ANTOOZA-BACKEND/Application/Features/Api/Stocks/GetEsgIndices/Handler.cs

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

namespace Application.Features.Api.Stocks.GetEsgIndices;

/// <summary>
/// ESG 지수 목록 — 지정일(미지정 시 최신 TradeDate) 행을 지수명순으로 페이징 (KRX ESG 지수 수집, 익명).
/// </summary>
internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    private const ushort MaxPerPage = 100;

    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        var page = request.Page < 1 ? 1 : request.Page;
        var perPage = request.PerPage is 0 or > MaxPerPage ? (ushort)20 : request.PerPage;

        var targetDate = request.Date;
        if (targetDate is null)
        {
            targetDate = await db.EsgIndexDailyPrice.AsNoTracking()
                .OrderByDescending(c => c.TradeDate)
                .Select(c => (DateOnly?)c.TradeDate)
                .FirstOrDefaultAsync(ct);
        }

        if (targetDate is null)
        {
            return new Response
            {
                Total = 0,
                TradeDate = null,
                List = []
            };
        }

        var query = db.EsgIndexDailyPrice.AsNoTracking().Where(c => c.TradeDate == targetDate.Value);

        var total = await query.CountAsync(ct);

        var list = await query
            .OrderBy(c => c.IndexName)
            .Skip((page - 1) * perPage)
            .Take(perPage)
            .Select(c => new Response.Row
            {
                Name = c.IndexName,
                Close = c.Close,
                ChangeVal = c.ChangeVal,
                FlucRateBp = c.FlucRateBp,
                ConstituentCount = c.ConstituentCount,
                Volume = c.Volume,
                Value = c.Value
            })
            .ToListAsync(ct);

        return new Response
        {
            Total = total,
            TradeDate = targetDate.Value,
            List = list
        };
    }
}