{-# LANGUAGE OverloadedStrings #-}

module Hasura.Server.Utils where

import qualified Database.PG.Query.Connection as Q

import           Data.Aeson
import           Data.List.Split
import           Network.URI
import           System.Exit
import           System.Process

import qualified Data.ByteString              as B
import qualified Data.Text                    as T
import qualified Data.Text.Encoding           as TE
import qualified Data.Text.Encoding.Error     as TE
import qualified Data.Text.IO                 as TI
import qualified Language.Haskell.TH.Syntax   as TH
import qualified Text.Ginger                  as TG

import           Hasura.Prelude

isXHasuraTxt :: T.Text -> Bool
isXHasuraTxt = T.isInfixOf "x-hasura-" . T.toLower

jsonHeader :: (T.Text, T.Text)
jsonHeader = ("Content-Type", "application/json; charset=utf-8")

userRoleHeader :: T.Text
userRoleHeader = "x-hasura-role"

accessKeyHeader :: T.Text
accessKeyHeader = "x-hasura-access-key"

userIdHeader :: T.Text
userIdHeader = "x-hasura-user-id"

bsToTxt :: B.ByteString -> T.Text
bsToTxt = TE.decodeUtf8With TE.lenientDecode

-- Parsing postgres database url
-- from: https://github.com/futurice/postgresql-simple-url/
parseDatabaseUrl :: String -> Maybe String -> Maybe Q.ConnInfo
parseDatabaseUrl databaseUrl opts = parseURI databaseUrl >>= uriToConnectInfo opts

uriToConnectInfo :: Maybe String -> URI -> Maybe Q.ConnInfo
uriToConnectInfo opts uri
  | uriScheme uri /= "postgres:" && uriScheme uri /= "postgresql:" = Nothing
  | otherwise = ($ Q.defaultConnInfo {Q.connOptions = opts}) <$> mkConnectInfo uri

type ConnectInfoChange = Q.ConnInfo -> Q.ConnInfo

mkConnectInfo :: URI -> Maybe ConnectInfoChange
mkConnectInfo uri = case uriPath uri of
                           ('/' : rest) | not (null rest) -> Just $ uriParameters uri
                           _                              -> Nothing

uriParameters :: URI -> ConnectInfoChange
uriParameters uri = (\info -> info { Q.connDatabase = tail $ uriPath uri }) . maybe id uriAuthParameters (uriAuthority uri)

dropLast :: [a] -> [a]
dropLast []     = []
dropLast [_]    = []
dropLast (x:xs) = x : dropLast xs

uriAuthParameters :: URIAuth -> ConnectInfoChange
uriAuthParameters uriAuth = port . host . auth
  where port = case uriPort uriAuth of
                 (':' : p) -> \info -> info { Q.connPort = read p }
                 _         -> id
        host = case uriRegName uriAuth of
                 h  -> \info -> info { Q.connHost = unEscapeString h }
        auth = case splitOn ":" (uriUserInfo uriAuth) of
                 [""]   -> id
                 [u]    -> \info -> info { Q.connUser = unEscapeString $ dropLast u }
                 [u, p] -> \info -> info { Q.connUser = unEscapeString u, Q.connPassword = unEscapeString $ dropLast p }
                 _      -> id

-- Running shell script during compile time
runScript :: FilePath -> TH.Q TH.Exp
runScript fp = do
  TH.addDependentFile fp
  fileContent <- TH.runIO $ TI.readFile fp
  (exitCode, stdOut, stdErr) <- TH.runIO $
    readProcessWithExitCode "/bin/sh" [] $ T.unpack fileContent
  when (exitCode /= ExitSuccess) $ fail $
    "Running shell script " ++ fp ++ " failed with exit code : "
    ++ show exitCode ++ " and with error : " ++ stdErr
  TH.lift stdOut

-- Ginger Templating
type GingerTmplt = TG.Template TG.SourcePos

parseGingerTmplt :: TG.Source -> Either String GingerTmplt
parseGingerTmplt src = either parseE Right res
  where
    res = runIdentity $ TG.parseGinger' parserOptions src
    parserOptions = TG.mkParserOptions resolver
    resolver = const $ return Nothing
    parseE e = Left $ TG.formatParserError (Just "") e

renderGingerTmplt :: (ToJSON a) => a -> GingerTmplt -> T.Text
renderGingerTmplt v = TG.easyRender (toJSON v)

-- find duplicates
duplicates :: Ord a => [a] -> [a]
duplicates = mapMaybe greaterThanOne . group . sort
  where
    greaterThanOne l = bool Nothing (Just $ head l) $ length l > 1