mcp-testing-harness/server.ts at main · Khan/mcp-testing-harness · GitHub

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import { Client } from "@modelcontextprotocol/sdk/client";
import { SSEClientTransport } from "@modelcontextprotocol/sdk/client/sse.js";
import Bun from "bun";

process.env.NODE_TLS_REJECT_UNAUTHORIZED = "0";

const showForm = (url: string, formItems: string[]) =>
	new Response(
		`<html>
        <title>MCP Testing Harness</title>
<body>
<h1>MCP Testing Harness</h1>
<a href="/?url=${encodeURIComponent(url)}">Reset</a>
<form method="GET" action="/">
${formItems.join("<br/>\n")}
<button type="submit">Next</button>
</form>
</body>`,
		{
			headers: { "Content-type": "text/html" },
		},
	);

const showIframeForm = (url: string, formItems: string[], initialUrl: string) =>
	new Response(
		`<html>
        <title>MCP Testing Harness</title>
<body>
<h1>MCP Testing Harness</h1>
<a href="/?url=${encodeURIComponent(url)}">Reset</a>
<form method="GET" action="/embed" target="embed">
${formItems.join("<br/>\n")}
<button type="submit">Submit</button>
</form>
<iframe name="embed" style="width: 50vw;min-width:300px;min-height:500px;height:50vh" src="${initialUrl}" />
</body>`,
		{
			headers: { "Content-type": "text/html" },
		},
	);

const server = Bun.serve({
	port: 3112,
	// `routes` requires Bun v1.2.3+
	routes: {
		"/": async (req) => {
			const formItems: string[] = [];

			const url = new URL(req.url);
			const serverUrl = url.searchParams.get("url");
			formItems.push(
				`URL: <input style="width:600px" name="url" value="${serverUrl ?? ""}" placeholder="MCP URL" />`,
			);
			if (!serverUrl) {
				return showForm("", formItems);
			}

			const transport = new SSEClientTransport(new URL(serverUrl));

			const client = new Client({
				name: "example-client",
				version: "1.0.0",
			});

			try {
				await client.connect(transport);
			} catch (err) {
				return new Response(
					`Unable to connect. Retrying in 3 seconds. ${err}`,
					{
						headers: {
							"Content-type": "text/html",
							status: "400",
							Refresh: "3",
						},
					},
				);
			}

			const { tools } = await client.listTools();

			const toolName = url.searchParams.get("tool");
			formItems.push(`Tool: <select name="tool" value="${toolName}">
    ${tools.map((tool) => `<option value="${tool.name}">${tool.name}</option>`).join("\n")}
    </select>`);
			if (!toolName) {
				return showForm(serverUrl, formItems);
			}

			const tool = tools.find((tool) => tool.name === toolName);
			if (!tool) {
				return new Response("tool not found", { status: 400 });
			}

			const tpl = tool._meta?.["openai/outputTemplate"] as string | null;
			if (!tpl) {
				console.log(tool._meta);
				return new Response("tool doesn't have openai/outputTemplate defined", {
					status: 400,
				});
			}

			const fields = Object.entries(tool.inputSchema.properties!).map(
				([key, defn]) => {
					const value = url.searchParams.get(key);
					const required = tool.inputSchema.required?.includes(key);

					switch ((defn as { type: string }).type) {
						case "integer":
							return `${key}: <input name="${key}" type="number" value="${value ?? ""}" placeholder="${key}" />${
								required ? ` - required` : ""
							}`;
						case "boolean":
							return `${key}: <input name="${key}" type="checkbox" value="${value ?? ""}" placeholder="${key}" />${
								required ? ` - required` : ""
							}`;
						case "string":
							return `${key}: <input style="width:600px" name="${key}" value="${value ?? ""}" placeholder="${key}" />${
								required ? ` - required` : ""
							}`;
						default:
							throw new Error(
								`not handling input property with schema ${JSON.stringify(defn)}`,
							);
					}
				},
			);
			formItems.push(
				`<ul>
                ${fields.map((item) => `<li>${item}</li>`).join("\n")}
                </ul>`,
			);

			return showIframeForm(serverUrl, formItems, `/preview${url.search}`);
		},
		"/preview": async (req) => {
			const url = new URL(req.url);
			const serverUrl = url.searchParams.get("url");
			if (!serverUrl) {
				throw new Error(`No url`);
			}
			const transport = new SSEClientTransport(new URL(serverUrl));

			const client = new Client({
				name: "example-client",
				version: "1.0.0",
			});

			try {
				await client.connect(transport);
			} catch (err) {
				return new Response(
					`Unable to connect. Retrying in 3 seconds. ${err}`,
					{
						headers: {
							"Content-type": "text/html",
							status: "400",
							Refresh: "3",
						},
					},
				);
			}

			const toolName = url.searchParams.get("tool");
			if (!toolName) {
				throw new Error(`tool`);
			}

			const { tools } = await client.listTools();
			const tool = tools.find((tool) => tool.name === toolName);
			if (!tool) {
				return new Response("tool not found", { status: 400 });
			}
			const tpl = tool._meta?.["openai/outputTemplate"] as string | null;
			if (!tpl) {
				return new Response("tool doesn't have openai/outputTemplate defined", {
					status: 400,
				});
			}
			const resource = await client.readResource({
				uri: tpl,
			});
			if (!resource.contents[0]) {
				return new Response("Resource invalid", { status: 500 });
			}
			const resourceContent = resource.contents[0];

			const widgetCSP = resourceContent._meta!["openai/widgetCSP"];
			const csp =
				typeof widgetCSP === "object" &&
				widgetCSP &&
				"resource_domains" in widgetCSP
					? (widgetCSP.resource_domains as string[])
					: [];

			return new Response(resourceContent.text as string, {
				headers: {
					"content-type": "text/html",
					"Content-Security-Policy": `default-src 'unsafe-inline' data: http://localhost:3112 wss://localhost:8225 https://localhost:8226 ${csp.join(
						" ",
					)}`,
				},
			});
		},
		"/embed": async (req) => {
			const url = new URL(req.url);
			const serverUrl = url.searchParams.get("url");
			if (!serverUrl) {
				throw new Error(`No url`);
			}
			const transport = new SSEClientTransport(new URL(serverUrl));

			const client = new Client({
				name: "example-client",
				version: "1.0.0",
			});

			try {
				await client.connect(transport);
			} catch (err) {
				return new Response(
					`Unable to connect. Retrying in 3 seconds. ${err}`,
					{
						headers: {
							"Content-type": "text/html",
							status: "400",
							Refresh: "3",
						},
					},
				);
			}

			const toolName = url.searchParams.get("tool");
			if (!toolName) {
				throw new Error(`tool`);
			}

			const { tools } = await client.listTools();
			const tool = tools.find((tool) => tool.name === toolName);
			if (!tool) {
				return new Response("tool not found", { status: 400 });
			}
			const tpl = tool._meta?.["openai/outputTemplate"] as string | null;
			if (!tpl) {
				return new Response("tool doesn't have openai/outputTemplate defined", {
					status: 400,
				});
			}
			const resource = await client.readResource({
				uri: tpl,
			});
			if (!resource.contents[0]) {
				return new Response("Resource invalid", { status: 500 });
			}
			const resourceContent = resource.contents[0];
			const values: Record<string, string | boolean | number | undefined> = {};
			const missing: string[] = [];
			Object.entries(tool.inputSchema.properties!).forEach(([key, defn]) => {
				const value = url.searchParams.get(key);
				const required = tool.inputSchema.required?.includes(key);
				switch ((defn as { type: string }).type) {
					case "boolean":
						values[key] = value === "true";
						break;
					case "integer":
						values[key] = value ? +value : undefined;
						break;
					case "string":
						if (value) {
							values[key] = value;
						} else if (required) {
							missing.push(key);
						}
						break;
					default:
						throw new Error(
							`not handling input property with schema ${JSON.stringify(defn)}`,
						);
				}
			});
			if (missing.length) {
				throw new Error(`missing required values: ${missing}`);
			}

			const widgetCSP = resourceContent._meta!["openai/widgetCSP"];
			const csp =
				typeof widgetCSP === "object" &&
				widgetCSP &&
				"resource_domains" in widgetCSP
					? (widgetCSP.resource_domains as string[])
					: [];

			console.log("got csp", csp);
			// Call a tool
			const result = await client.callTool({
				name: tool.name,
				arguments: values,
				_meta: {
					"openai/meta": "some-meta-value",
				},
			});
			if (!result.structuredContent) {
				return new Response(JSON.stringify(result));
			}

			return new Response(
				(resourceContent.text as string)
					.replace(
						"</head>",
						() =>
							`<script>openai = {toolOutput: ${JSON.stringify(result.structuredContent)}}</script></head>`,
					)
					.replace(
						"</body>",
						() =>
							`<pre>Structured content:\n\n${JSON.stringify(
								result.structuredContent,
								null,
								2,
							).replace(
								"<",
								"&lt;",
							)}\nMeta:\n${JSON.stringify(result._meta, null, 2)}</pre>
                            </body>`,
					),
				{
					headers: {
						"content-type": "text/html",
						"Content-Security-Policy": `default-src 'unsafe-inline' data: http://localhost:3112 wss://localhost:8225 https://localhost:8226 ${csp.join(
							" ",
						)}`,
					},
				},
			);
		},
	},
	idleTimeout: 100,
});

console.log(`serving http://localhost:${server.port}`);