module Parsing (
  splitByString,
  parseCoordinates
  ) where

import           Data.List (isPrefixOf)

splitByString :: String -> String -> [String]
splitByString _ "" = []
splitByString splitter string =
  let (chunk, rest) = spanNextSplit string
  in
    chunk:(splitByString splitter rest)
    where
      spanNextSplit :: String -> (String, String)
      spanNextSplit [] = ([], [])
      spanNextSplit everything@(char:rest)
        | splitter `isPrefixOf` rest =
          ([char], (drop ((length splitter) + 1) everything))
        | otherwise =
          let
            (start, end) = spanNextSplit rest
          in
            (char:start, end)

parseCoordinates :: String -> [(Int, Int)]
parseCoordinates =
  map (tuplify . map read . splitByString ",") . lines
  where
    tuplify :: [a] -> (a, a)
    tuplify [a, b] = (a, b)
    tuplify _      = error "Can't parse coordinates from non-2-sized lists"