using FluentAssertions;
using IBKRTrader.Modules.Accounting.Logic;
using IBKRTrader.Modules.Accounting.Models;

namespace IBKRTrader.Tests.Modules.Accounting;

[Trait("cat", "unit")]
public class AccountingEngineTests
{
    private static LedgerEntry E(LedgerEventType type, decimal net, decimal gross, int day, decimal fee = 0m) =>
        new()
        {
            AccountId = "U1", EventType = type, NetBase = net, GrossBase = gross, FeeBase = fee,
            Timestamp = new DateTime(2026, 3, day, 12, 0, 0, DateTimeKind.Utc)
        };

    [Fact]
    public void Statement_SatisfiesBalanceInvariant()
    {
        var entries = new[]
        {
            E(LedgerEventType.Deposit, 1000m, 1000m, 1),
            E(LedgerEventType.TradeBuy, -500m, 499m, 2, fee: 1m),
            E(LedgerEventType.TradeSell, 650m, 651m, 3, fee: 1m),
            E(LedgerEventType.Dividend, 20m, 20m, 4),
            E(LedgerEventType.Withdrawal, -200m, 200m, 5)
        };

        var s = AccountingEngine.BuildStatement(entries, new DateTime(2026, 3, 1, 0, 0, 0, DateTimeKind.Utc),
            new DateTime(2026, 3, 31, 23, 59, 59, DateTimeKind.Utc), "U1");

        // Invariante: Endsaldo − Anfang = Ergebnis + Einzahlungen − Auszahlungen
        s.BalanceChange.Should().Be(s.NetTradingResult + s.Deposits - s.Withdrawals);
        s.Deposits.Should().Be(1000m);
        s.Withdrawals.Should().Be(200m);
        s.Dividends.Should().Be(20m);
        s.Fees.Should().Be(2m);
        s.TradeCount.Should().Be(2);
        s.ClosingBalance.Should().Be(970m);   // 1000 -500 +650 +20 -200
    }

    [Fact]
    public void OpeningBalance_AccumulatesEntriesBeforeFrom()
    {
        var entries = new[]
        {
            E(LedgerEventType.Deposit, 500m, 500m, 1),     // vor dem Zeitraum
            E(LedgerEventType.Dividend, 30m, 30m, 20)      // im Zeitraum
        };

        var s = AccountingEngine.BuildStatement(entries, new DateTime(2026, 3, 10, 0, 0, 0, DateTimeKind.Utc),
            new DateTime(2026, 3, 31, 0, 0, 0, DateTimeKind.Utc), "U1");

        s.OpeningBalance.Should().Be(500m);
        s.ClosingBalance.Should().Be(530m);
    }

    [Fact]
    public void MonthlyBreakdown_ChainsOpeningBalances()
    {
        var entries = new[]
        {
            E(LedgerEventType.Deposit, 100m, 100m, 1),   // März
            E(LedgerEventType.Dividend, 10m, 10m, 5)
        };

        var monthly = AccountingEngine.BuildMonthlyBreakdown(entries,
            new DateTime(2026, 3, 1, 0, 0, 0, DateTimeKind.Utc),
            new DateTime(2026, 4, 30, 0, 0, 0, DateTimeKind.Utc), "U1");

        monthly.Should().HaveCount(2);
        monthly[0].From.Month.Should().Be(3);
        monthly[1].OpeningBalance.Should().Be(monthly[0].ClosingBalance);  // April startet mit März-Endsaldo
    }
}