{-# LANGUAGE DataKinds #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE TypeOperators #-}

----------------------------------------------------------------------
-- |
-- Module: Web.Slack
-- Description: Provides Slack's Web API functions.
-- *Since 0.4.0.0*: The API functions is now more intuitive for newbies
-- than before. If you need compatiblity with the previous version, use
-- 'Web.Slack.Classy' instead.
--
----------------------------------------------------------------------

module Web.Slack
  ( SlackConfig(..)
  , mkSlackConfig
  , apiTest
  , authTest
  , chatPostMessage
  , conversationsList
  , conversationsHistory
  , conversationsHistoryAll
  , conversationsReplies
  , repliesFetchAll
  , getUserDesc
  , usersList
  , userLookupByEmail
  , authenticateReq
  , Response
  , LoadPage
  )
  where

-- aeson
import Data.Aeson

-- base
import Control.Arrow ((&&&))
import Data.Maybe
import Data.Proxy (Proxy(..))

-- containers
import qualified Data.Map as Map

-- http-client
import Network.HTTP.Client (Manager, newManager)

-- http-client-tls
import Network.HTTP.Client.TLS (tlsManagerSettings)

-- mtl
import Control.Monad.Reader

-- servant
import Servant.API hiding (addHeader)

-- servant-client
import Servant.Client hiding (Response, baseUrl)

#if MIN_VERSION_servant(0,16,0)
import Servant.Client.Core (AuthClientData, AuthenticatedRequest, Request, mkAuthenticatedRequest, addHeader)
#else
import Servant.Client.Core.Internal.Auth
import Servant.Client.Core (Request, addHeader)
#endif

-- slack-web
import qualified Web.Slack.Api as Api
import qualified Web.Slack.Auth as Auth
import qualified Web.Slack.Conversation as Conversation
import qualified Web.Slack.Chat as Chat
import qualified Web.Slack.Common as Common
import qualified Web.Slack.User as User
import           Web.Slack.Pager

-- text
import Data.Text (Text)

#if !MIN_VERSION_servant(0,13,0)
mkClientEnv :: Manager -> BaseUrl -> ClientEnv
mkClientEnv = ClientEnv
#endif


data SlackConfig
  = SlackConfig
  { slackConfigManager :: Manager
  , slackConfigToken :: Text
  }


-- contains errors that can be returned by the slack API.
-- constrast with 'SlackClientError' which additionally
-- contains errors which occured during the network communication.
data ResponseSlackError = ResponseSlackError Text
  deriving (Eq, Show)


-- |
-- Internal type!
--
newtype ResponseJSON a = ResponseJSON (Either ResponseSlackError a)

instance FromJSON a => FromJSON (ResponseJSON a) where
    parseJSON = withObject "Response" $ \o -> do
        ok <- o .: "ok"
        ResponseJSON <$> if ok
           then Right <$> parseJSON (Object o)
           else Left . ResponseSlackError <$> o .: "error"


-- |
--
--
type Api =
    "api.test"
      :> ReqBody '[FormUrlEncoded] Api.TestReq
      :> Post '[JSON] (ResponseJSON Api.TestRsp)
  :<|>
    "auth.test"
      :> AuthProtect "token"
      :> Post '[JSON] (ResponseJSON Auth.TestRsp)
  :<|>
    "conversations.list"
      :> AuthProtect "token"
      :> ReqBody '[FormUrlEncoded] Conversation.ListReq
      :> Post '[JSON] (ResponseJSON Conversation.ListRsp)
  :<|>
    "conversations.history"
      :> AuthProtect "token"
      :> ReqBody '[FormUrlEncoded] Conversation.HistoryReq
      :> Post '[JSON] (ResponseJSON Conversation.HistoryRsp)
  :<|>
    "conversations.replies"
      :> AuthProtect "token"
      :> ReqBody '[FormUrlEncoded] Conversation.RepliesReq
      :> Post '[JSON] (ResponseJSON Conversation.HistoryRsp)
  :<|>
    "chat.postMessage"
      :> AuthProtect "token"
      :> ReqBody '[FormUrlEncoded] Chat.PostMsgReq
      :> Post '[JSON] (ResponseJSON Chat.PostMsgRsp)
  :<|>
    "users.list"
      :> AuthProtect "token"
      :> Post '[JSON] (ResponseJSON User.ListRsp)
  :<|>
    "users.lookupByEmail"
      :> AuthProtect "token"
      :> ReqBody '[FormUrlEncoded] User.Email
      :> Post '[JSON] (ResponseJSON User.UserRsp)


-- |
--
-- Check API calling code.
--
-- <https://api.slack.com/methods/api.test>

apiTest
  :: Manager
  -> Api.TestReq
  -> IO (Response Api.TestRsp)
apiTest mgr req = run (apiTest_ req) mgr

apiTest_
  :: Api.TestReq
  -> ClientM (ResponseJSON Api.TestRsp)


-- |
--
-- Check authentication and identity.
--
-- <https://api.slack.com/methods/auth.test>

authTest
  :: SlackConfig
  -> IO (Response Auth.TestRsp)
authTest = do
  authR <- mkSlackAuthenticateReq
  run (authTest_ authR) . slackConfigManager

authTest_
  :: AuthenticatedRequest (AuthProtect "token")
  -> ClientM (ResponseJSON Auth.TestRsp)

-- |
--
-- Retrieve conversations list.
--
-- <https://api.slack.com/methods/conversations.list>

conversationsList
  :: SlackConfig
  -> Conversation.ListReq
  -> IO (Response Conversation.ListRsp)
conversationsList = flip $ \listReq -> do
  authR <- mkSlackAuthenticateReq
  run (conversationsList_ authR listReq) . slackConfigManager

conversationsList_
  :: AuthenticatedRequest (AuthProtect "token")
  -> Conversation.ListReq
  -> ClientM (ResponseJSON Conversation.ListRsp)


-- |
--
-- Retrieve ceonversation history.
-- Consider using 'historyFetchAll' in combination with this function.
--
-- <https://api.slack.com/methods/conversations.history>

conversationsHistory
  :: SlackConfig
  -> Conversation.HistoryReq
  -> IO (Response Conversation.HistoryRsp)
conversationsHistory = flip $ \histReq -> do
  authR <- mkSlackAuthenticateReq
  run (conversationsHistory_ authR histReq) . slackConfigManager

conversationsHistory_
  :: AuthenticatedRequest (AuthProtect "token")
  -> Conversation.HistoryReq
  -> ClientM (ResponseJSON Conversation.HistoryRsp)


-- |
--
-- Retrieve replies of a conversation.
-- Consider using 'repliesFetchAll' if you want to get entire replies
-- of a conversation.
--
-- <https://api.slack.com/methods/conversations.replies>

conversationsReplies
  :: SlackConfig
  -> Conversation.RepliesReq
  -> IO (Response Conversation.HistoryRsp)
conversationsReplies = flip $ \repliesReq -> do
  authR <- mkSlackAuthenticateReq
  run (conversationsReplies_ authR repliesReq) . slackConfigManager

conversationsReplies_
  :: AuthenticatedRequest (AuthProtect "token")
  -> Conversation.RepliesReq
  -> ClientM (ResponseJSON Conversation.HistoryRsp)


-- |
--
-- Send a message to a channel.
--
-- <https://api.slack.com/methods/chat.postMessage>

chatPostMessage
  :: SlackConfig
  -> Chat.PostMsgReq
  -> IO (Response Chat.PostMsgRsp)
chatPostMessage = flip $ \postReq -> do
  authR <- mkSlackAuthenticateReq
  run (chatPostMessage_ authR postReq) . slackConfigManager

chatPostMessage_
  :: AuthenticatedRequest (AuthProtect "token")
  -> Chat.PostMsgReq
  -> ClientM (ResponseJSON Chat.PostMsgRsp)


-- |
--
-- This method returns a list of all users in the team.
-- This includes deleted/deactivated users.
--
-- <https://api.slack.com/methods/users.list>

usersList
  :: SlackConfig
  -> IO (Response User.ListRsp)
usersList = do
  authR <- mkSlackAuthenticateReq
  run (usersList_ authR) . slackConfigManager

usersList_
  :: AuthenticatedRequest (AuthProtect "token")
  -> ClientM (ResponseJSON User.ListRsp)

-- |
--
-- This method returns a list of all users in the team.
-- This includes deleted/deactivated users.
--
-- <https://api.slack.com/methods/users.lookupByEmail>

userLookupByEmail
  :: SlackConfig
  -> User.Email
  -> IO (Response User.UserRsp)
userLookupByEmail = flip $ \email -> do
  authR <- mkSlackAuthenticateReq
  run (userLookupByEmail_ authR email) . slackConfigManager

userLookupByEmail_
  :: AuthenticatedRequest (AuthProtect "token")
  -> User.Email
  -> ClientM (ResponseJSON User.UserRsp)


-- | Returns a function to get a username from a 'Common.UserId'.
-- Comes in handy to use 'Web.Slack.MessageParser.messageToHtml'
getUserDesc
  :: (Common.UserId -> Text)
  -- ^ A function to give a default username in case the username is unknown
  -> User.ListRsp
  -- ^ List of users as known by the slack server. See 'usersList'.
  -> (Common.UserId -> Text)
  -- ^ A function from 'Common.UserId' to username.
getUserDesc unknownUserFn users =
  let userMap = Map.fromList $ (User.userId &&& User.userName) <$> User.listRspMembers users
  in
    \userId -> fromMaybe (unknownUserFn userId) $ Map.lookup userId userMap


-- | Returns an action to send a request to get the history of a conversation.
--
--   To fetch all messages in the conversation, run the returned 'LoadPage' action
--   repeatedly until it returns an empty list.
conversationsHistoryAll
  :: SlackConfig
  -> Conversation.HistoryReq
  -- ^ The first request to send. _NOTE_: 'Conversation.historyReqCursor' is silently ignored.
  -> IO (LoadPage IO Common.Message)
  -- ^ An action which returns a new page of messages every time called.
  --   If there are no pages anymore, it returns an empty list.
conversationsHistoryAll = conversationsHistoryAllBy . conversationsHistory


-- | Returns an action to send a request to get the replies of a conversation.
--
--   To fetch all replies in the conversation, run the returned 'LoadPage' action
--   repeatedly until it returns an empty list.
--
--   *NOTE*: The conversations.replies endpoint always returns the first message
--           of the thread. So every page returned by the 'LoadPage' action includes
--           the first message of the thread. You should drop it if you want to
--           collect messages in a thread without duplicates.
repliesFetchAll
  :: SlackConfig
  ->  Conversation.RepliesReq
  -- ^ The first request to send. _NOTE_: 'Conversation.repliesReqCursor' is silently ignored.
  -> IO (LoadPage IO Common.Message)
  -- ^ An action which returns a new page of messages every time called.
  --   If there are no pages anymore, it returns an empty list.
repliesFetchAll = repliesFetchAllBy . conversationsReplies


apiTest_
  :<|> authTest_
  :<|> conversationsList_
  :<|> conversationsHistory_
  :<|> conversationsReplies_
  :<|> chatPostMessage_
  :<|> usersList_
  :<|> userLookupByEmail_
  =
  client (Proxy :: Proxy Api)


-- |
--
--

type instance AuthClientData (AuthProtect "token") =
  Text


-- |
--
--
authenticateReq
  :: Text
  -> Request
  -> Request
authenticateReq token =
  addHeader "Authorization" $ "Bearer " <> token


-- |
--
--

run
  :: ClientM (ResponseJSON a)
  -> Manager
  -> IO (Response a)
run clientAction mgr = do
  let baseUrl = BaseUrl Https "slack.com" 443 "/api"
  unnestErrors <$> liftIO (runClientM clientAction $ mkClientEnv mgr baseUrl)


mkSlackAuthenticateReq :: SlackConfig -> AuthenticatedRequest (AuthProtect "token")
mkSlackAuthenticateReq = (`mkAuthenticatedRequest` authenticateReq) . slackConfigToken


unnestErrors :: Either ClientError (ResponseJSON a) -> Response a
unnestErrors (Right (ResponseJSON (Right a))) = Right a
unnestErrors (Right (ResponseJSON (Left (ResponseSlackError serv))))
    = Left (Common.SlackError serv)
unnestErrors (Left slackErr) = Left (Common.ServantError slackErr)


-- | Prepare a SlackConfig from a slack token.
-- You can then call the other functions providing this in a reader context.
--
mkSlackConfig :: Text -> IO SlackConfig
mkSlackConfig token = SlackConfig <$> newManager tlsManagerSettings <*> pure token