i3status: add battery block

2 files changed, 102 insertions, 10 deletions

diff --git a/pkg/i3status/battery.go b/pkg/i3status/battery.go
new file mode 100644
index 0000000..0b6979d
--- /dev/null
+++ b/pkg/i3status/battery.go
@@ -0,0 +1,75 @@
+/*******************************************************************************
+*
+* Copyright 2017 Stefan Majewsky <majewsky@gmx.net>
+*
+* This program is free software: you can redistribute it and/or modify it under
+* the terms of the GNU General Public License as published by the Free Software
+* Foundation, either version 3 of the License, or (at your option) any later
+* version.
+*
+* This program is distributed in the hope that it will be useful, but WITHOUT ANY
+* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+* A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License along with
+* this program. If not, see <http://www.gnu.org/licenses/>.
+*
+*******************************************************************************/
+
+package i3status
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+)
+
+const (
+	batteryFullPath = "/sys/class/power_supply/BAT0/energy_full"
+	batteryNowPath  = "/sys/class/power_supply/BAT0/energy_now"
+	powerNowPath    = "/sys/class/power_supply/BAT0/power_now"
+)
+
+func getBatteryStatus() []Block {
+	//TODO: What's with /sys/class/power_supply/BAT0/uevent? Can this be used to
+	//remove all the polling overhead here?
+
+	energyFull, err := readNumberFromFile(batteryFullPath)
+	if err != nil {
+		return nil
+	}
+	energyNow, err := readNumberFromFile(batteryNowPath)
+	if err != nil {
+		return nil
+	}
+	powerNow, err := readNumberFromFile(powerNowPath)
+	if err != nil {
+		return nil
+	}
+
+	energyPerc := energyNow * 100 / energyFull
+	charging := powerNow == 0 //i.e. when we're not drawing power from the battery
+	color := "#AAAA00"
+	if charging {
+		color = "#00AA00"
+	} else if energyPerc < 10 {
+		color = "#AA0000"
+	}
+
+	return section(Block{
+		Name:     "battery",
+		Position: PositionBattery,
+		FullText: fmt.Sprintf("⚡ %d%%", energyPerc),
+		Urgent:   energyPerc < 10 && !charging,
+		Color:    color,
+	})
+}
+
+func readNumberFromFile(path string) (int64, error) {
+	buf, err := ioutil.ReadFile(path)
+	if err != nil {
+		return 0, err
+	}
+	return strconv.ParseInt(strings.TrimSpace(string(buf)), 0, 64)
+}
diff --git a/pkg/i3status/main.go b/pkg/i3status/main.go
index 1b16f21..a0c4342 100644
--- a/pkg/i3status/main.go
+++ b/pkg/i3status/main.go
@@ -43,22 +43,26 @@ func Exec(args []string) int {
 		//prepare clock (this is inline instead of split into a separate function
 		//because the wallclock also drives the main loop's clock, see below)
 		now := time.Now()
-		currentBlocks["clock"] = []Block{
-			{
-				Name:      "clock",
-				Instance:  "date",
-				Position:  PositionClock,
-				FullText:  now.Format("2006-01-02"),
-				ShortText: " ",
-				Color:     "#AAAAAA",
+		currentBlocks["clock"] = section(
+			Block{
+				Name:                "clock",
+				Instance:            "date",
+				Position:            PositionClock,
+				FullText:            now.Format("2006-01-02"),
+				ShortText:           " ",
+				Color:               "#AAAAAA",
+				SeparatorBlockWidth: 6,
 			},
-			{
+			Block{
 				Name:     "clock",
 				Instance: "time",
 				Position: PositionClock,
 				FullText: now.Format("15:04:05"),
 			},
-		}
+		)
+
+		//prepare other blocks
+		currentBlocks["battery"] = getBatteryStatus()
 
 		//put blocks in rendering order
 		var allBlocks []Block
@@ -133,5 +137,18 @@ type Position int
 //Acceptable values for Position, from left to right.
 const (
 	PositionNone Position = iota
+	PositionBattery
 	PositionClock
 )
+
+//Order the given blocks byPositionAndInstance, then add a separator to the last one.
+func section(blocks ...Block) []Block {
+	if len(blocks) == 0 {
+		return nil
+	}
+	sort.Sort(byPositionAndInstance(blocks))
+	last := len(blocks) - 1
+	blocks[last].Separator = true
+	blocks[last].SeparatorBlockWidth = 15
+	return blocks
+}