local logger = require("logger")
local BasePowerD = {
    fl_min = 0,                       -- min frontlight intensity
    fl_max = 10,                      -- max frontlight intensity
    fl_intensity = nil,               -- frontlight intensity
    battCapacity = 0,                 -- battery capacity
    device = nil,                     -- device object

    last_capacity_pull_time = 0,      -- timestamp of last pull

    is_fl_on = false,                 -- whether the frontlight is on
}

function BasePowerD:new(o)
    o = o or {}
    setmetatable(o, self)
    self.__index = self
    assert(o.fl_min < o.fl_max)
    if o.init then o:init() end
    if o.device and o.device:hasFrontlight() then
        o.fl_intensity = o:frontlightIntensityHW()
        o:_decideFrontlightState()
    end
    return o
end

function BasePowerD:init() end
function BasePowerD:setIntensityHW(intensity) end
function BasePowerD:getCapacityHW() return 0 end
function BasePowerD:getDissmisBatteryStatus() return self.battery_warning end
function BasePowerD:setDissmisBatteryStatus(status) self.battery_warning = status end
function BasePowerD:isChargingHW() return false end
function BasePowerD:frontlightIntensityHW() return 0 end
function BasePowerD:isFrontlightOnHW() return self.fl_intensity > self.fl_min end
function BasePowerD:turnOffFrontlightHW() self:setIntensityHW(self.fl_min) end
function BasePowerD:turnOnFrontlightHW() self:setIntensityHW(self.fl_intensity) end --- @fixme: what if fl_intensity == fl_min (c.f., kindle)?
-- Anything needs to be done before do a real hardware suspend. Such as turn off
-- front light.
function BasePowerD:beforeSuspend() end
-- Anything needs to be done after do a real hardware resume. Such as resume
-- front light state.
function BasePowerD:afterResume() end

function BasePowerD:isFrontlightOn()
    assert(self ~= nil)
    return self.is_fl_on
end

function BasePowerD:_decideFrontlightState()
    assert(self ~= nil)
    assert(self.device:hasFrontlight())
    self.is_fl_on = self:isFrontlightOnHW()
end

function BasePowerD:isFrontlightOff()
    return not self:isFrontlightOn()
end

function BasePowerD:frontlightIntensity()
    assert(self ~= nil)
    if not self.device:hasFrontlight() then return 0 end
    if self:isFrontlightOff() then return 0 end
    return self.fl_intensity
end

function BasePowerD:toggleFrontlight()
    assert(self ~= nil)
    if not self.device:hasFrontlight() then return false end
    if self:isFrontlightOn() then
        return self:turnOffFrontlight()
    else
        return self:turnOnFrontlight()
    end
end

function BasePowerD:turnOffFrontlight()
    assert(self ~= nil)
    if not self.device:hasFrontlight() then return end
    if self:isFrontlightOff() then return false end
    self:turnOffFrontlightHW()
    self.is_fl_on = false
    self:stateChanged()
    return true
end

function BasePowerD:turnOnFrontlight()
    assert(self ~= nil)
    if not self.device:hasFrontlight() then return end
    if self:isFrontlightOn() then return false end
    if self.fl_intensity == self.fl_min then return false end  --- @fixme what the hell?
    self:turnOnFrontlightHW()
    self.is_fl_on = true
    self:stateChanged()
    return true
end

function BasePowerD:read_int_file(file)
    local fd = io.open(file, "r")
    if fd then
        local int = fd:read("*number")
        fd:close()
        return int or 0
    else
        return 0
    end
end

function BasePowerD:read_str_file(file)
    local fd = io.open(file, "r")
    if fd then
        local str = fd:read("*line")
        fd:close()
        return str
    else
        return ""
    end
end

function BasePowerD:normalizeIntensity(intensity)
    intensity = intensity < self.fl_min and self.fl_min or intensity
    return intensity > self.fl_max and self.fl_max or intensity
end

function BasePowerD:setIntensity(intensity)
    if not self.device:hasFrontlight() then return false end
    if intensity == self:frontlightIntensity() then return false end
    self.fl_intensity = self:normalizeIntensity(intensity)
    self:_decideFrontlightState()
    logger.dbg("set light intensity", self.fl_intensity)
    self:setIntensityHW(self.fl_intensity)
    self:stateChanged()
    return true
end

function BasePowerD:getCapacity()
    local now_ts = os.time()
    if now_ts - self.last_capacity_pull_time >= 60 then
        self.battCapacity = self:getCapacityHW()
        self.last_capacity_pull_time = now_ts
    end
    return self.battCapacity
end

function BasePowerD:isCharging()
    return self:isChargingHW()
end

function BasePowerD:stateChanged()
    -- BasePowerD is loaded before UIManager. So we cannot broadcast events before UIManager has been loaded.
    if package.loaded["ui/uimanager"] ~= nil then
        local Event = require("ui/event")
        local UIManager = require("ui/uimanager")
        UIManager:broadcastEvent(Event:new("FrontlightStateChanged"))
    end
end

return BasePowerD