20221222113129-scriptinanylang.org

ScriptInAnyLang

ScriptInAnyLang

Sometimes it is necessary to handle all languages without making static type distinctions between languages. For example, when reading external input, or before the era context is known

-- ----------------------------------------------------------------------------
-- Scripts in any language
--

-- | Sometimes it is necessary to handle all languages without making static
-- type distinctions between languages. For example, when reading external
-- input, or before the era context is known.
--
-- Use 'toScriptInEra' to convert to a script in the context of an era.
--
data ScriptInAnyLang where
     ScriptInAnyLang :: ScriptLanguage lang
                     -> Script lang
                     -> ScriptInAnyLang

deriving instance Show ScriptInAnyLang

-- The GADT in the ScriptInAnyLang constructor requires a custom Eq instance
instance Eq ScriptInAnyLang where
    (==) (ScriptInAnyLang lang  script)
         (ScriptInAnyLang lang' script') =
      case testEquality lang lang' of
        Nothing   -> False
        Just Refl -> script == script'

instance ToJSON ScriptInAnyLang where
  toJSON (ScriptInAnyLang l s) =
    object [ "scriptLanguage" .= show l
           , "script" .= obtainScriptLangConstraint l
                           (serialiseToTextEnvelope Nothing s)
           ]
      where
       obtainScriptLangConstraint
         :: ScriptLanguage lang
         -> (IsScriptLanguage lang => a)
         -> a
       obtainScriptLangConstraint (SimpleScriptLanguage SimpleScriptV1) f = f
       obtainScriptLangConstraint (SimpleScriptLanguage SimpleScriptV2) f = f
       obtainScriptLangConstraint (PlutusScriptLanguage PlutusScriptV1) f = f
       obtainScriptLangConstraint (PlutusScriptLanguage PlutusScriptV2) f = f

instance FromJSON ScriptInAnyLang where
  parseJSON = Aeson.withObject "ScriptInAnyLang" $ \o -> do
    textEnvelopeScript <- o .: "script"
    case textEnvelopeToScript textEnvelopeScript of
      Left textEnvErr -> fail $ displayError textEnvErr
      Right (ScriptInAnyLang l s) -> pure $ ScriptInAnyLang l s

-- | Convert a script in a specific statically-known language to a
-- 'ScriptInAnyLang'.
--
-- No inverse to this is provided, just do case analysis on the 'ScriptLanguage'
-- field within the 'ScriptInAnyLang' constructor.
--
toScriptInAnyLang :: Script lang -> ScriptInAnyLang
toScriptInAnyLang s@(SimpleScript v _) =
    ScriptInAnyLang (SimpleScriptLanguage v) s
toScriptInAnyLang s@(PlutusScript v _) =
    ScriptInAnyLang (PlutusScriptLanguage v) s

instance HasTypeProxy ScriptInAnyLang where
    data AsType ScriptInAnyLang = AsScriptInAnyLang
    proxyToAsType _ = AsScriptInAnyLang