src/Main.hs

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