{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Data.Dwarf.AttrGetter
  ( AttrGetterT, run
  , findAttrVals, findAttrVal
  , findAttrs, findAttr
  , getAttr
  ) where

import Control.Applicative (Applicative(..), (<$>))
import Control.Lens ((^?))
import Control.Monad (liftM)
import Control.Monad.Trans.Class (MonadTrans(..))
import Control.Monad.Trans.Reader (ReaderT(..))
import Control.Monad.Trans.State (StateT(..))
import Data.Dwarf (DIE(..), DW_AT, DW_ATVAL)
import Data.List (partition)
import Data.Maybe (fromMaybe)
import qualified Control.Monad.Trans.Reader as Reader
import qualified Control.Monad.Trans.State as State
import qualified Data.Dwarf.Lens as DwarfLens

newtype AttrGetterT m a = AttrGetterT (ReaderT String (StateT [(DW_AT, DW_ATVAL)] m) a)
  deriving (Functor, Applicative, Monad)

instance MonadTrans AttrGetterT where
  lift = AttrGetterT . lift . lift

run :: DIE -> AttrGetterT m a -> m (a, [(DW_AT, DW_ATVAL)])
run die (AttrGetterT act) =
  (`runStateT` dieAttributes die) .
  (`runReaderT` (" in " ++ show die)) $
  act

getSuffix :: Monad m => AttrGetterT m String
getSuffix = AttrGetterT Reader.ask

findAttrVals :: Monad m => DW_AT -> AttrGetterT m [DW_ATVAL]
findAttrVals at = AttrGetterT . lift $ do
  (matches, mismatches) <- State.gets $ partition ((== at) . fst)
  State.put mismatches
  return $ snd <$> matches

findAttrVal :: Monad m => DW_AT -> AttrGetterT m (Maybe DW_ATVAL)
findAttrVal at = AttrGetterT . lift $ do
  (unmatched, rest) <- State.gets $ break ((at ==) . fst)
  case rest of
    (_, val) : afterMatch -> do
      State.put (unmatched ++ afterMatch)
      return $ Just val
    _ -> return Nothing

getATVal :: String -> String -> DwarfLens.ATVAL_NamedPrism a -> DW_ATVAL -> a
getATVal prefix suffix (typName, typ) atval =
  fromMaybe (error msg) $ atval ^? typ
  where
    msg = concat [prefix, " is: ", show atval, " but expected: ", typName, suffix]

toVal ::
  (Monad m, Functor f, Show a) =>
  (a -> AttrGetterT m (f DW_ATVAL)) ->
  a -> DwarfLens.ATVAL_NamedPrism b -> AttrGetterT m (f b)
toVal finder at prism = do
  suffix <- getSuffix
  (liftM . fmap) (getATVal (show at) suffix prism) $ finder at

findAttrs :: Monad m => DW_AT -> DwarfLens.ATVAL_NamedPrism a -> AttrGetterT m [a]
findAttrs = toVal findAttrVals

findAttr :: Monad m => DW_AT -> DwarfLens.ATVAL_NamedPrism a -> AttrGetterT m (Maybe a)
findAttr = toVal findAttrVal

getAttr :: Monad m => DW_AT -> DwarfLens.ATVAL_NamedPrism a -> AttrGetterT m a
getAttr at prism = do
  suffix <- getSuffix
  (liftM . fromMaybe . error) ("Could not find " ++ show at ++ suffix) $
    findAttr at prism