{-# language OverloadedStrings #-}
{-# language RecordWildCards #-}
{-# language NamedFieldPuns #-}
{-# language DeriveGeneric #-}
module Main where

import Data.Text (Text)
import Data.Text.Lazy.IO as TIO
import Text.RSS.Syntax
import Text.Feed.Types (Feed(RSSFeed))
import Text.Feed.Export (textFeed)

import qualified Data.Aeson as Json
import Data.Aeson (FromJSON)
import GHC.Generics (Generic)
import qualified Data.ByteString.Lazy as BS

-- | Info from the config file
data Config = Config
  { channelName :: Text
  , channelURL :: Text
  }
  deriving (Show, Generic)
instance FromJSON Config where

data Channel = Channel
  { channelInfo :: ChannelInfo
  , channelItems :: [ItemInfo]
  }
  deriving (Show, Generic)
instance FromJSON Channel where

-- | Info fetched from the channel
data ChannelInfo = ChannelInfo

  { channelDescription :: Text
  , channelLastUpdate :: DateString -- TODO
  , channelImage :: Maybe () --RSSImage
  }
  deriving (Show, Generic)
instance FromJSON ChannelInfo where

-- | Info of each channel item
data ItemInfo = ItemInfo
  { itemTitle :: Text
  , itemDescription :: Text
  , itemYoutubeLink :: Text
  , itemCategory :: Text
  , itemTags :: [Text]
  , itemURL :: Text
  , itemSizeBytes :: Integer
  , itemHash :: Text
  }
  deriving (Show, Generic)
instance FromJSON ItemInfo where

-- main = print $ textFeed $ RSSFeed $ toRSS
--   (ChannelInfo
--     { channelDescription = "description"
--     , channelLastUpdate = "some date"
--     , channelImage = nullImage "imageURL" "imageTitle" "imageLink"
--     })
--   []
main :: IO ()
main = do
  input <- BS.getContents
  let (Right rss) = Json.eitherDecode input
  let exConfig = (Config
        { channelName = "channel name"
        , channelURL = "channel url"
        })
  let (Just feed) = textFeed $ RSSFeed $ toRSS exConfig rss
  TIO.putStr feed

toRSS :: Config -> Channel -> RSS
toRSS Config{..} Channel{channelInfo, channelItems}  =
  let ChannelInfo{..} = channelInfo in
  (nullRSS channelName channelURL)
  { rssChannel = (nullChannel channelName channelURL)
      { rssDescription = channelDescription
      , rssLastUpdate = Just channelLastUpdate
      , rssImage = Nothing --channelImage TODO
      , rssGenerator = Just "youtube2audiopodcast"
      , rssItems = map rssItem channelItems
      }
  }

  where
    rssItem ItemInfo{..} = (nullItem itemTitle)
      { rssItemLink = Just itemYoutubeLink
      , rssItemDescription = Just itemDescription
      -- rssItemAuthor =
      , rssItemCategories =
        map (\name -> RSSCategory
              { rssCategoryDomain = Nothing
              , rssCategoryAttrs = []
              , rssCategoryValue = name
              }) $ itemCategory : itemTags
      , rssItemEnclosure = Just $ RSSEnclosure
          { rssEnclosureURL = itemURL
          , rssEnclosureLength = Just itemSizeBytes
          , rssEnclosureType = "audio/opus"
          , rssEnclosureAttrs = []
          }
      , rssItemGuid = Just $ RSSGuid
          { rssGuidPermanentURL = Just False
          , rssGuidAttrs = []
          , rssGuidValue = itemHash
          }
      -- TODO: date conversion
      -- https://tools.ietf.org/html/rfc822#section-5.1
      -- , rssItemPubDate 
      }