refactor: extract draggable pane and connection logic into hooks

- Create useDraggablePane hook for history pane drag behavior
- Create useConnection hook for MCP client connection and requests
- Update App.tsx to use both hooks

Author: ashwin-ant

client/src/App.tsx

@@ -1,37 +1,26 @@
-import { Client } from "@modelcontextprotocol/sdk/client/index.js";
-import { SSEClientTransport } from "@modelcontextprotocol/sdk/client/sse.js";
+import { useDraggablePane } from "./lib/hooks/useDraggablePane";
+import { useConnection } from "./lib/hooks/useConnection";
 import {
-  ClientNotification,
   ClientRequest,
   CompatibilityCallToolResult,
   CompatibilityCallToolResultSchema,
-  CreateMessageRequestSchema,
   CreateMessageResult,
   EmptyResultSchema,
   GetPromptResultSchema,
   ListPromptsResultSchema,
   ListResourcesResultSchema,
   ListResourceTemplatesResultSchema,
-  ListRootsRequestSchema,
-  ListToolsResultSchema,
-  ProgressNotificationSchema,
   ReadResourceResultSchema,
-  Request,
+  ListToolsResultSchema,
   Resource,
   ResourceTemplate,
   Root,
   ServerNotification,
-  Tool,
-  ServerCapabilitiesSchema,
-  Result,
+  Tool
 } from "@modelcontextprotocol/sdk/types.js";
-import { useCallback, useEffect, useRef, useState } from "react";
+import { useEffect, useRef, useState } from "react";
 
-import {
-  Notification,
-  StdErrNotification,
-  StdErrNotificationSchema,
-} from "./lib/notificationTypes";
+import { StdErrNotification } from "./lib/notificationTypes";
 
 import { Tabs, TabsList, TabsTrigger } from "@/components/ui/tabs";
 import {
@@ -43,8 +32,7 @@ import {
   MessageSquare,
 } from "lucide-react";
 
-import { toast } from "react-toastify";
-import { z, type ZodType } from "zod";
+import { z } from "zod";
 import "./App.css";
 import ConsoleTab from "./components/ConsoleTab";
 import HistoryAndNotifications from "./components/History";
@@ -56,21 +44,11 @@ import SamplingTab, { PendingRequest } from "./components/SamplingTab";
 import Sidebar from "./components/Sidebar";
 import ToolsTab from "./components/ToolsTab";
 
-type ServerCapabilities = z.infer<typeof ServerCapabilitiesSchema>;
-
-const DEFAULT_REQUEST_TIMEOUT_MSEC = 10000;
-
 const params = new URLSearchParams(window.location.search);
 const PROXY_PORT = params.get("proxyPort") ?? "3000";
-const REQUEST_TIMEOUT =
-  parseInt(params.get("timeout") ?? "") || DEFAULT_REQUEST_TIMEOUT_MSEC;
 const PROXY_SERVER_URL = `http://localhost:${PROXY_PORT}`;
 
 const App = () => {
-  const [connectionStatus, setConnectionStatus] = useState<
-    "disconnected" | "connected" | "error"
-  >("disconnected");
-  const [serverCapabilities, setServerCapabilities] = useState<ServerCapabilities | null>(null);
   const [resources, setResources] = useState<Resource[]>([]);
   const [resourceTemplates, setResourceTemplates] = useState<
     ResourceTemplate[]
@@ -95,10 +73,6 @@ const App = () => {
 
   const [sseUrl, setSseUrl] = useState<string>("http://localhost:3001/sse");
   const [transportType, setTransportType] = useState<"stdio" | "sse">("stdio");
-  const [requestHistory, setRequestHistory] = useState<
-    { request: string; response?: string }[]
-  >([]);
-  const [mcpClient, setMcpClient] = useState<Client | null>(null);
   const [notifications, setNotifications] = useState<ServerNotification[]>([]);
   const [stdErrNotifications, setStdErrNotifications] = useState<
     StdErrNotification[]
@@ -149,49 +123,64 @@ const App = () => {
   >();
   const [nextToolCursor, setNextToolCursor] = useState<string | undefined>();
   const progressTokenRef = useRef(0);
-  const [historyPaneHeight, setHistoryPaneHeight] = useState<number>(300);
-  const [isDragging, setIsDragging] = useState(false);
-  const dragStartY = useRef<number>(0);
-  const dragStartHeight = useRef<number>(0);
 
-  const handleDragStart = useCallback(
-    (e: React.MouseEvent) => {
-      setIsDragging(true);
-      dragStartY.current = e.clientY;
-      dragStartHeight.current = historyPaneHeight;
-      document.body.style.userSelect = "none";
+  const {
+    height: historyPaneHeight,
+    handleDragStart
+  } = useDraggablePane(300);
+
+  const {
+    connectionStatus,
+    serverCapabilities,
+    mcpClient,
+    requestHistory,
+    makeRequest: makeConnectionRequest,
+    sendNotification,
+    connect: connectMcpServer
+  } = useConnection({
+    transportType,
+    command,
+    args,
+    sseUrl,
+    env,
+    proxyServerUrl: PROXY_SERVER_URL,
+    onNotification: (notification) => {
+      setNotifications(prev => [...prev, notification as ServerNotification]);
     },
-    [historyPaneHeight],
-  );
-
-  const handleDragMove = useCallback(
-    (e: MouseEvent) => {
-      if (!isDragging) return;
-      const deltaY = dragStartY.current - e.clientY;
-      const newHeight = Math.max(
-        100,
-        Math.min(800, dragStartHeight.current + deltaY),
-      );
-      setHistoryPaneHeight(newHeight);
+    onStdErrNotification: (notification) => {
+      setStdErrNotifications(prev => [...prev, notification as StdErrNotification]);
     },
-    [isDragging],
-  );
-
-  const handleDragEnd = useCallback(() => {
-    setIsDragging(false);
-    document.body.style.userSelect = "";
-  }, []);
+    onPendingRequest: (request, resolve, reject) => {
+      setPendingSampleRequests(prev => [
+        ...prev,
+        { id: nextRequestId.current++, request, resolve, reject }
+      ]);
+    },
+    getRoots: () => rootsRef.current
+  });
 
-  useEffect(() => {
-    if (isDragging) {
-      window.addEventListener("mousemove", handleDragMove);
-      window.addEventListener("mouseup", handleDragEnd);
-      return () => {
-        window.removeEventListener("mousemove", handleDragMove);
-        window.removeEventListener("mouseup", handleDragEnd);
-      };
+  const makeRequest = async <T extends z.ZodType>(
+    request: ClientRequest,
+    schema: T,
+    tabKey?: keyof typeof errors,
+  ) => {
+    try {
+      const response = await makeConnectionRequest(request, schema);
+      if (tabKey !== undefined) {
+        clearError(tabKey);
+      }
+      return response;
+    } catch (e) {
+      const errorString = (e as Error).message ?? String(e);
+      if (tabKey !== undefined) {
+        setErrors((prev) => ({
+          ...prev,
+          [tabKey]: errorString,
+        }));
+      }
+      throw e;
     }
-  }, [isDragging, handleDragMove, handleDragEnd]);
+  };
 
   useEffect(() => {
     localStorage.setItem("lastCommand", command);
@@ -228,83 +217,10 @@ const App = () => {
     }
   }, []);
 
-  const pushHistory = (request: object, response?: object) => {
-    setRequestHistory((prev) => [
-      ...prev,
-      {
-        request: JSON.stringify(request),
-        response: response !== undefined ? JSON.stringify(response) : undefined,
-      },
-    ]);
-  };
-
   const clearError = (tabKey: keyof typeof errors) => {
     setErrors((prev) => ({ ...prev, [tabKey]: null }));
   };
 
-  const makeRequest = async <T extends ZodType<object>>(
-    request: ClientRequest,
-    schema: T,
-    tabKey?: keyof typeof errors,
-  ) => {
-    if (!mcpClient) {
-      throw new Error("MCP client not connected");
-    }
-
-    try {
-      const abortController = new AbortController();
-      const timeoutId = setTimeout(() => {
-        abortController.abort("Request timed out");
-      }, REQUEST_TIMEOUT);
-
-      let response;
-      try {
-        response = await mcpClient.request(request, schema, {
-          signal: abortController.signal,
-        });
-        pushHistory(request, response);
-      } catch (error) {
-        const errorMessage = error instanceof Error ? error.message : String(error);
-        pushHistory(request, { error: errorMessage });
-        throw error;
-      } finally {
-        clearTimeout(timeoutId);
-      }
-
-      if (tabKey !== undefined) {
-        clearError(tabKey);
-      }
-
-      return response;
-    } catch (e: unknown) {
-      const errorString = (e as Error).message ?? String(e);
-      if (tabKey === undefined) {
-        toast.error(errorString);
-      } else {
-        setErrors((prev) => ({
-          ...prev,
-          [tabKey]: errorString,
-        }));
-      }
-
-      throw e;
-    }
-  };
-
-  const sendNotification = async (notification: ClientNotification) => {
-    if (!mcpClient) {
-      throw new Error("MCP client not connected");
-    }
-
-    try {
-      await mcpClient.notification(notification);
-      pushHistory(notification);
-    } catch (e: unknown) {
-      toast.error((e as Error).message ?? String(e));
-      throw e;
-    }
-  };
-
   const listResources = async () => {
     const response = await makeRequest(
       {
@@ -407,82 +323,6 @@ const App = () => {
     await sendNotification({ method: "notifications/roots/list_changed" });
   };
 
-  const connectMcpServer = async () => {
-    try {
-      const client = new Client<Request, Notification, Result>(
-        {
-          name: "mcp-inspector",
-          version: "0.0.1",
-        },
-        {
-          capabilities: {
-            // Support all client capabilities since we're an inspector tool
-            sampling: {},
-            roots: {
-              listChanged: true,
-            },
-          },
-        },
-      );
-
-      const backendUrl = new URL(`${PROXY_SERVER_URL}/sse`);
-
-      backendUrl.searchParams.append("transportType", transportType);
-      if (transportType === "stdio") {
-        backendUrl.searchParams.append("command", command);
-        backendUrl.searchParams.append("args", args);
-        backendUrl.searchParams.append("env", JSON.stringify(env));
-      } else {
-        backendUrl.searchParams.append("url", sseUrl);
-      }
-
-      const clientTransport = new SSEClientTransport(backendUrl);
-      client.setNotificationHandler(
-        ProgressNotificationSchema,
-        (notification) => {
-          setNotifications((prevNotifications) => [
-            ...prevNotifications,
-            notification,
-          ]);
-        },
-      );
-
-      client.setNotificationHandler(
-        StdErrNotificationSchema,
-        (notification) => {
-          setStdErrNotifications((prevErrorNotifications) => [
-            ...prevErrorNotifications,
-            notification,
-          ]);
-        },
-      );
-
-      await client.connect(clientTransport);
-
-      const capabilities = client.getServerCapabilities();
-      setServerCapabilities(capabilities ?? null);
-
-      client.setRequestHandler(CreateMessageRequestSchema, (request) => {
-        return new Promise<CreateMessageResult>((resolve, reject) => {
-          setPendingSampleRequests((prev) => [
-            ...prev,
-            { id: nextRequestId.current++, request, resolve, reject },
-          ]);
-        });
-      });
-
-      client.setRequestHandler(ListRootsRequestSchema, async () => {
-        return { roots: rootsRef.current };
-      });
-
-      setMcpClient(client);
-      setConnectionStatus("connected");
-    } catch (e) {
-      console.error(e);
-      setConnectionStatus("error");
-    }
-  };
-
   return (
     <div className="flex h-screen bg-background">
       <Sidebar