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, int page, int pageSize)
    {
        var total = await repo.GetCountAsync(rideId, status);
        var items = await repo.GetAllAsync(rideId, status, 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, 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 an active loading sheet");

        var sheet = new LoadingSheet
        {
            FK_RideId = ride.Id,
            FK_SourceWarehouseId = ride.FK_SourceWarehouseId,
            Status = LoadingSheetStatus.Pending
        };

        if (ride.RideType == RideType.Delivery)
        {
            var orderItems = await repo.GetAggregatedOrderItemsByRouteIdAsync(ride.FK_RouteId);
            foreach (var (itemId, qty) in orderItems)
                sheet.Items.Add(new LoadingSheetItem { FK_ItemId = itemId, QuantityDispatched = qty });
        }

        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.Pending)
            throw new InvalidOperationException("Items can only be changed while the sheet is Pending");

        await uow.BeginAsync(ct);
        try
        {
            repo.RemoveItems(sheet.Items);
            await repo.AddItemsAsync(request.Items.Select(i => new LoadingSheetItem
            {
                FK_LoadingSheetId = sheet.Id,
                FK_ItemId = i.FK_ItemId,
                QuantityDispatched = i.Quantity
            }));
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

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

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

        if (sheet.Status != LoadingSheetStatus.Pending)
            throw new InvalidOperationException($"Cannot confirm dispatch for 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");

        sheet.Status = LoadingSheetStatus.DispatchConfirmed;
        sheet.DispatchConfirmedAt = DateTime.Now;
        sheet.DispatchConfirmedBy = userId;

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

        return ToResponse(sheet);
    }

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

        if (sheet.Status != LoadingSheetStatus.DispatchConfirmed)
            throw new InvalidOperationException("Receipt quantities can only be set after dispatch is confirmed");

        foreach (var input in request.Items)
        {
            var item = sheet.Items.FirstOrDefault(i => i.FK_ItemId == input.FK_ItemId)
                ?? throw new InvalidOperationException($"Item {input.FK_ItemId} is not on this loading sheet");
            item.QuantityReceived = input.QuantityReceived;
        }

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

        return ToResponse(sheet);
    }

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

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

        if (sheet.Items.Any(i => !i.QuantityReceived.HasValue))
            throw new InvalidOperationException("All items must have a received quantity before confirming receipt");

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

        var hasDiscrepancy = sheet.Items.Any(i => i.QuantityReceived != i.QuantityDispatched);

        await uow.BeginAsync(ct);
        try
        {
            if (hasDiscrepancy)
            {
                sheet.Status = LoadingSheetStatus.DiscrepancyFlagged;
            }
            else
            {
                sheet.Status = LoadingSheetStatus.ReceiptConfirmed;
                sheet.ReceiptConfirmedAt = DateTime.Now;
                sheet.ReceiptConfirmedBy = userId;

                var lines = sheet.Items.Select(i => (i.FK_ItemId, i.QuantityReceived!.Value)).ToList();
                await ApplyLoadMovementsAsync(sheet, ride.FK_VehicleId, lines, userId);

                ride.Status = RideStatus.Active;
                ride.ActivatedAt = DateTime.Now;
                ride.Meterstart = request.Meterstart;
                rideRepo.Update(ride);
            }

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

        return ToResponse(sheet);
    }

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

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

        foreach (var input in request.Items)
        {
            var item = sheet.Items.FirstOrDefault(i => i.FK_ItemId == input.FK_ItemId)
                ?? throw new InvalidOperationException($"Item {input.FK_ItemId} is not on this loading sheet");
            if (input.QuantityResolved < 0)
                throw new InvalidOperationException("Resolved quantity cannot be negative");
            item.QuantityResolved = input.QuantityResolved;
        }

        if (sheet.Items.Any(i => !i.QuantityResolved.HasValue))
            throw new InvalidOperationException("All items must have a resolved quantity");

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

        sheet.Status = LoadingSheetStatus.Resolved;
        sheet.ReceiptConfirmedAt = DateTime.Now;
        sheet.ReceiptConfirmedBy = userId;

        var lines = sheet.Items.Select(i => (i.FK_ItemId, i.QuantityResolved!.Value)).ToList();

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

            ride.Status = RideStatus.Active;
            ride.ActivatedAt = DateTime.Now;
            ride.Meterstart = request.Meterstart;
            rideRepo.Update(ride);

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

        return ToResponse(sheet);
    }

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

        if (sheet.Status != LoadingSheetStatus.DispatchConfirmed)
            throw new InvalidOperationException($"Cannot set receipt for a sheet in {sheet.Status} status");

        foreach (var input in items)
        {
            var sheetItem = sheet.Items.FirstOrDefault(i => i.FK_ItemId == input.ItemId)
                ?? throw new InvalidOperationException($"Item {input.ItemId} is not on this loading sheet");
            sheetItem.QuantityReceived = input.QuantityReceived;
        }

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

        var hasDiscrepancy = sheet.Items.Any(i => i.QuantityReceived != i.QuantityDispatched);

        await uow.BeginAsync(ct);
        try
        {
            if (hasDiscrepancy)
            {
                sheet.Status = LoadingSheetStatus.DiscrepancyFlagged;
            }
            else
            {
                sheet.Status = LoadingSheetStatus.ReceiptConfirmed;
                sheet.ReceiptConfirmedAt = DateTime.Now;
                sheet.ReceiptConfirmedBy = userId;

                var lines = sheet.Items.Select(i => (i.FK_ItemId, i.QuantityReceived!.Value)).ToList();
                await ApplyLoadMovementsAsync(sheet, ride.FK_VehicleId, lines, userId);

                ride.Status = RideStatus.Active;
                ride.ActivatedAt = DateTime.Now;
                ride.Meterstart = 0;
                rideRepo.Update(ride);
            }

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

        return ToResponse(sheet);
    }

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

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

        foreach (var item in sheet.Items)
        {
            if (!item.QuantityReceived.HasValue)
                throw new InvalidOperationException($"Item {item.FK_ItemId} has no received quantity to resolve from");
            item.QuantityResolved = item.QuantityReceived.Value;
        }

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

        sheet.Status = LoadingSheetStatus.Resolved;
        sheet.ReceiptConfirmedAt = DateTime.Now;
        sheet.ReceiptConfirmedBy = userId;

        var lines = sheet.Items.Select(i => (i.FK_ItemId, i.QuantityResolved!.Value)).ToList();

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

            ride.Status = RideStatus.Active;
            ride.ActivatedAt = DateTime.Now;
            ride.Meterstart = 0;
            rideRepo.Update(ride);

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

        return ToResponse(sheet);
    }

    private async Task ApplyLoadMovementsAsync(LoadingSheet sheet, Guid vehicleId, List<(Guid ItemId, decimal Qty)> lines, Guid userId)
    {
        foreach (var (itemId, qty) in lines.Where(l => l.Qty > 0))
        {
            var warehouseBalance = await stockRepo.GetBalanceAsync(itemId, sheet.FK_SourceWarehouseId)
                ?? throw new InvalidOperationException($"No stock found in warehouse for item {itemId}");
            if (warehouseBalance.Quantity < qty)
                throw new InvalidOperationException($"Insufficient warehouse stock for item {itemId}");

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

            var vehicleBalance = await stockRepo.GetBalanceAsync(itemId, vehicleId);
            if (vehicleBalance is null)
            {
                await stockRepo.AddBalanceAsync(new StockBalance
                {
                    FK_ItemId = itemId,
                    LocationId = vehicleId,
                    LocationType = LocationType.Vehicle,
                    Quantity = qty
                });
            }
            else
            {
                vehicleBalance.Quantity += qty;
                vehicleBalance.UpdatedAt = DateTime.Now;
                stockRepo.UpdateBalance(vehicleBalance);
            }

            await stockRepo.AddMovementAsync(new StockMovement
            {
                FK_ItemId = itemId,
                FromLocationId = sheet.FK_SourceWarehouseId,
                FromLocationType = LocationType.Warehouse,
                ToLocationId = vehicleId,
                ToLocationType = LocationType.Vehicle,
                Quantity = qty,
                Type = MovementType.Load,
                ReferenceId = sheet.Id,
                CreatedBy = userId
            });
        }
    }

    private static LoadingSheetResponse ToResponse(LoadingSheet s) =>
        new(s.Id, s.FK_RideId, s.FK_SourceWarehouseId,
            s.SourceWarehouse?.Name ?? string.Empty,
            s.Status,
            s.DispatchConfirmedAt, s.DispatchConfirmedBy,
            s.ReceiptConfirmedAt, s.ReceiptConfirmedBy,
            s.CreatedAt,
            s.Items.Select(i => new LoadingSheetItemResponse(
                i.Id, i.FK_ItemId, i.Item?.Name ?? string.Empty,
                i.QuantityDispatched, i.QuantityReceived, i.QuantityResolved)).ToList());
}