systemd power events

###############################
~ cat /etc/udev/rules.d/85-powertargets.rules
SUBSYSTEM=="power_supply", KERNEL=="AC", ATTR{online}=="0", RUN+="/usr/sbin/systemctl start battery.target"
SUBSYSTEM=="power_supply", KERNEL=="AC", ATTR{online}=="1", RUN+="/usr/sbin/systemctl start ac.target"

###############################
~  cat /etc/systemd/system/ac.target
[Unit]
Description=On AC power
DefaultDependencies=no
StopWhenUnneeded=yes

###############################
~ cat /etc/systemd/system/battery.target
[Unit]
Description=On battery power
DefaultDependencies=no
StopWhenUnneeded=yes

###############################
~ cat /etc/systemd/system/powerdown.service
# /etc/systemd/system/powerdown.service
[Unit]
Description=Laptop battery savings

[Service]
Type=oneshot
ExecStart=/usr/local/bin/powerdown

[Install]
WantedBy=battery.target

###############################
~ cat /etc/systemd/system/powerup.service
[Unit]
Description=Laptop battery savings

[Service]
Type=oneshot
ExecStart=/usr/local/bin/powerup

[Install]
WantedBy=ac.target