---------------------------------------------------
-- Licensed under the GNU General Public License v2
--  * (c) 2010, Adrian C. <anrxc@sysphere.org>
---------------------------------------------------

-- {{{ Grab environment
local ipairs = ipairs
local setmetatable = setmetatable
local table = { insert = table.insert }
local string = { gmatch = string.gmatch }
local helpers = require("vicious.helpers")
-- }}}


-- Disk I/O: provides I/O statistics for requested storage devices
-- vicious.contrib.dio
local dio = {}


-- Initialize function tables
local disk_usage = {}
local disk_total = {}
-- Variable definitions
local unit = { ["s"] = 1, ["kb"] = 2, ["mb"] = 2048 }

-- {{{ Disk I/O widget type
local function worker(format, disk)
  if not disk then return end

  local disk_lines = { [disk] = {} }
  local disk_stats = helpers.pathtotable("/sys/block/" .. disk)

  if disk_stats.stat then
    local match = string.gmatch(disk_stats.stat, "[%s]+([%d]+)")
    for i = 1, 11 do -- Store disk stats
      table.insert(disk_lines[disk], match())
    end
  end

  -- Ensure tables are initialized correctly
  local diff_total = { [disk] = {} }
  if not disk_total[disk] then
    disk_usage[disk] = {}
    disk_total[disk] = {}

    while #disk_total[disk] < #disk_lines[disk] do
      table.insert(disk_total[disk], 0)
    end
  end

  for i, v in ipairs(disk_lines[disk]) do
    -- Diskstats are absolute, substract our last reading
    diff_total[disk][i] = v - disk_total[disk][i]

    -- Store totals
    disk_total[disk][i] = v
  end

  -- Calculate and store I/O
  helpers.uformat(disk_usage[disk], "read",  diff_total[disk][3], unit)
  helpers.uformat(disk_usage[disk], "write", diff_total[disk][7], unit)
  helpers.uformat(disk_usage[disk], "total", diff_total[disk][7] + diff_total[disk][3], unit)

  -- Store I/O scheduler
  if disk_stats.queue and disk_stats.queue.scheduler then
    disk_usage[disk]["{sched}"] = string.gmatch(disk_stats.queue.scheduler, "%[([%a]+)%]")
  end

  return disk_usage[disk]
end
-- }}}

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