{-| graphql-engine used to have a query plan cache, which cached the execution
plan for a given graphql query (sans JSON variable values).  After the PDV
refactor (see
[hasura/graphql-engine#4111](https://github.com/hasura/graphql-engine/pull/4111)),
this query plan cache was not needed anymore.  For backwards compatibility
reasons, we still need to parse the configuration options from the CLI, although
the CLI option gets ignored.

Eventually, we can decide to stop parsing the CLI option
--query-plan-cache-size, at which point this module can be removed.
-}
module Hasura.Cache.Bounded
  ( CacheSize(..)
  , parseCacheSize
  ) where

import           Hasura.Prelude hiding (lookup)

import qualified Data.Aeson     as J

import           Data.Word      (Word16)
import           GHC.Natural    (Natural)

newtype CacheSize
  = CacheSize { unCacheSize :: Word16 }
  deriving (Show, Read, Eq, Ord, Bounded, Num, Real, Integral, Enum, J.ToJSON, J.FromJSON)

parseCacheSize :: String -> Either String CacheSize
parseCacheSize v =
  -- NOTE: naively using readMaybe Word16 will silently wrap
  case readMaybe v :: Maybe Natural of
    Just n | n <= max16 && n >= 0 -> return (CacheSize $ fromIntegral n)
    _ -> throwError "cache size must be given as a number between 0 and 65535"
  where
    max16 = fromIntegral (maxBound :: Word16) :: Natural