Another battery widget

This is ased on something similar for Ion3 (by Jari Eskelinen).

It shows the current charge of the battery and the time remaining until the battery is full or empty. If the system is on AC the prefix is 'AC', otherwise it's 'Battery'.

It doesn't do any error checking, so I don't even know what can happen if your system isn't exactly like mine. Use at your own risk, yada, yada, yada.

 -- {{{ Battery state Widget
 
 batterywidget = widget({
     type = 'textbox',
     name = 'batterywidget',
     align = 'right'
     })
 
 wicked.register(batterywidget, 'function', function (widget, args)
     local f = io.open('/proc/acpi/battery/BAT0/info')
     local infocontents = f:read('*all')
     f:close()
 
     f = io.open('/proc/acpi/battery/BAT0/state')
     local statecontents = f:read('*all')
     f:close()
 
     local status, _
     -- Find the full capacity (from info)
     local full_cap
     
     status, _, full_cap = string.find(infocontents, "last full capacity:%s+(%d+).*")
 
     -- Find the current capacity, state and (dis)charge rate (from state)
     local state, rate, current_cap
     
     status, _, state = string.find(statecontents, "charging state:%s+(%w+)")
     status, _, rate  = string.find(statecontents, "present rate:%s+(%d+).*")
     status, _, current_cap = string.find(statecontents, "remaining capacity:%s+(%d+).*")
 
     local prefix, percent, time
     percent = current_cap / full_cap * 100
     if state == "charged" then
         return "AC: " .. fg("green", "100%")
     elseif state == "charging" then
         prefix = "AC: "
         time = (full_cap - current_cap) / rate
     elseif state == "discharging" then
         prefix = "Battery: "
         time = current_cap / rate
     end
 
     time_hour = math.floor(time)
     time_minute = math.floor((time - time_hour) * 60)
     
     percent = math.floor(percent)
     local percent_string
     if percent < 25 then
         percent_string = fg("red", percent .. "%")
     elseif percent < 50 then
         percent_string = fg("orange", percent .. "%")
     else
         percent_string = fg("green", percent .. "%")
     end
 
     return prefix .. percent_string .. " " .. string.format("(%02d:%02d)", time_hour, time_minute)
 end, 2)
 -- }}}