using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Domain.Entities.Store.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Admin.Store.Order.Get;

public sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Result<Response>>
{
    public async Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        var order = await db.Order
            .AsNoTracking()
            .Include(o => o.Member)
            .Include(o => o.Channel)
            .Include(o => o.Items).ThenInclude(i => i.Product)
            .Include(o => o.Items).ThenInclude(i => i.IssuedCouponCode)
            .Include(o => o.Refunds)
            .Where(o => o.ID == request.OrderID)
            .FirstOrDefaultAsync(ct);

        if (order is null)
        {
            return Result.Failure<Response>(Error.NotFound("Order.NotFound", "주문을 찾을 수 없습니다."));
        }

        var shipment = await db.Shipment
            .AsNoTracking()
            .Where(s => s.OrderID == order.ID)
            .Select(s => new Response.ShipmentInfo(
                s.ID,
                s.Status,
                s.Carrier,
                s.TrackingNumber,
                s.ShippedAt,
                s.DeliveredAt
            ))
            .FirstOrDefaultAsync(ct);

        // OrderItem 별 발급 쿠폰 코드 일괄 조회 (N+1 방지).
        // MemberInventory 에 OrderItemID 별 Quantity 만큼의 행이 있음. CouponCode FK 조인.
        var orderItemIds = order.Items.Select(i => i.ID).ToList();

        var inventoryRows = await db.MemberInventory.AsNoTracking().Where(m => orderItemIds.Contains(m.OrderItemID) && m.CouponCode != null).OrderBy(m => m.OrderItemID).ThenBy(m => m.ID).Select(m => new
        {
            m.OrderItemID,
            CouponCodeID = m.CouponCode!.ID,
            Code = m.CouponCode.Code,
            m.CouponCode.UsedAt,
            IsUsed = m.CouponCode.Status == CouponCodeStatus.Used
        }).ToListAsync(ct);

        // 환불 요청에 이미 포함된 CouponCodeID → OrderRefund.ID 매핑 (체크박스 disable 용)
        var orderRefundIds = order.Refunds.Select(r => r.ID).ToList();
        var refundedCouponMap = await db.OrderRefundItem.AsNoTracking()
            .Where(x => orderRefundIds.Contains(x.OrderRefundID))
            .Select(x => new { x.CouponCodeID, x.OrderRefundID })
            .ToDictionaryAsync(x => x.CouponCodeID, x => (int?)x.OrderRefundID, ct);

        var couponMap = inventoryRows.GroupBy(x => x.OrderItemID).ToDictionary(g => g.Key, g => (IReadOnlyList<Response.CouponDetail>)g.Select(x => new Response.CouponDetail(
            CouponCodeID: x.CouponCodeID,
            Code: x.Code,
            UsedAt: x.UsedAt,
            IsUsed: x.IsUsed,
            RefundRequestID: refundedCouponMap.GetValueOrDefault(x.CouponCodeID)
        )).ToList());

        var items = order.Items.Select(i => new Response.ItemRow(
            ID: i.ID,
            ProductID: i.ProductID,
            ProductName: i.Product?.Name ?? "-",
            TypeText: i.Product?.Type == ProductType.Digital ? "쿠폰" : "실물",
            Quantity: i.Quantity,
            UnitPrice: i.UnitPrice,
            LineTotal: i.UnitPrice * i.Quantity,
            IssuedCouponCodeID: i.IssuedCouponCodeID,
            IssuedCouponCode: i.IssuedCouponCode?.Code,
            CouponCodes: couponMap.GetValueOrDefault(i.ID, [])
        )).ToList();

        // 환불 이력의 OrderRefundItem (포함 쿠폰) 일괄 조회.
        var refundItemRows = await db.OrderRefundItem.AsNoTracking()
            .Include(x => x.CouponCode)
            .Where(x => orderRefundIds.Contains(x.OrderRefundID))
            .Select(x => new
            {
                x.OrderRefundID,
                Code = x.CouponCode!.Code,
                x.PostRefundAction
            })
            .ToListAsync(ct);

        var refundItemMap = refundItemRows.GroupBy(x => x.OrderRefundID).ToDictionary(g => g.Key, g => (IReadOnlyList<Response.RefundCoupon>)g.Select(x => new Response.RefundCoupon(x.Code, x.PostRefundAction)).ToList());

        var refunds = order.Refunds.OrderByDescending(r => r.RequestedAt).Select(r => new Response.RefundRow(
            ID: r.ID,
            Type: r.Type,
            Status: r.Status,
            Amount: r.Amount,
            Reason: r.Reason,
            AdminMemo: r.AdminMemo,
            RequestedAt: r.RequestedAt,
            ResolvedAt: r.ResolvedAt,
            Coupons: refundItemMap.GetValueOrDefault(r.ID, [])
        )).ToList();

        return Result.Success(new Response(
            ID: order.ID,
            OrderNumber: order.OrderNumber,
            MemberID: order.MemberID,
            MemberEmail: order.Member?.Email ?? "-",
            ChannelID: order.ChannelID,
            ChannelName: order.Channel?.Name,
            TotalAmount: order.TotalAmount,
            PlatformFeeAmount: order.PlatformFeeAmount,
            GameRevenueAmount: order.GameRevenueAmount,
            ChannelRewardAmount: order.ChannelRewardAmount,
            Status: order.Status,
            CancelReason: order.CancelReason,
            RefundReason: order.RefundReason,
            CreatedAt: order.CreatedAt,
            PaidAt: order.PaidAt,
            Items: items,
            Refunds: refunds,
            Shipment: shipment
        ));
    }
}