{-
Copyright (C) 2014-2017 Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE RecordWildCards  #-}
{-# LANGUAGE ViewPatterns     #-}
{- |
   Module      : Text.Pandoc.Readers.Org.DocumentTree
   Copyright   : Copyright (C) 2014-2017 Albert Krewinkel
   License     : GNU GPL, version 2 or above

   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>

Parsers for org-mode headlines and document subtrees
-}
module Text.Pandoc.Readers.Org.DocumentTree
  ( headline
  , headlineToBlocks
  ) where

import Control.Monad (guard, void)
import Data.Char (toLower, toUpper)
import Data.Maybe (fromMaybe)
import Data.Monoid ((<>))
import Text.Pandoc.Builder (Blocks, Inlines)
import Text.Pandoc.Class (PandocMonad)
import Text.Pandoc.Definition
import Text.Pandoc.Readers.Org.BlockStarts
import Text.Pandoc.Readers.Org.Parsing
import Text.Pandoc.Readers.Org.ParserState

import qualified Text.Pandoc.Builder as B

--
-- Org headers
--
newtype Tag = Tag { fromTag :: String }
  deriving (Show, Eq)

-- | Create a tag containing the given string.
toTag :: String -> Tag
toTag = Tag

-- | The key (also called name or type) of a property.
newtype PropertyKey = PropertyKey { fromKey :: String }
  deriving (Show, Eq, Ord)

-- | Create a property key containing the given string.  Org mode keys are
-- case insensitive and are hence converted to lower case.
toPropertyKey :: String -> PropertyKey
toPropertyKey = PropertyKey . map toLower

-- | The value assigned to a property.
newtype PropertyValue = PropertyValue { fromValue :: String }

-- | Create a property value containing the given string.
toPropertyValue :: String -> PropertyValue
toPropertyValue = PropertyValue

-- | Check whether the property value is non-nil (i.e. truish).
isNonNil :: PropertyValue -> Bool
isNonNil p = map toLower (fromValue p) `notElem` ["()", "{}", "nil"]

-- | Key/value pairs from a PROPERTIES drawer
type Properties = [(PropertyKey, PropertyValue)]

-- | Org mode headline (i.e. a document subtree).
data Headline = Headline
  { headlineLevel      :: Int
  , headlineTodoMarker :: Maybe TodoMarker
  , headlineText       :: Inlines
  , headlineTags       :: [Tag]
  , headlineProperties :: Properties
  , headlineContents   :: Blocks
  , headlineChildren   :: [Headline]
  }

-- | Read an Org mode headline and its contents (i.e. a document subtree).
-- @lvl@ gives the minimum acceptable level of the tree.
headline :: PandocMonad m
         => OrgParser m (F Blocks)
         -> OrgParser m (F Inlines)
         -> Int
         -> OrgParser m (F Headline)
headline blocks inline lvl = try $ do
  level <- headerStart
  guard (lvl <= level)
  todoKw <- optionMaybe todoKeyword
  title <- trimInlinesF . mconcat <$> manyTill inline endOfTitle
  tags  <- option [] headerTags
  newline
  properties <- option mempty propertiesDrawer
  contents   <- blocks
  children   <- many (headline blocks inline (level + 1))
  return $ do
    title'    <- title
    contents' <- contents
    children' <- sequence children
    return $ Headline
      { headlineLevel = level
      , headlineTodoMarker = todoKw
      , headlineText = title'
      , headlineTags = tags
      , headlineProperties = properties
      , headlineContents = contents'
      , headlineChildren = children'
      }
 where
   endOfTitle :: Monad m => OrgParser m ()
   endOfTitle = void . lookAhead $ optional headerTags *> newline

   headerTags :: Monad m => OrgParser m [Tag]
   headerTags = try $
     let tag = many1 (alphaNum <|> oneOf "@%#_") <* char ':'
     in map toTag <$> (skipSpaces *> char ':' *> many1 tag <* skipSpaces)

-- | Convert an Org mode headline (i.e. a document tree) into pandoc's Blocks
headlineToBlocks :: Monad m => Headline -> OrgParser m Blocks
headlineToBlocks hdln@(Headline {..}) = do
  maxHeadlineLevels <- getExportSetting exportHeadlineLevels
  case () of
    _ | any isNoExportTag headlineTags     -> return mempty
    _ | any isArchiveTag  headlineTags     -> archivedHeadlineToBlocks hdln
    _ | isCommentTitle headlineText        -> return mempty
    _ | headlineLevel >= maxHeadlineLevels -> headlineToHeaderWithList hdln
    _ | otherwise                          -> headlineToHeaderWithContents hdln

isNoExportTag :: Tag -> Bool
isNoExportTag = (== toTag "noexport")

isArchiveTag :: Tag -> Bool
isArchiveTag = (== toTag "ARCHIVE")

-- | Check if the title starts with COMMENT.
-- FIXME: This accesses builder internals not intended for use in situations
-- like these.  Replace once keyword parsing is supported.
isCommentTitle :: Inlines -> Bool
isCommentTitle (B.toList -> (Str "COMMENT":_)) = True
isCommentTitle _                               = False

archivedHeadlineToBlocks :: Monad m => Headline -> OrgParser m Blocks
archivedHeadlineToBlocks hdln = do
  archivedTreesOption <- getExportSetting exportArchivedTrees
  case archivedTreesOption of
    ArchivedTreesNoExport     -> return mempty
    ArchivedTreesExport       -> headlineToHeaderWithContents hdln
    ArchivedTreesHeadlineOnly -> headlineToHeader hdln

headlineToHeaderWithList :: Monad m => Headline -> OrgParser m Blocks
headlineToHeaderWithList hdln@(Headline {..}) = do
  maxHeadlineLevels <- getExportSetting exportHeadlineLevels
  header        <- headlineToHeader hdln
  listElements  <- sequence (map headlineToBlocks headlineChildren)
  let listBlock  = if null listElements
                   then mempty
                   else B.orderedList listElements
  let headerText = if maxHeadlineLevels == headlineLevel
                   then header
                   else flattenHeader header
  return $ headerText <> headlineContents <> listBlock
 where
   flattenHeader :: Blocks -> Blocks
   flattenHeader blks =
     case B.toList blks of
       (Header _ _ inlns:_) -> B.para (B.fromList inlns)
       _                    -> mempty

headlineToHeaderWithContents :: Monad m => Headline -> OrgParser m Blocks
headlineToHeaderWithContents hdln@(Headline {..}) = do
  header         <- headlineToHeader hdln
  childrenBlocks <- mconcat <$> sequence (map headlineToBlocks headlineChildren)
  return $ header <> headlineContents <> childrenBlocks

headlineToHeader :: Monad m => Headline -> OrgParser m Blocks
headlineToHeader (Headline {..}) = do
  exportTodoKeyword <- getExportSetting exportWithTodoKeywords
  let todoText    = if exportTodoKeyword
                    then case headlineTodoMarker of
                      Just kw -> todoKeywordToInlines kw <> B.space
                      Nothing -> mempty
                    else mempty
  let text        = tagTitle (todoText <> headlineText) headlineTags
  let propAttr    = propertiesToAttr headlineProperties
  attr           <- registerHeader propAttr headlineText
  return $ B.headerWith attr headlineLevel text

todoKeyword :: Monad m => OrgParser m TodoMarker
todoKeyword = try $ do
  taskStates <- activeTodoMarkers <$> getState
  let kwParser tdm = try $ (tdm <$ string (todoMarkerName tdm) <* spaceChar)
  choice (map kwParser taskStates)

todoKeywordToInlines :: TodoMarker -> Inlines
todoKeywordToInlines tdm =
  let todoText  = todoMarkerName tdm
      todoState = map toLower . show $ todoMarkerState tdm
      classes = [todoState, todoText]
  in B.spanWith (mempty, classes, mempty) (B.str todoText)

propertiesToAttr :: Properties -> Attr
propertiesToAttr properties =
  let
    toStringPair prop = (fromKey (fst prop), fromValue (snd prop))
    customIdKey = toPropertyKey "custom_id"
    classKey    = toPropertyKey "class"
    unnumberedKey = toPropertyKey "unnumbered"
    specialProperties = [customIdKey, classKey, unnumberedKey]
    id'  = fromMaybe mempty . fmap fromValue . lookup customIdKey $ properties
    cls  = fromMaybe mempty . fmap fromValue . lookup classKey    $ properties
    kvs' = map toStringPair . filter ((`notElem` specialProperties) . fst)
           $ properties
    isUnnumbered =
      fromMaybe False . fmap isNonNil . lookup unnumberedKey $ properties
  in
    (id', words cls ++ (if isUnnumbered then ["unnumbered"] else []), kvs')

tagTitle :: Inlines -> [Tag] -> Inlines
tagTitle title tags = title <> (mconcat $ map tagToInline tags)

-- | Convert 
tagToInline :: Tag -> Inlines
tagToInline t = B.spanWith ("", ["tag"], [("data-tag-name", fromTag t)]) mempty

-- | Read a :PROPERTIES: drawer and return the key/value pairs contained
-- within.
propertiesDrawer :: Monad m => OrgParser m Properties
propertiesDrawer = try $ do
  drawerType <- drawerStart
  guard $ map toUpper drawerType == "PROPERTIES"
  manyTill property (try endOfDrawer)
 where
   property :: Monad m => OrgParser m (PropertyKey, PropertyValue)
   property = try $ (,) <$> key <*> value

   key :: Monad m => OrgParser m PropertyKey
   key = fmap toPropertyKey . try $
         skipSpaces *> char ':' *> many1Till nonspaceChar (char ':')

   value :: Monad m => OrgParser m PropertyValue
   value = fmap toPropertyValue . try $
           skipSpaces *> manyTill anyChar (try $ skipSpaces *> newline)

   endOfDrawer :: Monad m => OrgParser m String
   endOfDrawer = try $
     skipSpaces *> stringAnyCase ":END:" <* skipSpaces <* newline