Refactor: Prepare gateway for dynamic server configuration updates (#191)

* Refactor: Update mcpServer handler functions to use serverName

Changed the three mcpServer handler functions to take `serverName` string
parameter instead of `*catalog.ServerConfig`:
- mcpServerToolHandler
- mcpServerPromptHandler
- mcpServerResourceHandler

Each function now looks up the ServerConfig dynamically using
`g.configuration.Find(serverName)` at the start of the handler closure.

Benefits:
- Reduces coupling between handler registration and server configuration
- Handlers automatically use the latest configuration without re-registration
- Consistent pattern across all three handler types
- Better error handling with explicit server lookup failures

All call sites in capabilitites.go updated to pass serverConfig.Name
instead of serverConfig.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Refactor: Use slices.Contains instead of manual loop

Replace manual loop to check if serverName exists in serverNames slice
with slices.Contains for cleaner, more idiomatic Go code.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Refactor: Remove configuration parameter from listCapabilities

Changed listCapabilities to use g.configuration directly instead of
accepting it as a parameter. This simplifies the function signature
and ensures it always uses the gateway's current configuration.

Changes:
- Updated function signature to remove Configuration parameter
- Changed configuration.Find() to g.configuration.Find()
- Updated isToolEnabled() calls to use g.configuration
- Updated both call sites in reload.go

Benefits:
- Simpler function signature
- Eliminates possibility of passing stale configuration
- Consistent with other methods that access g.configuration directly
- Reduces parameter passing overhead

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: slimslenderslacks

pkg/gateway/capabilitites.go

@@ -110,7 +110,7 @@ func (caps *Capabilities) getResourceTemplateByURITemplate(resource string) (Res
 	return ResourceTemplateRegistration{}, fmt.Errorf("unable to find resource template")
 }
 
-func (g *Gateway) listCapabilities(ctx context.Context, configuration Configuration, serverNames []string, clientConfig *clientConfig) (*Capabilities, error) {
+func (g *Gateway) listCapabilities(ctx context.Context, serverNames []string, clientConfig *clientConfig) (*Capabilities, error) {
 	var (
 		lock            sync.Mutex
 		allCapabilities []Capabilities
@@ -119,7 +119,7 @@ func (g *Gateway) listCapabilities(ctx context.Context, configuration Configurat
 	errs, ctx := errgroup.WithContext(ctx)
 	errs.SetLimit(runtime.NumCPU())
 	for _, serverName := range serverNames {
-		serverConfig, toolGroup, found := configuration.Find(serverName)
+		serverConfig, toolGroup, found := g.configuration.Find(serverName)
 
 		switch {
 		case !found:
@@ -148,7 +148,7 @@ func (g *Gateway) listCapabilities(ctx context.Context, configuration Configurat
 					prefix := g.getToolNamePrefix(serverConfig)
 
 					for _, tool := range tools.Tools {
-						if !isToolEnabled(configuration, serverConfig.Name, serverConfig.Spec.Image, tool.Name, g.ToolNames) {
+						if !isToolEnabled(g.configuration, serverConfig.Name, serverConfig.Spec.Image, tool.Name, g.ToolNames) {
 							continue
 						}
 
@@ -159,7 +159,7 @@ func (g *Gateway) listCapabilities(ctx context.Context, configuration Configurat
 						capabilities.Tools = append(capabilities.Tools, ToolRegistration{
 							ServerName: serverConfig.Name,
 							Tool:       &prefixedTool,
-							Handler:    g.mcpServerToolHandler(serverConfig, g.mcpServer, tool.Annotations),
+							Handler:    g.mcpServerToolHandler(serverConfig.Name, g.mcpServer, tool.Annotations),
 						})
 					}
 				}
@@ -173,7 +173,7 @@ func (g *Gateway) listCapabilities(ctx context.Context, configuration Configurat
 						capabilities.Prompts = append(capabilities.Prompts, PromptRegistration{
 							ServerName: serverConfig.Name,
 							Prompt:     prompt,
-							Handler:    g.mcpServerPromptHandler(serverConfig, g.mcpServer),
+							Handler:    g.mcpServerPromptHandler(serverConfig.Name, g.mcpServer),
 						})
 					}
 				}
@@ -187,7 +187,7 @@ func (g *Gateway) listCapabilities(ctx context.Context, configuration Configurat
 						capabilities.Resources = append(capabilities.Resources, ResourceRegistration{
 							ServerName: serverConfig.Name,
 							Resource:   resource,
-							Handler:    g.mcpServerResourceHandler(serverConfig, g.mcpServer),
+							Handler:    g.mcpServerResourceHandler(serverConfig.Name, g.mcpServer),
 						})
 					}
 				}
@@ -201,7 +201,7 @@ func (g *Gateway) listCapabilities(ctx context.Context, configuration Configurat
 						capabilities.ResourceTemplates = append(capabilities.ResourceTemplates, ResourceTemplateRegistration{
 							ServerName:       serverConfig.Name,
 							ResourceTemplate: *resourceTemplate,
-							Handler:          g.mcpServerResourceHandler(serverConfig, g.mcpServer),
+							Handler:          g.mcpServerResourceHandler(serverConfig.Name, g.mcpServer),
 						})
 					}
 				}
@@ -241,7 +241,7 @@ func (g *Gateway) listCapabilities(ctx context.Context, configuration Configurat
 			}
 
 			for _, tool := range *toolGroup {
-				if !isToolEnabled(configuration, serverName, "", tool.Name, g.ToolNames) {
+				if !isToolEnabled(g.configuration, serverName, "", tool.Name, g.ToolNames) {
 					continue
 				}
 

pkg/gateway/dynamic_mcps.go

@@ -497,13 +497,7 @@ func (g *Gateway) createMcpAddTool(clientConfig *clientConfig) *ToolRegistration
 		}
 
 		// Append the new server to the current serverNames if not already present
-		found = false
-		for _, existing := range g.configuration.serverNames {
-			if existing == serverName {
-				found = true
-				break
-			}
-		}
+		found = slices.Contains(g.configuration.serverNames, serverName)
 		if !found {
 			g.configuration.serverNames = append(g.configuration.serverNames, serverName)
 		}

pkg/gateway/handlers.go

@@ -57,8 +57,14 @@ func (g *Gateway) mcpToolHandler(tool catalog.Tool) mcp.ToolHandler {
 	}
 }
 
-func (g *Gateway) mcpServerToolHandler(serverConfig *catalog.ServerConfig, server *mcp.Server, annotations *mcp.ToolAnnotations) mcp.ToolHandler {
+func (g *Gateway) mcpServerToolHandler(serverName string, server *mcp.Server, annotations *mcp.ToolAnnotations) mcp.ToolHandler {
 	return func(ctx context.Context, req *mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+		// Look up server configuration
+		serverConfig, _, ok := g.configuration.Find(serverName)
+		if !ok {
+			return nil, fmt.Errorf("server %q not found in configuration", serverName)
+		}
+
 		// Debug logging to stderr
 		if os.Getenv("DOCKER_MCP_TELEMETRY_DEBUG") != "" {
 			fmt.Fprintf(os.Stderr, "[MCP-HANDLER] Tool call received: %s from server: %s\n", req.Params.Name, serverConfig.Name)
@@ -152,8 +158,14 @@ func (g *Gateway) mcpServerToolHandler(serverConfig *catalog.ServerConfig, serve
 	}
 }
 
-func (g *Gateway) mcpServerPromptHandler(serverConfig *catalog.ServerConfig, server *mcp.Server) mcp.PromptHandler {
+func (g *Gateway) mcpServerPromptHandler(serverName string, server *mcp.Server) mcp.PromptHandler {
 	return func(ctx context.Context, req *mcp.GetPromptRequest) (*mcp.GetPromptResult, error) {
+		// Look up server configuration
+		serverConfig, _, ok := g.configuration.Find(serverName)
+		if !ok {
+			return nil, fmt.Errorf("server %q not found in configuration", serverName)
+		}
+
 		// Debug logging to stderr
 		if os.Getenv("DOCKER_MCP_TELEMETRY_DEBUG") != "" {
 			fmt.Fprintf(os.Stderr, "[MCP-HANDLER] Prompt get received: %s from server: %s\n", req.Params.Name, serverConfig.Name)
@@ -212,8 +224,14 @@ func (g *Gateway) mcpServerPromptHandler(serverConfig *catalog.ServerConfig, ser
 	}
 }
 
-func (g *Gateway) mcpServerResourceHandler(serverConfig *catalog.ServerConfig, server *mcp.Server) mcp.ResourceHandler {
+func (g *Gateway) mcpServerResourceHandler(serverName string, server *mcp.Server) mcp.ResourceHandler {
 	return func(ctx context.Context, req *mcp.ReadResourceRequest) (*mcp.ReadResourceResult, error) {
+		// Look up server configuration
+		serverConfig, _, ok := g.configuration.Find(serverName)
+		if !ok {
+			return nil, fmt.Errorf("server %q not found in configuration", serverName)
+		}
+
 		// Debug logging to stderr
 		if os.Getenv("DOCKER_MCP_TELEMETRY_DEBUG") != "" {
 			fmt.Fprintf(os.Stderr, "[MCP-HANDLER] Resource read received: %s from server: %s\n", req.Params.URI, serverConfig.Name)

pkg/gateway/reload.go

@@ -26,7 +26,7 @@ func (g *Gateway) reloadConfiguration(ctx context.Context, configuration Configu
 	// List all the available tools.
 	startList := time.Now()
 	log.Log("- Listing MCP tools...")
-	capabilities, err := g.listCapabilities(ctx, configuration, serverNames, clientConfig)
+	capabilities, err := g.listCapabilities(ctx, serverNames, clientConfig)
 	if err != nil {
 		return fmt.Errorf("listing resources: %w", err)
 	}
@@ -201,7 +201,7 @@ func (g *Gateway) reloadServerConfiguration(ctx context.Context, serverName stri
 	}
 
 	// Get current newServerCaps from the server (this reflects the server's current state after it notified us of changes)
-	newServerCaps, err := g.listCapabilities(ctx, g.configuration, []string{serverName}, clientConfig)
+	newServerCaps, err := g.listCapabilities(ctx, []string{serverName}, clientConfig)
 	if err != nil {
 		return fmt.Errorf("failed to list capabilities for %s: %w", serverName, err)
 	}