{-# LANGUAGE CPP, ForeignFunctionInterface, GeneralizedNewtypeDeriving,
    DeriveGeneric, DeriveDataTypeable, FlexibleContexts #-}

module CMark (
    commonmarkToHtml
  , commonmarkToXml
  , commonmarkToMan
  , commonmarkToNode
  , optSourcePos
  , optNormalize
  , optHardBreaks
  , optSmart
  , Node(..)
  , NodeType(..)
  , PosInfo(..)
  , DelimType(..)
  , ListType(..)
  , ListAttributes(..)
  , Url
  , Title
  , Level
  , Info
  , CMarkOption
  ) where

import Foreign
import Foreign.C.Types
import Foreign.C.String (CString)
import qualified System.IO.Unsafe as Unsafe
import GHC.Generics (Generic)
import Data.Data (Data)
import Data.Typeable (Typeable)
import Data.Text (Text, empty)
import qualified Data.Text.Foreign as TF

#include <cmark.h>

type NodePtr = Ptr ()

data Node = Node (Maybe PosInfo) NodeType [Node]
     deriving (Show, Read, Eq, Ord, Typeable, Data, Generic)

data DelimType =
    PERIOD_DELIM
  | PAREN_DELIM
  deriving (Show, Read, Eq, Ord, Typeable, Data, Generic)

data ListType =
    BULLET_LIST
  | ORDERED_LIST
  deriving (Show, Read, Eq, Ord, Typeable, Data, Generic)

data ListAttributes = ListAttributes{
    listType     :: ListType
  , listTight    :: Bool
  , listStart    :: Int
  , listDelim    :: DelimType
  } deriving (Show, Read, Eq, Ord, Typeable, Data, Generic)

type Url = Text

type Title = Text

type Level = Int

type Info = Text

data NodeType =
    DOCUMENT
  | HRULE
  | PARAGRAPH
  | BLOCK_QUOTE
  | HTML Text
  | CODE_BLOCK Info Text
  | HEADER Level
  | LIST ListAttributes
  | ITEM
  | TEXT Text
  | SOFTBREAK
  | LINEBREAK
  | INLINE_HTML Text
  | CODE Text
  | EMPH
  | STRONG
  | LINK Url Title
  | IMAGE Url Title
  deriving (Show, Read, Eq, Ord, Typeable, Data, Generic)

data PosInfo = PosInfo{ startLine   :: Int
                      , startColumn :: Int
                      , endLine     :: Int
                      , endColumn   :: Int
                      }
  deriving (Show, Read, Eq, Ord, Typeable, Data, Generic)

newtype CMarkOption = CMarkOption { unCMarkOption :: CInt }

-- | Combine a list of options into a single option, using bitwise or.
combineOptions :: [CMarkOption] -> CInt
combineOptions = foldr ((.|.) . unCMarkOption) 0

-- Include a @data-sourcepos@ attribute on block elements.
optSourcePos :: CMarkOption
optSourcePos = CMarkOption #const CMARK_OPT_SOURCEPOS

-- Render @softbreak@ elements as hard line breaks.
optHardBreaks :: CMarkOption
optHardBreaks = CMarkOption #const CMARK_OPT_HARDBREAKS

-- Normalize the document by consolidating adjacent text nodes.
optNormalize :: CMarkOption
optNormalize = CMarkOption #const CMARK_OPT_NORMALIZE

-- Convert straight quotes to curly, @---@ to em-dash, @--@ to en-dash.
optSmart :: CMarkOption
optSmart = CMarkOption #const CMARK_OPT_SMART

ptrToNodeType :: NodePtr -> NodeType
ptrToNodeType ptr =
  case (c_cmark_node_get_type ptr) of
             #const CMARK_NODE_DOCUMENT
               -> DOCUMENT
             #const CMARK_NODE_HRULE
               -> HRULE
             #const CMARK_NODE_PARAGRAPH
               -> PARAGRAPH
             #const CMARK_NODE_BLOCK_QUOTE
               -> BLOCK_QUOTE
             #const CMARK_NODE_HTML
               -> HTML literal
             #const CMARK_NODE_CODE_BLOCK
               -> CODE_BLOCK info literal
             #const CMARK_NODE_LIST
               -> LIST listAttr
             #const CMARK_NODE_ITEM
               -> ITEM
             #const CMARK_NODE_HEADER
               -> HEADER level
             #const CMARK_NODE_EMPH
               -> EMPH
             #const CMARK_NODE_STRONG
               -> STRONG
             #const CMARK_NODE_LINK
               -> LINK url title
             #const CMARK_NODE_IMAGE
               -> IMAGE url title
             #const CMARK_NODE_TEXT
               -> TEXT literal
             #const CMARK_NODE_CODE
               -> CODE literal
             #const CMARK_NODE_INLINE_HTML
               -> INLINE_HTML literal
             #const CMARK_NODE_SOFTBREAK
               -> SOFTBREAK
             #const CMARK_NODE_LINEBREAK
               -> LINEBREAK
             _ -> error "Unknown node type"
  where literal   = peekCString $ c_cmark_node_get_literal ptr
        level     = c_cmark_node_get_header_level ptr
        listAttr  = ListAttributes{
            listType  = case c_cmark_node_get_list_type ptr of
                             (#const CMARK_ORDERED_LIST) -> ORDERED_LIST
                             (#const CMARK_BULLET_LIST)  -> BULLET_LIST
                             _                           -> BULLET_LIST
          , listDelim  = case c_cmark_node_get_list_delim ptr of
                             (#const CMARK_PERIOD_DELIM) -> PERIOD_DELIM
                             (#const CMARK_PAREN_DELIM)  -> PAREN_DELIM
                             _                           -> PERIOD_DELIM
          , listTight  = c_cmark_node_get_list_tight ptr == 1
          , listStart  = c_cmark_node_get_list_start ptr
          }
        url       = peekCString $ c_cmark_node_get_url ptr
        title     = peekCString $ c_cmark_node_get_title ptr
        info      = peekCString $ c_cmark_node_get_fence_info ptr

getPosInfo :: NodePtr -> Maybe PosInfo
getPosInfo ptr =
   case (c_cmark_node_get_start_line ptr,
         c_cmark_node_get_start_column ptr,
         c_cmark_node_get_end_line ptr,
         c_cmark_node_get_end_column ptr) of
       (0, 0, 0, 0) -> Nothing
       (sl, sc, el, ec) -> Just PosInfo{ startLine = sl
                                       , startColumn = sc
                                       , endLine = el
                                       , endColumn = ec }

handleNode :: (Maybe PosInfo -> NodeType -> [a] -> a) -> NodePtr -> a
handleNode f ptr = f posinfo (ptrToNodeType ptr) children
   where children = handleNodes f $ c_cmark_node_first_child ptr
         posinfo  = getPosInfo ptr
         handleNodes f' ptr' =
           if ptr' == nullPtr
              then []
              else handleNode f' ptr' : handleNodes f' (c_cmark_node_next ptr')

toNode :: NodePtr -> Node
toNode = handleNode Node

foreign import ccall "string.h strlen"
    c_strlen :: CString -> Int

foreign import ccall "cmark.h cmark_markdown_to_html"
    c_cmark_markdown_to_html :: CString -> Int -> CInt -> CString

foreign import ccall "cmark.h cmark_render_xml"
    c_cmark_render_xml :: NodePtr -> CInt -> CString

foreign import ccall "cmark.h cmark_render_man"
    c_cmark_render_man :: NodePtr -> CInt -> CString

foreign import ccall "cmark.h cmark_parse_document"
    c_cmark_parse_document :: CString -> Int -> CInt -> NodePtr

foreign import ccall "cmark.h cmark_node_get_type"
    c_cmark_node_get_type :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_first_child"
    c_cmark_node_first_child :: NodePtr -> NodePtr

foreign import ccall "cmark.h cmark_node_next"
    c_cmark_node_next :: NodePtr -> NodePtr

foreign import ccall "cmark.h cmark_node_get_literal"
    c_cmark_node_get_literal :: NodePtr -> CString

foreign import ccall "cmark.h cmark_node_get_url"
    c_cmark_node_get_url :: NodePtr -> CString

foreign import ccall "cmark.h cmark_node_get_title"
    c_cmark_node_get_title :: NodePtr -> CString

foreign import ccall "cmark.h cmark_node_get_header_level"
    c_cmark_node_get_header_level :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_get_list_type"
    c_cmark_node_get_list_type :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_get_list_tight"
    c_cmark_node_get_list_tight :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_get_list_start"
    c_cmark_node_get_list_start :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_get_list_delim"
    c_cmark_node_get_list_delim :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_get_fence_info"
    c_cmark_node_get_fence_info :: NodePtr -> CString

foreign import ccall "cmark.h cmark_node_get_start_line"
    c_cmark_node_get_start_line :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_get_start_column"
    c_cmark_node_get_start_column :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_get_end_line"
    c_cmark_node_get_end_line :: NodePtr -> Int

foreign import ccall "cmark.h cmark_node_get_end_column"
    c_cmark_node_get_end_column :: NodePtr -> Int

-- | Convert CommonMark formatted text to Html, using cmark's
-- built-in renderer.
commonmarkToHtml :: [CMarkOption] -> Text -> Text
commonmarkToHtml opts s = io $
  TF.withCStringLen s $ \(ptr, len) ->
    return (peekCString $ c_cmark_markdown_to_html ptr len (combineOptions opts))

-- | Convert CommonMark formatted text to CommonMark XML, using cmark's
-- built-in renderer.
commonmarkToXml :: [CMarkOption] -> Text -> Text
commonmarkToXml opts s = io $
  TF.withCStringLen s $ \(ptr, len) -> do
    let opts' = combineOptions opts
    let doc = c_cmark_parse_document ptr len opts'
    return (peekCString $ c_cmark_render_xml doc opts')

-- | Convert CommonMark formatted text to groff man, using cmark's
-- built-in renderer.
commonmarkToMan :: [CMarkOption] -> Text -> Text
commonmarkToMan opts s = io $
  TF.withCStringLen s $ \(ptr, len) -> do
    let opts' = combineOptions opts
    let doc = c_cmark_parse_document ptr len opts'
    return (peekCString $ c_cmark_render_man doc opts')

-- | Convert CommonMark formatted text to a structured 'Node' tree,
-- which can be transformed or rendered using Haskell code.
commonmarkToNode :: [CMarkOption] -> Text -> Node
commonmarkToNode opts s = io $
      TF.withCStringLen s $ \(ptr, len) ->
        return $ toNode $ c_cmark_parse_document ptr len (combineOptions opts)

io :: IO a -> a
io = Unsafe.unsafePerformIO

peekCString :: CString -> Text
peekCString str
  | str == nullPtr = empty
  | otherwise      = io $ TF.peekCStringLen (str, c_strlen str)