using Xunit;
using Moq;
using System.Text.Json;
using System.Threading.Tasks;

namespace OpenHarbor.MCP.Core.Tests;

/// <summary>
/// Unit tests for McpServer following TDD approach.
/// Tests MCP protocol method routing and execution.
/// </summary>
public class McpServerTests
{
    [Fact]
    public void McpServer_ShouldInitializeWithToolRegistry()
    {
        // Arrange
        var registry = new ToolRegistry();

        // Act
        var server = new McpServer(registry);

        // Assert
        Assert.NotNull(server);
    }

    [Fact]
    public void McpServer_ShouldThrowOnNullRegistry()
    {
        // Act & Assert
        Assert.Throws<ArgumentNullException>(() =>
            new McpServer(null!)
        );
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithToolsList_ShouldReturnToolDescriptions()
    {
        // Arrange
        var registry = new ToolRegistry();
        var mockTool = CreateMockTool("test_tool", "Test tool description");
        registry.AddTool(mockTool.Object);

        var server = new McpServer(registry);
        var request = new McpRequest
        {
            Id = "1",
            Method = "tools/list"
        };

        // Act
        var response = await server.HandleRequestAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.Equal("1", response.Id);
        Assert.Null(response.Error);
        Assert.NotNull(response.Result);

        var result = response.Result.RootElement;
        Assert.True(result.TryGetProperty("tools", out var tools));
        Assert.Equal(JsonValueKind.Array, tools.ValueKind);
        Assert.Equal(1, tools.GetArrayLength());

        var tool = tools[0];
        Assert.True(tool.TryGetProperty("name", out var name));
        Assert.Equal("test_tool", name.GetString());
        Assert.True(tool.TryGetProperty("description", out var desc));
        Assert.Equal("Test tool description", desc.GetString());
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithToolsList_EmptyRegistry_ShouldReturnEmptyArray()
    {
        // Arrange
        var registry = new ToolRegistry();
        var server = new McpServer(registry);
        var request = new McpRequest
        {
            Id = "1",
            Method = "tools/list"
        };

        // Act
        var response = await server.HandleRequestAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.Null(response.Error);
        Assert.NotNull(response.Result);

        var result = response.Result.RootElement;
        Assert.True(result.TryGetProperty("tools", out var tools));
        Assert.Equal(0, tools.GetArrayLength());
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithToolsCall_ShouldExecuteTool()
    {
        // Arrange
        var registry = new ToolRegistry();
        var mockTool = CreateMockTool("search_codex", "Search tool");
        mockTool.Setup(t => t.ExecuteAsync(It.IsAny<JsonDocument>()))
                .ReturnsAsync(JsonDocument.Parse("""{"results": ["doc1", "doc2"]}"""));
        registry.AddTool(mockTool.Object);

        var server = new McpServer(registry);
        var request = new McpRequest
        {
            Id = "2",
            Method = "tools/call",
            Params = JsonDocument.Parse("""{"name":"search_codex","arguments":{"query":"test"}}""")
        };

        // Act
        var response = await server.HandleRequestAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.Equal("2", response.Id);
        Assert.Null(response.Error);
        Assert.NotNull(response.Result);

        var result = response.Result.RootElement;
        Assert.True(result.TryGetProperty("results", out var results));
        mockTool.Verify(t => t.ExecuteAsync(It.IsAny<JsonDocument>()), Times.Once);
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithToolsCall_NonexistentTool_ShouldReturnError()
    {
        // Arrange
        var registry = new ToolRegistry();
        var server = new McpServer(registry);
        var request = new McpRequest
        {
            Id = "3",
            Method = "tools/call",
            Params = JsonDocument.Parse("""{"name":"nonexistent_tool","arguments":{}}""")
        };

        // Act
        var response = await server.HandleRequestAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.Equal("3", response.Id);
        Assert.Null(response.Result);
        Assert.NotNull(response.Error);
        Assert.Equal(-32601, response.Error.Code); // Method not found
        Assert.Contains("nonexistent_tool", response.Error.Message);
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithUnknownMethod_ShouldReturnError()
    {
        // Arrange
        var registry = new ToolRegistry();
        var server = new McpServer(registry);
        var request = new McpRequest
        {
            Id = "4",
            Method = "unknown/method"
        };

        // Act
        var response = await server.HandleRequestAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.Equal("4", response.Id);
        Assert.Null(response.Result);
        Assert.NotNull(response.Error);
        Assert.Equal(-32601, response.Error.Code); // Method not found
        Assert.Contains("unknown/method", response.Error.Message);
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithToolsCall_MissingParams_ShouldReturnError()
    {
        // Arrange
        var registry = new ToolRegistry();
        var server = new McpServer(registry);
        var request = new McpRequest
        {
            Id = "5",
            Method = "tools/call"
            // No Params
        };

        // Act
        var response = await server.HandleRequestAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.Equal("5", response.Id);
        Assert.Null(response.Result);
        Assert.NotNull(response.Error);
        Assert.Equal(-32602, response.Error.Code); // Invalid params
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithToolsCall_MissingToolName_ShouldReturnError()
    {
        // Arrange
        var registry = new ToolRegistry();
        var server = new McpServer(registry);
        var request = new McpRequest
        {
            Id = "6",
            Method = "tools/call",
            Params = JsonDocument.Parse("""{"arguments":{}}""") // Missing "name"
        };

        // Act
        var response = await server.HandleRequestAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.Equal("6", response.Id);
        Assert.Null(response.Result);
        Assert.NotNull(response.Error);
        Assert.Equal(-32602, response.Error.Code); // Invalid params
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithNullRequest_ShouldThrow()
    {
        // Arrange
        var registry = new ToolRegistry();
        var server = new McpServer(registry);

        // Act & Assert
        await Assert.ThrowsAsync<ArgumentNullException>(async () =>
            await server.HandleRequestAsync(null!)
        );
    }

    [Fact]
    public async Task McpServer_HandleRequest_WithToolsList_MultipleTools_ShouldReturnAll()
    {
        // Arrange
        var registry = new ToolRegistry();
        registry.AddTool(CreateMockTool("tool1", "First tool").Object);
        registry.AddTool(CreateMockTool("tool2", "Second tool").Object);
        registry.AddTool(CreateMockTool("tool3", "Third tool").Object);

        var server = new McpServer(registry);
        var request = new McpRequest
        {
            Id = "7",
            Method = "tools/list"
        };

        // Act
        var response = await server.HandleRequestAsync(request);

        // Assert
        Assert.NotNull(response);
        Assert.NotNull(response.Result);
        var result = response.Result.RootElement;
        Assert.True(result.TryGetProperty("tools", out var tools));
        Assert.Equal(3, tools.GetArrayLength());
    }

    // Helper method to create mock tools
    private Mock<IMcpTool> CreateMockTool(string name, string description)
    {
        var mockTool = new Mock<IMcpTool>();
        mockTool.Setup(t => t.Name).Returns(name);
        mockTool.Setup(t => t.Description).Returns(description);
        mockTool.Setup(t => t.Schema).Returns(JsonDocument.Parse("""{"type": "object"}"""));
        mockTool.Setup(t => t.ExecuteAsync(It.IsAny<JsonDocument>()))
                .ReturnsAsync(JsonDocument.Parse("""{"status": "ok"}"""));
        return mockTool;
    }
}