module Handler.Hoogle where

import           Control.DeepSeq (NFData(..))
import           Control.DeepSeq.Generics (genericRnf)
import           Control.Spoon (spoon)
import           Data.Data (Data (..))
import           Data.Text.Read (decimal)
import qualified Hoogle
import           Import
import           Text.Blaze.Html (preEscapedToHtml)
import Stackage.Database
import qualified Stackage.Database.Cron as Cron

getHoogleDB :: SnapName -> Handler (Maybe FilePath)
getHoogleDB name = track "Handler.Hoogle.getHoogleDB" $ do
    app <- getYesod
    liftIO $ Cron.getHoogleDB True (appHttpManager app) name

getHoogleR :: SnapName -> Handler Html
getHoogleR name = track "Handler.Hoogle.getHoogleR" $ do
    Entity _ snapshot <- lookupSnapshot name >>= maybe notFound return
    mquery <- lookupGetParam "q"
    mpage <- lookupGetParam "page"
    exact <- maybe False (const True) <$> lookupGetParam "exact"
    mresults' <- lookupGetParam "results"
    let count' =
            case decimal <$> mresults' of
                Just (Right (i, "")) -> min perPage i
                _ -> perPage
        page =
            case decimal <$> mpage of
                Just (Right (i, "")) -> i
                _ -> 1
        offset = (page - 1) * perPage
    mdatabasePath <- getHoogleDB name
    heDatabase <- case mdatabasePath of
        Just x -> return $ liftIO $ Hoogle.loadDatabase x
        Nothing -> hoogleDatabaseNotAvailableFor name

    -- Avoid concurrent Hoogle queries, see
    -- https://github.com/fpco/stackage-server/issues/172
    lock <- appHoogleLock <$> getYesod
    mresults <- case mquery of
        Just query -> withMVar lock $ const $ runHoogleQuery heDatabase HoogleQueryInput
            { hqiQueryInput = query
            , hqiExactSearch = if exact then Just query else Nothing
            , hqiLimitTo = count'
            , hqiOffsetBy = offset
            }
        Nothing -> return $ HoogleQueryOutput "" [] Nothing
    let queryText = fromMaybe "" mquery
        pageLink p = (SnapshotR name HoogleR
            , (if exact then (("exact", "true"):) else id)
            $ (maybe id (\q' -> (("q", q'):)) mquery)
              [("page", tshow p)])
        snapshotLink = SnapshotR name StackageHomeR
        hoogleForm = $(widgetFile "hoogle-form")
    defaultLayout $ do
        setTitle "Hoogle Search"
        $(widgetFile "hoogle")

getHoogleDatabaseR :: SnapName -> Handler Html
getHoogleDatabaseR name = track "Handler.Hoogle.getHoogleDatabaseR" $ do
    mdatabasePath <- getHoogleDB name
    case mdatabasePath of
        Nothing -> hoogleDatabaseNotAvailableFor name
        Just path -> sendFile "application/octet-stream" path

hoogleDatabaseNotAvailableFor :: SnapName -> Handler a
hoogleDatabaseNotAvailableFor name = track "Handler.Hoogle.hoogleDatabaseNotAvailableFor" $ do
    (>>= sendResponse) $ defaultLayout $ do
        setTitle "Hoogle database not available"
        [whamlet|
            <div .container>
                <p>The given Hoogle database is not available.
                <p>
                    <a href=@{SnapshotR name StackageHomeR}>Return to snapshot homepage
        |]

getPageCount :: Int -> Int
getPageCount totalCount = 1 + div totalCount perPage

perPage :: Int
perPage = 10

data HoogleQueryInput = HoogleQueryInput
    { hqiQueryInput  :: Text
    , hqiExactSearch :: Maybe Text
    , hqiLimitTo     :: Int
    , hqiOffsetBy    :: Int
    }
    deriving (Eq, Read, Show, Data, Typeable, Ord, Generic)

data HoogleQueryOutput = HoogleQueryBad Text
                       | HoogleQueryOutput Text [HoogleResult] (Maybe Int) -- ^ Text == HTML version of query, Int == total count
    deriving (Read, Typeable, Data, Show, Eq)

data HoogleResult = HoogleResult
    { hrURL     :: String
    , hrSources :: [(PackageLink, [ModuleLink])]
    , hrTitle   :: String -- ^ HTML
    , hrBody    :: String -- ^ plain text
    }
    deriving (Eq, Read, Show, Data, Typeable, Ord, Generic)

data PackageLink = PackageLink
    { plName :: String
    , plURL  :: String
    }
    deriving (Eq, Read, Show, Data, Typeable, Ord, Generic)

data ModuleLink = ModuleLink
    { mlName :: String
    , mlURL :: String
    }
    deriving (Eq, Read, Show, Data, Typeable, Ord, Generic)

instance NFData HoogleResult where rnf = genericRnf
instance NFData PackageLink where rnf = genericRnf
instance NFData ModuleLink where rnf = genericRnf

runHoogleQuery :: MonadIO m
               => m Hoogle.Database
               -> HoogleQueryInput
               -> m HoogleQueryOutput
runHoogleQuery heDatabase HoogleQueryInput {..} =
    track "Handler.Hoogle.runHoogleQuery" $
    runQuery $ Hoogle.parseQuery Hoogle.Haskell query
  where
    query = unpack hqiQueryInput

    runQuery (Left err) = return $ HoogleQueryBad (tshow err)
    runQuery (Right query') = do
        hoogledb <- heDatabase
        let query'' = Hoogle.queryExact classifier query'
            rawRes  = concatMap fixResult
                    $ Hoogle.search hoogledb query''
            mres    = spoon
                    $ take (min 100 hqiLimitTo)
                    $ drop hqiOffsetBy rawRes
            mcount  = spoon $ limitedLength 0 rawRes
            limitedLength x [] = Just x
            limitedLength x (_:rest)
                | x >= 20 = Nothing
                | otherwise = limitedLength (x + 1) rest
            rendered = pack $ Hoogle.showTagHTML $ Hoogle.renderQuery query''
        return $ case (,) <$> mres <*> mcount of
            Nothing ->
                HoogleQueryOutput rendered [] (Just 0)
            Just (results, mcount') ->
                HoogleQueryOutput rendered (take hqiLimitTo results) mcount'

    classifier = maybe Nothing
        (const (Just Hoogle.UnclassifiedItem))
        hqiExactSearch

    fixResult (_, Hoogle.Result locs self docs) = do
        (loc, _) <- take 1 locs
        let sources' = unionsWith (++) $
                mapMaybe (getPkgModPair . snd) locs
        return HoogleResult
            { hrURL     = loc
            , hrSources = mapToList sources'
            , hrTitle   = Hoogle.showTagHTML self
            , hrBody    = fromMaybe "Problem loading documentation" $
                              spoon $ Hoogle.showTagText docs
            }

    getPkgModPair :: [(String, String)]
                  -> Maybe (Map PackageLink [ModuleLink])
    getPkgModPair [(pkg, pkgname), (modu, moduname)] = do
        let pkg' = PackageLink pkgname pkg
            modu' = ModuleLink moduname modu
        return $ asMap $ singletonMap pkg' [modu']
    getPkgModPair _ = Nothing