local fso = fs.open
local fsd = fs.delete
local fsc = fs.copy
local lock = true
local totalSize = 0
local maxSize = 512
local init = false

function loadSize()
  file = fs.open("size","r")
  totalSize = tonumber(file.readLine())
  file.close()
  init = true
end

function saveSize()
  if not init then return end
  lock = false
  file = fs.open("size","w")
  file.write(totalSize)
  file.close()
  lock = true
end

function fs.delete(file)
  if fs.exists(file) then
    totalSize = totalSize - fs.getSize(file)
    saveSize()
  end
  return fsd(file)
end

function fs.copy(file,nfile)
  if fs.exists(file) then
    if fs.getSize(file) + totalSize >= maxSize then
      error("Disk full.")
    else
      totalSize = totalSize + fs.getSize(file)
    end

  end
  fsc(file,nfile)
end

function fs.open(file,mode)
  if ( mode == "w" or mode == "a" or mode == "wb" or mode == "ab" ) then
    if file == "size" then
      if lock then
        return nil
      else
        return fso(file,mode)
      end
    end
  end
  local fSize = nil
  if fs.exists(file) then
    fSize = fs.getSize(file)
  end
  local tabl = fso(file,mode)
  if tabl then
    if mode == "w" or mode == "wb" then
      if fSize ~= nil then
        totalSize = totalSize - fSize
      end
    end
    if tabl.write then
      local otabwrite = tabl.write
      tabl.write = function(_sText)

        if string.len(_sText) + totalSize >= maxSize then
          error("Disk full.")
        else
          totalSize = totalSize + string.len(_sText)
          otabwrite(_sText)
        end
      end
    end
  end

  saveSize()
  return (tabl or nil)
end


local function fsunlock()
  lock = false
end

local function fslock()
  lock = true
end

loadSize()