From 1028991b87dd93445de76369240f683666f8f71b Mon Sep 17 00:00:00 2001
From: Josh Deprez <josh.deprez@gmail.com>
Date: Wed, 6 Nov 2024 09:26:14 +1100
Subject: [PATCH] use log.Fatalf

---
 exporter.go | 34 ++++++++++++----------------------
 1 file changed, 12 insertions(+), 22 deletions(-)

diff --git a/exporter.go b/exporter.go
index 99f418c..d227be9 100644
--- a/exporter.go
+++ b/exporter.go
@@ -29,10 +29,7 @@ import (
 	"periph.io/x/host/v3"
 )
 
-func mainImpl() error {
-	if _, err := host.Init(); err != nil {
-		return err
-	}
+func main() {
 	httpAddr := flag.String("http-address", ":9455", "Listen addr for HTTP handler")
 	i2cAddress := flag.Int("i2c-address", 0x45, "I²C address")
 	i2cBus := flag.String("i2c-bus", "", "I²C bus (/dev/i2c-1)")
@@ -43,27 +40,27 @@ func mainImpl() error {
 
 	resistor, err := parseNanoSI[physic.ElectricResistance](*senseResistor)
 	if err != nil {
-		return fmt.Errorf("parsing --sense-resistor: %w", err)
+		log.Fatalf("parsing --sense-resistor: %w", err)
 	}
 	if resistor <= 0 {
-		return fmt.Errorf("--sense-resistor must be positive")
+		log.Fatalf("--sense-resistor must be positive")
 	}
 	current, err := parseNanoSI[physic.ElectricCurrent](*maxCurrent)
 	if err != nil {
-		return fmt.Errorf("parsing --max-current: %w", err)
+		log.Fatalf("parsing --max-current: %w", err)
 	}
 	if current <= 0 {
-		return fmt.Errorf("--max-current must be positive")
+		log.Fatalf("--max-current must be positive")
 	}
 
 	if _, err := host.Init(); err != nil {
-		return err
+		log.Fatalf("host.Init() error: %v", err)
 	}
 
 	// Open default I²C bus.
 	bus, err := i2creg.Open(*i2cBus)
 	if err != nil {
-		return fmt.Errorf("failed to open I²C: %v", err)
+		log.Fatalf("i2creg.Open(%v): %v", *i2cBus, err)
 	}
 	defer bus.Close()
 
@@ -73,7 +70,7 @@ func mainImpl() error {
 		MaxCurrent:    current,
 	})
 	if err != nil {
-		return fmt.Errorf("failed to open new sensor: %v", err)
+		log.Fatalf("ina219.New(...): %v", err)
 	}
 
 	constLabels := prometheus.Labels{"i2c_addr": fmt.Sprintf("0x%x", *i2cAddress)}
@@ -162,18 +159,18 @@ func mainImpl() error {
 		case <-everySecond:
 			p, err := sensor.Sense()
 			if err != nil {
-				return fmt.Errorf("sensor reading error: %v", err)
+				log.Fatalf("sensor.Sense() error: %v", err)
 			}
 
 			// sanity check sensor outputs:
 			// current = shunt / resistor, but resistor is fixed,
 			// so if current == 0 if and only if shunt == 0
 			if (p.Current == 0) != (p.Shunt == 0) {
-				return fmt.Errorf("current = %v but shunt = %v", p.Current, p.Shunt)
+				log.Fatalf("Ohm's Law violation: current = %v but shunt = %v", p.Current, p.Shunt)
 			}
 			// power = current * voltage, similar logic
 			if (p.Power == 0) != (p.Current == 0 || p.Voltage == 0) {
-				return fmt.Errorf("power = %v but current = %v and voltage = %v", p.Power, p.Current, p.Voltage)
+				log.Fatalf("Joule's First Law violation: power = %v but current = %v and voltage = %v", p.Power, p.Current, p.Voltage)
 			}
 
 			busVolts := float64(p.Voltage) / float64(physic.Volt)
@@ -193,18 +190,11 @@ func mainImpl() error {
 			shuntVoltageSumm.Observe(shuntVolts)
 
 		case <-halt:
-			return nil
+			return
 		}
 	}
 }
 
-func main() {
-	if err := mainImpl(); err != nil {
-		fmt.Fprintf(os.Stderr, "ina219: %s.\n", err)
-		return
-	}
-}
-
 var siSmallRE = regexp.MustCompile(`^(\d+)(m|mu|µ|n)?$`)
 
 func parseNanoSI[U ~int64](s string) (U, error) {