-- Battery widget

local awful = require("awful")
local gears = require("gears")
local wibox = require("wibox")
local naughty = require("naughty")

local timer = gears.timer or timer
local watch = awful.spawn and awful.spawn.with_line_callback

------------------------------------------
-- Private utility functions
------------------------------------------

local tolower = string.lower

local function file_exists(command)
  local f = io.open(command)
  if f then f:close() end
  return f and true or false
end

local function readfile(command)
  local file = io.open(command)
  if not file then return nil end
  local text = file:read('*all')
  file:close()
  return text
end

local function color_tags(color)
  if color
  then
    return '<span color="' .. color .. '">', '</span>'
  else
    return '', ''
  end
end

local function round(value)
  return math.floor(value + 0.5)
end

local function trim(s)
  if not s then return nil end
  return (s:gsub("^%s*(.-)%s*$", "%1"))
end

local function read_trim(filename)
  return trim(readfile(filename)) or ""
end

local function substitute(template, context)
  if type(template) == "string" then
    return (template:gsub("%${([%w_]+)}", function(key)
      return tostring(context[key] or "Err!")
    end))
  else
    -- function / functor:
    return template(context)
  end
end

local function lookup_by_limits(limits, value)
  if type(limits) == "table" then
    local last = nil
    if value then
      for k, v in ipairs(limits) do
        if (value <= v[1]) then
          return v[2]
        end
        last = v[2]
      end
    end
    return last
  else
    return limits
  end
end

------------------------------------------
-- Battery widget interface
------------------------------------------

local battery_widget = {}
local sysfs_names = {
  charging = {
    present  = "present",
    state    = "status",
    rate     = "current_now",
    charge   = "charge_now",
    capacity = "charge_full",
    design   = "charge_full_design",
    percent  = "capacity",
  },
  discharging = {
    present  = "present",
    state    = "status",
    rate     = "power_now",
    charge   = "energy_now",
    capacity = "energy_full",
    design   = "energy_full_design",
    percent  = "capacity"
  },
}

function battery_widget:new(args)
  if args.adapter then
    return setmetatable({}, { __index = self }):init(args)
  end
  -- creates an empty container wibox, which can be added to your panel even if its empty
  local widgets = { layout = wibox.layout.fixed.horizontal }
  local batteries, mains, usb, ups = self:discover()
  local ac = mains[1] or usb[1] or ups[1]
  for i, adapter in ipairs(batteries) do
    local _args = setmetatable({ adapter = adapter, ac = ac }, { __index = args })
    table.insert(widgets, self(_args).widget)
  end
  return widgets
end

function battery_widget:discover()
  local pow      = "/sys/class/power_supply/"
  local adapters = { Battery = {}, UPS = {}, Mains = {}, USB = {} }
  for adapter in io.popen("ls -1 " .. pow):lines() do
    local type = read_trim(pow .. adapter .. "/type")
    table.insert(adapters[type], adapter)
  end
  return adapters.Battery, adapters.Mains, adapters.USB, adapters.UPS
end

function battery_widget:init(args)
  self.ac = args.ac or "AC"
  self.adapter = args.adapter or "BAT0"
  self.ac_prefix = args.ac_prefix or "AC: "
  self.battery_prefix = args.battery_prefix or "Bat: "
  self.percent_colors = args.percent_colors or args.limits or {
    { 25,  "red" },
    { 50,  "orange" },
    { 999, "green" },
  }

  self.widget_text = args.widget_text or (
    "${AC_BAT}${color_on}${percent}%${color_off}")
  self.tooltip_text = args.tooltip_text or (
    "Battery ${state}${time_est}\nCapacity: ${capacity_percent}%")

  self.alert_threshold = args.alert_threshold or 5
  self.alert_timeout = args.alert_timeout or 0
  self.alert_title = args.alert_title or "Low battery !"
  self.alert_text = args.alert_text or "${AC_BAT}${time_est}"
  self.alert_icon = args.alert_icon or nil

  self.widget = wibox.widget.textbox()
  self.widget.font = args.widget_font
  self.tooltip = awful.tooltip({ objects = { self.widget } })

  self.warn_full_battery = args.warn_full_battery
  self.full_battery_icon = args.full_battery_icon or nil

  self.widget:buttons(awful.util.table.join(
    awful.button({}, 1, function() self:update() end),
    awful.button({}, 3, function() self:update() end)
  ))

  self.timer = timer({ timeout = args.timeout or 10 })
  self.timer:connect_signal("timeout", function() self:update() end)
  self.timer:start()
  self:update()

  if (args.listen or args.listen == nil) and watch then
    self.listener = watch("acpi_listen", {
      stdout = function(line) self:update() end,
    })
    awesome.connect_signal("exit", function()
      awesome.kill(self.listener, awesome.unix_signal.SIGTERM)
    end)
  end

  return self
end

function battery_widget:get_state()
  local pow   = "/sys/class/power_supply/"
  local ac    = pow .. self.ac
  local bat   = pow .. self.adapter
  local sysfs = (file_exists(bat .. "/" .. sysfs_names.charging.rate)
    and sysfs_names.charging
    or sysfs_names.discharging)

  -- If there is no battery on this machine.
  if not sysfs.state then return nil end

  -- return value
  local r = {
    state    = tolower(read_trim(bat .. "/" .. sysfs.state)),
    present  = tonumber(read_trim(bat .. "/" .. sysfs.present)),
    rate     = tonumber(read_trim(bat .. "/" .. sysfs.rate)),
    charge   = tonumber(read_trim(bat .. "/" .. sysfs.charge)),
    capacity = tonumber(read_trim(bat .. "/" .. sysfs.capacity)),
    design   = tonumber(read_trim(bat .. "/" .. sysfs.design)),
    percent  = tonumber(read_trim(bat .. "/" .. sysfs.percent)),
  }

  r.ac_state = tonumber(read_trim(ac .. "/online"))

  if r.state == "unknown" then
    r.state = "charged"
  end

  if r.percent == nil and r.charge and r.capacity then
    r.percent = round(r.charge * 100 / r.capacity)
  end

  return r
end

function battery_widget:update()
  local ctx = self:get_state()

  -- If there is no battery on this machine.
  if not ctx then return nil end

  -- AC/battery prefix
  ctx.AC_BAT                  = (ctx.ac_state == 1
    and lookup_by_limits(self.ac_prefix, ctx.percent)
    or lookup_by_limits(self.battery_prefix, ctx.percent)
    or "Err!")

  -- Colors
  ctx.color_on, ctx.color_off = color_tags(
    lookup_by_limits(self.percent_colors, ctx.percent))

  -- estimate time
  ctx.charge_dir              = 0 -- +1|0|-1 -> charging|static|discharging
  ctx.time_left               = nil -- time until charging/discharging complete
  ctx.time_text               = ""
  ctx.time_est                = ""

  if ctx.rate and ctx.rate ~= 0 then
    if not ctx.state or ctx.state == "discharging" then
      ctx.charge_dir = -1
      ctx.time_left = ctx.charge / ctx.rate
    elseif ctx.state == "charging" then
      ctx.charge_dir = 1
      ctx.time_left = (ctx.capacity - ctx.charge) / ctx.rate
    end
  end

  if ctx.time_left then
    ctx.hours   = math.floor((ctx.time_left))
    ctx.minutes = math.floor((ctx.time_left - ctx.hours) * 60)
    if ctx.hours > 0
    then
      ctx.time_text = ctx.hours .. "h " .. ctx.minutes .. "m"
    else
      ctx.time_text = ctx.minutes .. "m"
    end
    ctx.time_est = ": " .. ctx.time_text .. " remaining"
  end

  -- capacity text
  if ctx.capacity and ctx.design then
    ctx.capacity_percent = round(ctx.capacity / ctx.design * 100)
  end

  -- for use in functions
  ctx.obj = self

  -- update text
  self.widget:set_markup(substitute(self.widget_text, ctx))
  self.tooltip:set_text(substitute(self.tooltip_text, ctx))

  -- low battery notification
  if naughty then
    if (ctx.state == "discharging" and
          ctx.percent and ctx.percent <= self.alert_threshold) then
      self:notify(substitute(self.alert_title, ctx),
        substitute(self.alert_text, ctx),
        self.alert_icon)
    elseif ctx.state == "full" and self.warn_full_battery then
      self:notify('Battery Full!', 'Remove power cord', self.full_battery_icon)
    else
      if self.alert then
        naughty.destroy(
          self.alert,
          naughty.notificationClosedReason.dismissedByCommand)
        self.alert = nil
      end
    end
  end
end

function battery_widget:notify(title, text, icon)
  if self.alert then
    naughty.replace_text(self.alert, title, text)
  else
    self.alert = naughty.notify({
      title = title,
      text = text,
      icon = icon,
      preset = naughty.config.presets.critical,
      timeout = self.alert_timeout
    })
  end
end

return setmetatable(battery_widget, {
  __call = battery_widget.new,
})