using FluentAssertions;
using IBKRTrader.Core.Capital;
using IBKRTrader.Core.Trading;

namespace IBKRTrader.Tests.Trading;

/// <summary>
/// Sell-to-open und Deckungsprüfung im Core (#300).
///
/// <para>Bis hierher lehnte <c>EvaluateSell</c> jeden Verkauf ohne Bestand grundsätzlich ab – und
/// genau das ist die Kernoperation des OptionsWheels. Die Prüfung sitzt bewusst im Core: ein
/// Modul, das sich selbst prüft, prüft sich irgendwann nicht mehr.</para>
/// </summary>
[Trait("cat", "unit")]
public class RiskServiceOptionTests
{
    private readonly RiskService _risk = new();

    private static readonly DateOnly Expiry = new(2026, 9, 18);
    private static readonly RiskParameters Params = new(5m, 20m, 5m);

    private static OptionSpec Put(decimal strike = 150m) => new("AAPL", Expiry, strike, OptionRight.Put);
    private static OptionSpec Call(decimal strike = 150m) => new("AAPL", Expiry, strike, OptionRight.Call);

    private static TradeSignal Sell(OptionSpec spec, int? qty = 1) => new()
    {
        Symbol = "AAPL", Side = TradeSide.Sell, SourceModule = "OW",
        Option = spec, SuggestedQuantity = qty
    };

    private static TradeSignal Buy(OptionSpec spec, int? qty = null) => new()
    {
        Symbol = "AAPL", Side = TradeSide.Buy, SourceModule = "OW",
        Option = spec, SuggestedQuantity = qty
    };

    /// <summary>Reichlich Konto, reichlich Spielraum – damit nur die geprüfte Regel greift.</summary>
    private static RiskContext Ctx(
        decimal price = 2.50m, int held = 0, int shares = 0, int boundShares = 0,
        decimal cash = 1_000_000m, decimal bookHeadroom = 1_000_000m,
        decimal symbolExposure = 0m, decimal symbolLimit = 0m, bool halted = false) => new()
    {
        Price                       = price,
        NetLiquidation              = 1_000_000m,
        ExistingQuantity            = held,
        Coverage                    = new CoverageCalculator.Coverage(shares, boundShares, 0m),
        AvailableCashForReservation = cash,
        BookHeadroom                = bookHeadroom,
        SymbolExposure              = symbolExposure,
        SymbolLimit                 = symbolLimit,
        BuyingHalted                = halted
    };

    // ─── Cash-Secured Put ────────────────────────────────────────────────────────

    [Fact]
    public void SellingAPutWithoutHolding_IsApproved_WhenCashCoversTheObligation()
    {
        var d = _risk.Evaluate(Sell(Put()), Ctx(cash: 15_000m), Params);

        d.Approved.Should().BeTrue();
        d.Quantity.Should().Be(1);
        d.ClosingQuantity.Should().Be(0);   // eroeffnet, schliesst nichts
    }

    [Fact]
    public void SellingAPut_IsRefused_WhenCashIsShort()
    {
        var d = _risk.Evaluate(Sell(Put()), Ctx(cash: 14_999m), Params);

        d.Approved.Should().BeFalse();
        d.Breach!.Kind.Should().Be(LimitKind.Coverage);
        d.Reason.Should().Contain("Deckung");
    }

    [Fact]
    public void SellingThreePuts_WithCashForTwo_IsRefused_AndSaysTwoWouldWork()
    {
        var d = _risk.Evaluate(Sell(Put(), qty: 3), Ctx(cash: 32_000m), Params);

        d.Approved.Should().BeFalse();
        d.Breach!.MaxQuantity.Should().Be(2);
    }

    // ─── Covered Call ────────────────────────────────────────────────────────────

    [Fact]
    public void SellingACall_IsApproved_WithOneHundredFreeShares()
    {
        var d = _risk.Evaluate(Sell(Call()), Ctx(shares: 100), Params);

        d.Approved.Should().BeTrue();
        d.Quantity.Should().Be(1);
    }

    [Fact]
    public void SellingASecondCallAgainstTheSameShares_IsRefused()
    {
        var d = _risk.Evaluate(Sell(Call()), Ctx(shares: 100, boundShares: 100), Params);

        d.Approved.Should().BeFalse();
        d.Breach!.Kind.Should().Be(LimitKind.Coverage);
    }

    [Fact]
    public void CashDoesNotCoverACall_OnlySharesDo()
    {
        // Ein Call wird mit Stuecken gedeckt, nicht mit Geld. Eine Million Bargeld traegt keinen
        // einzigen geschriebenen Call.
        var d = _risk.Evaluate(Sell(Call()), Ctx(shares: 0, cash: 1_000_000m), Params);

        d.Approved.Should().BeFalse();
    }

    // ─── Schließen ist nie limitiert ─────────────────────────────────────────────

    [Fact]
    public void BuyingToCloseAWrittenContract_IsAllowed_EvenWhenBuyingIsHalted()
    {
        // Ein Rueckkauf baut eine Verpflichtung ab. Der Kaufstopp soll Neuengagements verhindern,
        // nicht deren Aufloesung - sonst sperrt die Sicherung den Ausgang.
        var d = _risk.Evaluate(Buy(Put()), Ctx(held: -2, halted: true, cash: 0m, bookHeadroom: 0m), Params);

        d.Approved.Should().BeTrue();
        d.Quantity.Should().Be(2);
        d.ClosingQuantity.Should().Be(2);
    }

    [Fact]
    public void BuyingToClose_IsCappedAtTheWrittenQuantity()
    {
        var d = _risk.Evaluate(Buy(Put(), qty: 5), Ctx(held: -2), Params);

        d.Quantity.Should().Be(2);
    }

    [Fact]
    public void SellingToCloseABoughtContract_IsAllowed_WithoutAnyCoverage()
    {
        var d = _risk.Evaluate(Sell(Put(), qty: 1), Ctx(held: 3, cash: 0m), Params);

        d.Approved.Should().BeTrue();
        d.Quantity.Should().Be(1);
        d.ClosingQuantity.Should().Be(1);
    }

    // ─── Grenzen des eröffnenden Teils ───────────────────────────────────────────

    [Fact]
    public void OpeningIsRefused_WhenTheBookHasNoHeadroomLeft()
    {
        var d = _risk.Evaluate(Sell(Put()), Ctx(cash: 1_000_000m, bookHeadroom: 10_000m), Params);

        d.Approved.Should().BeFalse();
        d.Breach!.Kind.Should().Be(LimitKind.BookCap);
    }

    [Fact]
    public void OpeningIsRefused_WhenItWouldBreachTheSymbolConcentration()
    {
        var d = _risk.Evaluate(Sell(Put()),
            Ctx(cash: 1_000_000m, symbolExposure: 40_000m, symbolLimit: 50_000m), Params);

        d.Approved.Should().BeFalse();
        d.Breach!.Kind.Should().Be(LimitKind.SymbolConcentration);
    }

    [Fact]
    public void BuyingAnOption_SizesByContractCost_NotByShareCost()
    {
        // Kurs 2,50 je Kontrakt = 250 je Stueck. Bei 5 % von 1.000.000 = 50.000 Budget waeren das
        // 200 Kontrakte - ohne den Multiplikator kaeme das Hundertfache heraus.
        var d = _risk.Evaluate(Buy(Put()), Ctx(price: 2.50m), Params);

        d.Approved.Should().BeTrue();
        d.Quantity.Should().Be(200);
    }

    [Fact]
    public void BuyingIsRefused_WhileTheWatchdogHoldsTheLine()
    {
        var d = _risk.Evaluate(Buy(Put()), Ctx(halted: true), Params);

        d.Approved.Should().BeFalse();
        d.Breach!.Kind.Should().Be(LimitKind.BuyingHalted);
    }

    // ─── Der Aktienpfad bleibt, wie er war ───────────────────────────────────────

    [Fact]
    public void SellingStockWithoutHolding_IsStillRefused()
    {
        var signal = new TradeSignal { Symbol = "AAPL", Side = TradeSide.Sell, SourceModule = "CT" };

        var d = _risk.Evaluate(signal, Ctx(price: 100m, cash: 1_000_000m), Params);

        d.Approved.Should().BeFalse();
        d.Reason.Should().Contain("Keine Position");
    }

    [Fact]
    public void SellingStockYouHold_StillClosesTheWholePosition()
    {
        var signal = new TradeSignal { Symbol = "AAPL", Side = TradeSide.Sell, SourceModule = "CT" };

        var d = _risk.Evaluate(signal, Ctx(price: 100m, held: 7), Params);

        d.Approved.Should().BeTrue();
        d.Quantity.Should().Be(7);
        d.ClosingQuantity.Should().Be(7);
    }
}