult ExistingDeliveryResult(
            WorkOrderWebhookDelivery delivery,
            string bodySha256)
        {
            return new WorkOrderWebhookPersistenceResult(
                string.Equals(delivery.BodySha256, bodySha256, StringComparison.OrdinalIgnoreCase)
                    ? WorkOrderWebhookPersistenceStatus.Duplicate
                    : WorkOrderWebhookPersistenceStatus.HashConflict);
        }
    }
}