Fix build and code structure improvements. New but essential UI functionality. CI improvements. Documentation improvements. AI module improvements.

src/Router/__Libraries/StellaOps.Router.Gateway/Middleware/RoutingDecisionMiddleware.cs

@@ -0,0 +1,111 @@
+using Microsoft.Extensions.Options;
+using StellaOps.Router.Common.Abstractions;
+using StellaOps.Router.Common.Models;
+using StellaOps.Router.Gateway.Configuration;
+
+namespace StellaOps.Router.Gateway.Middleware;
+
+/// <summary>
+/// Makes routing decisions for resolved endpoints.
+/// </summary>
+public sealed class RoutingDecisionMiddleware
+{
+    private readonly RequestDelegate _next;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="RoutingDecisionMiddleware"/> class.
+    /// </summary>
+    public RoutingDecisionMiddleware(RequestDelegate next)
+    {
+        _next = next;
+    }
+
+    /// <summary>
+    /// Invokes the middleware.
+    /// </summary>
+    public async Task Invoke(
+        HttpContext context,
+        IRoutingPlugin routingPlugin,
+        IGlobalRoutingState routingState,
+        IOptions<RouterNodeConfig> gatewayConfig,
+        IOptions<RoutingOptions> routingOptions)
+    {
+        var endpoint = context.Items[RouterHttpContextKeys.EndpointDescriptor] as EndpointDescriptor;
+        if (endpoint is null)
+        {
+            await RouterErrorWriter.WriteAsync(
+                context,
+                statusCode: StatusCodes.Status500InternalServerError,
+                error: "Endpoint descriptor missing",
+                cancellationToken: context.RequestAborted);
+            return;
+        }
+
+        // Build routing context
+        var availableConnections = routingState.GetConnectionsFor(
+            endpoint.ServiceName,
+            endpoint.Version,
+            endpoint.Method,
+            endpoint.Path);
+
+        var headers = context.Request.Headers
+            .ToDictionary(h => h.Key, h => h.Value.ToString());
+
+        var routingContext = new RoutingContext
+        {
+            Method = context.Request.Method,
+            Path = context.Request.Path.ToString(),
+            Headers = headers,
+            Endpoint = endpoint,
+            AvailableConnections = availableConnections,
+            GatewayRegion = gatewayConfig.Value.Region,
+            RequestedVersion = ExtractVersionFromRequest(context, routingOptions.Value),
+            CancellationToken = context.RequestAborted
+        };
+
+        var decision = await routingPlugin.ChooseInstanceAsync(
+            routingContext,
+            context.RequestAborted);
+
+        if (decision is null)
+        {
+            await RouterErrorWriter.WriteAsync(
+                context,
+                statusCode: StatusCodes.Status503ServiceUnavailable,
+                error: "No instances available",
+                service: endpoint.ServiceName,
+                version: endpoint.Version,
+                cancellationToken: context.RequestAborted);
+            return;
+        }
+
+        context.Items[RouterHttpContextKeys.RoutingDecision] = decision;
+        await _next(context);
+    }
+
+    private static string? ExtractVersionFromRequest(HttpContext context, RoutingOptions options)
+    {
+        // Check for version in Accept header: Accept: application/vnd.stellaops.v1+json
+        var acceptHeader = context.Request.Headers.Accept.FirstOrDefault();
+        if (!string.IsNullOrEmpty(acceptHeader))
+        {
+            var versionMatch = System.Text.RegularExpressions.Regex.Match(
+                acceptHeader,
+                @"application/vnd\.stellaops\.v(\d+(?:\.\d+)*)\+json");
+            if (versionMatch.Success)
+            {
+                return versionMatch.Groups[1].Value;
+            }
+        }
+
+        // Check for X-Api-Version header
+        var versionHeader = context.Request.Headers["X-Api-Version"].FirstOrDefault();
+        if (!string.IsNullOrEmpty(versionHeader))
+        {
+            return versionHeader;
+        }
+
+        // Fall back to default version from options
+        return options.DefaultVersion;
+    }
+}