src/Main.hs

   1 module Main
   2 where
   3
   4 import Control.Monad (when)
   5 import Data.List ((\\), intercalate)
   6 import Data.Maybe (catMaybes, isNothing)
   7 import Data.String.Utils (splitWs)
   8 import System.Exit (ExitCode( ExitFailure ), exitWith)
   9 import System.IO (stderr, hPutStrLn)
  10 import Text.Read (readMaybe)
  11
  12 import Cidr (
  13   Cidr(),
  14   combine_all,
  15   enumerate,
  16   max_octet1,
  17   max_octet2,
  18   max_octet3,
  19   max_octet4,
  20   min_octet1,
  21   min_octet2,
  22   min_octet3,
  23   min_octet4 )
  24 import CommandLine(
  25   Args( Regexed, Reduced, Duped, Diffed, Listed, barriers ),
  26   get_args )
  27 import ExitCodes ( exit_invalid_cidr )
  28 import Octet ()
  29
  30
  31 -- | A regular expression that matches a non-address character.
  32 --
  33 non_addr_char :: String
  34 non_addr_char = "[^\\.0-9]"
  35
  36
  37 -- | Add non_addr_chars on either side of the given String. This
  38 --   prevents (for example) the regex '127.0.0.1' from matching
  39 --   '127.0.0.100'.
  40 --
  41 add_barriers :: String -> String
  42 add_barriers x = non_addr_char ++ x ++ non_addr_char
  43
  44
  45 -- | The magic happens here. We take a CIDR String as an argument, and
  46 --   return the equivalent regular expression. We do this as follows:
  47 --
  48 --   1. Compute the minimum possible value of each octet.
  49 --   2. Compute the maximum possible value of each octet.
  50 --   3. Generate a regex matching every value between those min and
  51 --      max values.
  52 --   4. Join the regexes from step 3 with regexes matching periods.
  53 --   5. Stick an address boundary on either side of the result if
  54 --      use_barriers is True.
  55 --
  56 cidr_to_regex :: Bool -> Cidr -> String
  57 cidr_to_regex use_barriers cidr =
  58     let f = if use_barriers then add_barriers else id in
  59       f (intercalate "\\." [range1, range2, range3, range4])
  60     where
  61       range1 = numeric_range min1 max1
  62       range2 = numeric_range min2 max2
  63       range3 = numeric_range min3 max3
  64       range4 = numeric_range min4 max4
  65       min1   = fromEnum (min_octet1 cidr)
  66       min2   = fromEnum (min_octet2 cidr)
  67       min3   = fromEnum (min_octet3 cidr)
  68       min4   = fromEnum (min_octet4 cidr)
  69       max1   = fromEnum (max_octet1 cidr)
  70       max2   = fromEnum (max_octet2 cidr)
  71       max3   = fromEnum (max_octet3 cidr)
  72       max4   = fromEnum (max_octet4 cidr)
  73
  74
  75
  76 -- | Take a list of Strings, and return a regular expression matching
  77 --   any of them.
  78 --
  79 alternate :: [String] -> String
  80 alternate terms = "(" ++ (intercalate "|" terms) ++ ")"
  81
  82
  83 -- | Take two Ints as parameters, and return a regex matching any
  84 --   integer between them (inclusive).
  85 --
  86 --   IMPORTANT: we match from max to min so that if e.g. the last
  87 --   octet is '255', we want '255' to match before '2' in the regex
  88 --   (255|254|...|3|2|1) which does not happen if we use
  89 --   (1|2|3|...|254|255).
  90 --
  91 numeric_range :: Int -> Int -> String
  92 numeric_range x y =
  93     alternate (map show $ reverse [lower..upper])
  94      where
  95        lower = minimum [x,y]
  96        upper = maximum [x,y]
  97
  98
  99 main :: IO ()
 100 main = do
 101   args <- get_args
 102
 103   -- This reads stdin.
 104   input <- getContents
 105
 106   let cidr_strings = splitWs input
 107   let cidrs = map readMaybe cidr_strings :: [Maybe Cidr]
 108
 109   when (any isNothing cidrs) $ do
 110     hPutStrLn stderr "ERROR: not valid CIDR notation:"
 111
 112     -- Output the bad lines, safely.
 113     let pairs = zip cidr_strings cidrs
 114
 115     let print_pair :: (String, Maybe Cidr) -> IO ()
 116         print_pair (x, Nothing) = hPutStrLn stderr ("  * " ++ x)
 117         print_pair (_, _) = return ()
 118
 119     mapM_ print_pair pairs
 120     exitWith (ExitFailure exit_invalid_cidr)
 121
 122   -- Filter out only the valid ones.
 123   let valid_cidrs = catMaybes cidrs
 124
 125   case args of
 126     Regexed{} -> do
 127       let cidrs' = combine_all valid_cidrs
 128       let regexes = map (cidr_to_regex (barriers args)) cidrs'
 129       putStrLn $ alternate regexes
 130     Reduced{} ->
 131       mapM_ print (combine_all valid_cidrs)
 132     Duped{} ->
 133        mapM_ print dupes
 134        where
 135          dupes = valid_cidrs \\ (combine_all valid_cidrs)
 136     Diffed{} -> do
 137        mapM_ putStrLn deletions
 138        mapM_ putStrLn additions
 139        where
 140          dupes = valid_cidrs \\ (combine_all valid_cidrs)
 141          deletions = map (\s -> '-' : (show s)) dupes
 142          newcidrs = (combine_all valid_cidrs) \\ valid_cidrs
 143          additions = map (\s -> '+' : (show s)) newcidrs
 144     Listed{} -> do
 145       let combined_cidrs = combine_all valid_cidrs
 146       let addrs = concatMap enumerate combined_cidrs
 147       mapM_ print addrs