module Data.Read (class Read, read) where

import Data.List (head, tail, last, init, reverse)
import Data.Semiring ((+))
import Data.Ring ((-))
import Data.Functor (map)
import Data.Function (error)
import Data.Eq ((==))
import Data.Bool ((||))
import Data.String (trim)
import Data.Binary as B
import Data.Pid (Pid)
import Data.Ordering (Ordering(..))
import Data.Maybe (Maybe(..))

class Read a where
  read :: String -> a

instance Read Integer where
  read = readIntImpl

instance Read Float where
  read = readFloatImpl

instance Read Char where
  read = readCharImpl

instance Read Atom where
  read = readAtomImpl

instance Read Pid where
  read = readPidImpl

instance Read Boolean where
  read "true" = true
  read "false" = false
  read _ = error "not a Boolean"

instance Read Binary where
  read x = B.listToBin (read x :: [Integer])

instance Read Ordering where
  read "LT" = LT
  read "GT" = GT
  read "EQ" = EQ
  read _ = error "not a Ordering"

instance Read a => Read (Maybe a) where
  read "Nothing" = Nothing
  read ['J'|['u'|['s'|['t'|[' '|xs]]]]] = Just (read xs)
  read _ = error "not Maybe"

foreign import readIntImpl :: String -> Integer
foreign import readFloatImpl :: String -> Float
foreign import readCharImpl :: String -> Char
foreign import readAtomImpl :: String -> Atom
foreign import readPidImpl :: String -> Pid

--                     0/1/2
--          bra lvl    is str     cache     origin
splitTop :: Integer -> Integer -> String -> String -> [String]
splitTop 0 0 "" []        = []
splitTop 0 0 s  []        = [reverse (trim s)]
splitTop _ _ _  []        = error "brackets missmatched"
splitTop 0 0 s  [','|xs]  = [reverse (trim s) | splitTop 0 0 "" xs]
splitTop n 0 s  ['\''|xs] = splitTop n 1 ['\''|s] xs
splitTop n 1 s  ['\''|xs] = splitTop n 0 ['\''|s] xs
splitTop n 0 s  ['"'|xs]  = splitTop n 2 ['"'|s] xs
splitTop n 2 s  ['"'|xs]  = splitTop n 0 ['"'|s] xs
splitTop n 0 s  [x|xs]
  | x == '[' || x == '{' || x == '(' = splitTop (n + 1) 0 [x|s] xs
  | x == ']' || x == '}' || x == ')' = splitTop (n - 1) 0 [x|s] xs
splitTop n z s  [x|xs]    = splitTop n z [x|s] xs

instance Read [Char] where
  read x = tail (init x)

else instance Read a => Read [a] where
  read ['[' | x] | last x == ']' = map read (splitTop 0 0 "" (init x))
  read _ = error "not a list"

instance (Read a, Read b) => Read (a, b) where
  read ['(' | x] | last x == ')' = (read (head lst), read (last lst))
    where lst = splitTop 0 0 "" (init x)
  read _ = error "not a tuple"