local inputs = { {"Play", SOURCE}, {"Dur", VALUE, 1, 30, 15}, {"Test", VALUE, 0, 1, 0} }
local outputs = { "Rate" }

local wait_end = 0
local Rate = 0
local History
local NumElements = 0
local PlayDone = false

List = {}
function List.new ()
  print ('list.new')
  return {first = 0, last = -1}
end


function List.pushleft (list, value)
  local first = list.first - 1
  list.first = first
  list[first] = value
end

function List.pushright (list, value)
  local last = list.last + 1
  list.last = last
  list[last] = value
end

function List.popleft (list)
  local first = list.first
  if first > list.last then error("list is empty") end
  local value = list[first]
  list[first] = nil        -- to allow garbage collection
  list.first = first + 1
  return value
end

function List.popright (list)
  local last = list.last
  if list.first > last then error("list is empty") end
  local value = list[last]
  list[last] = nil         -- to allow garbage collection
  list.last = last - 1
  return value
end


local function init()
  History = List.new()
end

local wait_end = 0

local function run(Play, Duration, Test)
  if getTime() >= wait_end then
    print ('working')
    wait_end = getTime() + 100
    local alt
    if Test == 0 then
      alt = getValue('altitude')
    else
      alt = getValue('thr') / 100
    end
    print ('pushing alt '.. alt)
    List.pushright(History, alt)
    NumElements = NumElements + 1
    while NumElements > Duration do
      List.popleft(History)
      NumElements = NumElements - 1
    end
    print ('num elements: '..NumElements)

    if NumElements == Duration then
      local StartAlt = List.popleft(History)
      NumElements = NumElements - 1
      Rate =  60 * (alt - StartAlt) / Duration   -- unit m/min
      print ('rate: '..Rate)
    end
  end
  if Play > 500 then
    if PlayDone == false then
      PlayDone = true
      local rr = math.floor(Rate * 10 + 0.5)
      print('rounded rate: '.. rr)
      playNumber(rr, 0, PREC1)
    end
  else
    PlayDone = false 
  end  
  return Rate * 10.24
end




return { run=run, input=inputs, output=outputs, init=init }