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 * OPC Foundation MIT License 1.00
 *
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 * obtaining a copy of this software and associated documentation
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using System;
using System.Threading.Tasks;
using Microsoft.Extensions.Time.Testing;
using NUnit.Framework;

namespace Opc.Ua.Core.Tests.Stack.Client
{
    [TestFixture]
    [Category("Client")]
    public sealed class RetryBudgetTests
    {
        [Test]
        public async Task BudgetExhaustsAfterMaxTimeAsync()
        {
            var timeProvider = new FakeTimeProvider();
            var budget = new RetryBudget(TimeSpan.FromSeconds(1), timeProvider);

            Assert.That(budget.TryConsume(out TimeSpan remaining), Is.True);
            Assert.That(remaining, Is.EqualTo(TimeSpan.FromSeconds(1)));

            timeProvider.Advance(TimeSpan.FromSeconds(1));
            await Task.Yield();

            Assert.That(budget.IsExhausted, Is.True);
            Assert.That(budget.TryConsume(out remaining), Is.False);
            Assert.That(remaining, Is.EqualTo(TimeSpan.Zero));
        }

        [Test]
        public void TryConsumeReturnsRemainingTime()
        {
            var timeProvider = new FakeTimeProvider();
            var budget = new RetryBudget(TimeSpan.FromSeconds(10), timeProvider);

            Assert.That(budget.TryConsume(out TimeSpan remaining), Is.True);
            Assert.That(remaining, Is.EqualTo(TimeSpan.FromSeconds(10)));

            timeProvider.Advance(TimeSpan.FromSeconds(4));

            Assert.That(budget.TryConsume(out remaining), Is.True);
            Assert.That(remaining, Is.EqualTo(TimeSpan.FromSeconds(6)));
        }

        [Test]
        public void ResetClearsElapsed()
        {
            var timeProvider = new FakeTimeProvider();
            var budget = new RetryBudget(TimeSpan.FromSeconds(10), timeProvider);

            Assert.That(budget.TryConsume(out _), Is.True);
            timeProvider.Advance(TimeSpan.FromSeconds(5));

            Assert.That(budget.ElapsedSinceFirstAttempt, Is.EqualTo(TimeSpan.FromSeconds(5)));

            budget.Reset();

            Assert.That(budget.ElapsedSinceFirstAttempt, Is.EqualTo(TimeSpan.Zero));
            Assert.That(budget.TryConsume(out TimeSpan remaining), Is.True);
            Assert.That(remaining, Is.EqualTo(TimeSpan.FromSeconds(10)));
        }
    }
}