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module Fig.Emulator.GB.Bus
( Addr(..)
, Component(..)
, Bus(..)
, update
, write
, read
) where
import Fig.Prelude
import Numeric (showHex)
import qualified Data.List as List
import Data.Word (Word16, Word8)
newtype Addr = Addr { unAddr :: Word16 }
deriving (Show, Num, Eq, Ord)
instance Pretty Addr where
pretty (Addr w) = "$" <> pack (showHex w "")
data Component = forall (s :: Type). Component
{ compState :: !s
, compMatches :: !(Addr -> Bool)
, compUpdate :: !(s -> Word16 -> IO s)
, compWrite :: !(s -> Addr -> Word8 -> IO s)
, compRead :: !(s -> Addr -> IO Word8)
}
newtype Bus = Bus { busComponents :: [Component] }
update :: Word16 -> Bus -> IO Bus
update t b = Bus <$> forM (busComponents b) \Component{..} -> do
s <- compUpdate compState t
pure Component { compState = s, ..}
write :: Bus -> Addr -> Word8 -> IO Bus
write b a v = Bus <$> forM (busComponents b) \c@Component{..} ->
if compMatches a
then do
s <- compWrite compState a v
pure Component { compState = s, ..}
else pure c
read :: Bus -> Addr -> IO (Maybe Word8)
read b a = case List.find (`compMatches` a) $ busComponents b of
Nothing -> pure Nothing
Just Component{..} -> Just <$> compRead compState a
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