{-# LANGUAGE DeriveDataTypeable #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Language.C.Data.Position
-- Copyright   :  (c) [1995..2000] Manuel M. T. Chakravarty
--                    [2008..2009] Benedikt Huber
-- License     :  BSD-style
-- Maintainer  :  benedikt.huber@gmail.com
-- Stability   :  experimental
-- Portability :  ghc
--
-- Source code position
-----------------------------------------------------------------------------
module Language.C.Data.Position (
  --
  -- source text positions
  --
  Position(),
  position,
  PosLength,
  posFile,posRow,posColumn,posOffset,posParent,
  initPos, isSourcePos,
  nopos, isNoPos,
  builtinPos, isBuiltinPos,
  internalPos, isInternalPos,
  incPos, retPos,
  incOffset,
  Pos(..),
) where
import Data.Data (Data)
import GHC.Generics (Generic)
import Control.DeepSeq (NFData)

-- | file position information
data FilePosition = FilePosition { posSrcFile    :: String,            -- ^ source file
                                   posParentFile :: (Maybe Position)   -- ^ including file, if any
                                 }
                    deriving (Eq, Ord, Data, Generic)

instance NFData FilePosition

-- | uniform representation of source file positions
data Position = Position { posOffset :: {-# UNPACK #-} !Int  -- ^ absolute offset in the preprocessed file
                         , posRow :: {-# UNPACK #-} !Int     -- ^ row (line)  in the original file. Affected by #LINE pragmas.
                         , posColumn :: {-# UNPACK #-} !Int  -- ^ column in the preprocessed file. Inaccurate w.r.t. to the original
                                                             --   file in the presence of preprocessor macros.
                         , posFileInfo :: FilePosition       -- ^ position in source file, including files
                         }
              | NoPosition
              | BuiltinPosition
              | InternalPosition
                deriving (Eq, Ord, Data, Generic)

instance NFData Position

posFile :: Position -> String
posFile = posSrcFile . posFileInfo

posParent :: Position -> (Maybe Position)
posParent = posParentFile . posFileInfo

-- | Position and length of a token
type PosLength = (Position,Int)

instance Show Position where
  showsPrec _ (Position _ row _ (FilePosition fname mparent)) =
    showString "(" . showsPrec 0 fname . showString ": line " . showsPrec 0 row .
    maybe id (\p -> showString ", in file included from " . showsPrec 0 p) mparent .
    showString ")"
  showsPrec _  NoPosition                     = showString "<no file>"
  showsPrec _  BuiltinPosition                = showString "<builtin>"
  showsPrec _ InternalPosition                = showString "<internal>"

-- | @position absoluteOffset fileName lineNumber columnNumber@ initializes a @Position@ using the given arguments
position :: Int -> String -> Int -> Int -> Maybe Position -> Position
position offset fname row col mparent = Position offset row col (FilePosition fname mparent)

-- | class of type which aggregate a source code location
class Pos a where
    posOf :: a -> Position

-- | initialize a Position to the start of the translation unit starting in the given file
initPos :: FilePath -> Position
initPos file = Position 0 1 1 (FilePosition file Nothing)

-- | returns @True@ if the given position refers to an actual source file
isSourcePos :: Position -> Bool
isSourcePos (Position _ _ _ _) = True
isSourcePos _                  = False

-- | no position (for unknown position information)
nopos :: Position
nopos  = NoPosition

-- | returns @True@ if the there is no position information available
isNoPos :: Position -> Bool
isNoPos NoPosition = True
isNoPos _          = False

-- | position attached to built-in objects
--
builtinPos :: Position
builtinPos  = BuiltinPosition

-- | returns @True@ if the given position refers to a builtin definition
isBuiltinPos :: Position -> Bool
isBuiltinPos BuiltinPosition = True
isBuiltinPos _               = False

-- | position used for internal errors
internalPos :: Position
internalPos = InternalPosition

-- | returns @True@ if the given position is internal
isInternalPos :: Position -> Bool
isInternalPos InternalPosition = True
isInternalPos _                = False

{-# INLINE incPos #-}
-- | advance column
incPos :: Position -> Int -> Position
incPos (Position offs row col fpos) n = Position (offs + n) row (col + n) fpos
incPos p _                             = p

{-# INLINE retPos #-}
-- | advance to next line
retPos :: Position -> Position
retPos (Position offs row _ fpos) = Position (offs+1) (row + 1) 1 fpos
retPos p                           = p

{-# INLINE incOffset #-}
-- | advance just the offset
incOffset :: Position -> Int -> Position
incOffset (Position o r c f) n = Position (o + n) r c f
incOffset pos _             = pos
