using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Microsoft.EntityFrameworkCore;

namespace Application.Features.Api.Member.Items.Equipped;

/// <summary>
/// 여러 회원의 장착 지위 아이템을 한 번에 조회한다 (댓글/채팅/프로필 목록 렌더용).
/// 만료(ExpiresAt 경과)·회수 아이템은 제외한다.
/// </summary>
internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    private const int MaxIDs = 200;

    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        var ids = request.MemberIDs.Where(id => id > 0).Distinct().Take(MaxIDs).ToList();

        if (ids.Count == 0)
        {
            return new Response([]);
        }

        var now = DateTime.UtcNow;

        var rows = await db.MemberItem.AsNoTracking()
            .Include(i => i.Product)
            .Where(i => ids.Contains(i.MemberID)
                && i.IsEquipped
                && i.EquipSlot != null
                && i.RevokedAt == null
                && (i.ExpiresAt == null || i.ExpiresAt > now))
            .Select(i => new
            {
                i.MemberID,
                Slot = i.EquipSlot!.Value,
                i.Kind,
                ProductName = i.Product!.Name,
                i.Product.EffectPayload,
                i.Product.Thumbnail
            })
            .ToListAsync(ct);

        var members = rows
            .GroupBy(r => r.MemberID)
            .Select(g => new Response.MemberEquip(
                g.Key,
                g.OrderBy(x => x.Slot)
                 .Select(x => new Response.EquippedItem(x.Slot, x.Kind, x.ProductName, x.EffectPayload, x.Thumbnail))
                 .ToList()))
            .ToList();

        return new Response(members);
    }
}