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

namespace Application.Features.Api.Forum.PostCheer.Get;

/// <summary>글의 응원 합계·건수 + 최근 N건 조회 — D3 M4 (익명 허용). 응원은 열람 조건이 아니므로 공개 표시.</summary>
public sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Result<Response>>
{
    public async Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        var take = Math.Clamp(request.Take <= 0 ? 20 : request.Take, 1, 100);

        var agg = await db.PostCheer.AsNoTracking()
            .Where(c => c.PostID == request.PostID)
            .GroupBy(c => 1)
            .Select(g => new
            {
                TotalAmount = g.Sum(c => (long)c.Amount),
                Count = g.Count()
            })
            .FirstOrDefaultAsync(ct);

        var recent = await db.PostCheer.AsNoTracking()
            .Where(c => c.PostID == request.PostID)
            .OrderByDescending(c => c.CreatedAt)
            .Take(take)
            .Select(c => new Response.Item
            {
                ID = c.ID,
                FromMemberID = c.FromMemberID,
                FromNickname = c.FromMember != null ? c.FromMember.Name : null,
                Amount = c.Amount,
                Message = c.Message,
                CreatedAt = c.CreatedAt
            })
            .ToListAsync(ct);

        return Result.Success(new Response
        {
            TotalAmount = agg?.TotalAmount ?? 0,
            Count = agg?.Count ?? 0,
            Recent = recent
        });
    }
}