btcpayserver/BTCPayServer/Payments/IPaymentFilter.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace BTCPayServer.Payments
{
    public interface IPaymentFilter
    {
        bool Match(PaymentMethodId paymentMethodId);
    }

    public class PaymentFilter
    {
        class OrPaymentFilter : IPaymentFilter
        {
            private readonly IPaymentFilter _a;
            private readonly IPaymentFilter _b;

            public OrPaymentFilter(IPaymentFilter a, IPaymentFilter b)
            {
                _a = a;
                _b = b;
            }
            public bool Match(PaymentMethodId paymentMethodId)
            {
                return _a.Match(paymentMethodId) || _b.Match(paymentMethodId);
            }
        }
        class NeverPaymentFilter : IPaymentFilter
        {

            private static readonly NeverPaymentFilter _Instance = new NeverPaymentFilter();
            public static NeverPaymentFilter Instance
            {
                get
                {
                    return _Instance;
                }
            }
            public bool Match(PaymentMethodId paymentMethodId)
            {
                return false;
            }
        }
        class CompositePaymentFilter : IPaymentFilter
        {
            private readonly IPaymentFilter[] _filters;

            public CompositePaymentFilter(IPaymentFilter[] filters)
            {
                _filters = filters;
            }
            public bool Match(PaymentMethodId paymentMethodId)
            {
                return _filters.Any(f => f.Match(paymentMethodId));
            }
        }
        class PaymentIdFilter : IPaymentFilter
        {
            private readonly PaymentMethodId _paymentMethodId;

            public PaymentIdFilter(PaymentMethodId paymentMethodId)
            {
                _paymentMethodId = paymentMethodId;
            }
            public bool Match(PaymentMethodId paymentMethodId)
            {
                return paymentMethodId == _paymentMethodId;
            }
        }
        class PredicateFilter : IPaymentFilter
        {
            private Func<PaymentMethodId, bool> predicate;

            public PredicateFilter(Func<PaymentMethodId, bool> predicate)
            {
                this.predicate = predicate;
            }

            public bool Match(PaymentMethodId paymentMethodId)
            {
                return this.predicate(paymentMethodId);
            }
        }
        public static IPaymentFilter Where(Func<PaymentMethodId, bool> predicate)
        {
            if (predicate == null)
                throw new ArgumentNullException(nameof(predicate));
            return new PredicateFilter(predicate);
        }
        public static IPaymentFilter Or(IPaymentFilter a, IPaymentFilter b)
        {
            if (a == null)
                throw new ArgumentNullException(nameof(a));
            if (b == null)
                throw new ArgumentNullException(nameof(b));
            return new OrPaymentFilter(a, b);
        }
        public static IPaymentFilter Never()
        {
            return NeverPaymentFilter.Instance;
        }
        public static IPaymentFilter Any(IPaymentFilter[] filters)
        {
            if (filters == null)
                throw new ArgumentNullException(nameof(filters));
            return new CompositePaymentFilter(filters);
        }
        public static IPaymentFilter WhereIs(PaymentMethodId paymentMethodId)
        {
            if (paymentMethodId == null)
                throw new ArgumentNullException(nameof(paymentMethodId));
            return new PaymentIdFilter(paymentMethodId);
        }
    }
}