print("-------------------")
--[[
This script is a engine heater script which turns the engine heater on and off depending on the out door temperature
There is currently a weekly schedule to program one leave time per day


Prerequisites:
User variable 'EngHeat_Mode' (string) must exist
User variable 'EngHeat_LeaveTime' (string) must exist
]]--

-- Set leave times.
leaveTime = {'Monday 07:25',
             'Tuesday 07:25',
             'Wednesday 07:25',
             'Thursday 07:25',
             'Friday 07:25' }

-- Enginge heater maximum runtime in seconds
MAXRUNTIME = 180 * 60

-- Name of the engine heater switch device
HEATERSWITCH = 'SWITCH_Fd_EngineHeater'
-- Name of the outdoor temperate sensor device
OUTDOORTEMP  = 'Utetemp'

--Name of engine heater watts measurement device
--Set to '' if no watt measure device exist
HEATERWATTS = 'SWITCH_Fd_EngineHeater_Watts'

-- Minimun time for watt measurements in seconds
HEATERWATTSPERIOD = 10*60

-- FUNCTIONS START --

--integer converts a float into an integer
function integer(x)
    return x<0 and math.ceil(x) or math.floor(x)
end

-- calculateRuntime calucates heater run time in seconds depending on outdoor temp
-- It has a different formula depending on if the outdoor temp is above or below zero
function calculateRuntime(temp)
   local ntemp = 11 - temp
   -- If temperature is above +10 set runtime to 0
   if (temp > 10) then
      return 0
   elseif (ntemp > 0) then
      return integer((0.0044*ntemp^3+0.3377*ntemp^2-1.1128*ntemp+21.496)) * 60
   else
      return integer((0.0036*ntemp^3-0.4179*ntemp^2+18.205*ntemp-99.417)) * 60
   end
end

-- secsToClock return a string representing seconds as HH:MM:SS
function secsToClock(seconds)
   if ((seconds == 0) or (seconds == nil) ) then
      return "00:00:00"
   else
      days  = integer(seconds / (60 * 60 * 24))
      hours = integer((seconds - days * 60 * 60 * 24) / (60 * 60))
      mins  = integer((seconds - days * 60 * 60 * 24 - hours * 60 * 60) / 60)
      secs  = seconds - days * 60 * 60 * 24 - hours * 60 * 60 - mins * 60;

      if (days > 99) then
         return string.format("%03d:%02d:%02d:%02d (DDD:HH:MM:SS)", days, hours, mins, secs)
      elseif (days > 0) then
         return string.format("%02d:%02d:%02d:%02d (DD:HH:MM:SS)", days, hours, mins, secs)
      else
         return string.format("%02d:%02d:%02d (HH:MM:SS)", hours, mins, secs)
      end
   end
end

-- getCurrentRunTime returns current runtime in seconds as an integer or nil if not available
function getCurrentRunTime()
   local lastupdated = getHeaterLastUpdate()

   if (lastupdated ~= nil) then
      return integer(os.difftime (os.time(), deviceToTime(lastupdated)))
   else
      return nil
   end
end

-- getHeaterWatts returns current heater watts in watts or nil if not available
function getHeaterWatts()
   if (HEATERWATTS == '') then
      return nil
   end

   if (otherdevices_lastupdate[HEATERWATTS] == nil) then
      return nil
   end

   -- if lastupdatediff is greater than HEATERWATTSPERIOD it probably means that the device has not yet reported any watts
   local timediff = integer(os.difftime (os.time(), deviceToTime(otherdevices_lastupdate[HEATERWATTS])))
   if (timediff > HEATERWATTSPERIOD) then
        return nil
   end

   if (otherdevices_svalues[HEATERWATTS] ~= nil) then
      return integer(tonumber(otherdevices_svalues[HEATERWATTS]))
    else
      return nil
    end
end

-- isHeaterOn returns true or false if heater is consuming power (on) or not consuming power (off). Returns nil if status is not available
function isHeaterRunning()
   local runtime = getCurrentRunTime()
   if (runtime == nil) then
      return nil
   end

   -- if runtime is less than HEATERWATTSPERIOD beacause the device has not yet reported any watts, return nil.
   if (runtime < HEATERWATTSPERIOD) then
      return nil
   end

   watts = getHeaterWatts()
   if (watts == nil) then
      return nil
   end

   -- return true if energy consumtion is greater than 5 watts
   return (watts > 5 and true or false)
end

function getHeaterLastUpdate()
   if (otherdevices_lastupdate[HEATERSWITCH] ~= nil) then
      return otherdevices_lastupdate[HEATERSWITCH]
   else
      return nil
   end
end
 -- deviceToTime returns a device time string in a format which can be used by the os.difftime function
function deviceToTime(time)
   return os.time { year  = string.sub(time, 1, 4),
                    month = string.sub(time, 6, 7),
                    day   = string.sub(time, 9, 10),
                    hour  = string.sub(time, 12, 13),
                    min   = string.sub(time, 15, 16),
                    sec   = string.sub(time, 18, 19) }
end

-- getOutdoorTemp gets the out door temp
-- TODO: If local temperature device is unreachable, fetch temp from weather service instead
function getOutdoorTemp()
   if ((otherdevices_lastupdate[OUTDOORTEMP] ~= nil) and (os.difftime(os.time(), deviceToTime(otherdevices_lastupdate[OUTDOORTEMP])) < 10*60)) then
      if (otherdevices_svalues[OUTDOORTEMP] ~= nil) then
         return tonumber(otherdevices_svalues[OUTDOORTEMP])
      else
         print("Error!! Could not get outdoor temp from otherdevices_svalues['"..OUTDOORTEMP.."'], key field does not exist")
      end
   else
      print("Warning. No updates for local outdpor temperature sensor has been registered for 10 minutes.")
      if (otherdevices_svalues[OUTDOORTEMP] ~= nil) then
         return tonumber(otherdevices_svalues[OUTDOORTEMP])
      else
         print("Error!! Could not get outdoor temp from otherdevices_svalues['"..OUTDOORTEMP.."'], key field does not exist")
      end
   end
   -- Todo, get temp from Internet weather service
   return 0
end

-- END OF FUNCTIONS --

-- Calculate timestamp for this day mid night
temp = os.date("*t", os.time())
todayMidnight = os.time{year=temp['year'], month=temp['month'], day=temp['day'], hour=0, min=0, sec=0 }
-- print("todayMidnight = "..os.date("%Y-%m-%d %H:%M:%S", todayMidnight))

-- Get Current weekday as a number. [0-6 = Sunday-Saturday]
currentWeekday = tonumber(os.date("%w",todayMidnight))

-- Calculate timestamp for sunday midnight
sundayMidnight = todayMidnight - (60 * 60 * 24 * currentWeekday)
-- print("sundayMidnight = "..os.date("%Y-%m-%d %H:%M:%S", sundayMidnight))

now = os.time()

-- Convert leave time to timestamps
local weekDays = { ['Sunday'] = 0, ['Monday'] = 1, ['Tuesday'] = 2, ['Wednesday'] = 3, ['Thursday'] = 4, ['Friday'] = 5, ['Saturday'] = 6 }
for key,value in pairs(leaveTime) do

   leaveWeekday = string.match(value, "^(%a+) ")
   if (weekDays[leaveWeekday] == nil) then
      print("Warning, scheduled weekday "..leaveWeekday.." in "..value.." is not a valid weekday")
   end

   leaveHours     = string.match(value, "[0-9][0-9]:+[0-9][0-9]")
   local tmp      = os.date("*t", sundayMidnight + weekDays[leaveWeekday] * 60 * 60 * 24)
   leaveTime[key] = tonumber(os.time{year=tmp['year'], month=tmp['month'], day=tmp['day'], hour = string.sub(leaveHours, 1, 2), min = string.sub(leaveHours, 4, 5), sec=0 })

   -- If leave time has passed current time add one week
   if (leaveTime[key] < now) then
      leaveTime[key] = leaveTime[key] + 60 * 60 * 24 * 7
   end
end
-- sort in ascending order
table.sort(leaveTime)

-- Print scheduled leave times in correct order
for key, dayLeaveTime in ipairs(leaveTime) do
   print("Next scheduled leave time is "..os.date("%Y-%m-%d %H:%M:%S", dayLeaveTime))
end

-- Get engine heater mode
if (uservariables['EngHeat_Mode'] ~= nil) then
   heaterMode = uservariables['EngHeat_Mode']
   print("Engine heating mode is "..heaterMode)
else
   heaterMode = "unknown"
   print("Warning! Cannot read user variable 'EngHeat_Mode")
end

-- Get engine heater switch status
if (otherdevices[HEATERSWITCH] ~= nil) then
   engineHeaterStatus = otherdevices[HEATERSWITCH]
else
   engineHeaterStatus = "unknown"
   print("Warning! Cannot read state for otherdevices['"..HEATERSWITCH.."']")
end
print ("Engine heater status is "..engineHeaterStatus)

-- Get outdoor temperature
currTemp = getOutdoorTemp()
print ("Current outdoor temperature is "..currTemp.." Celsius")

commandArray = {}

if ((heaterMode == "Off") and (engineHeaterStatus == "Off") ) then
   -- Calculate runtime in seconds
   calculatedRuntime = calculateRuntime(currTemp)

   -- Handle if calculated runtime exceed maximum runtime
   if (calculatedRuntime > MAXRUNTIME) then
      print ("Calculated runtime using outdoor temp "..currTemp.." is "..secsToClock(calculatedRuntime)..") which exceeds maximum runtime "..secsToClock(MAXRUNTIME)..". Setting calculated runtime to "..secsToClock(MAXRUNTIME))
      calculatedRuntime = MAXRUNTIME
   elseif (calculatedRuntime > 0) then
      print ("Calculated runtime using outdoor temp "..currTemp.." is "..secsToClock(calculatedRuntime))
   elseif (calculatedRuntime == 0) then
      print ("Calculated runtime using outdoor temp "..currTemp.." is zero. Outdoor temp too high")
   else
      print ("ERROR!! Calculated runtime using outdoor temp "..currTemp.." is out of boundary: "..calculatedRuntime..". Setting it to zero")
      calculatedRuntime = 0
   end

   -- Check if heater is running even if device is set to off in Domoticz (due to communication error?)
   runStatus = isHeaterRunning()
   if (runStatus == true) then
      print ("Engine heater current watts: "..getHeaterWatts())
      print ("Error! Engine heater is running despite heater switch is set to off. Stopping engine heater")
      commandArray[HEATERSWITCH]                 = "Off"
      commandArray['Variable:EngHeat_Mode']      = "Off"
      commandArray['Variable:EngHeat_LeaveTime'] = ""
      return commandArray
   end

   -- Check if any scheduled start condition is met
   for key, dayLeaveTime in ipairs(leaveTime) do

      dayStartTime = dayLeaveTime - calculatedRuntime

      if ((now > dayStartTime) and (now < dayLeaveTime)) then

         -- Start heater only if calculated runtime is greater than zero
         if (calculatedRuntime > 0) then
            print("Next leave time is "..os.date("%Y-%m-%d %H:%M:%S", dayLeaveTime))
            print("Engine heater start time is "..os.date("%Y-%m-%d %H:%M:%S", dayStartTime)..". Time to leave is "..secsToClock(dayLeaveTime-now))
            commandArray[HEATERSWITCH]                 = "On"
            commandArray['Variable:EngHeat_Mode']      = "Auto"
            commandArray['Variable:EngHeat_LeaveTime'] = os.date("%Y-%m-%d %H:%M:%S", dayLeaveTime)
            print("Starting Engine heater")
         elseif (calculatedRuntime == 0) then
            print("Today leave time is "..os.date("%Y-%m-%d %H:%M:%S", dayLeaveTime))
            print("Engine heater start time is "..os.date("%Y-%m-%d %H:%M:%S", dayStartTime))
            print("Engine heater not started since calculatedRuntime is zero")
         else
            Print("ERROR! Calculated runtime is out of boundary: "..calculatedRuntime)
         end
         break
      end
   end
elseif (engineHeaterStatus == "On")  then

   -- Get the last time engine heater was set to on
   lastupdated = getHeaterLastUpdate()
   if (lastupdated == nil) then
      print ("Could not detect when engine heater was automatically turned on. For security reasons engine heater is now turned off")
      print ("Automatic mode is turned off, you have to manually turn engine heater on")
      commandArray[HEATERSWITCH]                 = "Off"
      commandArray['Variable:EngHeat_Mode']      = "Stopped"
      commandArray['Variable:EngHeat_LeaveTime'] = ""
      return commandArray
   end

   -- get runtime in seconds
   currentRuntime = getCurrentRunTime()
   if (currentRuntime == nil) then
      print ("Could not detect current runtime. For security reasons engine heater is now turned off")
      print ("Automatic mode is turned off, you have to manually turn engine heater on")
      commandArray[HEATERSWITCH]                 = "Off"
      commandArray['Variable:EngHeat_Mode']      = "Stopped"
      commandArray['Variable:EngHeat_LeaveTime'] = ""
      return commandArray
   end

   runStatus = isHeaterRunning()
   if (runStatus == false) then
      print ("Engine heater plug is not connected, cancelling heating")
      commandArray[HEATERSWITCH]                 = "Off"
      commandArray['Variable:EngHeat_Mode']      = (heaterMode == "Auto" and "Cancel" or "Off")
      commandArray['Variable:EngHeat_LeaveTime'] = ""
      return commandArray
   elseif (runStatus == true) then
       print ("Engine heater current watts: "..getHeaterWatts())
   end

   -- Automatic mode
   if (heaterMode == "Auto") then
      print ("Engine heater was automatically set to on at "..lastupdated)

      -- Get leave time
      if (uservariables['EngHeat_LeaveTime'] == "") then
         print("Cannot read user variable 'EngHeat_LeaveTime'. Engine heater will run until max runtime is reached")
      else
         -- Assuming a date pattern like: yyyy-mm-dd hh:mm:ss
         dayLeaveTime = deviceToTime(uservariables['EngHeat_LeaveTime'])

         -- Has leave time passed?
         if (now > dayLeaveTime) then
            print("Today leave time is "..os.date("%Y-%m-%d %H:%M:%S", dayLeaveTime))
            commandArray[HEATERSWITCH]                 = "Off"
            commandArray['Variable:EngHeat_Mode']      = "Off"
            commandArray['Variable:EngHeat_LeaveTime'] = ""
            print("Leave time has passed. Stopping Engine heater")
            return commandArray
         else
            print("Leave time is "..os.date("%H:%M:%S", dayLeaveTime)..". Time to leave is "..secsToClock(dayLeaveTime-now))
         end
      end
   -- Manual mode
   elseif (heaterMode == "Manual") then
      print ("Engine heater was set to manually run at "..lastupdated)
   end

   print("Engine heater current runtime is "..secsToClock(currentRuntime))

   -- Check if max runtime is exceeded
   if (currentRuntime > MAXRUNTIME) then
      print ("Engine heater maximum runtime exceeded. Cancelling engine heater")
      commandArray[HEATERSWITCH]                 = "Off"
      commandArray['Variable:EngHeat_Mode']      = (heaterMode == "Auto" and "Cancel" or "Off")
      commandArray['Variable:EngHeat_LeaveTime'] = ""
      return commandArray
   end
-- If heaterMode is set to cancel and heater is manually shut off, heaterMode must be set to cancel until leave time has passed, otherwise it will start heating again
elseif (heaterMode == "Cancel") then

   if (uservariables['EngHeat_LeaveTime'] == "") then
      print("Engine heater logic ran into unknown state. Resetting")
      commandArray[HEATERSWITCH]                 = "Off"
      commandArray['Variable:EngHeat_Mode']      = "Off"
      commandArray['Variable:EngHeat_LeaveTime'] = ""
      return commandArray
   end

   runStatus = isHeaterRunning()
   if (runStatus == true) then
      print ("Engine heater current watts: "..getHeaterWatts())
      print ("Error! Engine heater is running despite heater switch is set to off. Stopping engine heater")
      commandArray[HEATERSWITCH]                 = "Off"
      commandArray['Variable:EngHeat_Mode']      = "Off"
      commandArray['Variable:EngHeat_LeaveTime'] = ""
      return commandArray
   end

   -- Assuming a date pattern like: yyyy-mm-dd hh:mm:ss
   dayLeaveTime = deviceToTime(uservariables['EngHeat_LeaveTime'])

   -- If leave time has passed
   if (now > dayLeaveTime) then

      -- Get the last time when engine heater was changed
      lastupdated = getHeaterLastUpdate()
      if (lastupdated == nil) then
         print("Engine heater logic ran into unkown state. Resetting")
         commandArray[HEATERSWITCH]                 = "Off"
         commandArray['Variable:EngHeat_Mode']      = "Off"
         commandArray['Variable:EngHeat_LeaveTime'] = ""
         return commandArray
      end

      print("Heating was manually canceled "..lastupdated)
      print("Today leave time was "..os.date("%Y-%m-%d %H:%M:%S", dayLeaveTime))
      print("Leave time has passed. Changine engine heater mode from Cancel to Off")
      commandArray['Variable:EngHeat_Mode']      = "Off"
      commandArray['Variable:EngHeat_LeaveTime'] = ""
      return commandArray
   end
elseif (heaterMode == "Stopped") then
      print("Engine heater mode is set to stopped. Check for errors in log. Heater must be manually started.")
end
return commandArray