From d1761c5975b7e99d4103998653858d15e61a014c Mon Sep 17 00:00:00 2001
From: Knut Ahlers <knut@ahlers.me>
Date: Sun, 4 Dec 2022 00:46:36 +0100
Subject: [PATCH] Fix: Gracefully handle data not being available for query
 type

Signed-off-by: Knut Ahlers <knut@ahlers.me>
---
 fetcher.go                | 50 +++++++++++++++++++--------------------
 internal/mercedes/impl.go |  6 +++++
 2 files changed, 30 insertions(+), 26 deletions(-)

diff --git a/fetcher.go b/fetcher.go
index 783379e..d68a186 100644
--- a/fetcher.go
+++ b/fetcher.go
@@ -1,6 +1,8 @@
 package main
 
 import (
+	"errors"
+
 	"github.com/sirupsen/logrus"
 
 	"github.com/Luzifer/mercedes-byocar-exporter/internal/mercedes"
@@ -19,39 +21,35 @@ func runFetcher(mc mercedes.Client, vehicleID string) {
 	logger.Info("fetching data")
 
 	s1, err := mc.GetPayAsYouDriveInsurance(cfg.VehicleID[0])
-	if err != nil {
-		logger.WithError(err).Error("fetching pay-as-you-go data")
-		return
-	}
-	enabledExporters.SetPayAsYouGo(vehicleID, s1)
+	handleMetricsEntries(logger, "pay-as-you-go", err, func() { enabledExporters.SetPayAsYouGo(vehicleID, s1) })
 
 	s2, err := mc.GetFuelStatus(cfg.VehicleID[0])
-	if err != nil {
-		logger.WithError(err).Error("fetching fuel-status data")
-		return
-	}
-	enabledExporters.SetFuelStatus(vehicleID, s2)
+	handleMetricsEntries(logger, "fuel-status", err, func() { enabledExporters.SetFuelStatus(vehicleID, s2) })
 
 	s3, err := mc.GetVehicleStatus(cfg.VehicleID[0])
-	if err != nil {
-		logger.WithError(err).Error("fetching vehicle-status data")
-		return
-	}
-	enabledExporters.SetVehicleStatus(vehicleID, s3)
+	handleMetricsEntries(logger, "vehicle-status", err, func() { enabledExporters.SetVehicleStatus(vehicleID, s3) })
 
 	s4, err := mc.GetLockStatus(cfg.VehicleID[0])
-	if err != nil {
-		logger.WithError(err).Error("fetching lock-status data")
-		return
-	}
-	enabledExporters.SetLockStatus(vehicleID, s4)
+	handleMetricsEntries(logger, "lock-status", err, func() { enabledExporters.SetLockStatus(vehicleID, s4) })
 
 	s5, err := mc.GetElectricStatus(cfg.VehicleID[0])
-	if err != nil {
-		logger.WithError(err).Error("fetching electric-status data")
-		return
-	}
-	enabledExporters.SetElectricStatus(vehicleID, s5)
+	handleMetricsEntries(logger, "electric-status", err, func() { enabledExporters.SetElectricStatus(vehicleID, s5) })
 
-	logger.Info("data updated successfully")
+	logger.Info("data updated")
+}
+
+func handleMetricsEntries(logger *logrus.Entry, dataType string, err error, submit func()) {
+	switch {
+	case err == nil:
+		submit()
+
+	case errors.Is(err, mercedes.ErrNoDataAvailable):
+		logger.Warnf("%s data is not available", dataType)
+		return
+
+	default:
+		logger.WithError(err).Errorf("fetching %s data", dataType)
+		return
+
+	}
 }
diff --git a/internal/mercedes/impl.go b/internal/mercedes/impl.go
index 025d2e4..2709f43 100644
--- a/internal/mercedes/impl.go
+++ b/internal/mercedes/impl.go
@@ -34,6 +34,8 @@ type (
 	}
 )
 
+var ErrNoDataAvailable = errors.New("no data available for this endpoint")
+
 var _ Client = (*APIClient)(nil)
 
 func New(clientID, clientSecret string, creds credential.Store) *APIClient {
@@ -202,6 +204,10 @@ func (a APIClient) request(path string, output any) error {
 	}
 	defer resp.Body.Close()
 
+	if resp.StatusCode == http.StatusNoContent {
+		return ErrNoDataAvailable
+	}
+
 	if resp.StatusCode != http.StatusOK {
 		body, err := io.ReadAll(resp.Body)
 		if err != nil {