{- |
Description: Add/Drop computed fields in metadata
-}
module Hasura.RQL.DDL.ComputedField
  ( AddComputedField(..)
  , ComputedFieldDefinition(..)
  , runAddComputedField
  , DropComputedField
  , runDropComputedField
  , dropComputedFieldInMetadata
  ) where

import           Hasura.Prelude

import qualified Data.HashMap.Strict.InsOrd as OMap

import           Data.Aeson
import           Data.Text.Extended

import qualified Hasura.SQL.AnyBackend      as AB

import           Hasura.Base.Error
import           Hasura.EncJSON
import           Hasura.RQL.DDL.Deps
import           Hasura.RQL.DDL.Permission
import           Hasura.RQL.Types


data AddComputedField b
  = AddComputedField
  { _afcSource     :: !SourceName
  , _afcTable      :: !(TableName b)
  , _afcName       :: !ComputedFieldName
  , _afcDefinition :: !(ComputedFieldDefinition b)
  , _afcComment    :: !(Maybe Text)
  } deriving stock (Generic)

instance (Backend b) => ToJSON (AddComputedField b) where
  toJSON = genericToJSON hasuraJSON

instance (Backend b) => FromJSON (AddComputedField b) where
  parseJSON = withObject "AddComputedField" $ \o ->
    AddComputedField
      <$> o .:? "source" .!= defaultSource
      <*> o .: "table"
      <*> o .: "name"
      <*> o .: "definition"
      <*> o .:? "comment"

runAddComputedField
  :: forall b m
   . (BackendMetadata b, MonadError QErr m, CacheRWM m, MetadataM m)
  => AddComputedField b
  -> m EncJSON
runAddComputedField q = do
  void $ withPathK "table" $ askTabInfo @b source table
  let metadataObj = MOSourceObjId source
                      $ AB.mkAnyBackend
                      $ SMOTableObj @b table
                      $ MTOComputedField computedFieldName
      metadata = ComputedFieldMetadata computedFieldName (_afcDefinition q) (_afcComment q)
  buildSchemaCacheFor metadataObj
    $ MetadataModifier
    $ tableMetadataSetter source table.tmComputedFields
      %~ OMap.insert computedFieldName metadata
  pure successMsg
  where
    source = _afcSource q
    table = _afcTable q
    computedFieldName = _afcName q

data DropComputedField b
  = DropComputedField
  { _dccSource  :: !SourceName
  , _dccTable   :: !(TableName b)
  , _dccName    :: !ComputedFieldName
  , _dccCascade :: !Bool
  }

instance (Backend b) => FromJSON (DropComputedField b) where
  parseJSON = withObject "DropComputedField" $ \o ->
    DropComputedField
      <$> o .:? "source" .!= defaultSource
      <*> o .: "table"
      <*> o .: "name"
      <*> o .:? "cascade" .!= False

runDropComputedField
  :: forall b m
   . (QErrM m, CacheRWM m, MetadataM m, BackendMetadata b)
  => DropComputedField b -> m EncJSON
runDropComputedField (DropComputedField source table computedField cascade) = do
  -- Validation
  fields <- withPathK "table" $ _tciFieldInfoMap <$> askTableCoreInfo @b source table
  void $ withPathK "name" $ askComputedFieldInfo fields computedField

  -- Dependencies check
  sc <- askSchemaCache
  let deps = getDependentObjs sc
               $ SOSourceObj source
               $ AB.mkAnyBackend
               $ SOITableObj @b table
               $ TOComputedField computedField
  when (not cascade && not (null deps)) $ reportDeps deps

  withNewInconsistentObjsCheck do
    metadataModifiers <- mapM purgeComputedFieldDependency deps
    buildSchemaCache $ MetadataModifier $
      tableMetadataSetter @b source table
      %~ dropComputedFieldInMetadata computedField . foldl' (.) id metadataModifiers
  pure successMsg
  where
    purgeComputedFieldDependency = \case
      -- TODO: do a better check of ensuring that the dependency is as expected.
      -- i.e, the only allowed dependent objects on a computed fields are permissions
      -- on the same table
      SOSourceObj _ exists
        | Just (SOITableObj _ (TOPerm roleName permType))
            <- AB.unpackAnyBackend @b exists ->
              pure $ dropPermissionInMetadata roleName permType
      d -> throw500 $ "unexpected dependency for computed field "
           <> computedField <<> "; " <> reportSchemaObj d

dropComputedFieldInMetadata
  :: ComputedFieldName -> TableMetadata b -> TableMetadata b
dropComputedFieldInMetadata name =
  tmComputedFields %~ OMap.delete name