{-# LANGUAGE BangPatterns               #-}
{-# LANGUAGE DataKinds                  #-}
{-# LANGUAGE DeriveAnyClass             #-}
{-# LANGUAGE DeriveGeneric              #-}
{-# LANGUAGE DerivingStrategies         #-}
{-# LANGUAGE ExistentialQuantification  #-}
{-# LANGUAGE ExplicitForAll             #-}
{-# LANGUAGE FlexibleContexts           #-}
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE LambdaCase                 #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE RecordWildCards            #-}
{-# LANGUAGE ScopedTypeVariables        #-}
{-# LANGUAGE StandaloneDeriving         #-}
{-# LANGUAGE TemplateHaskell            #-}
{-# LANGUAGE TupleSections              #-}
{-# LANGUAGE TypeApplications           #-}
{-# LANGUAGE TypeFamilies               #-}
{-# LANGUAGE TypeOperators              #-}
{-# LANGUAGE UndecidableInstances       #-}

module Server ( loadConfig
              , Org(..)
              , Sha1
              , Config, tmpdir, port, verbose, orgs, interval, exneuland, token
              , RemoteRef(..)
              , ServerState, emptyState, unState
              , JobStatus(..)
              , setJobStatus
              , prettySha,getJobStatus,adjustedPath) where

import           Universum

import           CheckDir                   (DirResult)
import           CheckMap                   (ResultKind (Shrunk))
import           Control.Arrow              ((>>>))
import           Control.Concurrent         (modifyMVar_, withMVar)
import           Crypto.Hash.SHA1           (hash)
import           Data.Aeson                 (FromJSON, ToJSON, ToJSONKey (..),
                                             eitherDecodeFileStrict')
import qualified Data.Aeson                 as A
import qualified Data.ByteString.Base64.URL as Base64
import           Data.Coerce                (coerce)
import           Data.Either.Extra          (mapLeft)
import           Data.Functor.Contravariant (contramap)
import qualified Data.Map.Strict            as M
import           Lens.Micro.Platform        (at, ix, makeLenses, traverseOf)
import           LintConfig                 (LintConfig')
import           Servant                    (FromHttpApiData)
import           Servant.Client             (BaseUrl, parseBaseUrl)
import qualified Text.Show                  as TS
import           Toml                       (BiMap (BiMap), TomlBiMap,
                                             TomlBiMapError (ArbitraryError),
                                             TomlCodec, prettyTomlDecodeErrors,
                                             (.=))
import qualified Toml                       as T

-- | a reference in a remote git repository
data RemoteRef = RemoteRef
  { repourl  :: Text
  , reporef  :: Text
  , reponame :: Text
  -- ^ the "world name" for the hub / world:// links
  } deriving (Generic, FromJSON, ToJSON, Eq, Ord, Show, NFData)

type family ConfigRes (b :: Bool) a where
  ConfigRes True a = a
  ConfigRes False a = FilePath

-- | the internal text is actually already base64-encoded
newtype Sha1 = Sha1 Text
  deriving newtype (Eq, Show, Ord, FromHttpApiData, ToJSON, NFData)

-- | base64-encoded sha1
prettySha :: Sha1 -> Text
prettySha (Sha1 text) = text

instance ToJSONKey Sha1

toSha :: RemoteRef -> Sha1
toSha ref = Sha1
  . decodeUtf8
  . Base64.encode
  . hash
  . encodeUtf8
  $ (show ref :: Text)

data Org (loaded :: Bool) = Org
  { orgSlug       :: Text
  , orgLintconfig :: ConfigRes loaded LintConfig'
  , orgEntrypoint :: FilePath
  , orgGeneration :: Int
  , orgRepos      :: [RemoteRef]
  , orgUrl        :: Text
  , orgWebdir     :: Text
  } deriving (Generic)

instance NFData LintConfig' => NFData (Org True)

-- | Orgs are compared via their slugs only
-- TODO: the server should probably refuse to start if two orgs have the
-- same slug … (or really the toml format shouldn't allow that syntactically)
instance Eq (Org True) where
  a == b = orgSlug a == orgSlug b

instance Ord (Org True) where
  a <= b = orgSlug a <= orgSlug b

-- this instance exists since it's required for ToJSONKey,
-- but it shouldn't really be used
instance ToJSON (Org True) where
  toJSON Org { .. } = A.object [ "slug" A..= orgSlug ]

-- orgs used as keys just reduce to their slug
instance ToJSONKey (Org True) where
  toJSONKey = contramap orgSlug (toJSONKey @Text)

-- | the server's configuration
data Config (loaded :: Bool) = Config
  { _tmpdir    :: FilePath
  -- ^ dir to clone git things in
  , _port      :: Int
  , _verbose   :: Bool
  , _interval  :: Int
  -- ^ port to bind to
  , _exneuland :: Maybe BaseUrl
  , _token     :: Maybe Text
  , _orgs      :: [Org loaded]
  } deriving Generic

makeLenses ''Config


remoteCodec :: TomlCodec RemoteRef
remoteCodec = RemoteRef
  <$> T.text "url" .= repourl
  <*> T.text "ref" .= reporef
  <*> T.text "name" .= reponame

orgCodec :: TomlCodec (Org False)
orgCodec = Org
  <$> T.text "slug" .= orgSlug
  <*> T.string "lintconfig" .= orgLintconfig
  <*> T.string "entrypoint" .= orgEntrypoint
  <*> T.int "generation" .= orgGeneration
  <*> T.list remoteCodec "repo" .= orgRepos
  <*> T.text "url" .= orgUrl
  <*> T.text "webdir" .= orgWebdir

-- why exactly does everything in tomland need to be invertable
urlBimap :: TomlBiMap BaseUrl String
urlBimap = BiMap
  (Right . show)
  (mapLeft (ArbitraryError . show) . parseBaseUrl)

configCodec :: TomlCodec (Config False)
configCodec = Config
    <$> T.string "tmpdir" .= _tmpdir
    <*> T.int "port" .= _port
    <*> T.bool "verbose" .= _verbose
    <*> T.int "interval" .= _interval
    <*> coerce (T.first (T.match (urlBimap >>> T._String)) "exneuland") .= _exneuland
    -- First is just Maybe but with different semantics
    <*> coerce (T.first T.text "token") .= _token
    <*> T.list orgCodec "org" .= _orgs

-- | a job status (of a specific uuid)
data JobStatus =
  Pending | Linted !(DirResult Shrunk) Text | Failed Text
  deriving (Generic, ToJSON, NFData)

instance TS.Show JobStatus where
  show = \case
    Pending        -> "Pending"
    Linted res rev -> "Linted result"
    Failed err     -> "Failed with: " <> show err

-- | the server's global state; might eventually end up with more
-- stuff in here, hence the newtype
newtype ServerState = ServerState
  { _unState :: Map (Org True) (Map Sha1 (RemoteRef, JobStatus)) }
  deriving Generic

instance NFData LintConfig' => NFData ServerState

makeLenses ''ServerState

-- | the inital state must already contain empty orgs, since setJobStatus
-- will default to a noop otherwise
emptyState :: Config True -> ServerState
emptyState config = ServerState
  $ M.fromList $ map (, mempty) (view orgs config)

-- | loads a config, along with all things linked in it
-- (e.g. linterconfigs for each org)
loadConfig :: FilePath -> IO (Config True)
loadConfig path = do
  res <- T.decodeFileEither configCodec path
  case res of
    Right config -> traverseOf orgs (mapM loadOrg) config
    Left err     -> error $ prettyTomlDecodeErrors err
    where
      loadOrg :: Org False -> IO (Org True)
      loadOrg org = do
        lintconfig <- eitherDecodeFileStrict' (orgLintconfig org) >>= \case
          Right c  -> pure c
          Left err -> error $ show err
        pure $ org { orgLintconfig = lintconfig }


-- | NOTE: this does not create the org if it does not yet exist!
setJobStatus :: MVar ServerState -> Org True -> RemoteRef -> JobStatus -> IO ()
setJobStatus mvar !org !ref !status = do
  modifyMVar_ mvar $ \state -> do
    -- will otherwise cause a thunk leak, since Data.Map is annoyingly un-strict
    -- even in its strict variety. for some reason it also doesn't work when
    -- moved inside the `over` though …
    _ <- evaluateNF (view (unState . ix org) state)
    pure $ over (unState . ix org . at (toSha ref))
                (const $ Just (ref, status)) state

getJobStatus :: MVar ServerState -> Text -> Sha1 -> IO (Maybe (RemoteRef, JobStatus))
getJobStatus mvar orgslug sha = withMVar mvar $ \state ->
  pure (M.lookup sha (view (unState . ix (Org { orgSlug = orgslug })) state))

-- | the path (relative to a baseurl / webdir) where an adjusted
-- map should go
adjustedPath :: Text -> Org True -> Text -- TODO: filepath library using Text?
adjustedPath rev Org {..} =
  orgWebdir <> "/" <> (rev <> show orgGeneration)