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{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Text.RE.ZeInternals.Types.CaptureID where
import qualified Data.HashMap.Strict as HMS
import Data.Hashable
import Data.Ix
import qualified Data.Text as T
-- | CaptureID identifies captures, either by number
-- (e.g., [cp|1|]) or name (e.g., [cp|foo|]).
data CaptureID
= IsCaptureOrdinal CaptureOrdinal -- [cp|3|]
| IsCaptureName CaptureName -- [cp|y|]
deriving (Show,Ord,Eq)
-- | the dictionary for named captures stored in compiled regular
-- expressions associates
type CaptureNames = HMS.HashMap CaptureName CaptureOrdinal
-- | an empty 'CaptureNames' dictionary
noCaptureNames :: CaptureNames
noCaptureNames = HMS.empty
-- | a 'CaptureName' is just the text of the name
newtype CaptureName = CaptureName { getCaptureName :: T.Text }
deriving (Show,Ord,Eq)
instance Hashable CaptureName where
hashWithSalt i = hashWithSalt i . getCaptureName
-- | a 'CaptureOrdinal' is just the number of the capture, starting
-- with 0 for the whole of the text matched, then in leftmost,
-- outermost
newtype CaptureOrdinal = CaptureOrdinal { getCaptureOrdinal :: Int }
deriving (Show,Ord,Eq,Enum,Ix,Num)
-- | look up a 'CaptureID' in the 'CaptureNames' dictionary
findCaptureID :: CaptureID -> CaptureNames -> Either String CaptureOrdinal
findCaptureID (IsCaptureOrdinal o) _ = Right o
findCaptureID (IsCaptureName n) hms =
maybe oops Right $ HMS.lookup n hms
where
oops = Left $ unlines $
("lookupCaptureID: " ++ T.unpack t ++ " not found in:") :
[ " "++T.unpack (getCaptureName nm) | nm <- HMS.keys hms ]
t = getCaptureName n
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