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

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

namespace Application.Features.Api.Stocks.GetExchangeRates;

/// <summary>
/// 환율 목록 — 지정일(미지정 시 최신 TradeDate)의 전 통화 환율을 통화코드 오름차순으로 반환 (수출입은행 AP01 수집, 익명).
/// </summary>
internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        var targetDate = request.Date;
        if (targetDate is null)
        {
            targetDate = await db.ExchangeRate.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 list = await db.ExchangeRate.AsNoTracking()
            .Where(c => c.TradeDate == targetDate.Value)
            .OrderBy(c => c.CurrencyUnit)
            .Select(c => new Response.Row
            {
                CurrencyUnit = c.CurrencyUnit,
                CurrencyName = c.CurrencyName,
                DealBasRate = c.DealBasRate,
                Ttb = c.Ttb,
                Tts = c.Tts
            })
            .ToListAsync(ct);

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