eta.lua

local scale = 0.75
local avgs = {}

local function calcAvg(last)
  if #avgs == 0 then
    table.insert(avgs, last)
    return last
  end
  local len = #avgs
  local sum = 0
  local div = 0
  for n, v in pairs(avgs) do
    local s = 1/((len - n + 1)^scale)
    sum = sum + s * v
    div = div + s
  end
  local result = (last + sum) / (1 + div)
  table.insert(avgs, result)
  return result
end

local function calcSpeed(len, time)
  return len / time
end

local function eta(avg, got, total)
  return (total - got) / avg
end

local total = 100
for i = 0, total, 10 do
  local speed = calcSpeed(10, i / 10 + 1)
  local avg = calcAvg(speed)
  print("got: " .. ("%.5f"):format(i) ..
        ",\t total: " .. ("%.5f"):format(total) ..
        ",\t speed: " .. ("%.5f"):format(speed) ..
        ",\t avg: " .. ("%.5f"):format(avg) ..
        ",\t eta: " .. ("%.5f"):format(eta(avg, i, total)))
end