{-# Language OverloadedStrings #-}

-- todo [release] date?

module Main where

import Control.Applicative
import System.Environment
import Network.HTTP.Simple
import Text.HTML.Scalpel.Core
import Text.RSS.Syntax
import Text.RSS.Export

import qualified Paths_gscholar_rss as P
import qualified Control.Exception  as E
import qualified Data.List          as L
import qualified Data.String        as DS
import qualified Data.Text          as T
import qualified Data.Text.Lazy.IO  as TLI
import qualified Data.Text.Encoding as TE
import qualified Data.Version       as V
import qualified Data.XML.Types     as XT
import qualified Text.Atom.Feed     as AF
import qualified Text.URI           as U

main :: IO ()
main = errorPress work
    where
          work :: IO ()
          work =
               -- get args
               map T.pack <$> getArgs >>= \as ->

               -- malformed input
               if null as ||
                  length as > 1 ||
                  head as `elem` ["--help", "-h", "-v", "--version"]
               then putStrLn helps
               else

               -- scrape
               let url = head as in
               scrapeGet url (page url) >>= \p ->
               printRSS url p

          scrapeGet :: URL -> Scraper T.Text a -> IO a
          scrapeGet url s = getURLBody url  >>= \b ->
                            let r = maybe (error "Nothing in scrapeGet")
                                          id
                                          (scrapeStringLike b s)
                            in return r


-----------
-- TYPES --
-----------

type Title = T.Text
type URL = T.Text
data Page = Page Title URL [Article]
          deriving (Show, Eq)
    -- URL: url of the feed/page

type Author = T.Text
type Description = T.Text
data Article = Article Title URL Author Description
             deriving (Show, Eq)


------------
-- SCRAPE --
------------

page :: URL -> Scraper T.Text Page
page u = Page <$> text "title"
              <*> pure u
              <*> chroot ("div" @: ["id" @= "gs_res_ccl_mid"]) entries

entries :: Scraper T.Text [Article]
entries = chroots ("div" @: [hasClass "gs_ri"]) paper
    where
          paper = Article <$> text ("h3" @: [hasClass "gs_rt"])
                          <*> (cleanGBooks <$> attr "href" "a")
                          <*> text ("div" @: [hasClass "gs_a"])
                          <*> description

description :: Scraper T.Text Description
description = text ("div" @: [hasClass "gs_rs"]) <|>
              pure "No description available."
                    -- todo rimuovi span?
                    -- todo aggiungi test

-- Title: channel title
buildRSS :: Title -> Page -> RSS
buildRSS pt (Page _ u as) =
        (nullRSS "NULL-WRONG-T" "NULL-WRONG-L") {
          rssAttrs   = [dublinNamespace],
          rssChannel = (nullChannel pt u) {rssItems = map buildItem as} }
    where
          buildItem :: Article -> RSSItem
          buildItem (Article t wu a d) =
                (nullItem t) {
                    rssItemLink = Just wu,
                    -- rssItemAuthor = Just $ a,
                    rssItemOther = [dcCreator a],
                    rssItemDescription = Just d }

          -- http://www.rssboard.org/rss-profile#namespace-elements-dublin-creator
          dcCreator :: Author -> XT.Element
          dcCreator a = XT.Element "dc:creator" []
                            [XT.NodeContent $ XT.ContentText a]

          -- needed for dcCreator
          dublinNamespace :: AF.Attr
          dublinNamespace =
                ("xmlns:dc",
                 [XT.ContentText "http://purl.org/dc/elements/1.1/"])


-------------
-- GET/PUT --
-------------

getURLBody :: URL -> IO T.Text
getURLBody url = getResponseBody <$> httpBS req >>= \b ->
                 return (TE.decodeLatin1 b)
    where
          req = DS.fromString (T.unpack url)

-- todo non funziona con q dopo ?, usa new-uri (uri-modern? scordato)
feedTitle :: URL -> Title
feedTitle url = case lookup "q" (U.queryToPairs $ T.unpack url) of
                  Nothing -> "Wrong: title not found"
                  Just t  -> "gscholar-rss: " <> T.pack t

-- removes 'ots' and 'sig' from a google books url
cleanGBooks :: URL -> URL
cleanGBooks url
        | condA =
            let
                qry = U.uriQueryItems uri
                fqr = filter filtFun qry
                u'  = uri { U.uriQuery = Just (U.pairsToQuery fqr)}
            in
            T.pack . show $ u'
        | otherwise = url
    where
          uri = maybe (error "misparse in gclean")
                      id
                      (U.parseURI $ T.unpack url)

          condA = case U.uriRegName uri of
                    Nothing -> False -- citation, no uri
                    Just rn -> L.isPrefixOf "books.google" rn

          filtFun :: (String, String) -> Bool
          filtFun (l, _) = notElem l ["ots", "sig"]

printRSS :: URL -> Page -> IO ()
printRSS url s =
    case textRSS . buildRSS (feedTitle url) $ s of
      Nothing -> error "Nothing in printRSS"
      Just ms -> TLI.putStrLn ms

helps :: String
helps = unlines
    ["invoke as: gscholar-rss <search-url>",
     "manual and examples: http://ariis.it/static/articles/gscholar-rss/page.html",
     version ++ " -- GPLv3"]


-- error handling lifted from ansi-terminal-game
-- wraps error call with version/contact info
errorPress :: IO () -> IO ()
errorPress m = E.catch m errorDisplay
    where
          errorDisplay :: E.SomeException -> IO ()
          errorDisplay se =
              putStrLn . unlines $
                  [show se,
                   "gscholar-rss " ++ version,
                   "Can't fix this? Please report to <fa-ml@ariis.it>"]

version :: String
version = 'v' : V.showVersion P.version