using Distribution.Features.Ride;
using Distribution.Features.Stock;
using Distribution.Infra.UoW;
using Distribution.Models;

namespace Distribution.Features.LoadingEvent;

public class LoadingSheetService(
    ILoadingSheetRepository repo,
    IRideRepository rideRepo,
    IStockRepository stockRepo,
    IUnitOfWork uow)
{
    public async Task<PagedResponse<LoadingSheetResponse>> GetAllAsync(Guid? rideId, LoadingSheetStatus? status, Guid? routeId, Guid? regionId, int page, int pageSize)
    {
        var total = await repo.GetCountAsync(rideId, status, routeId, regionId);
        var items = await repo.GetAllAsync(rideId, status, routeId, regionId, page, pageSize);
        return new PagedResponse<LoadingSheetResponse>(page, pageSize, total, items.Select(ToResponse).ToList());
    }

    public async Task<LoadingSheetResponse?> GetByIdAsync(Guid id)
    {
        var sheet = await repo.GetByIdAsync(id);
        return sheet is null ? null : ToResponse(sheet);
    }

    public async Task<LoadingSheetResponse> CreateAsync(CreateLoadingSheetRequest request, Guid userId, CancellationToken ct = default)
    {
        var ride = await rideRepo.GetByIdAsync(request.FK_RideId)
            ?? throw new KeyNotFoundException("Ride not found");

        if (ride.Status != RideStatus.Open)
            throw new InvalidOperationException("A loading sheet can only be created for an Open ride");

        var existing = await repo.GetActiveByRideIdAsync(request.FK_RideId);
        if (existing is not null)
            throw new InvalidOperationException("This ride already has a Planned loading sheet");

        var sheet = new LoadingSheet
        {
            FK_RideId = ride.Id,
            Status = LoadingSheetStatus.Planned,
            PopulatedBy = userId,
            PopulatedAt = DateTime.Now
        };

        await uow.BeginAsync(ct);
        try
        {
            await repo.AddAsync(sheet);
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

        var saved = await repo.GetByIdAsync(sheet.Id);
        return ToResponse(saved!);
    }

    public async Task<LoadingSheetResponse> SetItemsAsync(Guid id, SetItemsRequest request, CancellationToken ct = default)
    {
        var sheet = await repo.GetByIdAsync(id)
            ?? throw new KeyNotFoundException("Loading sheet not found");

        if (sheet.Status != LoadingSheetStatus.Planned)
            throw new InvalidOperationException("Items can only be changed while the sheet is Planned");

        // The request is the full desired item list: a row matching (item, warehouse,
        // shop PO item) gets its quantity updated in place, a new combination is added,
        // and rows for combinations not present in the request are removed.
        await uow.BeginAsync(ct);
        try
        {
            var newItems = new List<LoadingSheetItem>();
            var keptItems = new List<LoadingSheetItem>();
            foreach (var input in request.Items)
            {
                var existing = sheet.Items.FirstOrDefault(i =>
                    i.FK_ItemId == input.FK_ItemId &&
                    i.FK_WarehouseId == input.FK_WarehouseId &&
                    i.FK_ShopPOItemId == input.FK_ShopPOItemId);

                if (existing is not null)
                {
                    existing.QuantityDispatched = input.Quantity;
                    keptItems.Add(existing);
                }
                else
                    newItems.Add(new LoadingSheetItem
                    {
                        FK_LoadingSheetId = sheet.Id,
                        FK_ItemId = input.FK_ItemId,
                        FK_WarehouseId = input.FK_WarehouseId,
                        FK_ShopPOItemId = input.FK_ShopPOItemId,
                        QuantityDispatched = input.Quantity
                    });
            }

            var removedItems = sheet.Items.Where(i => !keptItems.Contains(i)).ToList();
            if (removedItems.Count > 0)
                repo.RemoveItems(removedItems);
            if (newItems.Count > 0)
                await repo.AddItemsAsync(newItems);

            var shopPOItemIds = keptItems.Select(i => i.FK_ShopPOItemId)
                .Concat(newItems.Select(i => i.FK_ShopPOItemId))
                .Where(x => x.HasValue)
                .Select(x => x!.Value)
                .Distinct()
                .ToList();
            var shopPOIds = shopPOItemIds.Count > 0
                ? await repo.GetShopPOIdsByItemIdsAsync(shopPOItemIds)
                : new List<Guid>();

            await repo.ReplaceOrdersAsync(sheet.Id, shopPOIds);
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

        var saved = await repo.GetByIdAsync(sheet.Id);
        return ToResponse(saved!);
    }

    public async Task<LoadingSheetResponse> ConfirmAsync(Guid id, Guid userId, CancellationToken ct = default)
    {
        var sheet = await repo.GetByIdAsync(id)
            ?? throw new KeyNotFoundException("Loading sheet not found");

        if (sheet.Status != LoadingSheetStatus.Planned)
            throw new InvalidOperationException($"Cannot confirm a sheet in {sheet.Status} status");

        if (!sheet.Items.Any(i => i.QuantityDispatched > 0))
            throw new InvalidOperationException("Sheet must have at least one item with quantity greater than zero");

        var ride = await rideRepo.GetByIdAsync(sheet.FK_RideId)
            ?? throw new KeyNotFoundException("Ride not found");

        await uow.BeginAsync(ct);
        try
        {
            await ApplyLoadMovementsAsync(sheet.Id, ride.FK_VehicleId, sheet.Items, userId);

            sheet.Status = LoadingSheetStatus.Confirmed;
            sheet.ConfirmedAt = DateTime.Now;
            sheet.ConfirmedBy = userId;

            repo.Update(sheet);
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

        var saved = await repo.GetByIdAsync(id);
        return ToResponse(saved!);
    }

    private async Task ApplyLoadMovementsAsync(Guid sheetId, Guid vehicleId, List<LoadingSheetItem> items, Guid userId)
    {
        // Vehicle balances created during this confirm are only tracked, not yet saved, so a
        // later row for the same item would not find them via the repository and would try to
        // insert a duplicate (item, vehicle) balance.
        var createdVehicleBalances = new Dictionary<Guid, StockBalance>();

        foreach (var item in items.Where(i => i.QuantityDispatched > 0))
        {
            var warehouseBalance = await stockRepo.GetBalanceAsync(item.FK_ItemId, item.FK_WarehouseId)
                ?? throw new InvalidOperationException(
                    $"No stock found for '{item.Item?.Name ?? item.FK_ItemId.ToString()}' in warehouse '{item.Warehouse?.Name ?? item.FK_WarehouseId.ToString()}'");

            if (warehouseBalance.Quantity < item.QuantityDispatched)
                throw new InvalidOperationException(
                    $"Insufficient stock for '{item.Item?.Name ?? item.FK_ItemId.ToString()}' in warehouse '{item.Warehouse?.Name ?? item.FK_WarehouseId.ToString()}' " +
                    $"(available {warehouseBalance.Quantity}, needed {item.QuantityDispatched})");

            warehouseBalance.Quantity -= item.QuantityDispatched;
            warehouseBalance.UpdatedAt = DateTime.Now;
            stockRepo.UpdateBalance(warehouseBalance);

            var vehicleBalance = createdVehicleBalances.GetValueOrDefault(item.FK_ItemId)
                ?? await stockRepo.GetBalanceAsync(item.FK_ItemId, vehicleId);
            if (vehicleBalance is null)
            {
                var created = new StockBalance
                {
                    FK_ItemId = item.FK_ItemId,
                    LocationId = vehicleId,
                    LocationType = LocationType.Vehicle,
                    Quantity = item.QuantityDispatched
                };
                createdVehicleBalances[item.FK_ItemId] = created;
                await stockRepo.AddBalanceAsync(created);
            }
            else
            {
                vehicleBalance.Quantity += item.QuantityDispatched;
                vehicleBalance.UpdatedAt = DateTime.Now;
                stockRepo.UpdateBalance(vehicleBalance);
            }

            await stockRepo.AddMovementAsync(new StockMovement
            {
                FK_ItemId = item.FK_ItemId,
                FromLocationId = item.FK_WarehouseId,
                FromLocationType = LocationType.Warehouse,
                ToLocationId = vehicleId,
                ToLocationType = LocationType.Vehicle,
                Quantity = item.QuantityDispatched,
                Type = MovementType.Load,
                ReferenceId = sheetId,
                CreatedBy = userId
            });
        }
    }

    private static LoadingSheetResponse ToResponse(LoadingSheet s) =>
        new(s.Id, s.FK_RideId, s.Status, s.PopulatedBy, s.PopulatedAt,
            s.ConfirmedAt, s.ConfirmedBy, s.CreatedAt,
            s.Items.Select(i => new LoadingSheetItemResponse(
                i.Id, i.FK_ItemId, i.Item?.Name ?? string.Empty,
                i.FK_WarehouseId, i.Warehouse?.Name ?? string.Empty,
                i.QuantityDispatched, i.FK_ShopPOItemId,
                i.ShopPOItem?.FK_ShopPOId,
                i.ShopPOItem?.ShopPO?.FK_StoreId,
                i.ShopPOItem?.ShopPO?.Store?.StoreName)).ToList(),
            s.Orders.Select(o => new LoadingSheetOrderResponse(o.FK_ShopPOId)).ToList());
}