using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace Domain.Entities.Paper;

/// <summary>
/// 모의투자 보유 포지션 — (AccountID, StockCode) UNIQUE. StockCode 는 FK 없이 denorm 보관 (d0 §2.1).
/// ReservedQuantity 로 이중 매도를 차단한다.
/// </summary>
public class PaperPosition
{
    [ForeignKey(nameof(AccountID))]
    public virtual PaperAccount Account { get; private set; } = null!;

    [Key]
    public int ID { get; private set; }

    public int AccountID { get; private set; }

    /// <summary>단축코드 (char 6)</summary>
    public string StockCode { get; private set; } = default!;

    /// <summary>보유 수량</summary>
    public int Quantity { get; private set; }

    /// <summary>매도 주문으로 예약된 수량</summary>
    public int ReservedQuantity { get; private set; }

    /// <summary>평균 단가 (18,4) — 매수 체결 시 평균단가법 갱신</summary>
    public decimal AvgPrice { get; private set; }

    public DateTime UpdatedAt { get; private set; } = DateTime.UtcNow;

    [Timestamp]
    public byte[] RowVersion { get; private set; } = default!;

    private PaperPosition() { }

    public static PaperPosition Create(int accountID, string stockCode, int quantity, decimal avgPrice)
    {
        if (accountID <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(accountID));
        }

        if (stockCode is not { Length: 6 })
        {
            throw new ArgumentException("stockCode must be 6 chars", nameof(stockCode));
        }

        if (quantity < 0)
        {
            throw new ArgumentOutOfRangeException(nameof(quantity));
        }

        return new PaperPosition
        {
            AccountID = accountID,
            StockCode = stockCode,
            Quantity = quantity,
            ReservedQuantity = 0,
            AvgPrice = avgPrice
        };
    }

    /// <summary>매도 주문 접수 시 수량 예약 — 가용 수량(Quantity - ReservedQuantity) 부족 시 실패.</summary>
    public void ReserveSell(int quantity)
    {
        if (quantity <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(quantity));
        }

        if (Quantity - ReservedQuantity < quantity)
        {
            throw new InvalidOperationException("매도 가능한 수량이 부족합니다.");
        }

        ReservedQuantity += quantity;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>매도 예약 환원 (주문 취소·거부).</summary>
    public void ReleaseSellReserve(int quantity)
    {
        if (quantity <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(quantity));
        }

        if (ReservedQuantity < quantity)
        {
            throw new InvalidOperationException("환원할 예약 수량이 부족합니다.");
        }

        ReservedQuantity -= quantity;
        UpdatedAt = DateTime.UtcNow;
    }
}