svrnty-mcp-gateway/tests/Svrnty.MCP.Gateway.Infrastructure.Tests/Routing/GatewayRouterTests.cs

using Xunit;
using Moq;
using Svrnty.MCP.Gateway.Infrastructure.Routing;
using Svrnty.MCP.Gateway.Infrastructure.Connection;
using Svrnty.MCP.Gateway.Core.Interfaces;
using Svrnty.MCP.Gateway.Core.Models;

namespace Svrnty.MCP.Gateway.Infrastructure.Tests.Routing;

/// <summary>
/// Unit tests for GatewayRouter following TDD approach.
/// Tests routing, server registration, and health tracking.
/// </summary>
public class GatewayRouterTests
{
    [Fact]
    public async Task RegisterServerAsync_AddsServerToPool()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        var mockPool = new Mock<IServerConnectionPool>();
        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);

        var serverConfig = new ServerConfig
        {
            Id = "server-1",
            Name = "Test Server",
            TransportType = "Http",
            BaseUrl = "http://localhost:5000"
        };

        // Act
        await router.RegisterServerAsync(serverConfig);

        // Assert
        var health = await router.GetServerHealthAsync();
        Assert.Contains(health, s => s.ServerId == "server-1");
    }

    [Fact]
    public async Task UnregisterServerAsync_RemovesServerFromPool()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        var mockPool = new Mock<IServerConnectionPool>();
        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);

        var serverConfig = new ServerConfig
        {
            Id = "server-1",
            Name = "Test Server",
            TransportType = "Http",
            BaseUrl = "http://localhost:5000"
        };

        await router.RegisterServerAsync(serverConfig);

        // Act
        var result = await router.UnregisterServerAsync("server-1");

        // Assert
        Assert.True(result);
        var health = await router.GetServerHealthAsync();
        Assert.DoesNotContain(health, s => s.ServerId == "server-1");
    }

    [Fact]
    public async Task UnregisterServerAsync_WithNonExistentServer_ReturnsFalse()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        var mockPool = new Mock<IServerConnectionPool>();
        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);

        // Act
        var result = await router.UnregisterServerAsync("non-existent");

        // Assert
        Assert.False(result);
    }

    [Fact]
    public async Task RouteAsync_WithValidRequest_RoutesToSelectedServer()
    {
        // Arrange
        var serverConfig = new ServerConfig
        {
            Id = "server-1",
            Name = "Test Server",
            TransportType = "Http",
            BaseUrl = "http://localhost:5000"
        };

        var mockConnection = new Mock<IServerConnection>();
        mockConnection.Setup(c => c.IsConnected).Returns(true);
        mockConnection.Setup(c => c.ServerInfo).Returns(new ServerInfo { Id = "server-1", Name = "Test Server", IsHealthy = true });
        mockConnection.Setup(c => c.SendRequestAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new GatewayResponse { Success = true });

        var mockPool = new Mock<IServerConnectionPool>();
        mockPool.Setup(p => p.GetConnectionAsync(It.IsAny<ServerConfig>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(mockConnection.Object);

        var mockStrategy = new Mock<IRoutingStrategy>();
        mockStrategy.Setup(s => s.SelectServerAsync(It.IsAny<IEnumerable<ServerInfo>>(), It.IsAny<RoutingContext>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new ServerInfo { Id = "server-1", Name = "Test Server", IsHealthy = true });

        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);
        await router.RegisterServerAsync(serverConfig);

        var request = new GatewayRequest { ToolName = "test_tool" };

        // Act
        var response = await router.RouteAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.True(response.Success);
        mockConnection.Verify(c => c.SendRequestAsync(request, It.IsAny<CancellationToken>()), Times.Once);
    }

    [Fact]
    public async Task RouteAsync_WithNoHealthyServers_ReturnsErrorResponse()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        mockStrategy.Setup(s => s.SelectServerAsync(It.IsAny<IEnumerable<ServerInfo>>(), It.IsAny<RoutingContext>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync((ServerInfo?)null);

        var mockPool = new Mock<ServerConnectionPool>();
        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);

        var request = new GatewayRequest { ToolName = "test_tool" };

        // Act
        var response = await router.RouteAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.False(response.Success);
        Assert.Contains("No healthy servers", response.Error);
    }

    [Fact]
    public async Task GetServerHealthAsync_ReturnsAllRegisteredServers()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        var mockPool = new Mock<IServerConnectionPool>();
        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);

        var server1 = new ServerConfig { Id = "server-1", Name = "Server 1", TransportType = "Http", BaseUrl = "http://localhost:5000" };
        var server2 = new ServerConfig { Id = "server-2", Name = "Server 2", TransportType = "Http", BaseUrl = "http://localhost:5001" };

        await router.RegisterServerAsync(server1);
        await router.RegisterServerAsync(server2);

        // Act
        var health = await router.GetServerHealthAsync();

        // Assert
        Assert.Equal(2, health.Count());
        Assert.Contains(health, s => s.ServerId == "server-1");
        Assert.Contains(health, s => s.ServerId == "server-2");
    }

    [Fact]
    public async Task RouteAsync_UsesRoutingStrategy()
    {
        // Arrange
        var serverConfig = new ServerConfig
        {
            Id = "selected-server",
            Name = "Selected Server",
            TransportType = "Http",
            BaseUrl = "http://localhost:5000"
        };

        var mockConnection = new Mock<IServerConnection>();
        mockConnection.Setup(c => c.IsConnected).Returns(true);
        mockConnection.Setup(c => c.ServerInfo).Returns(new ServerInfo { Id = "selected-server", IsHealthy = true });
        mockConnection.Setup(c => c.SendRequestAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new GatewayResponse { Success = true });

        var mockPool = new Mock<IServerConnectionPool>();
        mockPool.Setup(p => p.GetConnectionAsync(It.Is<ServerConfig>(sc => sc.Id == "selected-server"), It.IsAny<CancellationToken>()))
            .ReturnsAsync(mockConnection.Object);

        var mockStrategy = new Mock<IRoutingStrategy>();
        mockStrategy.Setup(s => s.SelectServerAsync(It.IsAny<IEnumerable<ServerInfo>>(), It.IsAny<RoutingContext>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new ServerInfo { Id = "selected-server", IsHealthy = true });

        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);
        await router.RegisterServerAsync(serverConfig);

        var request = new GatewayRequest { ToolName = "test_tool", ClientId = "test-client" };

        // Act
        await router.RouteAsync(request);

        // Assert - verify strategy was called
        mockStrategy.Verify(s => s.SelectServerAsync(
            It.IsAny<IEnumerable<ServerInfo>>(),
            It.Is<RoutingContext>(rc => rc.ToolName == "test_tool" && rc.ClientId == "test-client"),
            It.IsAny<CancellationToken>()), Times.Once);
    }

    [Fact]
    public async Task RouteAsync_SetsServerIdInResponse()
    {
        // Arrange
        var serverConfig = new ServerConfig
        {
            Id = "server-1",
            Name = "Test Server",
            TransportType = "Http",
            BaseUrl = "http://localhost:5000"
        };

        var mockConnection = new Mock<IServerConnection>();
        mockConnection.Setup(c => c.IsConnected).Returns(true);
        mockConnection.Setup(c => c.ServerInfo).Returns(new ServerInfo { Id = "server-1", IsHealthy = true });
        mockConnection.Setup(c => c.SendRequestAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new GatewayResponse { Success = true });

        var mockPool = new Mock<IServerConnectionPool>();
        mockPool.Setup(p => p.GetConnectionAsync(It.IsAny<ServerConfig>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(mockConnection.Object);

        var mockStrategy = new Mock<IRoutingStrategy>();
        mockStrategy.Setup(s => s.SelectServerAsync(It.IsAny<IEnumerable<ServerInfo>>(), It.IsAny<RoutingContext>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new ServerInfo { Id = "server-1", IsHealthy = true });

        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);
        await router.RegisterServerAsync(serverConfig);

        var request = new GatewayRequest { ToolName = "test_tool" };

        // Act
        var response = await router.RouteAsync(request);

        // Assert
        Assert.Equal("server-1", response.ServerId);
    }

    [Fact]
    public async Task RouteAsync_TracksPassiveHealth_OnSuccess()
    {
        // Arrange
        var serverConfig = new ServerConfig
        {
            Id = "server-1",
            Name = "Test Server",
            TransportType = "Http",
            BaseUrl = "http://localhost:5000"
        };

        var mockConnection = new Mock<IServerConnection>();
        mockConnection.Setup(c => c.IsConnected).Returns(true);
        mockConnection.Setup(c => c.ServerInfo).Returns(new ServerInfo { Id = "server-1", IsHealthy = true, ResponseTime = TimeSpan.FromMilliseconds(50) });
        mockConnection.Setup(c => c.SendRequestAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new GatewayResponse { Success = true });

        var mockPool = new Mock<IServerConnectionPool>();
        mockPool.Setup(p => p.GetConnectionAsync(It.IsAny<ServerConfig>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(mockConnection.Object);

        var mockStrategy = new Mock<IRoutingStrategy>();
        mockStrategy.Setup(s => s.SelectServerAsync(It.IsAny<IEnumerable<ServerInfo>>(), It.IsAny<RoutingContext>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new ServerInfo { Id = "server-1", IsHealthy = true });

        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);
        await router.RegisterServerAsync(serverConfig);

        var request = new GatewayRequest { ToolName = "test_tool" };

        // Act
        await router.RouteAsync(request);

        // Assert - passive health should be tracked (implementation will verify this)
        mockConnection.Verify(c => c.SendRequestAsync(request, It.IsAny<CancellationToken>()), Times.Once);
    }

    [Fact]
    public async Task RouteAsync_TracksPassiveHealth_OnFailure()
    {
        // Arrange
        var serverConfig = new ServerConfig
        {
            Id = "server-1",
            Name = "Test Server",
            TransportType = "Http",
            BaseUrl = "http://localhost:5000"
        };

        var mockConnection = new Mock<IServerConnection>();
        mockConnection.Setup(c => c.IsConnected).Returns(true);
        mockConnection.Setup(c => c.ServerInfo).Returns(new ServerInfo { Id = "server-1", IsHealthy = true });
        mockConnection.Setup(c => c.SendRequestAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ThrowsAsync(new Exception("Request failed"));

        var mockPool = new Mock<IServerConnectionPool>();
        mockPool.Setup(p => p.GetConnectionAsync(It.IsAny<ServerConfig>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(mockConnection.Object);

        var mockStrategy = new Mock<IRoutingStrategy>();
        mockStrategy.Setup(s => s.SelectServerAsync(It.IsAny<IEnumerable<ServerInfo>>(), It.IsAny<RoutingContext>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new ServerInfo { Id = "server-1", IsHealthy = true });

        var router = new GatewayRouter(mockStrategy.Object, mockPool.Object);
        await router.RegisterServerAsync(serverConfig);

        var request = new GatewayRequest { ToolName = "test_tool" };

        // Act
        var response = await router.RouteAsync(request);

        // Assert
        Assert.False(response.Success);
        Assert.Contains("Request failed", response.Error);
    }
}