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
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.Writers.Shared
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 Text.Pandoc.Pretty
import Data.Time
import System.Locale (defaultTimeLocale)
import qualified Text.Pandoc.Builder as B

-- | Convert Pandoc document to string in OPML format.
writeOPML :: WriterOptions -> Pandoc -> String
writeOPML opts (Pandoc meta blocks) =
  let elements = hierarchicalize blocks
      colwidth = if writerWrapText opts
                    then Just $ writerColumns opts
                    else Nothing
      meta' = B.setMeta "date" (B.str $ convertDate $ docDate meta) meta
      Just metadata = metaToJSON opts
                      (Just . writeMarkdown def . Pandoc nullMeta)
                      (Just . trimr . writeMarkdown def . Pandoc nullMeta .
                         (\ils -> [Plain ils]))
      main     = render colwidth $ vcat (map (elementToOPML opts) elements)
      context = defField "body" main metadata
  in  if writerStandalone opts
         then renderTemplate' (writerTemplate opts) context
         else main

writeHtmlInlines :: [Inline] -> String
writeHtmlInlines ils = trim $ writeHtmlString def
                            $ Pandoc nullMeta [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 nullMeta
                              (map fromBlk blocks)))
                | not (null blocks)]
  in  inTags True "outline" attrs $
      vcat (map (elementToOPML opts) rest)