-----------------------------------
-- Author: Uli Schlachter        --
-- Copyright 2009 Uli Schlachter --
-----------------------------------

local io = io
local setmetatable = setmetatable
local tonumber = tonumber
local pairs = pairs
local lib = {
  widget = require("obvious.lib.widget")
}

local function info(dev)
  local f = io.open("/proc/diskstats")
  local line

  if f == nil then
    return ret
  end

  line = f:read()

  while line and not line:match(dev) do
    line = f:read()
  end

  f:close()

  if not line then
    return nil
  end

  local ret = { }
  -- each time matches() is called it returns the next number from line
  local matches = line:gmatch("%d+")

  -- First two are device numbers, skip them
  matches()
  matches()

  ret.reads_completed  = tonumber(matches())
  ret.reads_merged     = tonumber(matches())
  ret.reads_sectors    = tonumber(matches())
  ret.reads_time_ms    = tonumber(matches())
  ret.writes_completed = tonumber(matches())
  ret.writes_merged    = tonumber(matches())
  ret.writes_sectors   = tonumber(matches())
  ret.writes_time_ms   = tonumber(matches())
  ret.in_progress      = tonumber(matches())
  ret.time_ms          = tonumber(matches())
  ret.time_ms_weight   = tonumber(matches())

  return ret
end

local function get_increase(data)
  local last = data.last
  local cur = info(data.device)

  if not cur then
    return nil
  end

  data.last = cur

  -- Fake for starting
  if last == nil then
    last = cur
  end

  local ret = { }
  for k, v in pairs(cur) do
    ret[k] = cur[k] - last[k]
  end

  return ret
end

local function get(data)
  local val = get_increase(data)
  if not val then
    return
  end
  return val.writes_sectors + val.reads_sectors
end

local function get_data_source(device)
  local device = device or "sda"
  local ret = {}

  ret.get = get
  ret.device = device

  return lib.widget.from_data_source(ret)
end

return setmetatable({}, { __call = function (_, ...) return get_data_source(...) end })

-- vim:ft=lua:ts=2:sw=2:sts=2:tw=80:et
