{-
Copyright (C) 2013 John MacFarlane <jgm@berkeley.edu>

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
-}

{- |
   Module      : Text.Pandoc.Writers.OPML
   Copyright   : Copyright (C) 2013 John MacFarlane
   License     : GNU GPL, version 2 or above

   Maintainer  : John MacFarlane <jgm@berkeley.edu>
   Stability   : alpha
   Portability : portable

Conversion of 'Pandoc' documents to OPML XML.
-}
module Text.Pandoc.Writers.OPML ( writeOPML) where
import Text.Pandoc.Definition
import Text.Pandoc.XML
import Text.Pandoc.Shared
import Text.Pandoc.Options
import Text.Pandoc.Templates (renderTemplate)
import Text.Pandoc.Writers.HTML (writeHtmlString)
import Text.Pandoc.Writers.Markdown (writeMarkdown)
import Data.List ( intercalate )
import Text.Pandoc.Pretty
import Data.Time
import System.Locale (defaultTimeLocale)

-- | Convert Pandoc document to string in OPML format.
writeOPML :: WriterOptions -> Pandoc -> String
writeOPML opts (Pandoc (Meta tit auths dat) blocks) =
  let title = writeHtmlInlines tit
      author = writeHtmlInlines $ intercalate [Space,Str ";",Space] auths
      date = convertDate dat
      elements = hierarchicalize blocks
      colwidth = if writerWrapText opts
                    then Just $ writerColumns opts
                    else Nothing
      main     = render colwidth $ vcat (map (elementToOPML opts) elements)
      context = writerVariables opts ++
                [ ("body", main)
                , ("title", title)
                , ("date", date)
                , ("author", author) ]
  in  if writerStandalone opts
         then renderTemplate context $ writerTemplate opts
         else main

writeHtmlInlines :: [Inline] -> String
writeHtmlInlines ils = trim $ writeHtmlString def
                            $ Pandoc (Meta [] [] []) [Plain ils]

-- date format: RFC 822: Thu, 14 Jul 2005 23:41:05 GMT
showDateTimeRFC822 :: UTCTime -> String
showDateTimeRFC822 = formatTime defaultTimeLocale "%a, %d %b %Y %X %Z"

convertDate :: [Inline] -> String
convertDate ils = maybe "" showDateTimeRFC822
  $ parseTime defaultTimeLocale "%F" =<< (normalizeDate $ stringify ils)

-- | Convert an Element to OPML.
elementToOPML :: WriterOptions -> Element -> Doc
elementToOPML _ (Blk _) = empty
elementToOPML opts (Sec _ _num _ title elements) =
  let isBlk (Blk _) = True
      isBlk _     = False
      fromBlk (Blk x) = x
      fromBlk _ = error "fromBlk called on non-block"
      (blocks, rest) = span isBlk elements
      attrs = [("text", writeHtmlInlines title)] ++
              [("_note", writeMarkdown def (Pandoc (Meta [] [] [])
                              (map fromBlk blocks)))
                | not (null blocks)]
  in  inTags True "outline" attrs $
      vcat (map (elementToOPML opts) rest)