using Xunit;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.TestHost;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Svrnty.MCP.AspNetCore.Extensions;
using System;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;

namespace Svrnty.MCP.Core.Tests;

/// <summary>
/// Unit tests for HttpTransport following TDD approach.
/// Tests JSON-RPC 2.0 protocol over HTTP REST endpoints.
/// </summary>
public class HttpTransportTests : IDisposable
{
    private readonly WebApplication _app;
    private readonly HttpClient _client;
    private readonly McpServer _server;

    public HttpTransportTests()
    {
        // Create a test MCP server with a mock tool
        var registry = new ToolRegistry();
        registry.AddTool(new TestTool());
        _server = new McpServer(registry);

        // Create test web application
        var builder = WebApplication.CreateBuilder();
        builder.WebHost.UseTestServer();
        builder.Services.AddMcpServer(_server);

        _app = builder.Build();
        _app.MapMcpEndpoints(_server);

        _app.StartAsync().Wait();
        _client = _app.GetTestClient();
    }

    [Fact]
    public async Task HttpTransport_HealthEndpoint_ReturnsOk()
    {
        // Act
        var response = await _client.GetAsync("/health");

        // Assert
        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
        var content = await response.Content.ReadAsStringAsync();
        Assert.Contains("Healthy", content);
        Assert.Contains("MCP Server", content);
    }

    [Fact]
    public async Task HttpTransport_InvokeEndpoint_WithValidRequest_ReturnsSuccess()
    {
        // Arrange
        var request = new
        {
            jsonrpc = "2.0",
            method = "tools/list",
            id = "test-1"
        };

        var json = JsonSerializer.Serialize(request);
        var content = new StringContent(json, Encoding.UTF8, "application/json");

        // Act
        var response = await _client.PostAsync("/mcp/invoke", content);

        // Assert
        Assert.Equal(HttpStatusCode.OK, response.StatusCode);

        var responseJson = await response.Content.ReadAsStringAsync();
        var responseObj = JsonSerializer.Deserialize<JsonDocument>(responseJson);
        Assert.NotNull(responseObj);
        Assert.Equal("2.0", responseObj.RootElement.GetProperty("jsonrpc").GetString());
        Assert.Equal("test-1", responseObj.RootElement.GetProperty("id").GetString());
    }

    [Fact]
    public async Task HttpTransport_InvokeEndpoint_WithEmptyBody_ReturnsBadRequest()
    {
        // Arrange
        var content = new StringContent("", Encoding.UTF8, "application/json");

        // Act
        var response = await _client.PostAsync("/mcp/invoke", content);

        // Assert
        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);

        var responseJson = await response.Content.ReadAsStringAsync();
        Assert.Contains("error", responseJson);
        Assert.Contains("-32700", responseJson); // Parse error code
    }

    [Fact]
    public async Task HttpTransport_InvokeEndpoint_WithInvalidJson_ReturnsBadRequest()
    {
        // Arrange
        var content = new StringContent("{invalid json}", Encoding.UTF8, "application/json");

        // Act
        var response = await _client.PostAsync("/mcp/invoke", content);

        // Assert
        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);

        var responseJson = await response.Content.ReadAsStringAsync();
        Assert.Contains("error", responseJson);
        Assert.Contains("Parse error", responseJson);
    }

    [Fact]
    public async Task HttpTransport_InvokeEndpoint_WithToolsCall_ExecutesTool()
    {
        // Arrange
        var request = new
        {
            jsonrpc = "2.0",
            method = "tools/call",
            id = "test-call-1",
            @params = new
            {
                name = "test_tool",
                arguments = new
                {
                    query = "test query"
                }
            }
        };

        var json = JsonSerializer.Serialize(request);
        var content = new StringContent(json, Encoding.UTF8, "application/json");

        // Act
        var response = await _client.PostAsync("/mcp/invoke", content);

        // Assert
        Assert.Equal(HttpStatusCode.OK, response.StatusCode);

        var responseJson = await response.Content.ReadAsStringAsync();
        var responseObj = JsonSerializer.Deserialize<JsonDocument>(responseJson);
        Assert.NotNull(responseObj);
        Assert.Equal("test-call-1", responseObj.RootElement.GetProperty("id").GetString());
    }

    [Fact]
    public async Task HttpTransport_ContentTypeHeader_IsApplicationJson()
    {
        // Arrange
        var request = new
        {
            jsonrpc = "2.0",
            method = "tools/list",
            id = "test-header"
        };

        var json = JsonSerializer.Serialize(request);
        var content = new StringContent(json, Encoding.UTF8, "application/json");

        // Act
        var response = await _client.PostAsync("/mcp/invoke", content);

        // Assert
        Assert.Equal("application/json", response.Content.Headers.ContentType?.MediaType);
    }

    [Fact]
    public async Task HttpTransport_MultipleRequests_AllSucceed()
    {
        // Arrange
        var request = new
        {
            jsonrpc = "2.0",
            method = "tools/list",
            id = "multi-1"
        };

        var json = JsonSerializer.Serialize(request);

        // Act - Send 5 requests
        for (int i = 0; i < 5; i++)
        {
            var content = new StringContent(json, Encoding.UTF8, "application/json");
            var response = await _client.PostAsync("/mcp/invoke", content);

            // Assert
            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
        }
    }

    [Fact]
    public async Task HttpTransport_ToolsListRequest_ReturnsToolInfo()
    {
        // Arrange
        var request = new
        {
            jsonrpc = "2.0",
            method = "tools/list",
            id = "list-test"
        };

        var json = JsonSerializer.Serialize(request);
        var content = new StringContent(json, Encoding.UTF8, "application/json");

        // Act
        var response = await _client.PostAsync("/mcp/invoke", content);

        // Assert
        Assert.Equal(HttpStatusCode.OK, response.StatusCode);

        var responseJson = await response.Content.ReadAsStringAsync();
        Assert.Contains("test_tool", responseJson);
    }

    [Fact]
    public async Task HttpTransport_ServerError_Returns500WithJsonRpcError()
    {
        // This test would need a tool that throws an exception
        // For now, we test the error handling structure

        // Arrange
        var request = new
        {
            jsonrpc = "2.0",
            method = "invalid/method",
            id = "error-test"
        };

        var json = JsonSerializer.Serialize(request);
        var content = new StringContent(json, Encoding.UTF8, "application/json");

        // Act
        var response = await _client.PostAsync("/mcp/invoke", content);

        // Assert - Should handle gracefully
        var responseJson = await response.Content.ReadAsStringAsync();
        Assert.Contains("jsonrpc", responseJson);
    }

    [Fact]
    public void HttpTransport_AddMcpServer_ThrowsOnNullServices()
    {
        // Arrange
        IServiceCollection? services = null;
        var server = new McpServer(new ToolRegistry());

        // Act & Assert
        Assert.Throws<ArgumentNullException>(() =>
            services!.AddMcpServer(server)
        );
    }

    [Fact]
    public void HttpTransport_AddMcpServer_ThrowsOnNullServer()
    {
        // Arrange
        var services = new ServiceCollection();
        McpServer? server = null;

        // Act & Assert
        Assert.Throws<ArgumentNullException>(() =>
            services.AddMcpServer(server!)
        );
    }

    public void Dispose()
    {
        _client?.Dispose();
        _app?.DisposeAsync().AsTask().Wait();
    }

    /// <summary>
    /// Test tool for HTTP transport tests.
    /// </summary>
    private class TestTool : IMcpTool
    {
        public string Name => "test_tool";
        public string Description => "Test tool for HTTP transport tests";

        public JsonDocument Schema => JsonDocument.Parse("""
        {
            "type": "object",
            "properties": {
                "query": {
                    "type": "string",
                    "description": "Test query parameter"
                }
            }
        }
        """);

        public async Task<JsonDocument> ExecuteAsync(JsonDocument? arguments)
        {
            await Task.CompletedTask;
            return JsonDocument.Parse("""{"result": "success", "tool": "test_tool"}""");
        }
    }
}