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

using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Application.Helpers;
using Domain.Entities.Common.ValueObject;
using Domain.Entities.Paper.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;
using PaperAccountEntity = Domain.Entities.Paper.PaperAccount;
using PaperLedgerEntity = Domain.Entities.Paper.PaperLedger;

namespace Application.Features.Api.Paper.Deposit;

/// <summary>
/// 모의투자 입금 — 지갑 토큰(Reward → Airdrop) 차감 → 계좌 입금. 계좌 없으면 자동 개설.
/// 좌수 발행: 입금 직전 nav = Equity/Units (Units=0 이면 1) → unitsIssued = tokenAmount / nav (d4 §③).
/// </summary>
internal sealed class Handler(IAppDbContext db) : ICommandHandler<Command, Result<Response>>
{
    public async Task<Result<Response>> Handle(Command request, CancellationToken ct)
    {
        var paper = await db.Config.AsNoTracking().OrderByDescending(c => c.ID).Select(c => c.Paper).FirstOrDefaultAsync(ct);

        if (paper is null || !paper.Enabled)
        {
            return Result.Failure<Response>(Error.Problem("Paper.Disabled", "모의투자가 비활성화되어 있습니다."));
        }

        if (request.TokenAmount <= 0)
        {
            return Result.Failure<Response>(Error.Problem("Paper.InvalidAmount", "입금액은 0보다 커야 합니다."));
        }

        if (request.TokenAmount < paper.MinDeposit)
        {
            return Result.Failure<Response>(Error.Problem("Paper.BelowMinDeposit", $"최소 입금 토큰은 {paper.MinDeposit:N0} 입니다."));
        }

        var account = await db.PaperAccount.FirstOrDefaultAsync(c => c.MemberID == request.MemberID, ct);

        if (account is null)
        {
            account = PaperAccountEntity.Create(request.MemberID);
            db.PaperAccount.Add(account);
        }

        // MaxHolding 검증 (0 = 무제한)
        if (paper.MaxHolding > 0 && account.Token + account.ReservedToken + request.TokenAmount > paper.MaxHolding)
        {
            return Result.Failure<Response>(Error.Conflict("Paper.MaxHoldingExceeded", $"계좌 최대 보유 토큰({paper.MaxHolding:N0})을 초과합니다."));
        }

        // 지갑 로드 + 토큰 파티션 잔액 검증
        var wallet = await db.Wallet.Include(c => c.Balances).Include(c => c.Transactions).FirstOrDefaultAsync(c => c.MemberID == request.MemberID, ct);

        if (wallet is null)
        {
            return Result.Failure<Response>(Error.NotFound("Wallet.NotFound", "지갑을 찾을 수 없습니다."));
        }

        var tokenAvailable = wallet.GetPaperTokenAvailable();

        if (tokenAvailable.Value < request.TokenAmount)
        {
            return Result.Failure<Response>(Error.Conflict("Wallet.InsufficientToken", $"토큰 잔액이 부족합니다. 필요: {request.TokenAmount:N0} / 보유: {(long)tokenAvailable.Value:N0}."));
        }

        // 입금 직전 nav 계산 (신규 계좌는 Units=0 → nav=1)
        var positions = await db.PaperPosition.AsNoTracking()
            .Where(c => c.AccountID == account.ID && c.Quantity > 0)
            .Select(c => new { c.StockCode, c.Quantity })
            .ToListAsync(ct);

        var codes = positions.Select(c => c.StockCode).Distinct().ToList();
        var latestCloses = await PaperValuation.GetLatestClosesAsync(db, codes, ct);
        var equity = PaperValuation.ComputeEquity(account.Token, account.ReservedToken, positions.Select(c => (c.StockCode, c.Quantity)), latestCloses);
        var nav = PaperValuation.ComputeNav(equity, account.Units);
        var unitsIssued = request.TokenAmount / nav;

        var refID = $"paper-deposit:{request.MemberID}:{Guid.NewGuid():N}";

        // 지갑 차감 (Reward → Airdrop) + PaperDeposit 트랜잭션
        wallet.DebitForPaperDeposit(Money.KRW(request.TokenAmount), reason: "PAPER_DEPOSIT", refID: refID);

        // 계좌 반영
        account.Deposit(request.TokenAmount, unitsIssued);

        db.PaperLedger.Add(PaperLedgerEntity.CreateFor(
            account,
            PaperLedgerType.Deposit,
            request.TokenAmount,
            unitsIssued,
            refID,
            account.Token));

        await db.SaveChangesAsync(ct);

        return Result.Success(new Response(account.Token, account.Units, unitsIssued));
    }
}