feat: move runner to typescript, refactor

apps/eval/lib/mcpClient.ts

@@ -0,0 +1,76 @@
+const ACCEPT = "application/json, text/event-stream";
+
+interface JsonRpcResponse {
+  result?: unknown;
+  error?: { code: number; message: string };
+}
+
+interface McpTool {
+  name: string;
+  description?: string;
+  inputSchema?: unknown;
+}
+
+type McpContentBlock = { type: string; text: string } | { type: string; [key: string]: unknown };
+
+interface McpToolResult {
+  content?: McpContentBlock[];
+}
+
+function parseMcpResponse(text: string): JsonRpcResponse {
+  const trimmed = text.trim();
+  if (!trimmed) throw new Error("Empty MCP response");
+  if (trimmed.startsWith("{")) {
+    return JSON.parse(trimmed) as JsonRpcResponse;
+  }
+  if (trimmed.includes("event:") || trimmed.includes("data:")) {
+    let payload = "";
+    for (const line of trimmed.split(/\r?\n/)) {
+      if (line.startsWith("data:")) payload += line.slice(5).trim();
+    }
+    if (payload.startsWith("{")) return JSON.parse(payload) as JsonRpcResponse;
+  }
+  throw new Error(`Unrecognized MCP response format: ${trimmed.slice(0, 200)}`);
+}
+
+export class McpClient {
+  private url: string;
+  private seq: number;
+
+  constructor(url: string) {
+    this.url = url;
+    this.seq = 0;
+  }
+
+  async request(method: string, params: Record<string, unknown> = {}): Promise<JsonRpcResponse> {
+    this.seq += 1;
+    const res = await fetch(this.url, {
+      method: "POST",
+      headers: { "Content-Type": "application/json", Accept: ACCEPT },
+      body: JSON.stringify({ jsonrpc: "2.0", id: this.seq, method, params }),
+    });
+    if (!res.ok) {
+      throw new Error(`MCP HTTP ${res.status}: ${(await res.text()).slice(0, 300)}`);
+    }
+    const rpc = parseMcpResponse(await res.text());
+    if (rpc.error) throw new Error(`MCP RPC error ${rpc.error.code}: ${rpc.error.message}`);
+    return rpc;
+  }
+
+  async listTools(): Promise<McpTool[]> {
+    const rpc = await this.request("tools/list");
+    return (rpc.result as { tools?: McpTool[] })?.tools ?? [];
+  }
+
+  async callTool(name: string, args: Record<string, unknown> = {}): Promise<McpToolResult> {
+    const rpc = await this.request("tools/call", { name, arguments: args });
+    return rpc.result as McpToolResult;
+  }
+}
+
+export function textContentFrom(result: McpToolResult | null | undefined): string {
+  if (!result?.content) return "";
+  return result.content
+    .map((b) => (b.type === "text" ? b.text : JSON.stringify(b)))
+    .join(" ");
+}