From c6126c13e96371bd14c06381bcd6c64e631a8502 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Kr=C3=BCger?= <valknar@pivoine.art>
Date: Thu, 5 Mar 2026 10:22:49 +0100
Subject: [PATCH] feat: add backend logger matching frontend text format

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 packages/backend/src/index.ts      |  7 +--
 packages/backend/src/lib/logger.ts | 91 ++++++++++++++++++++++++++++++
 2 files changed, 93 insertions(+), 5 deletions(-)
 create mode 100644 packages/backend/src/lib/logger.ts

diff --git a/packages/backend/src/index.ts b/packages/backend/src/index.ts
index 40967ba..f75cb1c 100644
--- a/packages/backend/src/index.ts
+++ b/packages/backend/src/index.ts
@@ -13,17 +13,14 @@ import { schema } from "./graphql/index";
 import { buildContext } from "./graphql/context";
 import { db } from "./db/connection";
 import { redis } from "./lib/auth";
+import { logger } from "./lib/logger";
 
 const PORT = parseInt(process.env.PORT || "4000");
 const UPLOAD_DIR = process.env.UPLOAD_DIR || "/data/uploads";
 const CORS_ORIGIN = process.env.CORS_ORIGIN || "http://localhost:3000";
 
 async function main() {
-  const fastify = Fastify({
-    logger: {
-      level: process.env.LOG_LEVEL || "info",
-    },
-  });
+  const fastify = Fastify({ loggerInstance: logger });
 
   await fastify.register(fastifyCookie, {
     secret: process.env.COOKIE_SECRET || "change-me-in-production",
diff --git a/packages/backend/src/lib/logger.ts b/packages/backend/src/lib/logger.ts
new file mode 100644
index 0000000..993c00d
--- /dev/null
+++ b/packages/backend/src/lib/logger.ts
@@ -0,0 +1,91 @@
+type LogLevel = "trace" | "debug" | "info" | "warn" | "error" | "fatal";
+
+const LEVEL_VALUES: Record<LogLevel, number> = {
+  trace: 10,
+  debug: 20,
+  info: 30,
+  warn: 40,
+  error: 50,
+  fatal: 60,
+};
+
+function createLogger(bindings: Record<string, unknown> = {}, initialLevel: LogLevel = "info") {
+  let currentLevel = initialLevel;
+
+  function shouldLog(level: LogLevel): boolean {
+    return LEVEL_VALUES[level] >= LEVEL_VALUES[currentLevel];
+  }
+
+  function formatMessage(level: LogLevel, arg: unknown, msg?: string): string {
+    const timestamp = new Date().toISOString();
+
+    let message: string;
+    const meta: Record<string, unknown> = { ...bindings };
+
+    if (typeof arg === "string") {
+      message = arg;
+    } else if (arg !== null && typeof arg === "object") {
+      // Pino-style: log(obj, msg?) — strip internal pino keys
+      const { msg: m, level: _l, time: _t, pid: _p, hostname: _h, req: _req, res: _res, reqId, ...rest } = arg as Record<string, unknown>;
+      message = msg || (typeof m === "string" ? m : "");
+      if (reqId) meta.reqId = reqId;
+      Object.assign(meta, rest);
+    } else {
+      message = String(arg ?? "");
+    }
+
+    const parts = [`[${timestamp}]`, `[${level.toUpperCase()}]`, message];
+    let result = parts.join(" ");
+
+    const metaEntries = Object.entries(meta).filter(([k]) => k !== "reqId");
+    const reqId = meta.reqId;
+    if (reqId) result = `[${timestamp}] [${level.toUpperCase()}] [${reqId}] ${message}`;
+
+    if (metaEntries.length > 0) {
+      result += " " + JSON.stringify(Object.fromEntries(metaEntries));
+    }
+
+    return result;
+  }
+
+  function write(level: LogLevel, arg: unknown, msg?: string) {
+    if (!shouldLog(level)) return;
+    const formatted = formatMessage(level, arg, msg);
+    switch (level) {
+      case "trace":
+      case "debug":
+        console.debug(formatted);
+        break;
+      case "info":
+        console.info(formatted);
+        break;
+      case "warn":
+        console.warn(formatted);
+        break;
+      case "error":
+      case "fatal":
+        console.error(formatted);
+        break;
+    }
+  }
+
+  return {
+    get level() {
+      return currentLevel;
+    },
+    set level(l: string) {
+      currentLevel = l as LogLevel;
+    },
+    trace: (arg: unknown, msg?: string) => write("trace", arg, msg),
+    debug: (arg: unknown, msg?: string) => write("debug", arg, msg),
+    info: (arg: unknown, msg?: string) => write("info", arg, msg),
+    warn: (arg: unknown, msg?: string) => write("warn", arg, msg),
+    error: (arg: unknown, msg?: string) => write("error", arg, msg),
+    fatal: (arg: unknown, msg?: string) => write("fatal", arg, msg),
+    silent: () => {},
+    child: (newBindings: Record<string, unknown>) =>
+      createLogger({ ...bindings, ...newBindings }, currentLevel),
+  };
+}
+
+export const logger = createLogger({}, (process.env.LOG_LEVEL as LogLevel) || "info");