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

namespace Application.Features.Admin.Store.Coupon.ListCodes;

public sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        var baseQuery = db.CouponCode.AsNoTracking().Where(c => c.CouponID == request.CouponID);

        // 상태별 카운트 (필터 무관, 전체 통계)
        var counts = await db.CouponCode
            .AsNoTracking()
            .Where(c => c.CouponID == request.CouponID)
            .GroupBy(c => c.Status)
            .Select(g => new { Status = g.Key, Count = g.Count() })
            .ToListAsync(ct);

        var available = counts.FirstOrDefault(x => x.Status == CouponCodeStatus.Available)?.Count ?? 0;
        var reserved = counts.FirstOrDefault(x => x.Status == CouponCodeStatus.Reserved)?.Count ?? 0;
        var issued = counts.FirstOrDefault(x => x.Status == CouponCodeStatus.Issued)?.Count ?? 0;
        var used = counts.FirstOrDefault(x => x.Status == CouponCodeStatus.Used)?.Count ?? 0;
        var expired = counts.FirstOrDefault(x => x.Status == CouponCodeStatus.Expired)?.Count ?? 0;

        // 필터 적용
        var query = baseQuery;

        if (request.Status.HasValue)
        {
            query = query.Where(c => c.Status == request.Status.Value);
        }

        var total = await query.CountAsync(ct);

        var list = await query
            .Include(c => c.IssuedToMember)
            .OrderByDescending(c => c.ID)
            .Skip((request.Page - 1) * request.PerPage)
            .Take(request.PerPage)
            .Select(c => new
            {
                c.ID,
                c.Code,
                c.Status,
                c.IssuedToMemberID,
                IssuedToMemberName = c.IssuedToMember != null ? c.IssuedToMember.Name : null,
                IssuedToMemberEmail = c.IssuedToMember != null ? c.IssuedToMember.Email : null,
                c.IssuedAt,
                c.UsedAt,
                c.CreatedAt
            })
            .ToListAsync(ct);

        var startNum = total - ((request.Page - 1) * request.PerPage);

        return new Response(
            Total: total,
            AvailableCount: available,
            ReservedCount: reserved,
            IssuedCount: issued,
            UsedCount: used,
            ExpiredCount: expired,
            List: [.. list.Select((c, i) => new Response.Row(
                Num: startNum - i,
                c.ID,
                c.Code,
                c.Status,
                c.IssuedToMemberID,
                c.IssuedToMemberName,
                c.IssuedToMemberEmail,
                c.IssuedAt,
                c.UsedAt,
                c.CreatedAt
            ))]
        );
    }
}