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

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

/// <summary>
/// Unit tests for ServerConnection following TDD approach.
/// Tests connection lifecycle and request handling.
/// </summary>
public class ServerConnectionTests
{
    [Fact]
    public async Task ConnectAsync_OpensTransport()
    {
        // Arrange
        var mockTransport = new Mock<IServerTransport>();
        mockTransport.Setup(t => t.ConnectAsync(It.IsAny<CancellationToken>()))
            .Returns(Task.CompletedTask)
            .Callback(() => mockTransport.Setup(t => t.IsConnected).Returns(true));
        mockTransport.Setup(t => t.IsConnected).Returns(false); // Initially not connected

        var serverConfig = new ServerConfig { Id = "test", Name = "Test Server" };
        var connection = new ServerConnection(serverConfig, mockTransport.Object);

        // Act
        await connection.ConnectAsync();

        // Assert
        mockTransport.Verify(t => t.ConnectAsync(It.IsAny<CancellationToken>()), Times.Once);
        Assert.True(connection.IsConnected);
    }

    [Fact]
    public async Task DisconnectAsync_ClosesTransport()
    {
        // Arrange
        var mockTransport = new Mock<IServerTransport>();
        mockTransport.Setup(t => t.DisconnectAsync(It.IsAny<CancellationToken>())).Returns(Task.CompletedTask);
        mockTransport.Setup(t => t.IsConnected).Returns(false);

        var serverConfig = new ServerConfig { Id = "test", Name = "Test Server" };
        var connection = new ServerConnection(serverConfig, mockTransport.Object);

        // Act
        await connection.DisconnectAsync();

        // Assert
        mockTransport.Verify(t => t.DisconnectAsync(It.IsAny<CancellationToken>()), Times.Once);
        Assert.False(connection.IsConnected);
    }

    [Fact]
    public async Task SendRequestAsync_ForwardsToTransport()
    {
        // Arrange
        var mockTransport = new Mock<IServerTransport>();
        var request = new GatewayRequest { ToolName = "test_tool" };
        var expectedResponse = new GatewayResponse { Success = true };

        mockTransport
            .Setup(t => t.SendRequestAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(expectedResponse);
        mockTransport.Setup(t => t.IsConnected).Returns(true);

        var serverConfig = new ServerConfig { Id = "test", Name = "Test Server" };
        var connection = new ServerConnection(serverConfig, mockTransport.Object);

        // Act
        var response = await connection.SendRequestAsync(request);

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

    [Fact]
    public async Task SendRequestAsync_WithTimeout_ThrowsOperationCanceledException()
    {
        // Arrange
        var mockTransport = new Mock<IServerTransport>();
        mockTransport
            .Setup(t => t.SendRequestAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .Returns(async (GatewayRequest req, CancellationToken ct) =>
            {
                // Respect cancellation token
                await Task.Delay(5000, ct);
                return new GatewayResponse { Success = true };
            });
        mockTransport.Setup(t => t.IsConnected).Returns(true);

        var serverConfig = new ServerConfig { Id = "test", Name = "Test Server" };
        var connection = new ServerConnection(serverConfig, mockTransport.Object) { RequestTimeout = TimeSpan.FromMilliseconds(100) };

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

        // Act & Assert
        await Assert.ThrowsAnyAsync<OperationCanceledException>(() => connection.SendRequestAsync(request));
    }

    [Fact]
    public void ServerInfo_ReturnsCorrectInfo()
    {
        // Arrange
        var mockTransport = new Mock<IServerTransport>();
        mockTransport.Setup(t => t.IsConnected).Returns(true);

        var serverConfig = new ServerConfig { Id = "test-123", Name = "Test Server" };
        var connection = new ServerConnection(serverConfig, mockTransport.Object);

        // Act
        var info = connection.ServerInfo;

        // Assert
        Assert.NotNull(info);
        Assert.Equal("test-123", info.Id);
        Assert.Equal("Test Server", info.Name);
        Assert.True(info.IsHealthy);
    }

    [Fact]
    public void IsConnected_ReflectsTransportState()
    {
        // Arrange
        var mockTransport = new Mock<IServerTransport>();
        mockTransport.Setup(t => t.IsConnected).Returns(false);

        var serverConfig = new ServerConfig { Id = "test", Name = "Test Server" };
        var connection = new ServerConnection(serverConfig, mockTransport.Object);

        // Act & Assert
        Assert.False(connection.IsConnected);

        // Change transport state
        mockTransport.Setup(t => t.IsConnected).Returns(true);
        Assert.True(connection.IsConnected);
    }

    [Fact]
    public async Task ConnectAsync_CalledMultipleTimes_CallsTransportEachTime()
    {
        // Arrange
        var mockTransport = new Mock<IServerTransport>();
        mockTransport.Setup(t => t.ConnectAsync(It.IsAny<CancellationToken>())).Returns(Task.CompletedTask);
        mockTransport.Setup(t => t.IsConnected).Returns(true);

        var serverConfig = new ServerConfig { Id = "test", Name = "Test Server" };
        var connection = new ServerConnection(serverConfig, mockTransport.Object);

        // Act
        await connection.ConnectAsync();
        await connection.ConnectAsync(); // Second call

        // Assert - ConnectAsync delegates to transport, which handles idempotency
        mockTransport.Verify(t => t.ConnectAsync(It.IsAny<CancellationToken>()), Times.Exactly(2));
    }

    [Fact]
    public void Dispose_DisposesTransport()
    {
        // Arrange
        var mockTransport = new Mock<IServerTransport>();
        var serverConfig = new ServerConfig { Id = "test", Name = "Test Server" };
        var connection = new ServerConnection(serverConfig, mockTransport.Object);

        // Act
        connection.Dispose();

        // Assert
        mockTransport.Verify(t => t.Dispose(), Times.Once);
    }
}