local script = {}
local P = {}

script.input =
    {
        { "LStelem", SOURCE},             -- a switch detecting telemetry OK
        
        { "Window", VALUE, 1, 99, 5 },   -- window in time for running average
        { "Freq", VALUE, 1, 5, 5 },      -- number of samples / second  for running average
        { "Alpha%", VALUE, 1, 99, 25 },   -- attenuation factor for lowpass filter
                                         -- 100 is no attentuation, direct response
        { "Misses%", VALUE, 1, 99, 50 },  -- max percentage of misses over Window, 
                                         --below which value is kept at previous
                                         -- when #misses reached, value is set to ZERO
        { "Misses#", VALUE, 1, 99, 25 },  -- max number of misses, below which value is kept at previous
                                         -- when #misses reached, value is set to ZERO
    }

script.output = { "mean","lowP","mis%","mis#","#mis","raw" }

P.time = 0

P.values = {}       --fifo buffer for SOURCE
P.values[0] = 0     --0 element is used as index

P.nMissed = 0       --initialisation

P.missing = {}      --fifo buffer
P.missing[0] = 0    --0 element is used as index

function script.run(telemSwitch,window,frequency,alpha,pMissing,nMissed)
  P.time = P.time or getTime()
  local dt = math.ceil(100/frequency)
  local nValues = window*frequency
  if getTime() >= (P.time + dt) then
    getValueSource = (telemSwitch==-1024) and 0 or getValue("RSSI")*1024/100
    
    --simple running average
    P.values[0] = P.values[0] % nValues + 1
    P.values[P.values[0]] = getValueSource 
    P.mean = 0
    for n,v in ipairs(P.values) do
      P.mean = P.mean + v/#P.values
    end
  
    --see https://en.wikipedia.org/wiki/Low-pass_filter
    P.lowPass = (P.lowPass or getValueSource) + alpha/100*(getValueSource - (P.lowPass or getValueSource) )
    
    --hold on miss until treshold misses reached
    P.nMissed = (getValueSource==0) and (P.nMissed +1) or 0
    
    --          (treshold NOT reached) and ((NO VALUES)         then     HOLD) else  SOURCE (is 0 if No Values!!)
    P.nMisses = (P.nMissed <  nMissed) and ((getValueSource==0) and P.nMisses) or    getValueSource
    
    --HOLD on missing SOURCE until treshold missing% reached, nValues from average
    --simple running average
    P.missing[0] = P.missing[0] % nValues + 1
    P.missing[P.missing[0] ] = (getValueSource==0) and 100 or 0 --set 100% when missing
    P.pMissing = 0
    for n,v in ipairs(P.missing) do
      P.pMissing = P.pMissing + v/#P.missing
    end
    --          (treshold NOT reached ) and ((NO VALUES)         then     HOLD) else  SOURCE (is 0 if No Values!!)
    P.pMisses = (P.pMissing < pMissing) and ((getValueSource==0) and P.pMisses) or    getValueSource
    
    P.time = nil --reset timer
  end
  return P.mean,P.lowPass,P.pMisses,P.nMisses,P.nMissed*1024/100,getValueSource
end

return script