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+{-# LANGUAGE NoImplicitPrelude #-}
+{- |
+ Module : Text.Pandoc.Lua.Marshaling.MediaBag
+ Copyright : © 2012-2019 John MacFarlane
+ © 2017-2019 Albert Krewinkel
+ License : GNU GPL, version 2 or above
+ Maintainer : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+ Stability : alpha
+
+Instances to marshal (push) and unmarshal (peek) media data.
+-}
+module Text.Pandoc.Lua.Marshaling.MediaBag (pushIterator) where
+
+import Prelude
+import Foreign.Ptr (Ptr)
+import Foreign.StablePtr (StablePtr, deRefStablePtr, newStablePtr)
+import Foreign.Lua (Lua, NumResults, Peekable, Pushable, StackIndex)
+import Foreign.Lua.Types.Peekable (reportValueOnFailure)
+import Foreign.Lua.Userdata (ensureUserdataMetatable, pushAnyWithMetatable,
+ toAnyWithName)
+import Text.Pandoc.MediaBag (MediaBag, mediaItems)
+import Text.Pandoc.MIME (MimeType)
+import Text.Pandoc.Lua.Marshaling.AnyValue (AnyValue (..))
+
+import qualified Data.ByteString.Lazy as BL
+import qualified Foreign.Lua as Lua
+import qualified Foreign.Storable as Storable
+
+-- | A list of 'MediaBag' items.
+newtype MediaItems = MediaItems [(String, MimeType, BL.ByteString)]
+
+instance Pushable MediaItems where
+ push = pushMediaItems
+
+instance Peekable MediaItems where
+ peek = peekMediaItems
+
+-- | Push an iterator triple to be used with Lua's @for@ loop construct.
+-- Each iterator invokation returns a tripple consisting of an item's
+-- filename, MIME type, and content.
+pushIterator :: MediaBag -> Lua NumResults
+pushIterator mb = do
+ Lua.pushHaskellFunction nextItem
+ Lua.push (MediaItems $ mediaItems mb)
+ Lua.pushnil
+ return 3
+
+-- | Lua type name for @'MediaItems'@.
+mediaItemsTypeName :: String
+mediaItemsTypeName = "pandoc MediaItems"
+
+-- | Push a @MediaItems@ element to the stack.
+pushMediaItems :: MediaItems -> Lua ()
+pushMediaItems xs = pushAnyWithMetatable pushMT xs
+ where
+ pushMT = ensureUserdataMetatable mediaItemsTypeName (return ())
+
+-- | Retrieve a @MediaItems@ element from the stack.
+peekMediaItems :: StackIndex -> Lua MediaItems
+peekMediaItems = reportValueOnFailure mediaItemsTypeName
+ (`toAnyWithName` mediaItemsTypeName)
+
+-- | Retrieve a list of items from an iterator state, return the first
+-- item (if present), and advance the state.
+nextItem :: Ptr (StablePtr MediaItems) -> AnyValue -> Lua NumResults
+nextItem ptr _ = do
+ (MediaItems items) <- Lua.liftIO $ deRefStablePtr =<< Storable.peek ptr
+ case items of
+ [] -> 2 <$ (Lua.pushnil *> Lua.pushnil)
+ (key, mt, content):xs -> do
+ Lua.liftIO $ Storable.poke ptr =<< newStablePtr (MediaItems xs)
+ Lua.push key
+ Lua.push mt
+ Lua.push content
+ return 3