{-# LANGUAGE TypeSynonymInstances, FlexibleInstances #-}
{-# LANGUAGE OverloadedStrings, RecordWildCards #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}

module JSON where

import Control.Applicative ((<$>), (<*>))
import Control.Arrow (first)
import Control.Monad (mzero)
import Data.Aeson
import Data.Aeson.Types
import Data.ByteString (ByteString)
import qualified Data.ByteString as BS
import qualified Data.ByteString.Char8 as B8
import Data.HashMap.Strict (union)
import Data.Maybe (fromJust)
import Data.Text (Text)
import qualified Data.Text as T

import Network.HTTP2

----------------------------------------------------------------

byteStringToText :: ByteString -> Text
byteStringToText = T.pack . B8.unpack

textToByteString :: Text -> ByteString
textToByteString = B8.pack . T.unpack

(+++) :: Value -> Value -> Value
Object x +++ Object y = Object $ x `union` y
Null     +++ x        = x
x        +++ Null     = x
_        +++ _        = error "+++"

----------------------------------------------------------------

data FramePad = FramePad {
    fpFrame :: Frame
  , fpPad :: Maybe Pad
  } deriving (Show, Read)

data Pad = Pad Padding deriving (Show, Read)

unPad :: Pad -> Padding
unPad (Pad x) = x

----------------------------------------------------------------

data Case = Case {
    draft :: Int
  , description :: String
  , wire :: ByteString
  , frame :: Maybe FramePad
  , err :: Maybe [ErrorCode]
  } deriving (Show, Read)

----------------------------------------------------------------

instance ToJSON StreamIdentifier where
    toJSON (StreamIdentifier s) = toJSON s

instance FromJSON StreamIdentifier where
    parseJSON x = StreamIdentifier <$> parseJSON x

instance ToJSON Priority where
    toJSON (Priority e s w) = object [
        "exclusive" .= e
      , "stream_dependency" .= s
      , "weight" .= w
      ]

instance FromJSON Priority where
    parseJSON (Object o) = Priority <$> o .: "exclusive"
                                    <*> o .: "stream_dependency"
                                    <*> o .: "weight"
    parseJSON _          = mzero

instance ToJSON ErrorCodeId where
    toJSON e = toJSON $ fromErrorCodeId e

instance FromJSON ErrorCodeId where
    parseJSON e = toErrorCodeId <$> parseJSON e

instance ToJSON SettingsList where
    toJSON settings = toJSON $ map (first fromSettingsKeyId) settings

instance FromJSON SettingsList where
    parseJSON x = map (first (fromJust . toSettingsKeyId)) <$> parseJSON x

instance ToJSON ByteString where
    toJSON bs = toJSON $ byteStringToText bs

instance FromJSON ByteString where
    parseJSON x = textToByteString <$> parseJSON x

----------------------------------------------------------------

instance ToJSON FramePayload where
    toJSON (DataFrame body) = object [
        "data" .= body
      ]
    toJSON (HeadersFrame mpri hdr) = object [
        "priority" .= mpri
      , "header_block_fragment" .= hdr
      ]
    toJSON (PriorityFrame pri) = object [
        "priority" .= pri
      ]
    toJSON (RSTStreamFrame e) = object [
        "error_code" .= e
      ]
    toJSON (SettingsFrame settings) = object [
        "settings" .= settings
      ]
    toJSON (PushPromiseFrame sid hdr) = object [
        "promised_stream_id" .= sid
      , "header_block_fragment" .= hdr
      ]
    toJSON (PingFrame odata) = object [
        "opaque_data" .= odata
      ]
    toJSON (GoAwayFrame sid e debug) = object [
        "last_stream_id" .= sid
      , "error_code" .= e
      , "additional_debug_data" .= debug
      ]
    toJSON (WindowUpdateFrame size) = object [
        "window_size_increment" .= size
      ]
    toJSON (ContinuationFrame hdr) = object [
        "header_block_fragment" .= hdr
      ]
    toJSON (UnknownFrame _ opaque) = object [
        "payload" .= opaque
      ]

----------------------------------------------------------------

instance ToJSON FramePad where
    toJSON FramePad{fpFrame = Frame{..},..} = object [
        "length" .= payloadLength frameHeader
      , "type" .= framePayloadToFrameType framePayload
      , "flags" .= flags frameHeader
      , "stream_identifier" .= fromStreamIdentifier (streamId frameHeader)
      , "frame_payload" .= (toJSON framePayload +++ padObj)
      ]
      where
        padObj = case toJSON fpPad of
            Null -> emptyPad
            x    -> x

instance FromJSON FramePad where
    parseJSON (Object o) = do
        len <- o .: "length"
        typ <- o .: "type"
        flg <- o .: "flags"
        sid <- o .: "stream_identifier"
        pld <- o .: "frame_payload"
        (payload,mpad) <- parsePayloadPad typ pld
        return FramePad {
            fpFrame = Frame {
                 frameHeader = FrameHeader len flg sid
               , framePayload = payload
               }
          , fpPad = mpad
          }
    parseJSON _ = mzero

parsePayloadPad :: FrameType -> Object -> Parser (FramePayload, Maybe Pad)
parsePayloadPad ftyp o = do
    mpad <- (Pad <$>) <$> o .:? "padding"
    payload <- parsePayload ftid o
    return (payload, mpad)
  where
    ftid = fromJust $ toFrameTypeId ftyp

parsePayload :: FrameTypeId -> Object -> Parser FramePayload
parsePayload FrameData o = DataFrame <$> o .: "data"
parsePayload FrameHeaders o = HeadersFrame <$> o .: "priority"
                                           <*> o .: "header_block_fragment"
parsePayload FramePriority o = PriorityFrame <$> o .: "priority"
parsePayload FrameRSTStream o = RSTStreamFrame <$> o .: "error_code"
parsePayload FrameSettings o = SettingsFrame <$> o .: "settings"
parsePayload FramePushPromise o = PushPromiseFrame <$> o .: "promised_stream_id"
                                                   <*> o .: "header_block_fragment"
parsePayload FramePing o = PingFrame <$> o .: "opaque_data"
parsePayload FrameGoAway o = GoAwayFrame <$> o .: "last_stream_id"
                                         <*> o .: "error_code"
                                         <*> o .: "additional_debug_data"
parsePayload FrameWindowUpdate o = WindowUpdateFrame <$> o .: "window_size_increment"
parsePayload FrameContinuation o = ContinuationFrame <$> o .: "header_block_fragment"

instance ToJSON Pad where
    toJSON (Pad padding) = object [
        "padding_length" .= BS.length padding
      , "padding" .= padding
      ]

emptyPad :: Value
emptyPad = object [
    "padding_length" .= Null
  , "padding" .= Null
  ]

----------------------------------------------------------------

instance ToJSON Case where
    toJSON Case{..} = object [
        "draft" .= draft
      , "description" .= description
      , "wire" .= wire
      , "frame" .= frame
      , "error" .= err
      ]

instance FromJSON Case where
    parseJSON (Object o) = Case <$> o .: "draft"
                                <*> o .: "description"
                                <*> o .: "wire"
                                <*> o .:? "frame"
                                <*> o .:? "error"
    parseJSON _          = mzero