module RSS (make, make') where

import Date
import Info
import BuilderQQ

import Data.List (sortBy, intersperse)
import Data.Maybe (catMaybes)
import Data.Function (on)
import qualified Data.Text as Strict
import qualified Data.Text.Lazy as Lazy
import System.FilePath (takeDirectory)
import Control.Monad


make :: Strict.Text    -- ^ website root e.g. @https://gallery.niss.website@
     -> Strict.Text    -- ^ website name e.g. @nissart@
     -> GalleryInfo
     -> Maybe FilePath -- ^ output filename for self link
     -> [(FilePath, Info)]
     -> Lazy.Text
make root name ginfo output infos =
  toLazyText $ make' root name ginfo output infos

make' :: Strict.Text -> Strict.Text -> GalleryInfo
      -> Maybe FilePath -> [(FilePath, Info)] -> Builder
make' root name ginfo@(GalleryInfo {title, desc, prefix}) output infos = [b|
    <?xml version="1.0" encoding="UTF-8"?>
    <rss version="2.0">
      <channel>
        <title>$name—$title</title>
        <link>$link</link>
        <description>$desc</description>
        $selflink

        $items
      </channel>
    </rss>
  |]
 where
  link = [b|$root/$prefix|]
  nsfw = ginfo.nsfw
  items = map (uncurry $ makeItem root prefix nsfw) $
    sortBy (flip (compareFor nsfw `on` snd)) $
    filter (not . (.unlisted) . snd) infos
  selflink = case output of
    Nothing -> ""
    Just o  -> [b|<link href="$link/$o" rel="self" />|]

makeItem :: Strict.Text -> FilePath -> Bool -> FilePath -> Info -> Builder
makeItem root prefix nsfw path info@(Info {title}) = [b|
    <item>
      <title>$title$suffix</title>
      <link>$link</link>
      <guid>$link</guid>
      $body
      <pubDate>$date</pubDate>
    </item>
  |]
 where
  body = [b|
      <description> <![CDATA[
        $image
        $artist
        $desc
      ]]> </description>
    |]

  suffix = if null parts then ""
           else " (" <> mconcat (intersperse ", " parts) <> ")"
  parts = catMaybes [o18, cnt, up]
  up   = do guard $ hasUpdatesFor nsfw info; Just "updated"
  o18  = do guard $ nsfw && anyNsfw info; Just "🔞"
  cnt  = do let len = maybe 0 length $ allImages <$> imagesFor nsfw info
            guard $ len /= 1; Just [b|$len images|]

  dir  = takeDirectory path
  link = [b|$root/$prefix/$dir|]

  date = formatRSS $ latestDateFor nsfw info
  artist = ifJust info.artist \case
    Artist name Nothing    -> [b|<p>by $name|]
    Artist name (Just url) -> [b|<p>by <a href="$url">$name</a>|]
  desc = makeDesc $ descFor nsfw info

  image = case previewImage info of
    Just (PFull img) -> figure $ pageFile img
    Just (PThumb th) -> figure $ thumbFile th
    Nothing          -> ""
  figure p = [b|<figure> <a href="$link"><img src="$link/$p"></a> </figure>|]

makeDesc :: Desc -> Builder
makeDesc NoDesc = ""
makeDesc (TextDesc txt) = [b|$txt|]
makeDesc (LongDesc fs) = [b|<dl>$fields</dl>|]
  where fields = map (\(DescField {name, text}) -> [b|<dt>$name <dd>$text|]) fs