using Distribution.Features.Item;
using Distribution.Infra.UoW;

namespace Distribution.Features.PriceList;

public class PriceListService(IPriceListRepository repo, IItemRepository itemRepo, IUnitOfWork uow)
{
    private static PriceListItemResponse MapItem(Models.PriceListItem i) =>
        new(i.Id, i.FK_ItemId, i.Item.Sku, i.Item.Name, i.Price, i.MinPrice);

    private static PriceListResponse MapDetail(Models.PriceList pl) =>
        new(pl.Id, pl.Name, pl.FK_RegionId, pl.Region?.Name,
            pl.EffectiveFrom, pl.EffectiveTo, pl.IsActive, pl.CreatedAt,
            pl.Items.Where(i => i.IsActive).Select(MapItem).ToList());

    public async Task<List<PriceListResponse>> GetAllAsync(Guid? regionId = null)
    {
        var lists = await repo.GetAllAsync(regionId);
        return lists.Select(pl => new PriceListResponse(
            pl.Id, pl.Name, pl.FK_RegionId, pl.Region?.Name,
            pl.EffectiveFrom, pl.EffectiveTo, pl.IsActive, pl.CreatedAt, [])).ToList();
    }

    public async Task<PriceListResponse?> GetByIdAsync(Guid id)
    {
        var pl = await repo.GetByIdAsync(id);
        if (pl is null || !pl.IsActive) return null;
        return MapDetail(pl);
    }

    public async Task<PriceListResponse> CreateAsync(CreatePriceListRequest request, CancellationToken ct = default)
    {
        var priceList = new Models.PriceList
        {
            Name = request.Name,
            FK_RegionId = request.RegionId,
            EffectiveFrom = request.EffectiveFrom,
            EffectiveTo = request.EffectiveTo
        };

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

        return (await GetByIdAsync(priceList.Id))!;
    }

    public async Task<PriceListResponse?> UpdateAsync(Guid id, UpdatePriceListRequest request, CancellationToken ct = default)
    {
        var priceList = await repo.GetByIdAsync(id);
        if (priceList is null || !priceList.IsActive) return null;

        foreach (var item in priceList.Items.Where(i => i.IsActive))
        {
            if (await repo.HasOverlapAsync(item.FK_ItemId, request.RegionId, request.EffectiveFrom, request.EffectiveTo, id))
                throw new InvalidOperationException(
                    $"Overlapping price list already exists for item '{item.Item.Sku}' in the same region for the requested date range.");
        }

        priceList.Name = request.Name;
        priceList.FK_RegionId = request.RegionId;
        priceList.EffectiveFrom = request.EffectiveFrom;
        priceList.EffectiveTo = request.EffectiveTo;

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

        return (await GetByIdAsync(id))!;
    }

    public async Task<bool> DeleteAsync(Guid id, CancellationToken ct = default)
    {
        var priceList = await repo.GetByIdAsync(id);
        if (priceList is null || !priceList.IsActive) return false;

        await uow.BeginAsync(ct);
        try
        {
            foreach (var item in priceList.Items.Where(i => i.IsActive))
                repo.RemoveItem(item);
            repo.Remove(priceList);
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

        return true;
    }

    public async Task<PriceListResponse?> UpsertItemAsync(Guid priceListId, string sku, UpsertPriceListItemRequest request, CancellationToken ct = default)
    {
        var priceList = await repo.GetByIdAsync(priceListId);
        if (priceList is null || !priceList.IsActive) return null;

        var item = await itemRepo.GetBySkuAsync(sku);
        if (item is null) return null;

        if (request.MinPrice.HasValue && request.MinPrice.Value > request.Price)
            throw new InvalidOperationException(
                $"MinPrice ({request.MinPrice}) cannot exceed Price ({request.Price}) for item '{sku}'.");

        if (await repo.HasOverlapAsync(item.Id, priceList.FK_RegionId, priceList.EffectiveFrom, priceList.EffectiveTo, priceListId))
            throw new InvalidOperationException(
                $"Overlapping price list already exists for item '{sku}' in the same region for this date range.");

        var existing = await repo.GetItemAsync(priceListId, item.Id);

        await uow.BeginAsync(ct);
        try
        {
            if (existing is null)
            {
                await repo.AddItemAsync(new Models.PriceListItem
                {
                    FK_PriceListId = priceListId,
                    FK_ItemId = item.Id,
                    Price = request.Price,
                    MinPrice = request.MinPrice
                });
            }
            else
            {
                existing.Price = request.Price;
                existing.MinPrice = request.MinPrice;
                repo.UpdateItem(existing);
            }
            await uow.CommitAsync(ct);
        }
        catch { await uow.RollbackAsync(ct); throw; }

        return (await GetByIdAsync(priceListId))!;
    }

    public async Task<PriceListResponse?> RemoveItemAsync(Guid priceListId, string sku, CancellationToken ct = default)
    {
        var priceList = await repo.GetByIdAsync(priceListId);
        if (priceList is null || !priceList.IsActive) return null;

        var item = await itemRepo.GetBySkuAsync(sku);
        if (item is null) return null;

        var existing = await repo.GetItemAsync(priceListId, item.Id);
        if (existing is null) return null;

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

        return (await GetByIdAsync(priceListId))!;
    }

    /// <summary>
    /// applyPricingAndDiscounts (price-list half): region-scoped active price list -> global
    /// active price list -> Item.SalePrice -> null if none apply. The returned PriceResolution
    /// carries MinPrice so the caller can validate a negotiated UnitPrice against the band;
    /// the Item.SalePrice fallback has no MinPrice (fixed, non-negotiable).
    /// </summary>
    public async Task<PriceResolution?> ResolvePriceAsync(Guid itemId, Guid? regionId, decimal? itemSalePrice, DateTime orderDate)
    {
        if (regionId.HasValue)
        {
            var regionMatches = await repo.GetActiveItemsAsync(itemId, regionId, orderDate);
            if (regionMatches.Count > 0) return new PriceResolution(regionMatches[0].Price, regionMatches[0].MinPrice);
        }

        var globalMatches = await repo.GetActiveItemsAsync(itemId, null, orderDate);
        if (globalMatches.Count > 0) return new PriceResolution(globalMatches[0].Price, globalMatches[0].MinPrice);

        return itemSalePrice.HasValue ? new PriceResolution(itemSalePrice.Value, null) : null;
    }
}