{-# language BangPatterns #-}
{-# language DuplicateRecordFields #-}
{-# language NamedFieldPuns #-}
{-# language DerivingStrategies #-}

module Kafka.Header.Response.V1
  ( Header(..)
  , Headed(..)
  , parser
  , decode
  ) where

import Data.Primitive (SmallArray)
import Data.Int (Int32)
import Kafka.Parser.Context (Context)
import Data.Bytes.Parser (Parser)
import Data.Bytes (Bytes)
import Kafka.TaggedField (TaggedField)

import qualified Data.Bytes.Parser as Parser
import qualified Kafka.Parser.Context as Ctx
import qualified Kafka.TaggedField as TaggedField
import qualified Kafka.Parser

data Headed a = Headed
  { header :: !Header
  , response :: !a
  } deriving stock (Show)

data Header = Header
  { correlationId :: !Int32
  , taggedFields :: !(SmallArray TaggedField)
  } deriving (Show)

-- | Note: Decode is here for the benefit of the test suite. A response
-- header prefaces another message, so in an actual kafka client,
-- it makes more sense to monadically sequence the two parsers.
decode :: Bytes -> Either Context Header
decode !b = Parser.parseBytesEither (parser Ctx.Top <* Parser.endOfInput Ctx.End) b

parser :: Context -> Parser Context s Header
parser ctx = do
  correlationId <- Kafka.Parser.int32 (Ctx.Field Ctx.CorrelationId ctx)
  taggedFields <- TaggedField.parserMany (Ctx.Field Ctx.TagBuffer ctx)
  pure Header{correlationId,taggedFields}