src/Main.hs

   1 import Data.List (intercalate, intersperse)
   2 import System.Exit (ExitCode(..), exitWith)
   3 import System.IO (stderr, hPutStrLn)
   4
   5 import Text.Regex.Posix
   6
   7 import Cidr (Cidr,
   8              from_string,
   9              min_first_octet,
  10              min_second_octet,
  11              min_third_octet,
  12              min_fourth_octet,
  13              max_first_octet,
  14              max_second_octet,
  15              max_third_octet,
  16              max_fourth_octet)
  17
  18 import CommandLine (help_set,
  19                     help_text,
  20                     input_function,
  21                     parse_errors)
  22
  23 -- Some exit codes, used in the ExitFailure constructor.
  24 exit_invalid_cidr :: Int
  25 exit_invalid_cidr = 1
  26
  27 exit_args_parse_failed :: Int
  28 exit_args_parse_failed = 2
  29
  30
  31 -- A regular expression that matches a non-address character.
  32 non_addr_char :: String
  33 non_addr_char = "[^\\.0-9]"
  34
  35
  36 -- Add non_addr_chars on either side of the given String. This
  37 -- prevents (for example) the regex '127.0.0.1' from matching
  38 -- '127.0.0.100'.
  39 addr_barrier :: String -> String
  40 addr_barrier x = non_addr_char ++ x ++ non_addr_char
  41
  42
  43 -- The magic happens here. We take a CIDR String as an argument, and
  44 -- return the equivalent regular expression. We do this as follows:
  45 --
  46 -- 1. Compute the minimum possible value of each octet.
  47 -- 2. Compute the maximum possible value of each octet.
  48 -- 3. Generate a regex matching every value between those min and
  49 --    max values.
  50 -- 4. Join the regexes from step 3 with regexes matching periods.
  51 -- 5. Stick an address boundary on either side of the result.
  52 --cidr_to_regex :: String -> String
  53 cidr_to_regex :: Cidr.Cidr -> String
  54 cidr_to_regex cidr =
  55     addr_barrier (intercalate "\\." [range1, range2, range3, range4])
  56     where
  57       range1 = numeric_range min1 max1
  58       range2 = numeric_range min2 max2
  59       range3 = numeric_range min3 max3
  60       range4 = numeric_range min4 max4
  61       min1   = min_first_octet cidr
  62       min2   = min_second_octet cidr
  63       min3   = min_third_octet cidr
  64       min4   = min_fourth_octet cidr
  65       max1   = max_first_octet cidr
  66       max2   = max_second_octet cidr
  67       max3   = max_third_octet cidr
  68       max4   = max_fourth_octet cidr
  69
  70
  71 -- Will return True if the passed String is in CIDR notation, False
  72 -- otherwise.
  73 is_valid_cidr :: String -> Bool
  74 is_valid_cidr cidr = cidr =~ "([0-9]{1,3}\\.){3}[0-9]{1,3}/[0-9]{1,2}"
  75
  76
  77 -- Take a list of Strings, and return a regular expression matching
  78 -- any of them.
  79 alternate :: [String] -> String
  80 alternate terms = "(" ++ (concat (intersperse "|" terms)) ++ ")"
  81
  82
  83 -- Take two Ints as parameters, and return a regex matching any
  84 -- integer between them (inclusive).
  85 numeric_range :: Int -> Int -> String
  86 numeric_range x y =
  87     alternate (map show [lower..upper])
  88      where
  89        lower = minimum [x,y]
  90        upper = maximum [x,y]
  91
  92
  93 -- Take a CIDR String, and exit with a failure if it's invalid.
  94 validate_or_die :: String -> IO ()
  95 validate_or_die cidr = do
  96   if (is_valid_cidr cidr)
  97     then do
  98       return ()
  99     else do
 100         putStrLn "Error: not valid CIDR notation."
 101         exitWith (ExitFailure exit_invalid_cidr)
 102
 103
 104
 105 main :: IO ()
 106 main = do
 107   -- First, check for any errors that occurred while parsing
 108   -- the command line options.
 109   errors <- CommandLine.parse_errors
 110   if not (null errors)
 111     then do
 112       hPutStrLn stderr (concat errors)
 113       putStrLn CommandLine.help_text
 114       exitWith (ExitFailure exit_args_parse_failed)
 115     else do -- Nothing
 116
 117   -- Next, check to see if the 'help' option was passed to the
 118   -- program. If it was, display the help, and exit successfully.
 119   help_opt_set <- CommandLine.help_set
 120   if help_opt_set
 121     then do
 122       putStrLn CommandLine.help_text
 123       exitWith ExitSuccess
 124     else do -- Nothing
 125
 126   -- The input function we receive here should know what to read.
 127   inputfunc <- (CommandLine.input_function)
 128   input <- inputfunc
 129   let cidr_strings = lines input
 130   mapM validate_or_die cidr_strings
 131   let cidrs = map Cidr.from_string cidr_strings
 132   let regexes = map cidr_to_regex cidrs
 133   putStrLn $ alternate regexes