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

namespace Application.Helpers;

/// <summary>
/// 모의투자 평가값 계산 — 최근 일별 종가(StockDailyPrice)로 포지션·Equity·nav 를 산출한다 (d4 §③).
/// Position.StockCode(char6) → Stock.ID → 최근 StockDailyPrice.Close 로 평가한다.
/// </summary>
public static class PaperValuation
{
    /// <summary>지정 종목코드들의 최근 종가 맵 (없는 코드는 제외).</summary>
    public static async Task<Dictionary<string, decimal>> GetLatestClosesAsync(
        IAppDbContext db,
        IReadOnlyCollection<string> stockCodes,
        CancellationToken ct)
    {
        if (stockCodes.Count == 0)
        {
            return [];
        }

        // 코드 → 종목 ID
        var idByCode = await db.Stock.AsNoTracking()
            .Where(c => stockCodes.Contains(c.Code))
            .Select(c => new { c.Code, c.ID })
            .ToListAsync(ct);

        var result = new Dictionary<string, decimal>();

        foreach (var s in idByCode)
        {
            var close = await db.StockDailyPrice.AsNoTracking()
                .Where(c => c.StockID == s.ID)
                .OrderByDescending(c => c.TradingDate)
                .Select(c => (int?)c.Close)
                .FirstOrDefaultAsync(ct);

            if (close.HasValue)
            {
                result[s.Code] = close.Value;
            }
        }

        return result;
    }

    /// <summary>단일 종목코드의 최근 종가 (없으면 null).</summary>
    public static async Task<decimal?> GetLatestCloseAsync(IAppDbContext db, string stockCode, CancellationToken ct)
    {
        var stockID = await db.Stock.AsNoTracking()
            .Where(c => c.Code == stockCode)
            .Select(c => (int?)c.ID)
            .FirstOrDefaultAsync(ct);

        if (stockID is null)
        {
            return null;
        }

        var close = await db.StockDailyPrice.AsNoTracking()
            .Where(c => c.StockID == stockID.Value)
            .OrderByDescending(c => c.TradingDate)
            .Select(c => (int?)c.Close)
            .FirstOrDefaultAsync(ct);

        return close;
    }

    /// <summary>
    /// 계좌 평가자산 Equity = Token + ReservedToken + Σ(포지션 수량 × 최근 종가).
    /// 시세 없는 포지션은 0 으로 평가(보수적).
    /// </summary>
    public static decimal ComputeEquity(
        decimal token,
        decimal reservedToken,
        IEnumerable<(string StockCode, int Quantity)> positions,
        IReadOnlyDictionary<string, decimal> latestCloses)
    {
        var positionsValue = 0m;

        foreach (var p in positions)
        {
            if (latestCloses.TryGetValue(p.StockCode, out var close))
            {
                positionsValue += close * p.Quantity;
            }
        }

        return token + reservedToken + positionsValue;
    }

    /// <summary>좌당 순자산 nav = Units &gt; 0 ? Equity / Units : 1.</summary>
    public static decimal ComputeNav(decimal equity, decimal units)
    {
        return units > 0 ? equity / units : 1m;
    }
}