Add low battery alerts

internal/providers/battery.go

@@ -3,9 +3,12 @@ package providers
 import (
 	"fmt"
 	"io/ioutil"
+	"os"
 	"path"
 	"strconv"
 	"strings"
+	"os/exec"
+	"path/filepath"
 
 	"github.com/codemicro/bar/internal/i3bar"
 )
@@ -29,6 +32,7 @@ type Battery struct {
 	name                         string
 	previousWasBackgroundWarning bool
 	isAlert                      bool
+	previousValue                string
 }
 
 func NewBattery(deviceName string, fullThreshold, okThreshold, warningThreshold float32) i3bar.BlockGenerator {
@@ -120,17 +124,31 @@ func (g *Battery) Block(colors *i3bar.ColorSet) (*i3bar.Block, error) {
 	if err != nil {
 		return nil, err
 	}
-
+	
 	state, err := g.getState()
 	if err != nil {
 		return nil, err
 	}
 
+	percentageString := fmt.Sprintf("%.1f", percentage)
+	shortPercentageString := strings.Split(percentageString, ".")[0]
+	if g.previousValue != shortPercentageString && state == batteryStateDischarging {
+		switch shortPercentageString {
+		case "20":
+			_ = g.SendNotification("Battery is getting low", "At 20% and discharging. Consider plugging in.", "low")
+		case "12":
+			_ = g.SendNotification("Battery is getting lower", "At 12% and discharging. Plug in now.", "normal")
+		case "5":
+			_ = g.SendNotification("Battery is really low", "At 5% and discharging. PLUG IN NOW.", "critical")
+		}
+	}
+	g.previousValue = shortPercentageString
+	
 	block := &i3bar.Block{
 		Name:      g.name,
 		Instance:  g.DeviceName,
-		FullText:  fmt.Sprintf("%s %.1f%%", state, percentage),
+		FullText:  fmt.Sprintf("%s %s%%", state, percentageString),
-		ShortText: fmt.Sprintf("%.1f%%", percentage),
+		ShortText: percentageString,
 	}
 
 	if percentage < g.WarningThreshold && g.WarningThreshold != 0 {
@@ -173,3 +191,19 @@ func (g *Battery) Block(colors *i3bar.ColorSet) (*i3bar.Block, error) {
 func (g *Battery) GetNameAndInstance() (string, string) {
 	return g.name, g.DeviceName
 }
+
+func (g *Battery) SendNotification(summary, message, priority string) error {
+	fname, err := exec.LookPath("notify-send")
+	if err == nil {
+		fname, err = filepath.Abs(fname)
+	}
+	if err != nil {
+		return err
+	}
+	process, err := os.StartProcess(fname, []string{fname, "--urgency", priority, summary, message}, &os.ProcAttr{Files: []*os.File{os.Stdin, os.Stdout, os.Stderr}})
+	if err != nil {
+		return err
+	}
+	_ = process.Release()
+	return nil
+}