Add battery info

internal/collectors/battery.go

@@ -1 +1,62 @@
 package collectors
+
+import (
+	"bufio"
+	"log"
+	"os"
+	"strconv"
+)
+
+func batteryCapacity() (capacity int) {
+	const filename string = "/sys/class/power_supply/BAT0/capacity"
+	var rawCapacity string
+
+	file, err := os.Open(filename)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+
+	if scanner.Scan() {
+		rawCapacity = scanner.Text()
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+	capacity, err = strconv.Atoi(rawCapacity)
+	if err != nil {
+		log.Fatal(err)
+	}
+	return capacity
+}
+
+func batteryStatus() (status string) {
+	const filename string = "/sys/class/power_supply/BAT0/status"
+
+	file, err := os.Open(filename)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+
+	if scanner.Scan() {
+		status = scanner.Text()
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+	return status
+}
+
+func batteryInfo() (capacity int, status string) {
+	const statusFile string = "/sys/class/power_supply/BAT0/status"
+	capacity = batteryCapacity()
+	status = batteryStatus()
+	return capacity, status
+}