{-# LANGUAGE CPP                    #-}
{-# LANGUAGE ConstraintKinds        #-}
{-# LANGUAGE FlexibleContexts       #-}
{-# LANGUAGE FlexibleInstances      #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE OverloadedStrings      #-}
{-# LANGUAGE RecordWildCards        #-}
{-# LANGUAGE TemplateHaskell        #-}
{-# LANGUAGE TypeFamilies           #-}
{-# LANGUAGE UndecidableInstances   #-}

-- |
-- Module      :  Network.JsonRpc.TinyClient
-- Copyright   :  Aleksandr Krupenkin 2016-2018
-- License     :  Apache-2.0
--
-- Maintainer  :  mail@akru.me
-- Stability   :  experimental
-- Portability :  portable
--
-- Tiny JSON-RPC 2.0 client.
-- Functions for implementing the client side of JSON-RPC 2.0.
-- See <http://www.jsonrpc.org/specification>.
--
-- If you have monad with 'MonadIO', 'MonadThrow' and 'MonadReader' instances,
-- it can be used as base for JSON-RPC calls.
--
-- Example:
--
-- @
--   newtype MyMonad a = ...
--
--   instance JsonRpc MyMonad
--
--   foo :: Mymonad Text
--   foo = remote "foo"
-- @
--
-- Arguments of function are stored into @params@ request array.
--
-- Example:
--
-- @
--   myMethod :: JsonRpc m => Int -> Bool -> m String
--   myMethod = remote "myMethod"
-- @
--

module Network.JsonRpc.TinyClient
    (
    -- * The JSON-RPC remote call monad
      JsonRpc(..)
    , MethodName

    -- * JSON-RPC client settings
    , JsonRpcClient(..)
    , defaultSettings

    -- * Error handling
    , JsonRpcException(..)
    , RpcError(..)
    ) where

import           Control.Applicative     ((<|>))
import           Control.Exception       (Exception)
import           Control.Monad           ((<=<))
import           Control.Monad.Catch     (MonadThrow (..))
import           Control.Monad.IO.Class  (MonadIO (..))
import           Control.Monad.State     (MonadState, get)
import           Data.Aeson              (FromJSON (..), ToJSON (..),
                                          Value (String), eitherDecode, encode,
                                          object, withObject, (.:), (.:?), (.=))
import           Data.ByteString.Lazy    (ByteString)
import           Data.Text               (Text, unpack)
import           Network.HTTP.Client     (Manager, RequestBody (RequestBodyLBS),
                                          httpLbs, method, newManager,
                                          parseRequest, requestBody,
                                          requestHeaders, responseBody)
import           Network.HTTP.Client.TLS (tlsManagerSettings)
import qualified Network.WebSockets      as WS (Connection, receiveData,
                                                sendTextData)
import           System.Random           (randomRIO)

-- | JSON-RPC monad constrait.
type JsonRpcM m = (MonadIO m, MonadThrow m, MonadState JsonRpcClient m)

-- | JSON-RPC client state vars.
data JsonRpcClient = JsonRpcHttpClient
    { jsonRpcManager :: Manager
    -- ^ HTTP connection manager.
    , jsonRpcServer  :: String
    -- ^ Remote server URI.
    }
    | JsonRpcWsClient
    { jsonRpcWsConnection :: WS.Connection
    -- ^ WebSocket connection.
    }

-- | Create default 'JsonRpcClient' settings.
defaultSettings :: MonadIO m
                => String           -- ^ JSON-RPC server URI
                -> m JsonRpcClient
defaultSettings srv = liftIO $ JsonRpcHttpClient
  <$> newManager tlsManagerSettings
  <*> pure srv

instance Show JsonRpcClient where
    show JsonRpcHttpClient{..} = "<JSON-RPC HTTP Client>"
    show JsonRpcWsClient{..} = "<JSON-RPC WebSocket Client>"

-- | JSON-RPC request.
data Request = Request
    { rqMethod :: !Text
    , rqId     :: !Int
    , rqParams :: !Value
    }
    deriving (Eq, Show)

instance ToJSON Request where
    toJSON rq = object [ "jsonrpc" .= String "2.0"
                       , "method"  .= rqMethod rq
                       , "params"  .= rqParams rq
                       , "id"      .= rqId rq
                       ]

-- | JSON-RPC response.
data Response = Response
    { rsResult :: !(Either RpcError Value)
    }
    deriving (Eq, Show)

instance FromJSON Response where
    parseJSON =
        withObject "JSON-RPC response object" $
            \v -> Response <$>
                (Right <$> v .: "result" <|> Left <$> v .: "error")

-- | JSON-RPC error message
data RpcError = RpcError
    { errCode    :: !Int
    , errMessage :: !Text
    , errData    :: !(Maybe Value)
    }
    deriving Eq

instance Show RpcError where
    show (RpcError code msg dat) =
        "JSON-RPC error " ++ show code ++ ": " ++ unpack msg
         ++ ". Data: " ++ show dat

instance FromJSON RpcError where
    parseJSON = withObject "JSON-RPC error object" $
        \v -> RpcError <$> v .: "code"
                       <*> v .: "message"
                       <*> v .:? "data"

data JsonRpcException = ParsingException String
    | CallException RpcError
    deriving (Show, Eq)

instance Exception JsonRpcException

class JsonRpcM m => Remote m a | a -> m where
    remote' :: ([Value] -> m ByteString) -> a

instance (ToJSON a, Remote m b) => Remote m (a -> b) where
    remote' f x = remote' (\xs -> f (toJSON x : xs))

instance {-# INCOHERENT #-} (JsonRpcM m, FromJSON b) => Remote m (m b) where
    remote' f = decodeResponse =<< f []

-- | Name of called method.
type MethodName = Text

-- | JSON-RPC call monad.
class JsonRpcM m => JsonRpc m where
    -- | Remote call of JSON-RPC method.
    remote :: Remote m a => MethodName -> a
    {-# INLINE remote #-}
    remote = remote' . call

call :: JsonRpcM m
     => MethodName
     -> [Value]
     -> m ByteString
call m r = do
  rid <- liftIO $ randomRIO (0, maxInt)
  connection . encode $ Request m (fromInteger rid) (toJSON r)
  where
    maxInt = toInteger (maxBound :: Int)
    connection body = do
        jsonRpcInstance <- get
        case jsonRpcInstance of
            JsonRpcHttpClient{..} -> do
                request <- parseRequest jsonRpcServer
                let request' = request {
                      requestBody = RequestBodyLBS body
                    , requestHeaders = [("Content-Type", "application/json")]
                    , method = "POST"
                    }
                responseBody <$> liftIO (httpLbs request' jsonRpcManager)

            JsonRpcWsClient{..} -> liftIO $ do
                WS.sendTextData jsonRpcWsConnection body
                WS.receiveData jsonRpcWsConnection



decodeResponse :: (MonadThrow m, FromJSON a)
               => ByteString
               -> m a
decodeResponse = (tryParse . eitherDecode . encode)
               <=< tryResult . rsResult
               <=< tryParse . eitherDecode
  where
    tryParse = either (throwM . ParsingException) return
    tryResult = either (throwM . CallException) return