using PnvPanel.Domain.Billing;
using PnvPanel.Domain.Pricing;
using Xunit;

namespace PnvPanel.Domain.Tests.Billing;

public class RoleChangeTopUpTests
{
    private static readonly DateTimeOffset Now = new(2026, 1, 1, 0, 0, 0, TimeSpan.Zero);

    [Fact]
    public void Compute_WhenNewRoleCheaper_ReturnsNull()
    {
        var amount = RoleChangeTopUp.Compute(
            pricePerConfigPerMonth: 200,
            oldMaxConfigs: 10,
            newMaxConfigs: 3,
            discountTiers: [],
            paidUntil: Now.AddDays(30),
            now: Now
        );

        Assert.Null(amount);
    }

    [Fact]
    public void Compute_WhenPaidUntilAlreadyExpired_ReturnsNull()
    {
        var amount = RoleChangeTopUp.Compute(
            pricePerConfigPerMonth: 200,
            oldMaxConfigs: 3,
            newMaxConfigs: 10,
            discountTiers: [],
            paidUntil: Now.AddDays(-1),
            now: Now
        );

        Assert.Null(amount);
    }

    [Fact]
    public void Compute_WhenEitherRoleUnlimited_ReturnsNull()
    {
        var amount = RoleChangeTopUp.Compute(
            pricePerConfigPerMonth: 200,
            oldMaxConfigs: 3,
            newMaxConfigs: -1,
            discountTiers: [],
            paidUntil: Now.AddDays(30),
            now: Now
        );

        Assert.Null(amount);
    }

    [Fact]
    public void Compute_WhenUpgrading_ReturnsProratedDifference()
    {
        // Старая роль: 200 * 3 = 600 ₽/мес. Новая: 200 * 10 = 2000 ₽/мес. Разница 1400 ₽/мес,
        // за 30 дней (ровно месяц) — 1400 ₽.
        var amount = RoleChangeTopUp.Compute(
            pricePerConfigPerMonth: 200,
            oldMaxConfigs: 3,
            newMaxConfigs: 10,
            discountTiers: [],
            paidUntil: Now.AddDays(30),
            now: Now
        );

        Assert.Equal(1400, amount);
    }

    [Fact]
    public void Compute_ProratesToRemainingDaysOnly()
    {
        // Та же разница 1400 ₽/мес, но остаётся только 15 из 30 дней — половина.
        var amount = RoleChangeTopUp.Compute(
            pricePerConfigPerMonth: 200,
            oldMaxConfigs: 3,
            newMaxConfigs: 10,
            discountTiers: [],
            paidUntil: Now.AddDays(15),
            now: Now
        );

        Assert.Equal(700, amount);
    }

    [Fact]
    public void Compute_AppliesDiscountTiersToBothRoles()
    {
        var tiers = new[] { PricingDiscountTier.Create(Guid.NewGuid(), minConfigs: 10, discountPercent: 10) };

        // Старая роль (3 конфига, без скидки): 200*3 = 600. Новая (10 конфигов, порог скидки достигнут):
        // 200*10 = 2000, -10% = 1800. Разница 1200 ₽/мес, за 30 дней — 1200 ₽.
        var amount = RoleChangeTopUp.Compute(
            pricePerConfigPerMonth: 200,
            oldMaxConfigs: 3,
            newMaxConfigs: 10,
            discountTiers: tiers,
            paidUntil: Now.AddDays(30),
            now: Now
        );

        Assert.Equal(1200, amount);
    }
}