Add basic LaTeX support

cards/images-and-formulas.txt

@@ -0,0 +1,18 @@
+# What type of fruit is this?
+![](pear.jpeg)
+- Apple
+* Pear
+- Orange
+- Banana
+---
+# Is the following statement true?
+![](lp.pdf)
+- No
+* Yes
+---
+# The l^p metric space
+```
+The space $(\ell^p, d)$ is a metric space, when $d:\ell^p \times \ell^p \rightarrow \mathbb{R}$ is defined as
+$$d(x, y) = \left(\sum_{n=1}^\infty |x_n-y_n|^p\right)^{1/p}$$
+```
+---

cards/images.txt

@@ -1,15 +0,0 @@
-# What type of fruit is this?
-![](pear.jpeg)
-- Apple
-* Pear
-- Orange
-- Banana
----
-# Fruit 1
-![](pear.jpeg)
-This is a pear
----
-# Is the following statement true?
-![](lp.pdf)
-- No
-* Yes

src/Parser.hs

@@ -41,7 +41,7 @@ pHeader = do
   spaceChar
   many (noneOf ['\n', '\r'])
 
-pImage :: Parser Image
+pImage :: Parser External
 pImage = do
   many eol
   char '!'
@@ -51,14 +51,21 @@ pImage = do
   img <- manyTill anySingle (char ')')
   return $ Image alt img
 
-pMaybeImage :: Parser (Maybe Image)
+pLatex :: Parser External
-pMaybeImage =  Just <$> try pImage
+pLatex = do
-           <|> pure Nothing
+  many eol
+  string "```"
+  Latex <$> manyTill anySingle (try (string "```"))
+
+pMaybeExternal :: Parser (Maybe External)
+pMaybeExternal =  Just <$> try pImage
+              <|> Just <$> try pLatex
+              <|> pure Nothing
 
 pMultChoice :: CardParser
 pMultChoice = do
   header <- pHeader
-  img <- pMaybeImage
+  img <- pMaybeExternal
   many eol
   choices <- pChoice `sepBy1` lookAhead (try choicePrefix)
   msgOrResult <- makeMultipleChoice choices
@@ -81,7 +88,7 @@ choicePrefix =  string "- "
 pMultAnswer :: CardParser
 pMultAnswer = do
   header <- pHeader
-  img <- pMaybeImage
+  img <- pMaybeExternal
   many eol
   options <- pOption `sepBy1` lookAhead (try (char '['))
   return . Right $ MultipleAnswer header img (NE.fromList options)
@@ -97,7 +104,7 @@ pOption = do
 pReorder :: CardParser
 pReorder = do
   header <- pHeader
-  img <- pMaybeImage
+  img <- pMaybeExternal
   many eol
   elements <- pReorderElement `sepBy1` lookAhead (try pReorderPrefix)
   let numbers = map fst elements
@@ -122,7 +129,7 @@ pReorderPrefix = do
 pOpen :: CardParser
 pOpen = do
   header <- pHeader
-  img <- pMaybeImage
+  img <- pMaybeExternal
   many eol
   (pre, gap) <- pGap
   sentence <- pSentence
@@ -161,7 +168,7 @@ pNormal = do
 pDef :: CardParser
 pDef = do
   header <- pHeader
-  img <- pMaybeImage
+  img <- pMaybeExternal
   many eol
   descr <- manyTill chars $ lookAhead $ try $ seperator <|> eof'
   return $ Right (Definition header img (dropWhileEnd isSpace' descr))

src/Runners.hs

@@ -64,7 +64,7 @@ cardsState doReview fp deck = do
            , _popup = Nothing
            , _pathToFile = fp }
  
-  openCardImage (takeDirectory fp) firstCard
+  openCardExternal (takeDirectory fp) firstCard
   return $ CardsState initialState
 
 cardsWithOptionsState :: GlobalState -> FilePath -> [Card] -> IO State

src/Types.hs

@@ -3,32 +3,33 @@ import Data.Functor
 import Data.List
 import Data.List.NonEmpty (NonEmpty)
 import System.FilePath
-import System.Process (runCommand)
+import System.Process
 import System.Info
+import System.IO
 import qualified Data.List.NonEmpty as NE
 import qualified System.Directory as D
 
 --                     Word   Description
 data Card = Definition { 
             question   :: String,
-            image      :: Maybe Image,
+            external   :: Maybe External,
             definition :: String }
           | OpenQuestion {
             question   :: String,
-            image      :: Maybe Image,
+            external   :: Maybe External,
             perforated :: Perforated }
           | MultipleChoice {
             question   :: String,
-            image      :: Maybe Image,
+            external   :: Maybe External,
             correct    :: CorrectOption,
             incorrects :: [IncorrectOption]}
           | MultipleAnswer {
             question   :: String,
-            image      :: Maybe Image,
+            external   :: Maybe External,
             options    :: NonEmpty Option }
           | Reorder {
             question   :: String,
-            image      :: Maybe Image,
+            external   :: Maybe External,
             elements   :: NonEmpty (Int, String)
           }
 
@@ -44,11 +45,13 @@ instance Show Card where
       Reorder h img elts -> 
         showHeader h <> show img<> "\n" <> unlines' (NE.toList (NE.map showReorder elts))
 
---                 alt    file
+--              alt   file
-data Image = Image String String
+data External = Image String String
+              | Latex String
 
-instance Show Image where
+instance Show External where
   show (Image alt file) = "![" <> alt <> "]" <> "(" <> file <> ")"
+  show (Latex text) = "```\n" <> text <> "```" 
 
 openCommand :: String
 openCommand = case os of
@@ -56,8 +59,8 @@ openCommand = case os of
   "linux"  -> "xdg-open"
   _        -> error "Unkown OS for opening images"
 
-openImage :: FilePath -> Image -> IO ()
+openImage :: FilePath -> FilePath -> IO ()
-openImage origin (Image _ relative) = openImage' (origin </> relative)
+openImage origin relative = openImage' (origin </> relative)
 
 openImage' :: FilePath -> IO ()
 openImage' fp = do
@@ -66,8 +69,28 @@ openImage' fp = do
     then void $ runCommand (openCommand <> " \"" <> fp <> "\"")
     else error $ "The image you were trying to open does not exist: " <> fp
 
-openCardImage :: FilePath -> Card -> IO ()
+openLatex :: String -> IO ()
-openCardImage fp = flip whenJust (openImage fp) . image
+openLatex latex = do
+  let packages = ["amsfonts", "mathtools"]
+      text = unlines $
+          [ "\\documentclass[preview]{standalone}" ]
+          ++ map (\p -> "\\usepackage{"<>p<>"}") packages ++
+          [ "\\begin{document}"
+          , latex
+          , "\\end{document}" ]
+  dir <- D.getTemporaryDirectory
+  (tempfile, temph) <- openTempFile dir "hascard-latex-"
+  hPutStrLn temph text
+  hClose temph
+  callProcess "pdflatex" ["-output-directory", dir, tempfile]
+  openImage' (tempfile <> ".pdf")
+
+openCardExternal :: FilePath -> Card -> IO ()
+openCardExternal origin card =
+  case external card of
+    Nothing -> pure ()
+    Just (Image _ relative) -> openImage origin relative
+    Just (Latex text) -> openLatex text
 
 whenJust :: Applicative m => Maybe a -> (a -> m ()) -> m ()
 whenJust mg f = maybe (pure ()) f mg 

src/UI.hs

@@ -6,7 +6,7 @@ module UI
 , GenIO
 , Chunk(..)
 , Card
-, Image
+, External
 , ImportType(..)
 , Parameters(..)
 
@@ -27,7 +27,7 @@ import Glue
 import Import
 import States
 import StateManagement
-import Types (Card, Image, cardsToString)
+import Types (Card, External, cardsToString)
 
 runBrickFlashcards :: GlobalState -> IO ()
 runBrickFlashcards gs = do

src/UI/Cards.hs

@@ -418,7 +418,7 @@ handleEvent gs _ _ = continue gs
 
 next :: GlobalState -> CS -> EventM Name (Next GlobalState)
 next gs s
-  | s ^. index + 1 < length (s ^. cards) = liftIO (openCardImage (takeDirectory (s^.pathToFile)) ((s^.cards) !! (s^.index + 1))) *> (continue . updateCS gs . straightenState $ s & index +~ 1)
+  | s ^. index + 1 < length (s ^. cards) = liftIO (openCardExternal (takeDirectory (s^.pathToFile)) ((s^.cards) !! (s^.index + 1))) *> (continue . updateCS gs . straightenState $ s & index +~ 1)
   | s ^. reviewMode                      =
       let thePopup =
             if null (s^.correctCards) || length (s^. correctCards) == length (s^.cards)
@@ -428,7 +428,7 @@ next gs s
   | otherwise                            = halt' gs
 
 previous :: GlobalState -> CS -> EventM Name (Next GlobalState)
-previous gs s | s ^. index > 0 = continue . updateCS gs . straightenState $ s & index -~ 1
+previous gs s | s ^. index > 0 = liftIO (openCardExternal (takeDirectory (s^.pathToFile)) ((s^.cards) !! (s^.index - 1))) *> (continue . updateCS gs . straightenState $ s & index -~ 1)
               | otherwise      = continue gs
 
 straightenState :: CS -> CS