using Distribution.Features.Invoice;
using Distribution.Features.PriceList;
using Distribution.Features.Stock;
using Distribution.Infra.UoW;
using Distribution.Models;

namespace Distribution.Features.ShopPO;

public class ShopPOService(
    IShopPORepository repo,
    IInvoiceRepository invoiceRepo,
    PriceListService priceListService,
    IUnitOfWork uow)
{
    private static ShopPOResponse ToResponse(Models.ShopPO p, Dictionary<Guid, (string Name, string Role)>? users = null) =>
        new(p.Id, p.FK_StoreId, p.Store?.StoreName ?? string.Empty,
            p.Store?.StoreAddress, p.Store?.ContactNumber,
            p.RaisedById, p.InvoiceId, p.TotalAmount, p.Status,
            p.ConfirmedAt, p.ConfirmedBy, p.FulfilledAt,
            p.Items.Where(i => i.IsActive).Select(i =>
                new ShopPOItemResponse(i.Id, i.FK_ItemId, i.Item?.Name ?? string.Empty,
                    i.Quantity, i.QuantityFulfilled, i.UnitPrice, i.IsActive)).ToList(),
            p.IsActive, p.CreatedAt,
            users != null && users.TryGetValue(p.RaisedById, out var u) ? u.Name : null,
            users != null && users.TryGetValue(p.RaisedById, out var r) ? r.Role : null,
            users != null && p.ConfirmedBy is Guid cb && users.TryGetValue(cb, out var c) ? c.Name : null,
            users != null && p.ConfirmedBy is Guid cb2 && users.TryGetValue(cb2, out var c2) ? c2.Role : null,
            p.CancelledBy, p.CancelledAt, p.CancelReason,
            users != null && p.CancelledBy is Guid xb && users.TryGetValue(xb, out var x) ? x.Name : null,
            users != null && p.CancelledBy is Guid xb2 && users.TryGetValue(xb2, out var x2) ? x2.Role : null);

    private static IEnumerable<Guid> UserIds(Models.ShopPO p)
    {
        yield return p.RaisedById;
        if (p.ConfirmedBy is Guid cb) yield return cb;
        if (p.CancelledBy is Guid xb) yield return xb;
    }

    private async Task<ShopPOResponse> ToResponseWithUserAsync(Models.ShopPO p) =>
        ToResponse(p, await repo.GetUserInfoAsync(UserIds(p)));

    public async Task<PagedResponse<ShopPOResponse>> GetAllAsync(Guid? agentId, Guid? routeId, Guid? regionId, Guid? shopId, bool? confirmed, ShopPOStatus? status, int page, int pageSize)
    {
        var total = await repo.GetCountAsync(agentId, routeId, regionId, shopId, confirmed, status);
        var items = await repo.GetAllAsync(agentId, routeId, regionId, shopId, confirmed, status, page, pageSize);
        var users = await repo.GetUserInfoAsync(items.SelectMany(UserIds));
        return new PagedResponse<ShopPOResponse>(page, pageSize, total, items.Select(p => ToResponse(p, users)).ToList());
    }

    public async Task<ShopPOResponse?> GetByIdAsync(Guid id)
    {
        var po = await repo.GetByIdAsync(id);
        if (po is null) return null;
        var users = await repo.GetUserInfoAsync(UserIds(po));
        return ToResponse(po, users);
    }

    public async Task<List<ShopPOResponse>> GetConfirmedWithoutInvoiceAsync(Guid? agentId, Guid? routeId, Guid? shopId)
    {
        var items = await repo.GetConfirmedWithoutInvoiceAsync(agentId, routeId, shopId);
        var users = await repo.GetUserInfoAsync(items.SelectMany(UserIds));
        return items.Select(p => ToResponse(p, users)).ToList();
    }

    public async Task<ShopPOResponse> CreateAsync(CreateShopPORequest request, Guid raisedById, CancellationToken ct = default)
    {
        if (request.Items.Count == 0)
            throw new InvalidOperationException("At least one item is required");

        var items = new List<ShopPOItem>();
        decimal total = 0;

        foreach (var line in request.Items)
        {
            var unitPrice = line.UnitPrice
                ?? (await priceListService.ResolveByStoreAsync(line.ItemId, request.StoreId, DateTime.Now))?.Price
                ?? throw new InvalidOperationException($"No resolvable price for item {line.ItemId}");

            items.Add(new ShopPOItem
            {
                FK_ItemId = line.ItemId,
                Quantity = line.Quantity,
                QuantityFulfilled = 0,
                UnitPrice = unitPrice
            });
            total += line.Quantity * unitPrice;
        }

        var po = new Models.ShopPO
        {
            FK_StoreId = request.StoreId,
            RaisedById = raisedById,
            TotalAmount = total,
            Status = ShopPOStatus.Pending
        };

        await uow.BeginAsync(ct);
        try
        {
            await repo.AddAsync(po);
            foreach (var item in items) item.FK_ShopPOId = po.Id;
            await repo.AddItemsAsync(items);
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

        var saved = await repo.GetByIdAsync(po.Id);
        return await ToResponseWithUserAsync(saved!);
    }

    public async Task<ShopPOResponse> UpdateItemsAsync(Guid id, UpdateShopPOItemsRequest request, CancellationToken ct = default)
    {
        var po = await repo.GetByIdAsync(id)
            ?? throw new KeyNotFoundException("Shop PO not found");

        if (po.Status == ShopPOStatus.Cancelled)
            throw new InvalidOperationException("Cannot edit a cancelled Shop PO");

        if (po.ConfirmedAt is not null)
            throw new InvalidOperationException("Items can only be changed before the Shop PO is confirmed");

        if (request.Items.Count == 0)
            throw new InvalidOperationException("At least one item is required");

        var newItems = new List<ShopPOItem>();
        decimal total = 0;

        foreach (var line in request.Items)
        {
            var unitPrice = line.UnitPrice
                ?? (await priceListService.ResolveByStoreAsync(line.ItemId, po.FK_StoreId, DateTime.Now))?.Price
                ?? throw new InvalidOperationException($"No resolvable price for item {line.ItemId}");

            newItems.Add(new ShopPOItem
            {
                FK_ShopPOId = id,
                FK_ItemId = line.ItemId,
                Quantity = line.Quantity,
                QuantityFulfilled = 0,
                UnitPrice = unitPrice
            });
            total += line.Quantity * unitPrice;
        }

        po.TotalAmount = total;

        await uow.BeginAsync(ct);
        try
        {
            await repo.ReplaceItemsAsync(id, newItems);
            repo.Update(po);
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

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

    public async Task<ShopPOResponse> ConfirmAsync(Guid id, Guid confirmedBy, CancellationToken ct = default)
    {
        var po = await repo.GetByIdAsync(id)
            ?? throw new KeyNotFoundException("Shop PO not found");

        if (po.ConfirmedAt is not null)
            throw new InvalidOperationException("Shop PO is already confirmed");

        if (po.Status == ShopPOStatus.Cancelled)
            throw new InvalidOperationException("Cannot confirm a cancelled Shop PO");

        po.ConfirmedAt = DateTime.Now;
        po.ConfirmedBy = confirmedBy;

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

        return await ToResponseWithUserAsync(po);
    }

    public async Task<ShopPOResponse> ConfirmAndCreateInvoiceAsync(Guid id, Guid userId, CancellationToken ct = default)
    {
        var po = await repo.GetByIdAsync(id)
            ?? throw new KeyNotFoundException("Shop PO not found");

        if (po.ConfirmedAt is not null)
            throw new InvalidOperationException("Shop PO is already confirmed");

        if (po.Status == ShopPOStatus.Cancelled)
            throw new InvalidOperationException("Cannot confirm a cancelled Shop PO");

        po.ConfirmedAt = DateTime.Now;
        po.ConfirmedBy = userId;

        var invoice = new Models.Invoice
        {
            FK_ShopPOId = po.Id,
            Status = InvoiceStatus.Draft,
            PaymentStatus = PaymentStatus.Pending,
            CreatedBy = userId,
            TotalAmount = po.TotalAmount
        };

        await uow.BeginAsync(ct);
        try
        {
            await invoiceRepo.AddAsync(invoice);
            po.InvoiceId = invoice.Id;
            repo.Update(po);
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

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

    public async Task<ShopPOResponse> CancelAsync(Guid id, Guid cancelledBy, string reason, CancellationToken ct = default)
    {
        if (string.IsNullOrWhiteSpace(reason))
            throw new InvalidOperationException("A cancellation reason is required");

        var po = await repo.GetByIdAsync(id)
            ?? throw new KeyNotFoundException("Shop PO not found");

        if (po.Status == ShopPOStatus.Cancelled)
            throw new InvalidOperationException("Shop PO is already cancelled");

        if (po.Status is ShopPOStatus.PartiallyFulfilled or ShopPOStatus.Fulfilled)
            throw new InvalidOperationException($"Cannot cancel a Shop PO in {po.Status} status");

        po.Status = ShopPOStatus.Cancelled;
        po.CancelledAt = DateTime.Now;
        po.CancelledBy = cancelledBy;
        po.CancelReason = reason.Trim();

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

        return await ToResponseWithUserAsync(po);
    }
}