-----------------------------------------------------------------------------
-- |
-- Module      :  Text.ParserCombinators.Parsec.Pos
-- Copyright   :  (c) Daan Leijen 1999-2001
-- License     :  BSD-style (see the file libraries/parsec/LICENSE)
-- 
-- Maintainer  :  Antoine Latter <aslatter@gmail.com>
-- Stability   :  provisional
-- Portability :  portable
--
-- Textual source positions.
-- 
-----------------------------------------------------------------------------

module Text.ParserCombinators.Parsec.Pos
                  ( SourceName, Line, Column                 
                  , SourcePos
                  , sourceLine, sourceColumn, sourceName
                  , incSourceLine, incSourceColumn
                  , setSourceLine, setSourceColumn, setSourceName
                  , newPos, initialPos
                  , updatePosChar, updatePosString
                  ) where

-----------------------------------------------------------
-- Source Positions, a file name, a line and a column.
-- upper left is (1,1)
-----------------------------------------------------------                         
type SourceName     = String
type Line           = Int
type Column         = Int

-- | The abstract data type @SourcePos@ represents source positions. It
-- contains the name of the source (i.e. file name), a line number and
-- a column number. @SourcePos@ is an instance of the 'Show', 'Eq' and
-- 'Ord' class.
data SourcePos      = SourcePos SourceName !Line !Column
                    deriving (Eq,Ord)

-- | Create a new 'SourcePos' with the given source name,
-- line number and column number.
newPos :: SourceName -> Line -> Column -> SourcePos
newPos sourceName line column
    = SourcePos sourceName line column

-- | Create a new 'SourcePos' with the given source name,
-- and line number and column number set to 1, the upper left.
initialPos :: SourceName -> SourcePos
initialPos sourceName
    = newPos sourceName 1 1

-- | Extracts the name of the source from a source position.
sourceName :: SourcePos -> SourceName
sourceName (SourcePos name line column) = name 

-- | Extracts the line number from a source position.
sourceLine :: SourcePos -> Line
sourceLine (SourcePos name line column) = line

-- | Extracts the column number from a source position.
sourceColumn :: SourcePos -> Column
sourceColumn (SourcePos name line column) = column

-- | Increments the line number of a source position.
incSourceLine :: SourcePos -> Line -> SourcePos
incSourceLine (SourcePos name line column) n = SourcePos name (line+n) column

-- | Increments the column number of a source position.
incSourceColumn :: SourcePos -> Column -> SourcePos
incSourceColumn (SourcePos name line column) n = SourcePos name line (column+n)

-- | Set the name of the source.
setSourceName :: SourcePos -> SourceName -> SourcePos
setSourceName (SourcePos name line column) n = SourcePos n line column

-- | Set the line number of a source position.
setSourceLine :: SourcePos -> Line -> SourcePos
setSourceLine (SourcePos name line column) n = SourcePos name n column

-- | Set the column number of a source position.
setSourceColumn :: SourcePos -> Column -> SourcePos
setSourceColumn (SourcePos name line column) n = SourcePos name line n

-- | The expression @updatePosString pos s@ updates the source position
-- @pos@ by calling 'updatePosChar' on every character in @s@, ie.
-- @foldl updatePosChar pos string@.
updatePosString :: SourcePos -> String -> SourcePos
updatePosString pos string
    = forcePos (foldl updatePosChar pos string)

updatePosChar   :: SourcePos -> Char -> SourcePos
updatePosChar pos@(SourcePos name line column) c   
    = forcePos $
      case c of
        '\n' -> SourcePos name (line+1) 1
        '\t' -> SourcePos name line (column + 8 - ((column-1) `mod` 8))
        _    -> SourcePos name line (column + 1)
        

forcePos :: SourcePos -> SourcePos      
forcePos pos@(SourcePos name line column)
    = seq line (seq column (pos))

-----------------------------------------------------------
-- Show positions 
-----------------------------------------------------------                                                 
instance Show SourcePos where
  show (SourcePos name line column)
    | null name = showLineColumn
    | otherwise = "\"" ++ name ++ "\" " ++ showLineColumn
    where
      showLineColumn    = "(line " ++ show line ++
                          ", column " ++ show column ++
                          ")"