local gettimeofday = os.gettimeofday

local record TopicTimerRecord
  subtopics: {string: integer}
  collect: function(): integer
  start: function(): integer
  stop: function(integer)
  stop_subtopic: function(integer, string)
  wrap: function(function())
  wrap_subtopic: function(function(): string)
end
local topics: {string: TopicTimerRecord} = setmetatable({}, {__index = function(t: {string: TopicTimerRecord}, topic: string): TopicTimerRecord
  local total_time = 0
  local subtopics: {string: integer} = {}
  local function record_and_return(t0: integer, ...: any): any...
    total_time = total_time + (gettimeofday() - t0)
    return ...
  end
  local function record_and_return_subtopic(t0: integer, subtopic: string, ...: any): any...
    local dt = gettimeofday() - t0
    subtopics[subtopic] = (subtopics[subtopic]) + dt
    total_time = total_time + dt
    return ...
  end
  local result: TopicTimerRecord = {
    subtopics = subtopics,
    collect = function(): integer return total_time end,
    start = gettimeofday,
    stop = function(t0: integer)
      total_time = total_time + (gettimeofday() - t0)
    end,
    stop_subtopic = function(t0: integer, subtopic: string)
      local dt = gettimeofday() - t0
      subtopics[subtopic] = (subtopics[subtopic]) + dt
      total_time = total_time + (gettimeofday() - t0)
    end,
    wrap = function(f: function(...: any): any...): function(...: any): any...
      return function(...: any): any...
        return record_and_return(gettimeofday(), f(...))
      end
    end,
    wrap_subtopic = function(f: (function(...: any): string, any...)): function(...: any): any...
      return function(...: any): any...
        return record_and_return_subtopic(gettimeofday(), f(...))
      end
    end,
  }
  t[topic] = result
  return result
end})

--[[
luatexbase.add_to_callback('finish_pdffile', function() -- wrapup_run would be better but overwrites useful built-in functionality.
  local all_topics = {}
  for topic in pairs(topics) do
    all_topics[#all_topics + 1] = topic
  end
  table.sort(all_topics)
  texio.write_nl("Timings:")
  for _, topic in ipairs(all_topics) do
    texio.write_nl(string.format("  %s:\t%fs", topic, topics[topic].collect()))
  end
end, 'luatagging.timing')
]]

return topics