first commit

packages/core/src/logging.ts

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+/**
+ * Structured request logging middleware. Emits one record per request with a
+ * request id, method, path, status, and duration — as pretty text (dev) or JSON
+ * (production/log aggregation). The request id is stored on `ctx.locals` so
+ * downstream handlers can correlate their own logs.
+ */
+
+import type { Context, Middleware } from "./context.ts";
+
+export interface RequestRecord {
+  time: string;
+  id: string;
+  method: string;
+  path: string;
+  status: number;
+  durationMs: number;
+}
+
+export interface RequestLoggerOptions {
+  /** "pretty" (default) for humans, "json" for machines. */
+  format?: "pretty" | "json";
+  /** Where each finished record goes. Default console.log. */
+  sink?: (line: string, record: RequestRecord) => void;
+  /** ctx.locals key for the request id. Default "requestId". */
+  requestIdKey?: string;
+  /** Clock injection for tests. Default Date.now. */
+  now?: () => number;
+}
+
+export function requestLogger(options: RequestLoggerOptions = {}): Middleware {
+  const format = options.format ?? "pretty";
+  const sink = options.sink ?? ((line) => console.log(line));
+  const idKey = options.requestIdKey ?? "requestId";
+  const now = options.now ?? Date.now;
+
+  return async (ctx: Context, next) => {
+    const start = now();
+    const id = (ctx.locals[idKey] as string | undefined) ?? crypto.randomUUID();
+    ctx.locals[idKey] = id;
+
+    let status = 500;
+    try {
+      const res = await next();
+      status = res.status;
+      return res;
+    } finally {
+      const record: RequestRecord = {
+        time: new Date(start).toISOString(),
+        id,
+        method: ctx.req.method,
+        path: ctx.url.pathname,
+        status,
+        durationMs: now() - start,
+      };
+      sink(format === "json" ? JSON.stringify(record) : formatPretty(record), record);
+    }
+  };
+}
+
+function formatPretty(r: RequestRecord): string {
+  return `${r.method} ${r.path} → ${r.status} ${r.durationMs}ms [${r.id.slice(0, 8)}]`;
+}