    {-# LANGUAGE GeneralizedNewtypeDeriving #-}
    {-# LANGUAGE OverloadedStrings          #-}
    {-# LANGUAGE PackageImports             #-}
    {-# LANGUAGE ScopedTypeVariables        #-}

    module Heist.Interpreted.Internal where

    ------------------------------------------------------------------------------
    import           Blaze.ByteString.Builder
    import           Control.Monad
    import           Control.Monad.State.Strict
    import qualified Data.Attoparsec.Text          as AP
    import           Data.ByteString               (ByteString)
    import qualified Data.HashMap.Strict           as Map
    import qualified Data.HeterogeneousEnvironment as HE
    import           Data.Map.Syntax
    import           Data.Maybe
    import           Data.Text                     (Text)
    import qualified Data.Text                     as T
    import qualified Text.XmlHtml                  as X
    ------------------------------------------------------------------------------
    import           Heist.Common
    import           Heist.Internal.Types.HeistState
    ------------------------------------------------------------------------------

    type Splice n = HeistT n n Template

    ------------------------------------------------------------------------------
    -- HeistState functions
    ------------------------------------------------------------------------------

    ------------------------------------------------------------------------------
    -- | Binds a new splice declaration to a tag name within a 'HeistState'.
    bindSplice :: Text            -- ^ tag name
               -> Splice n        -- ^ splice action
               -> HeistState n    -- ^ source state
               -> HeistState n
    bindSplice n v hs = hs {_spliceMap = Map.insert n v (_spliceMap hs)}

    ------------------------------------------------------------------------------
    -- | Binds a set of new splice declarations within a 'HeistState'.
    bindSplices :: Splices (Splice n) -- ^ splices to bind
                -> HeistState n       -- ^ start state
                -> HeistState n
    bindSplices ss hs =
        hs { _spliceMap = Map.union (runMapNoErrors ss) (_spliceMap hs) }

    ------------------------------------------------------------------------------
    -- | Converts 'Text' to a splice returning a single 'TextNode'.
    textSplice :: Monad m => Text -> HeistT n m Template
    textSplice t = return [X.TextNode t]

    ------------------------------------------------------------------------------
    -- | Runs the parameter node's children and returns the resulting node list.
    -- By itself this function is a simple passthrough splice that makes the
    -- spliced node disappear.  In combination with locally bound splices, this
    -- function makes it easier to pass the desired view into your splices.
    runChildren :: Monad n => Splice n
    runChildren = runNodeList . X.childNodes =<< getParamNode

    ------------------------------------------------------------------------------
    -- | Binds a list of splices before using the children of the spliced node as
    -- a view.
    runChildrenWith :: (Monad n)
                    => Splices (Splice n)
                    -- ^ List of splices to bind before running the param nodes.
                    -> Splice n
                    -- ^ Returns the passed in view.
    runChildrenWith splices = localHS (bindSplices splices) runChildren

    ------------------------------------------------------------------------------
    -- | Wrapper around runChildrenWith that applies a transformation function to
    -- the second item in each of the tuples before calling runChildrenWith.
    runChildrenWithTrans :: (Monad n)
              => (b -> Splice n)
              -- ^ Splice generating function
              -> Splices b
              -- ^ List of tuples to be bound
              -> Splice n
    runChildrenWithTrans f = runChildrenWith . mapV f

    ------------------------------------------------------------------------------
    -- | Like runChildrenWith but using constant templates rather than dynamic
    -- splices.
    runChildrenWithTemplates :: (Monad n) => Splices Template -> Splice n
    runChildrenWithTemplates = runChildrenWithTrans return

    ------------------------------------------------------------------------------
    -- | Like runChildrenWith but using literal text rather than dynamic splices.
    runChildrenWithText :: (Monad n) => Splices Text -> Splice n
    runChildrenWithText = runChildrenWithTrans textSplice

    ------------------------------------------------------------------------------
    -- | Convenience function for looking up a splice.
    lookupSplice :: Text
                 -> HeistState n
                 -> Maybe (Splice n)
    lookupSplice nm hs = Map.lookup nm $ _spliceMap hs
    {-# INLINE lookupSplice #-}

    ------------------------------------------------------------------------------
    -- | Adds an HTML format template to the heist state.
    addTemplate :: ByteString
                -- ^ Path that the template will be referenced by
                -> Template
                -- ^ The template's DOM nodes
                -> Maybe FilePath
                -- ^ An optional path to the actual file on disk where the
                -- template is stored
                -> HeistState n
                -> HeistState n
    addTemplate n t mfp st =
        insertTemplate (splitTemplatePath n) doc st
      where
        doc = DocumentFile (X.HtmlDocument X.UTF8 Nothing t) mfp

    ------------------------------------------------------------------------------
    -- | Adds an XML format template to the heist state.
    addXMLTemplate :: ByteString
                   -- ^ Path that the template will be referenced by
                   -> Template
                   -- ^ The template's DOM nodes
                   -> Maybe FilePath
                   -- ^ An optional path to the actual file on disk where the
                   -- template is stored
                   -> HeistState n
                   -> HeistState n
    addXMLTemplate n t mfp st =
        insertTemplate (splitTemplatePath n) doc st
      where
        doc = DocumentFile (X.XmlDocument X.UTF8 Nothing t) mfp

    ------------------------------------------------------------------------------
    -- | Stops the recursive processing of splices.  Consider the following
    -- example:
    --
    --   > <foo>
    --   >   <bar>
    --   >     ...
    --   >   </bar>
    --   > </foo>
    --
    -- Assume that @\"foo\"@ is bound to a splice procedure. Running the @foo@
    -- splice will result in a list of nodes @L@.  Normally @foo@ will recursively
    -- scan @L@ for splices and run them.  If @foo@ calls @stopRecursion@, @L@
    -- will be included in the output verbatim without running any splices.
    stopRecursion :: Monad m => HeistT n m ()
    stopRecursion = modifyHS (\st -> st { _recurse = False })

    ------------------------------------------------------------------------------
    -- | Performs splice processing on a single node.
    runNode :: Monad n => X.Node -> Splice n
    runNode (X.Element nm at ch) = do
        newAtts <- runAttributes at
        let n = X.Element nm newAtts ch
        s <- liftM (lookupSplice nm) getHS
        maybe (runKids newAtts) (recurseSplice n) s
      where
        runKids newAtts = do
            newKids <- runNodeList ch
            return [X.Element nm newAtts newKids]
    runNode n                    = return [n]

    ------------------------------------------------------------------------------
    -- | Performs splice processing on a list of attributes.  This is useful in
    -- situations where you need to stop recursion, but still run splice
    -- processing on the node's attributes.
    runAttributes :: Monad n => [(Text, Text)] -> HeistT n n [(Text, Text)]
    runAttributes attrs = (return . concat) =<< mapM runAttrSplice attrs

    ------------------------------------------------------------------------------
    -- | Runs the attribute splice if it exists, otherwise it does inline $()
    -- substitution.
    runAttrSplice :: (Monad n) => (Text, Text) -> HeistT n n [(Text, Text)]
    runAttrSplice a@(k,v) = do
        splice <- getsHS (Map.lookup k . _attrSpliceMap)
        maybe (liftM (:[]) $ attSubst a)
              (lift . flip evalStateT HE.empty . unRT . ($v)) splice

    ------------------------------------------------------------------------------
    -- | Helper function for substituting a parsed attribute into an attribute
    -- tuple.
    attSubst :: (Monad n) => (t, Text) -> HeistT n n (t, Text)
    attSubst (n,v) = do
        v' <- parseAtt v
        return (n,v')

    ------------------------------------------------------------------------------
    -- | Parses an attribute for any identifier expressions and performs
    -- appropriate substitution.
    parseAtt :: (Monad n) => Text -> HeistT n n Text
    parseAtt bs = do
        let ast = case AP.feed (AP.parse attParser bs) "" of
                    (AP.Done _ res) -> res
                    (AP.Fail _ _ _) -> []
                    (AP.Partial _)  -> []
        chunks <- mapM cvt ast
        return $ T.concat chunks
      where
        cvt (Literal x) = return x
        cvt (Ident x)   =
            localParamNode (const $ X.Element x [] []) $ getAttributeSplice x

    ------------------------------------------------------------------------------
    -- | Gets the attribute value.  If the splice's result list contains non-text
    -- nodes, this will translate them into text nodes with nodeText and
    -- concatenate them together.
    --
    -- Originally, this only took the first node from the splices's result list,
    -- and only if it was a text node. This caused problems when the splice's
    -- result contained HTML entities, as they would split a text node. This was
    -- then fixed to take the first consecutive bunch of text nodes, and return
    -- their concatenation. This was seen as more useful than throwing an error,
    -- and more intuitive than trying to render all the nodes as text.
    --
    -- However, it was decided in the end to render all the nodes as text, and
    -- then concatenate them. If a splice returned
    -- \"some \<b\>text\<\/b\> foobar\", the user would almost certainly want
    -- \"some text foobar\" to be rendered, and Heist would probably seem
    -- annoyingly limited for not being able to do this. If the user really did
    -- want it to render \"some \", it would probably be easier for them to
    -- accept that they were silly to pass more than that to be substituted than
    -- it would be for the former user to accept that
    -- \"some \<b\>text\<\/b\> foobar\" is being rendered as \"some \" because
    -- it's \"more intuitive\".
    getAttributeSplice :: Monad n => Text -> HeistT n n Text
    getAttributeSplice name = do
        hs <- getHS
        let noSplice = return $ T.concat ["${", name, "}"]
            s = lookupSplice name hs
        maybe noSplice (liftM (T.concat . map X.nodeText)) s

    ------------------------------------------------------------------------------
    -- | Performs splice processing on a list of nodes.
    runNodeList :: Monad n => [X.Node] -> Splice n
    runNodeList = mapSplices runNode
    {-# INLINE runNodeList #-}

    ------------------------------------------------------------------------------
    -- | The maximum recursion depth.  (Used to prevent infinite loops.)
    mAX_RECURSION_DEPTH :: Int
    mAX_RECURSION_DEPTH = 50

    ------------------------------------------------------------------------------
    -- | Checks the recursion flag and recurses accordingly.  Does not recurse
    -- deeper than mAX_RECURSION_DEPTH to avoid infinite loops.
    recurseSplice :: Monad n => X.Node -> Splice n -> Splice n
    recurseSplice node splice = do
        result <- localParamNode (const node) splice
        hs <- getHS
        if _recurse hs
            then if _recursionDepth hs < mAX_RECURSION_DEPTH
                   then do modRecursionDepth (+1)
                           res <- runNodeList result
                           restoreHS hs
                           return res
                   else return result `orError` err
            else do modifyHS (\st -> st { _recurse = True })
                    return result
      where
        err = unwords
            ["Recursion limit reached in node"
            ,"<"++(T.unpack $ X.elementTag node)++">.  You"
            ,"probably have infinite splice recursion!"
            ]

    ------------------------------------------------------------------------------
    -- | Looks up a template name runs a 'HeistT' computation on it.
    lookupAndRun :: Monad m
                 => ByteString
                 -> ((DocumentFile, TPath) -> HeistT n m (Maybe a))
                 -> HeistT n m (Maybe a)
    lookupAndRun name k = do
        hs <- getHS
        let mt = lookupTemplate name hs _templateMap
        let curPath = join $ fmap (dfFile . fst) mt
        modifyHS (setCurTemplateFile curPath)
        maybe (return Nothing) k mt

    ------------------------------------------------------------------------------
    -- | Looks up a template name evaluates it by calling runNodeList.
    evalTemplate :: Monad n
                 => ByteString
                 -> HeistT n n (Maybe Template)
    evalTemplate name = lookupAndRun name
        (\(t,ctx) -> localHS (\hs -> hs {_curContext = ctx})
                             (liftM Just $ runNodeList $ X.docContent $ dfDoc t))

    ------------------------------------------------------------------------------
    -- | Sets the document type of a 'X.Document' based on the 'HeistT'
    -- value.
    fixDocType :: Monad m => X.Document -> HeistT n m X.Document
    fixDocType d = do
        dts <- getsHS _doctypes
        return $ d { X.docType = listToMaybe dts }

    ------------------------------------------------------------------------------
    -- | Runs a template and sets the doctype properly.  This is the right thing
    -- to do if we are starting at the top level.
    evalWithDoctypes :: Monad n
                     => ByteString
                     -> HeistT n n (Maybe X.Document)
    evalWithDoctypes name = lookupAndRun name $ \(t,ctx) -> do
        addDoctype $ maybeToList $ X.docType $ dfDoc t
        hs <- getHS
        let nodes = X.docContent $ dfDoc t
        putHS (hs {_curContext = ctx})
        newNodes <- runNodeList nodes
        restoreHS hs
        newDoc   <- fixDocType $ (dfDoc t) { X.docContent = newNodes }
        return (Just newDoc)

    ------------------------------------------------------------------------------
    -- | Binds a list of constant string splices.
    bindStrings :: Monad n
                => Splices Text
                -> HeistState n
                -> HeistState n
    bindStrings splices = bindSplices (mapV textSplice splices)

    ------------------------------------------------------------------------------
    -- | Binds a single constant string splice.
    bindString :: Monad n
               => Text
               -> Text
               -> HeistState n
               -> HeistState n
    bindString n = bindSplice n . textSplice

    ------------------------------------------------------------------------------
    -- | Renders a template with the specified parameters.  This is the function
    -- to use when you want to "call" a template and pass in parameters from
    -- inside a splice.  If the template does not exist, this version simply
    -- returns an empty list.
    callTemplate :: Monad n
                 => ByteString         -- ^ The name of the template
                 -> Splices (Splice n) -- ^ Splices to call the template with
                 -> HeistT n n Template
    callTemplate name splices = do
        modifyHS $ bindSplices splices
        liftM (maybe [] id) $ evalTemplate name

    ------------------------------------------------------------------------------
    -- | Like callTemplate except the splices being bound are constant text
    -- splices.
    callTemplateWithText :: Monad n
                         => ByteString     -- ^ The name of the template
                         -> Splices Text -- ^ Splices to call the template with
                         -> HeistT n n Template
    callTemplateWithText name splices = callTemplate name $ mapV textSplice splices

    ------------------------------------------------------------------------------
    -- | Renders a template from the specified HeistState to a 'Builder'.  The
    -- MIME type returned is based on the detected character encoding, and whether
    -- the root template was an HTML or XML format template.  It will always be
    -- @text/html@ or @text/xml@.  If a more specific MIME type is needed for a
    -- particular XML application, it must be provided by the application.
    renderTemplate :: Monad n
                   => HeistState n
                   -> ByteString
                   -> n (Maybe (Builder, MIMEType))
    renderTemplate hs name = evalHeistT tpl (X.TextNode "") hs
      where tpl = do mt <- evalWithDoctypes name
                     case mt of
                        Nothing  -> return Nothing
                        Just doc -> return $ Just $ (X.render doc, mimeType doc)

    ------------------------------------------------------------------------------
    -- | Renders a template with the specified arguments passed to it.  This is a
    -- convenience function for the common pattern of calling renderTemplate after
    -- using bindString, bindStrings, or bindSplice to set up the arguments to the
    -- template.
    renderWithArgs :: Monad n
                   => Splices Text
                   -> HeistState n
                   -> ByteString
                   -> n (Maybe (Builder, MIMEType))
    renderWithArgs args hs = renderTemplate (bindStrings args hs)