-- |
-- Module : Text.Subtitles.SRT
-- Copyright : Ruben Astudillo 2012
-- License : BSD3
--
-- Maintainer : ruben.astud@gmail.com
-- Portability : unknown
--
-- A basic parser for .srt files (subtitles) based on 'Attoparsec' and 'Text'
module Text.Subtitles.SRT
(
-- * Don't use parseOnly!
-- $noParseOnly
-- * Terminology of the module
-- $example
-- * Re-exported Datatypes
module Text.Subtitles.SRT.Datatypes,
-- * Main parsers
parseSRT,
parseSingleLine,
-- * Temporal solutions
parseOnly'
) where
import Prelude hiding (takeWhile)
import Control.Applicative
import Data.Attoparsec.Text hiding (parseOnly)
import qualified Data.Text as T
-- in project modules
import Text.Subtitles.SRT.Datatypes
-- $noParseOnly
--
-- This module uses now peekChar in parseDialog, which replaces the ad-hoc
-- method used before. As a consequence it doesn't play well with
-- Data.Attoparsec.Text.parseOnly on some conditions.
--
-- You should use just 'parse' or the parseOnly' function I provide to avoid
-- problems until further notice. /Hopefully/ in the next version of attoparsec
-- this will be solved , so keep an eye for removal!.
-- $example
--
-- All the sections of a Line have their corresponding ADT in
-- "Text.Subtitles.SRT.Datatypes"
--
-- >2
-- >00:00:50,050 --> 00:00:52,217 X1:1 X2:2 Y1:1 Y2:2
-- >Drama here
--
-- The whole Line is represented in the 'Line' ADT which constructors
-- represented by different ADTs
--
-- * The first line is called index, which is the first constructor of
-- 'Line'.
--
-- * The second one is called 'Range', which correspond to two separated 'Time'.
--
-- * After the range is an optional field called Rectangle which says what
-- geometry should the text obey.
--
-- * The last one is the 'subs'. Which is just Text and correspond to the third
-- constructor of 'Line'.
-- |Main Parser, gives you a list of all the Lines of the subtitle. It fails if
-- the subtitle doesn't have any Lines.
parseSRT :: Parser Subtitles
parseSRT = many1 parseSingleLine
-- |The individual Line parser. Given the upper example return the
-- corresponding Line representation
parseSingleLine :: Parser Line
parseSingleLine =
Line <$> parseIndex <*> parseRange <*> optionalGeometry <*> parseDialog T.empty
parseIndex :: Parser Int
parseIndex = decimal <* eol
eol :: Parser ()
eol = endOfLine
-- |This version avoid the problems associated with peekChar and thus is safe to
-- use in this module. Subject to removal once parseOnly is fixed.
parseOnly' :: Parser a -> Text -> Either String a
parseOnly' p t = eitherResult $ feed (parse p t) T.empty
{- Is clear that this just aplies parseTime breaking down the "-->" string -}
parseRange :: Parser Range
parseRange = Range <$> parseTime <* arrowString <*> parseTime <* skipSpace
where
arrowString :: Parser Text
arrowString = string (T.pack " --> ")
{- the order X1 X2 Y1 Y2 seems to be enforced, so we can check only for order
- instead of keywords -}
optionalGeometry :: Parser (Maybe Rectangle)
optionalGeometry = option Nothing (Just <$> rectangle <* eol)
where rectangle = R <$> valueSpace <*> valueSpace <*> valueSpace <*> value
value = letter *> digit *> char ':' *> decimal
valueSpace = value <* space
parseTime :: Parser Time
parseTime = Time <$> numDot <*> numDot <*> decimal <* char ',' <*> decimal
where
numDot :: Parser Int
numDot = decimal <* char ':'
{- return the dialog checking for newlines that could be in there. That why is
- written in a monad instead of applicative. More efficient version welcome -}
parseDialog :: Text -> Parser Text
parseDialog stateLine = do
line <- takeWhile1 (not . isEndOfLine)
endOfLine
let stateCurrent = T.append stateLine line
lineState = T.snoc stateCurrent '\n' --takeWhile1 didn't consume \n
next <- peekChar
case next of
Nothing -> return stateCurrent -- the end of the file
(Just '\n') -> eol >> return stateCurrent -- End of this Line, new Line coming.
(Just _) -> parseDialog lineState {- in between lines, the next one belong to this Line
explicit eol required -}