ANTOOZA-BACKEND/Application/Features/Api/Paper/GetPositions/Handler.cs

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

namespace Application.Features.Api.Paper.GetPositions;

internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        var accountID = await db.PaperAccount.AsNoTracking().Where(c => c.MemberID == request.MemberID).Select(c => (int?)c.ID).FirstOrDefaultAsync(ct);

        if (accountID is null)
        {
            return new Response([]);
        }

        var positions = await db.PaperPosition.AsNoTracking()
            .Where(c => c.AccountID == accountID.Value && c.Quantity > 0)
            .Select(c => new { c.StockCode, c.Quantity, c.ReservedQuantity, c.AvgPrice })
            .ToListAsync(ct);

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

        var codes = positions.Select(c => c.StockCode).Distinct().ToList();
        var latestCloses = await PaperValuation.GetLatestClosesAsync(db, codes, ct);

        var names = await db.Stock.AsNoTracking()
            .Where(c => codes.Contains(c.Code))
            .Select(c => new { c.Code, c.Name })
            .ToDictionaryAsync(c => c.Code, c => c.Name, ct);

        var rows = new List<Response.Row>();

        foreach (var p in positions)
        {
            decimal? latestClose = latestCloses.TryGetValue(p.StockCode, out var close) ? close : null;
            var marketValue = (latestClose ?? 0m) * p.Quantity;
            var costBasis = p.AvgPrice * p.Quantity;
            var unrealizedPnL = marketValue - costBasis;
            var unrealizedBp = costBasis > 0 ? (int)Math.Round(unrealizedPnL / costBasis * 10000m, MidpointRounding.AwayFromZero) : 0;

            rows.Add(new Response.Row(
                p.StockCode,
                names.GetValueOrDefault(p.StockCode, p.StockCode),
                p.Quantity,
                p.ReservedQuantity,
                p.AvgPrice,
                latestClose,
                marketValue,
                unrealizedPnL,
                unrealizedBp));
        }

        return new Response(rows);
    }
}