{-# LANGUAGE ForeignFunctionInterface #-}

import Foreign
import Foreign.C.Types

data Point =
  Point Float Float deriving (Show)

data Circle =
  Circle Point Float deriving (Show)

distance :: Point -> Point -> Float
distance (Point x1 y1) (Point x2 y2) =
  sqrt $ (abs $ x1 - x2) + (abs $ y1 - y2)

intersect :: Circle -> Circle -> Bool
intersect (Circle p1 r1) (Circle p2 r2) =
  distance p1 p2 <= r1 + r2

area :: Circle -> Float
area (Circle _ r) = r * r * 2 * pi

data Option
  = PosixSyntax
  | LongestMatch
  | LogError
  | Literal
  | NeverNl
  | DotNl
  | NeverCapture
  | CaseSensitive
  | PerlCases
  | WordBoundary
  | OneLine
  deriving (Show)

data Re = Re
  { regex :: [Char]
  , options :: [(Option, Bool)]
  } deriving (Show)

defaultOptions =
  [ (PosixSyntax, False)
  , (LongestMatch, False)
  , (LogError, False)
  , (Literal, False)
  , (NeverNl, False)
  , (DotNl, False)
  , (NeverCapture, False)
  , (CaseSensitive, False)
  , (PerlCases, False)
  , (WordBoundary, False)
  , (OneLine, False)
  ]

makeRe :: [Char] -> Re
makeRe x = Re { regex = x,  options = defaultOptions }

makeRe' :: [Char] -> [(Option, Bool)] -> Re
makeRe' x o = Re { regex = x, options = o }

main :: IO()
main = do
  putStrLn $ show $ distance (Point 0 0) (Point 1 1)
  putStrLn $ show $ (Point 10 5)
  putStrLn $ show $
    intersect (Circle (Point 1 1) 1)
              (Circle (Point 5 5) 1)
  putStrLn $ show $ area (Circle (Point 0 0) 5)
  putStrLn $ show $ makeRe "Hello, World!"
  putStrLn $ show $ makeRe' "Hello, World" []