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

namespace Application.Features.Api.Stocks.GetMeetingCalendar;

internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Result<Response>>
{
    private const ushort MaxPerPage = 200;

    public async Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        var page = request.Page < 1 ? 1 : request.Page;
        var perPage = request.PerPage is 0 or > MaxPerPage ? (ushort)30 : request.PerPage;

        var query = db.GeneralMeeting.AsNoTracking();

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

        if (request.To.HasValue)
        {
            query = query.Where(c => c.GmetDt <= request.To.Value);
        }

        var total = await query.CountAsync(ct);

        var meetings = await query
            .OrderByDescending(c => c.GmetDt)
            .ThenBy(c => c.IssucoCustno)
            .ThenBy(c => c.GmetKacd)
            .Skip((page - 1) * perPage)
            .Take(perPage)
            .Select(c => new
            {
                c.IssucoCustno,
                c.RgtStdDt,
                c.GmetDt,
                c.GmetTtm,
                c.GmetKacd,
                c.GmetPlace,
                c.EvoteYn,
                c.DferYn
            })
            .ToListAsync(ct);

        if (meetings.Count == 0)
        {
            return new Response { Total = total, List = [] };
        }

        var custnos = meetings.Select(c => c.IssucoCustno).Distinct().ToList();
        var stdDts = meetings.Select(c => c.RgtStdDt).Distinct().ToList();

        // 종목명·단축코드 (IssucoCustno 조인 — 한 회사에 여러 종목이면 대표 1개)
        var stockRows = await db.Stock.AsNoTracking()
            .Where(c => c.IssucoCustno != null && custnos.Contains(c.IssucoCustno.Value))
            .Select(c => new { Custno = c.IssucoCustno!.Value, c.Name, c.Code })
            .ToListAsync(ct);
        var stockByCustno = stockRows.GroupBy(c => c.Custno).ToDictionary(g => g.Key, g => g.First());

        // 안건수 집계 (회사, 기준일) 단위
        var agendaCounts = await db.MeetingAgenda.AsNoTracking()
            .Where(c => custnos.Contains(c.IssucoCustno) && stdDts.Contains(c.RgtStdDt))
            .GroupBy(c => new { c.IssucoCustno, c.RgtStdDt })
            .Select(g => new { g.Key.IssucoCustno, g.Key.RgtStdDt, Count = g.Count() })
            .ToListAsync(ct);
        var agendaLookup = agendaCounts.ToDictionary(c => (c.IssucoCustno, c.RgtStdDt), c => c.Count);

        var list = meetings.Select(c =>
        {
            stockByCustno.TryGetValue(c.IssucoCustno, out var stock);
            agendaLookup.TryGetValue((c.IssucoCustno, c.RgtStdDt), out var agendaCount);
            return new Response.Row
            {
                IssucoCustno = c.IssucoCustno,
                Name = stock?.Name,
                Code = stock?.Code,
                RgtStdDt = c.RgtStdDt,
                GmetDt = c.GmetDt,
                GmetTtm = c.GmetTtm,
                MeetingKind = c.GmetKacd,
                Place = c.GmetPlace,
                Evote = c.EvoteYn,
                Deferred = c.DferYn,
                AgendaCount = agendaCount
            };
        }).ToList();

        return new Response
        {
            Total = total,
            List = list
        };
    }
}