feat: add systemlog shim (#127)

* feat: add systemlog shim

* fix: add json.stringify so its all in one line

* feat: adopt structured logger from edge utils

Author: Skn0tt

src/run/handlers/server.ts

@@ -11,6 +11,7 @@ import {
   setVaryHeaders,
 } from '../headers.js'
 import { nextResponseProxy } from '../revalidate.js'
+import { logger } from '../systemlog.js'
 
 let nextHandler: WorkerRequestHandler, nextConfig: NextConfigComplete, tagsManifest: TagsManifest
 
@@ -42,6 +43,7 @@ export default async (request: Request) => {
     // console.log('Next server request:', req.url)
     await nextHandler(req, resProxy)
   } catch (error) {
+    logger.withError(error).error('next handler error')
     console.error(error)
     resProxy.statusCode = 500
     resProxy.end('Internal Server Error')

src/run/systemlog.ts

@@ -0,0 +1,61 @@
+const systemLogTag = '__nfSystemLog'
+
+const serializeError = (error: Error): Record<string, unknown> => {
+  const cause = error?.cause instanceof Error ? serializeError(error.cause) : error.cause
+
+  return {
+    error: error.message,
+    error_cause: cause,
+    error_stack: error.stack,
+  }
+}
+
+export class StructuredLogger {
+  private fields: Record<string, unknown>
+  private message: string
+
+  constructor(message?: string, fields?: Record<string, unknown>) {
+    this.fields = fields ?? {}
+    this.message = message ?? ''
+  }
+
+  // TODO: add sampling
+  private doLog(logger: typeof console.log, message: string) {
+    logger(systemLogTag, JSON.stringify({ msg: message, fields: this.fields }))
+  }
+
+  log(message: string) {
+    this.doLog(console.log, message)
+  }
+
+  info(message: string) {
+    this.doLog(console.info, message)
+  }
+
+  debug(message: string) {
+    this.doLog(console.debug, message)
+  }
+
+  warn(message: string) {
+    this.doLog(console.warn, message)
+  }
+
+  error(message: string) {
+    this.doLog(console.error, message)
+  }
+
+  withError(error: unknown) {
+    const fields = error instanceof Error ? serializeError(error) : { error }
+
+    return this.withFields(fields)
+  }
+
+  withFields(fields: Record<string, unknown>) {
+    return new StructuredLogger(this.message, {
+      ...this.fields,
+      ...fields,
+    })
+  }
+}
+
+export const logger = new StructuredLogger()