local Util		= require 'Util'
local Common	= require 'Common'
local Geometry = require 'Geometry'

local __tonumber 	= tonumber
local __string_match = string.match
local __math_floor = math.floor

local _PLOT_SEC_BREAK_ = 20
local _PLOT_HEIGHT_ = 56

local BLOCK_SIZE_BYTES = 512
local STAT_FILE = '/sys/block/sda/stat'

-- fields 3 and 7 (sectors read and written)
local RW_REGEX = '%s+%d+%s+%d+%s+(%d+)%s+%d+%s+%d+%s+%d+%s+(%d+)'

local read_stat_file = function()
	local bytes_r, bytes_w = __string_match(Util.read_file(STAT_FILE), RW_REGEX)
	return __tonumber(bytes_r) * BLOCK_SIZE_BYTES, __tonumber(bytes_w) * BLOCK_SIZE_BYTES
end

local io_label_function = function(bytes)
	local new_unit, new_value = Util.convert_data_val(bytes)
	return __math_floor(new_value)..' '..new_unit..'B/s'
end

local format_value_function = function(bps)
   local unit, value = Util.convert_data_val(bps)
   return Util.precision_round_to_string(value, 3)..' '..unit..'B/s'
end

return function(update_freq)
   local header = Common.Header(
      Geometry.CENTER_LEFT_X,
      Geometry.TOP_Y,
      Geometry.SECTION_WIDTH,
      'INPUT / OUTPUT'
   )

   local reads = Common.initLabeledScalePlot(
      Geometry.CENTER_LEFT_X,
      header.bottom_y,
      Geometry.SECTION_WIDTH,
      _PLOT_HEIGHT_,
      format_value_function,
      io_label_function,
      _PLOT_SEC_BREAK_,
      'Reads',
      2,
      update_freq
   )

   local writes = Common.initLabeledScalePlot(
      Geometry.CENTER_LEFT_X,
      header.bottom_y + _PLOT_HEIGHT_ + _PLOT_SEC_BREAK_ * 2,
      Geometry.SECTION_WIDTH,
      _PLOT_HEIGHT_,
      format_value_function,
      io_label_function,
      _PLOT_SEC_BREAK_,
      'Writes',
      2,
      update_freq
   )

   reads.byte_cnt = 0
   writes.byte_cnt = 0
   reads.prev_byte_cnt, writes.prev_byte_cnt = read_stat_file()

   local update_stat = function(cr, stat, byte_cnt)
      local delta_bytes = byte_cnt - stat.prev_byte_cnt
      stat.prev_byte_cnt = byte_cnt

      local plot_value = 0
      if delta_bytes > 0 then
         local bps = delta_bytes * update_freq
         plot_value = bps
      end
      Common.annotated_scale_plot_set(stat, cr, plot_value)
   end

   local update = function(cr)
      local read_byte_cnt, write_byte_cnt = read_stat_file()
      update_stat(cr, reads, read_byte_cnt)
      update_stat(cr, writes, write_byte_cnt)
   end

   local draw_static = function(cr)
      Common.drawHeader(cr, header)
      Common.annotated_scale_plot_draw_static(reads, cr)
      Common.annotated_scale_plot_draw_static(writes, cr)
   end

   local draw_dynamic = function(cr)
      update(cr)
      Common.annotated_scale_plot_draw_dynamic(reads, cr)
      Common.annotated_scale_plot_draw_dynamic(writes, cr)
   end

   return {static = draw_static, dynamic = draw_dynamic}
end