local GFile             = require("lgi").Gio.File

local gears             = require("gears")
local spawn             = require("awful.spawn")
local wibox             = require("wibox")

local utils             = require('utils')

local BatteryWidget     = require('battery_wgt')
local Battery           = require('battery')


local BatteryManager = {}
BatteryManager.__index = BatteryManager

setmetatable(BatteryManager, {
    __call = function (cls, ...) return cls.new(...) end,
})

function BatteryManager:_log(msg, ...)
    utils.log('BatteryManager', msg, ...)
end

function BatteryManager:_warn(msg, ...)
    utils.warn('BatteryManager', msg, ...)
end

function BatteryManager:_battery_add(name)
    if self._batteries[name] ~= nil then
        -- only warn for usable batteries that are added twice for some reason
        if self._batteries[name] ~= false then
            self:_warn('Battery %s already exists', name)
        end
        return
    end

    self:_log('Trying power supply: ' .. name)

    local bat = Battery(name)
    if not bat then
        self:_log('Skipping ' .. name .. ': could not be opened or is not a battery')
        -- remember device as unusable
        self._batteries[name] = false
        return
    end
    self:_log('Opened battery %s: %s', name, bat.desc)

    local wgt = BatteryWidget(bat)

    self._layout:add(wgt)

    self._batteries[name] = { widget = wgt, battery = bat }
end

function BatteryManager:_battery_remove(name)
    self:_log('Removing battery ' .. name)

    local tbl = self._batteries[name]
    if tbl then
        self._layout:remove_widgets(tbl.widget)
    end
    self._batteries[name] = nil
end

function BatteryManager:_refresh()
    for name, item in pairs(self._batteries) do
        if item and not item.battery:update() then
            self:_log('Could not update battery %s, removing', name)
            self:_battery_remove(name)
        end
    end
end

function BatteryManager.new()
    local self = setmetatable({}, BatteryManager)

    -- the layout containing the individual battery widgets
    self._layout    = wibox.layout.flex.horizontal()

    -- entries are either
    -- - tables { battery, widget } for existing batteries
    -- - false for devices that we've seen, but are not valid batteries
    self._batteries = {}

    -- try adding all existing batteries
    local ps = GFile.new_for_path('/sys/class/power_supply')
    local ret = ps:enumerate_children('*', 0)
    while true do
        local file_info = ret:next_file()
        if not file_info then
            break
        end

        self:_battery_add(file_info:get_name())
    end

    -- monitor udev events
    local function monitor_stdout(line)
        local action, device = string.match(line, '^KERNEL%[%d+.%d*%]%s+(%a+)%s+([^%s]+)%s+%(power_supply%)$')
        if action then
            local name = string.match(device, '([^/]+)$')
            if name == nil then
                self:_warn('Could not extract device name from path: %s', device)
                return
            end

            if action == 'add' or action == 'change' then
                -- battery device not seen before, try adding
                if self._batteries[name] == nil then
                    self:_battery_add(name)
                end

                -- device is a valid battery, refresh state
                if self._batteries[name] then
                    self._batteries[name].battery:update()
                end
            elseif action == 'remove' then
                self:_battery_remove(name)
            end
        end
    end

    local function monitor_exit(reason, code)
        self:_warn('udevadm monitor exited: %s/%d', reason, code)
    end

    spawn.with_line_callback('udevadm monitor --kernel --subsystem-match=power_supply',
                             { stdout = monitor_stdout, exit = monitor_exit, })

    self:_refresh()
    gears.timer.start_new(5, function ()
        self:_refresh()
        return true
    end)

    return self._layout
end

return BatteryManager