with $HAFAS_REQ_RES_LOG_FILE, log HAFAS requests/responses to a file

api.js

@@ -11,6 +11,7 @@ import {
 	createVbbHafas as createHafas,
 	defaults as vbbHafasDefaults,
 } from 'vbb-hafas'
+import {createWriteStream} from 'node:fs'
 import createHealthCheck from 'hafas-client-health-check'
 import Redis from 'ioredis'
 import {createCachedHafasClient as withCache} from 'cached-hafas-client'
@@ -46,6 +47,21 @@ if (process.env.RANDOM_LOCAL_ADDRESSES_RANGE) {
 	}
 }
 
+if (process.env.HAFAS_REQ_RES_LOG_FILE) {
+	const hafasLogPath = process.env.HAFAS_REQ_RES_LOG_FILE
+	const hafasLog = createWriteStream(hafasLogPath, {flags: 'a'}) // append-only
+	hafasLog.on('error', (err) => console.error('hafasLog error', err))
+
+	customVbbProfile.logRequest = (ctx, req, reqId) => {
+		console.error(reqId, 'req', req.body + '') // todo: remove
+		hafasLog.write(JSON.stringify([reqId, 'req', req.body + '']) + '\n')
+	}
+	customVbbProfile.logResponse = (ctx, res, body, reqId) => {
+		console.error(reqId, 'res', body + '') // todo: remove
+		hafasLog.write(JSON.stringify([reqId, 'res', body + '']) + '\n')
+	}
+}
+
 let hafas = createHafas(
 	// seems like `vbb-rest` is being redirected
 	// pkg.name,