Implement basic functionality

RateLimiter.Tests/DelayRateLimiterRuleTests.cs

@@ -0,0 +1,58 @@
+using System;
+using NUnit.Framework;
+using RateLimiter.Exceptions;
+using RateLimiter.Implementations;
+
+namespace RateLimiter.Tests;
+
+[TestFixture]
+public class DelayRateLimiterRuleTests
+{
+    [Test]
+    public void Validate_EnoughTime_Ok()
+    {
+        // Arrange
+        const int delay = 10;
+        var token = Guid.NewGuid().ToString("N");
+        var previousRequests = Moq.RequestsDates(delay + delay / 2, delay * 2);
+        var limiter = new DelayRateLimiterRule(TimeSpan.FromSeconds(delay));
+        // Act, Assert
+        Assert.DoesNotThrow(() => limiter.Validate(token, previousRequests));
+    }
+
+    [Test]
+    public void Validate_NotEnoughTime_ThrowsException()
+    {
+        // Arrange
+        const int delay = 10;
+        var token = Guid.NewGuid().ToString("N");
+        var previousRequests = Moq.RequestsDates(delay / 2);
+        var limiter = new DelayRateLimiterRule(TimeSpan.FromSeconds(delay));
+        // Act, Assert
+        Assert.Throws<RateLimitException>(() => limiter.Validate(token, previousRequests));
+    }
+
+    [Test]
+    public void Validate_NotEnoughTimeWithSelector_ThrowsException()
+    {
+        // Arrange
+        const int delay = 10;
+        var token = "US-" + Guid.NewGuid().ToString("N");
+        var previousRequests = Moq.RequestsDates(delay / 2);
+        var limiter = new DelayRateLimiterRule(TimeSpan.FromSeconds(delay), Moq.PrefixSelector("US-"));
+        // Act, Assert
+        Assert.Throws<RateLimitException>(() => limiter.Validate(token, previousRequests));
+    }
+
+    [Test]
+    public void Validate_NotApplicable_Ok()
+    {
+        // Arrange
+        const int delay = 10;
+        var token = "EU-" + Guid.NewGuid().ToString("N");
+        var previousRequests = Moq.RequestsDates(delay / 2);
+        var limiter = new DelayRateLimiterRule(TimeSpan.FromSeconds(delay), Moq.PrefixSelector("US-"));
+        // Act, Assert
+        Assert.DoesNotThrow(() => limiter.Validate(token, previousRequests));
+    }
+}

RateLimiter.Tests/Moq.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Moq;
+using RateLimiter.Abstractions;
+using RateLimiter.Exceptions;
+using RateLimiter.Infrastructure;
+
+namespace RateLimiter.Tests;
+
+public static class Moq
+{
+    public static IRateLimiterRule Rule(bool isSuccess)
+    {
+        var mock = new Mock<IRateLimiterRule>();
+        if (!isSuccess)
+        {
+            mock.Setup(x => x.Validate(It.IsAny<string>(), It.IsAny<IReadOnlyCollection<DateTime>>()))
+                .Throws(new RateLimitException(string.Empty, string.Empty));
+        }
+        return mock.Object;
+    }
+
+    public static Func<string, bool> PrefixSelector(string prefix) => x => x.StartsWith(prefix);
+
+    public static IRequestsRepository RepositoryFromDelays(params int[] delays)
+    {
+        var mock = new Mock<IRequestsRepository>();
+        mock.Setup(x => x.GetPreviousRequests(It.IsAny<string>()))
+            .Returns(RequestsDates(delays));
+        return mock.Object;
+    }
+
+    public static List<DateTime> RequestsDates(params int[] delays) => delays.Select(x => DateTime.UtcNow.AddSeconds(-x)).ToList();
+}

RateLimiter.Tests/RateLimiter.Tests.csproj

@@ -9,6 +9,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
+    <PackageReference Include="Moq" Version="4.20.72" />
     <PackageReference Include="NUnit" Version="3.13.3" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.4.2" />
   </ItemGroup>

RateLimiter.Tests/RateLimiterTest.cs

@@ -1,13 +1,35 @@
-using NUnit.Framework;
+using System;
+using Microsoft.Extensions.Logging;
+using Moq;
+using NUnit.Framework;
+using RateLimiter.Exceptions;
 
 namespace RateLimiter.Tests;
 
 [TestFixture]
 public class RateLimiterTest
 {
-	[Test]
-	public void Example()
-	{
-		Assert.That(true, Is.True);
-	}
+    [Test]
+    public void LimitRequestsForToken_Ok()
+    {
+        // Arrange
+        var token = Guid.NewGuid().ToString("N");
+        var limiter = new Implementations.RateLimiter([Moq.Rule(true)],
+                                                      Moq.RepositoryFromDelays(),
+                                                      Mock.Of<ILogger<Implementations.RateLimiter>>());
+        // Act, Assert
+        Assert.DoesNotThrow(() => limiter.LimitRequestsForToken(token));
+    }
+
+    [Test]
+    public void LimitRequestsForToken_Fails()
+    {
+        // Arrange
+        var token = Guid.NewGuid().ToString("N");
+        var limiter = new Implementations.RateLimiter([Moq.Rule(false)],
+                                                      Moq.RepositoryFromDelays(),
+                                                      Mock.Of<ILogger<Implementations.RateLimiter>>());
+        // Act, Assert
+        Assert.Throws<RateLimitException>(() => limiter.LimitRequestsForToken(token));
+    }
 }

RateLimiter.Tests/TimeWindowRateLimiterRuleTests.cs

@@ -0,0 +1,62 @@
+using System;
+using NUnit.Framework;
+using RateLimiter.Exceptions;
+using RateLimiter.Implementations;
+
+namespace RateLimiter.Tests;
+
+[TestFixture]
+public class TimeWindowRateLimiterRuleTests
+{
+    [Test]
+    public void Validate_EnoughTime_Ok()
+    {
+        // Arrange
+        const int delay = 10;
+        const int maxRequests = 3;
+        var token = Guid.NewGuid().ToString("N");
+        var previousRequests = Moq.RequestsDates(delay / 2, delay / 2, delay * 2);
+        var limiter = new TimeWindowRateLimiterRule(TimeSpan.FromSeconds(delay), maxRequests);
+        // Act, Assert
+        Assert.DoesNotThrow(() => limiter.Validate(token, previousRequests));
+    }
+
+    [Test]
+    public void Validate_NotEnoughTime_ThrowsException()
+    {
+        // Arrange
+        const int delay = 10;
+        const int maxRequests = 3;
+        var token = Guid.NewGuid().ToString("N");
+        var previousRequests = Moq.RequestsDates(delay / 2, delay / 2, delay / 2);
+        var limiter = new TimeWindowRateLimiterRule(TimeSpan.FromSeconds(delay), maxRequests);
+        // Act, Assert
+        Assert.Throws<RateLimitException>(() => limiter.Validate(token, previousRequests));
+    }
+
+    [Test]
+    public void Validate_NotEnoughTimeWithSelector_ThrowsException()
+    {
+        // Arrange
+        const int delay = 10;
+        const int maxRequests = 3;
+        var token = "US-" + Guid.NewGuid().ToString("N");
+        var previousRequests = Moq.RequestsDates(delay / 2, delay / 2, delay / 2);
+        var limiter = new TimeWindowRateLimiterRule(TimeSpan.FromSeconds(delay), maxRequests, Moq.PrefixSelector("US-"));
+        // Act, Assert
+        Assert.Throws<RateLimitException>(() => limiter.Validate(token, previousRequests));
+    }
+
+    [Test]
+    public void Validate_NotApplicable_Ok()
+    {
+        // Arrange
+        const int delay = 10;
+        const int maxRequests = 3;
+        var token = "EU-" + Guid.NewGuid().ToString("N");
+        var previousRequests = Moq.RequestsDates(delay / 2, delay / 2, delay / 2);
+        var limiter = new TimeWindowRateLimiterRule(TimeSpan.FromSeconds(delay), maxRequests, Moq.PrefixSelector("US-"));
+        // Act, Assert
+        Assert.DoesNotThrow(() => limiter.Validate(token, previousRequests));
+    }
+}

RateLimiter.sln.DotSettings.user

@@ -0,0 +1,8 @@
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+  &lt;TestAncestor&gt;&#xD;
+    &lt;TestId&gt;NUnit3x::C4F9249B-010E-46BE-94B8-DD20D82F1E60::net6.0::RateLimiter.Tests.DelayRateLimiterRuleTests&lt;/TestId&gt;&#xD;
+    &lt;TestId&gt;NUnit3x::C4F9249B-010E-46BE-94B8-DD20D82F1E60::net6.0::RateLimiter.Tests.TimeWindowRateLimiterRuleTests&lt;/TestId&gt;&#xD;
+    &lt;TestId&gt;NUnit3x::C4F9249B-010E-46BE-94B8-DD20D82F1E60::net6.0::RateLimiter.Tests.RateLimiterTest&lt;/TestId&gt;&#xD;
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+&lt;/SessionState&gt;</s:String></wpf:ResourceDictionary>

RateLimiter/Abstractions/IRateLimiter.cs

@@ -0,0 +1,6 @@
+namespace RateLimiter.Abstractions;
+
+public interface IRateLimiter
+{
+    public void LimitRequestsForToken(string token);
+}

RateLimiter/Abstractions/IRateLimiterRule.cs

@@ -0,0 +1,9 @@
+using System;
+using System.Collections.Generic;
+
+namespace RateLimiter.Abstractions;
+
+public interface IRateLimiterRule
+{
+    void Validate(string token, IReadOnlyCollection<DateTime> previousRequests);
+}

RateLimiter/Exceptions/RateLimitException.cs

@@ -0,0 +1,8 @@
+using System;
+
+namespace RateLimiter.Exceptions;
+
+public class RateLimitException(string message, string ruleType) : Exception(message)
+{
+    public string RuleType => ruleType;
+}

RateLimiter/Implementations/DelayRateLimiterRule.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using RateLimiter.Exceptions;
+
+namespace RateLimiter.Implementations;
+
+public class DelayRateLimiterRule(TimeSpan timeSpan, Func<string, bool>? selector = null) : SpecificRateLimiterRule(selector)
+{
+    protected override void ValidateIfRequired(string token, IReadOnlyCollection<DateTime> previousRequests)
+    {
+        if (previousRequests.Any(x => x + timeSpan >= DateTime.UtcNow))
+        {
+            throw new RateLimitException("Not enough Time since last request", nameof(DelayRateLimiterRule));
+        }
+    }
+}

RateLimiter/Implementations/RateLimiter.cs

@@ -0,0 +1,39 @@
+using System.Collections.Generic;
+using Microsoft.Extensions.Logging;
+using RateLimiter.Abstractions;
+using RateLimiter.Exceptions;
+using RateLimiter.Infrastructure;
+
+namespace RateLimiter.Implementations;
+
+public class RateLimiter : IRateLimiter
+{
+    private readonly ILogger<RateLimiter> _logger;
+    private readonly IRequestsRepository _requestsRepository;
+    private readonly IEnumerable<IRateLimiterRule> _rules;
+
+    public RateLimiter(IEnumerable<IRateLimiterRule> rules, IRequestsRepository requestsRepository, ILogger<RateLimiter> logger)
+    {
+        _rules = rules;
+        _requestsRepository = requestsRepository;
+        _logger = logger;
+    }
+
+    public void LimitRequestsForToken(string token)
+    {
+        var previousRequests = _requestsRepository.GetPreviousRequests(token);
+
+        try
+        {
+            foreach (var rule in _rules)
+            {
+                rule.Validate(token, previousRequests);
+            }
+        }
+        catch (RateLimitException ex)
+        {
+            _logger.LogInformation("Too many Attempts for Token: {Token}; Rule: {Rule}.", token, ex.RuleType);
+            throw;
+        }
+    }
+}

RateLimiter/Implementations/SpecificRateLimiterRule.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using RateLimiter.Abstractions;
+
+namespace RateLimiter.Implementations;
+
+public abstract class SpecificRateLimiterRule(Func<string, bool>? selector = null) : IRateLimiterRule
+{
+    private readonly Func<string, bool> _appliedRule = selector ?? (_ => true);
+
+    public void Validate(string token, IReadOnlyCollection<DateTime> previousRequests)
+    {
+        if (!_appliedRule(token))
+        {
+            return;
+        }
+
+        ValidateIfRequired(token, previousRequests);
+    }
+
+    protected abstract void ValidateIfRequired(string token, IReadOnlyCollection<DateTime> previousRequests);
+}

RateLimiter/Implementations/TimeWindowRateLimiterRule.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using RateLimiter.Exceptions;
+
+namespace RateLimiter.Implementations;
+
+public class TimeWindowRateLimiterRule(TimeSpan timeSpan, int maxRequests, Func<string, bool>? selector = null) : SpecificRateLimiterRule(selector)
+{
+    protected override void ValidateIfRequired(string token, IReadOnlyCollection<DateTime> previousRequests)
+    {
+        if (previousRequests.Count(x => DateTime.UtcNow - x <= timeSpan) >= maxRequests)
+        {
+            throw new RateLimitException("Expected less requests", nameof(TimeWindowRateLimiterRule));
+        }
+    }
+}

RateLimiter/Infrastructure/IRequestsRepository.cs

@@ -0,0 +1,10 @@
+using System;
+using System.Collections.Generic;
+
+namespace RateLimiter.Infrastructure;
+
+public interface IRequestsRepository
+{
+    public IReadOnlyCollection<DateTime> GetPreviousRequests(string token);
+    public void AddRequest(string token, DateTime date);
+}