local util = {}

function util.split_str(str, sep)
  local tbl = {}
  local n = 0
  if sep == nil then sep = "%S+" end
  for sub in string.gmatch(str, sep) do
    n = n + 1
    tbl[n] = sub
  end
  return tbl
end


function util.extract_str(full_str, find_str, end_str)
  fi1, fi2 = string.find(full_str, find_str, 1)
  ei1, ei2 = string.find(full_str, end_str, fi2)
  return string.sub(full_str, fi2 + 1, ei1 - 1)
end


function util.extract_file_date(dir, file)
  -- Atom feed date format: 2022-01-15T00:00:00+00:00
  local ls_cmd = io.popen("ls -l --time-style=\"+%Y-%m-%dT%H:%M:%S%z\" " ..
    dir .. " | grep " .. file .. " | awk '{print $6}'")
  return ls_cmd:read("*a")
end


function util.read_file(file)
  local fh = io.open(file, "r")
  local text = ""
  io.input(fh)
  text = io.read("*a")
  io.close(fh)
  return text
end


function util.write_file(file, str)
  local fh = io.open(file, "w")
  io.output(fh)
  io.write(str)
  io.close(fh)
end

return util