implement google analytics

Reference: <https://deno.land/x/g_a@0.1.2>

deno.json

@@ -15,7 +15,8 @@
     "highlight.js": "npm:highlight.js@^11.9.0",
     "markdown-it": "npm:markdown-it@^14.1.0",
     "markdown-it-anchor": "npm:markdown-it-anchor@^9.0.0",
-    "simplex-noise": "npm:simplex-noise@^4.0.1"
+    "simplex-noise": "npm:simplex-noise@^4.0.1",
+    "ga": "https://deno.land/x/g_a@0.1.2/mod.ts"
   },
   "tasks": {
     "generate": "deno run --allow-read --allow-write codegen/codegen.ts",

google-analytics.ts

@@ -0,0 +1,30 @@
+import { createReporter } from "ga";
+
+const GOOGLE_ANALYTICS_ID = Deno.env.get("GOOGLE_ANALYTICS_ID")!;
+
+const ga = createReporter({ id: GOOGLE_ANALYTICS_ID });
+
+export function useGoogleAnalytics(
+  fn: (
+    request: Request,
+    info: Deno.ServeHandlerInfo<Deno.NetAddr>,
+  ) => Response | Promise<Response>,
+) {
+  return async function (
+    request: Request,
+    info: Deno.ServeHandlerInfo<Deno.NetAddr>,
+  ) {
+    let error;
+    let response: Response;
+    const start = performance.now();
+    try {
+      response = await fn(request, info);
+    } catch (e) {
+      error = e;
+    } finally {
+      ga(request, info, response!, start, error);
+    }
+
+    return response!;
+  };
+}

main.ts

@@ -1,3 +1,6 @@
 import { serveDir } from "@std/http/file-server";
+import { useGoogleAnalytics } from "./google-analytics.ts";
 
-Deno.serve((request) => serveDir(request, { fsRoot: Deno.args[0] ?? "." }));
+Deno.serve(useGoogleAnalytics(
+  (request) => serveDir(request, { fsRoot: Deno.args[0] ?? "." }),
+));