using Microsoft.EntityFrameworkCore;
using PnvPanel.Application.Auth;
using PnvPanel.Application.Common.Concurrency;
using PnvPanel.Application.Common.Interfaces;
using PnvPanel.Application.Common.Messaging;
using PnvPanel.Application.Common.Models;
using PnvPanel.Domain.Billing;
using PnvPanel.Domain.Pricing;

namespace PnvPanel.Application.Billing.CreatePaymentRequest;

/// <summary>Проверка "нет активной заявки" + создание — под AdvisoryLock (по UserId): без неё
/// два одновременных запроса (двойной клик, повтор при таймауте) оба могли бы пройти проверку и
/// создать по заявке каждый — а дальше их обе можно независимо подтвердить, продлив оплату дважды.</summary>
public sealed class CreatePaymentRequestCommandHandler(
    IAppDbContext dbContext,
    IIdentityService identityService,
    ICurrentUser currentUser
) : ICommandHandler<CreatePaymentRequestCommand, Result<PaymentRequestDto>>
{
    public async Task<Result<PaymentRequestDto>> Handle(
        CreatePaymentRequestCommand command,
        CancellationToken cancellationToken
    )
    {
        if (currentUser.UserId is not { } userId)
            return Result.Failure<PaymentRequestDto>(AuthErrors.Unauthorized);

        var profile = await identityService.GetProfileAsync(userId, cancellationToken);
        if (profile is null)
            return Result.Failure<PaymentRequestDto>(AuthErrors.Unauthorized);

        if (!profile.BillingEnabled)
            return Result.Failure<PaymentRequestDto>(BillingErrors.NotEnabled);

        if (profile.ConfigQuota == RoleQuota.Unlimited)
            return Result.Failure<PaymentRequestDto>(BillingErrors.UnlimitedRoleNotSupported);

        var pricing = await dbContext.PricingSettings.AsNoTracking().FirstOrDefaultAsync(cancellationToken);
        if (pricing is null)
            return Result.Failure<PaymentRequestDto>(BillingErrors.PricingNotConfigured);

        var ratePerMonth = command.Period switch
        {
            PaymentPeriod.Quarter => pricing.PricePerConfigPerQuarter,
            PaymentPeriod.HalfYear => pricing.PricePerConfigPerHalfYear,
            PaymentPeriod.Year => pricing.PricePerConfigPerYear,
            _ => null,
        };
        if (ratePerMonth is not { } rate)
            return Result.Failure<PaymentRequestDto>(BillingErrors.PricingNotConfigured);

        var discountTiers = await dbContext
            .PricingDiscountTiers.AsNoTracking()
            .Where(t => t.PricingSettingsId == pricing.Id)
            .ToListAsync(cancellationToken);
        var discountPercent = PricingDiscount.ResolvePercent(discountTiers, profile.ConfigQuota);

        var amount = PricingDiscount.Apply(rate * profile.ConfigQuota * command.Period.ToMonths(), discountPercent);

        var claimed = await AdvisoryLock.RunAsync(
            dbContext,
            userId,
            async lockedCancellationToken =>
            {
                // PlanChangeTopUp не считается активной подписной заявкой — доплата за смену тарифа не
                // должна мешать пользователю продлить/оформить обычную подписку.
                var hasActiveRequest = await dbContext.PaymentRequests.AnyAsync(
                    r =>
                        r.UserId == userId
                        && r.Kind == PaymentRequestKind.Subscription
                        && (
                            r.Status == PaymentRequestStatus.AwaitingPayment
                            || r.Status == PaymentRequestStatus.AwaitingConfirmation
                        ),
                    lockedCancellationToken
                );
                if (hasActiveRequest)
                    return Result.Failure<PaymentRequest>(BillingErrors.ActiveRequestExists);

                var request = PaymentRequest.Create(userId, command.Period, amount);
                dbContext.PaymentRequests.Add(request);
                return Result.Success(request);
            },
            cancellationToken
        );

        return claimed.IsSuccess
            ? Result.Success(PaymentRequestDto.FromDomain(claimed.Value))
            : Result.Failure<PaymentRequestDto>(claimed.Error);
    }
}