{- |
Description: Add/Drop computed fields in metadata
-}
module Hasura.RQL.DDL.ComputedField
  ( AddComputedField(..)
  , ComputedFieldDefinition(..)
  , runAddComputedField
  , addComputedFieldP2Setup
  , DropComputedField
  , runDropComputedField
  , dropComputedFieldInMetadata
  ) where

import           Hasura.Prelude

import qualified Control.Monad.Validate             as MV
import qualified Data.HashMap.Strict.InsOrd         as OMap
import qualified Data.HashSet                       as S
import qualified Data.Sequence                      as Seq
import qualified Language.GraphQL.Draft.Syntax      as G

import           Data.Aeson
import           Data.Aeson.TH
import           Data.Text.Extended

import           Hasura.Backends.Postgres.SQL.Types
import           Hasura.EncJSON
import           Hasura.Incremental                 (Cacheable)
import           Hasura.RQL.DDL.Deps
import           Hasura.RQL.DDL.Permission
import           Hasura.RQL.DDL.Schema.Function     (mkFunctionArgs)
import           Hasura.RQL.Types
import           Hasura.SQL.Types
import           Hasura.Server.Utils                (makeReasonMessage)


data AddComputedField
  = AddComputedField
  { _afcSource     :: !SourceName
  , _afcTable      :: !QualifiedTable
  , _afcName       :: !ComputedFieldName
  , _afcDefinition :: !ComputedFieldDefinition
  , _afcComment    :: !(Maybe Text)
  } deriving (Show, Eq, Generic)
instance NFData AddComputedField
instance Cacheable AddComputedField
$(deriveToJSON hasuraJSON ''AddComputedField)

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

runAddComputedField :: (MonadError QErr m, CacheRWM m, MetadataM m) => AddComputedField -> m EncJSON
runAddComputedField q = do
  withPathK "table" $ askTabInfo source table
  let metadataObj = MOSourceObjId source $
                    SMOTableObj 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 ComputedFieldValidateError
  = CFVENotValidGraphQLName !ComputedFieldName
  | CFVEInvalidTableArgument !InvalidTableArgument
  | CFVEInvalidSessionArgument !InvalidSessionArgument
  | CFVENotBaseReturnType !PGScalarType
  | CFVEReturnTableNotFound !QualifiedTable
  | CFVENoInputArguments
  | CFVEFunctionVolatile
  deriving (Show, Eq)

data InvalidTableArgument
  = ITANotFound !FunctionArgName
  | ITANotComposite !FunctionTableArgument
  | ITANotTable !QualifiedTable !FunctionTableArgument
  deriving (Show, Eq)

data InvalidSessionArgument
  = ISANotFound !FunctionArgName
  | ISANotJSON !FunctionSessionArgument
  deriving (Show, Eq)

showError :: QualifiedFunction -> ComputedFieldValidateError -> Text
showError qf = \case
  CFVENotValidGraphQLName computedField ->
    computedField <<> " is not valid GraphQL name"
  CFVEInvalidTableArgument (ITANotFound argName) ->
    argName <<> " is not an input argument of the function " <>> qf
  CFVEInvalidTableArgument (ITANotComposite functionArg) ->
    showFunctionTableArgument functionArg <> " is not COMPOSITE type"
  CFVEInvalidTableArgument (ITANotTable ty functionArg) ->
    showFunctionTableArgument functionArg <> " of type " <> ty
    <<> " is not the table to which the computed field is being added"
  CFVEInvalidSessionArgument (ISANotFound argName) ->
    argName <<> " is not an input argument of the function " <>> qf
  CFVEInvalidSessionArgument (ISANotJSON functionArg) ->
    showFunctionSessionArgument functionArg <> " is not of type JSON"
  CFVENotBaseReturnType scalarType ->
    "the function " <> qf <<> " returning type " <> toSQLTxt scalarType
    <> " is not a BASE type"
  CFVEReturnTableNotFound table ->
    "the function " <> qf <<> " returning set of table " <> table
    <<> " is not tracked or not found in database"
  CFVENoInputArguments ->
    "the function " <> qf <<> " has no input arguments"
  CFVEFunctionVolatile ->
    "the function " <> qf <<> " is of type VOLATILE; cannot be added as a computed field"
  where
    showFunctionTableArgument = \case
      FTAFirst           -> "first argument of the function " <>> qf
      FTANamed argName _ -> argName <<> " argument of the function " <>> qf
    showFunctionSessionArgument = \case
      FunctionSessionArgument argName _ -> argName <<> " argument of the function " <>> qf

addComputedFieldP2Setup
  :: (QErrM m)
  => S.HashSet QualifiedTable
  -- ^ the set of all tracked tables
  -> QualifiedTable
  -> ComputedFieldName
  -> ComputedFieldDefinition
  -> RawFunctionInfo
  -> Maybe Text
  -> m (ComputedFieldInfo 'Postgres)
addComputedFieldP2Setup trackedTables table computedField definition rawFunctionInfo comment =
  either (throw400 NotSupported . showErrors) pure =<< MV.runValidateT mkComputedFieldInfo
  where
    inputArgNames = rfiInputArgNames rawFunctionInfo
    ComputedFieldDefinition function maybeTableArg maybeSessionArg = definition
    functionReturnType = QualifiedPGType (rfiReturnTypeSchema rawFunctionInfo)
                         (rfiReturnTypeName rawFunctionInfo)
                         (rfiReturnTypeType rawFunctionInfo)

    computedFieldGraphQLName = G.mkName $ computedFieldNameToText computedField

    mkComputedFieldInfo :: (MV.MonadValidate [ComputedFieldValidateError] m)
                          => m (ComputedFieldInfo 'Postgres)
    mkComputedFieldInfo = do
      -- Check if computed field name is a valid GraphQL name
      unless (isJust computedFieldGraphQLName) $
        MV.dispute $ pure $ CFVENotValidGraphQLName computedField

      -- Check if function is VOLATILE
      when (rfiFunctionType rawFunctionInfo == FTVOLATILE) $
        MV.dispute $ pure CFVEFunctionVolatile

      -- Validate and resolve return type
      returnType <-
        if rfiReturnsTable rawFunctionInfo then do
          let returnTable = typeToTable functionReturnType
          unless (returnTable `S.member` trackedTables) $ MV.dispute $ pure $
            CFVEReturnTableNotFound returnTable
          pure $ CFRSetofTable returnTable
        else do
          let scalarType = _qptName functionReturnType
          unless (isBaseType functionReturnType) $ MV.dispute $ pure $
            CFVENotBaseReturnType scalarType
          pure $ CFRScalar scalarType

      -- Validate and resolve table argument
      let inputArgs = mkFunctionArgs (rfiDefaultArgs rawFunctionInfo)
                         (rfiInputArgTypes rawFunctionInfo) inputArgNames
      tableArgument <- case maybeTableArg of
        Just argName ->
          case findWithIndex ((Just argName ==) . faName) inputArgs of
            Just (tableArg, index) -> do
              let functionTableArg = FTANamed argName index
              validateTableArgumentType functionTableArg $ faType tableArg
              pure functionTableArg
            Nothing ->
              MV.refute $ pure $ CFVEInvalidTableArgument $ ITANotFound argName
        Nothing -> do
          case inputArgs of
            []           -> MV.dispute $ pure CFVENoInputArguments
            (firstArg:_) ->
              validateTableArgumentType FTAFirst $ faType firstArg
          pure FTAFirst

      maybePGSessionArg <- sequence $ do
          argName <- maybeSessionArg
          return $ case findWithIndex ((Just argName ==) . faName) inputArgs of
            Just (sessionArg, index) -> do
              let functionSessionArg = FunctionSessionArgument argName index
              validateSessionArgumentType functionSessionArg $ faType sessionArg
              pure functionSessionArg
            Nothing ->
              MV.refute $ pure $ CFVEInvalidSessionArgument $ ISANotFound argName


      let inputArgSeq = Seq.fromList $ dropTableAndSessionArgument tableArgument
                        maybePGSessionArg inputArgs
          computedFieldFunction =
            ComputedFieldFunction function inputArgSeq tableArgument maybePGSessionArg $
            rfiDescription rawFunctionInfo

      pure $ ComputedFieldInfo () computedField computedFieldFunction returnType comment

    validateTableArgumentType :: (MV.MonadValidate [ComputedFieldValidateError] m)
                              => FunctionTableArgument
                              -> QualifiedPGType
                              -> m ()
    validateTableArgumentType tableArg qpt = do
      when (_qptType qpt /= PGKindComposite) $
        MV.dispute $ pure $ CFVEInvalidTableArgument $ ITANotComposite tableArg
      let typeTable = typeToTable qpt
      unless (table == typeTable) $
        MV.dispute $ pure $ CFVEInvalidTableArgument $ ITANotTable typeTable tableArg

    validateSessionArgumentType :: (MV.MonadValidate [ComputedFieldValidateError] m)
                                => FunctionSessionArgument
                                -> QualifiedPGType
                                -> m ()
    validateSessionArgumentType sessionArg qpt = do
      unless (isJSONType $ _qptName qpt) $
        MV.dispute $ pure $ CFVEInvalidSessionArgument $ ISANotJSON sessionArg

    showErrors :: [ComputedFieldValidateError] -> Text
    showErrors allErrors =
      "the computed field " <> computedField <<> " cannot be added to table "
      <> table <<> " " <> reasonMessage
      where
        reasonMessage = makeReasonMessage allErrors (showError function)

    dropTableAndSessionArgument :: FunctionTableArgument
                                -> Maybe FunctionSessionArgument -> [FunctionArg 'Postgres]
                                -> [FunctionArg 'Postgres]
    dropTableAndSessionArgument tableArg sessionArg inputArgs =
      let withoutTable = case tableArg of
            FTAFirst  -> tail inputArgs
            FTANamed argName _ ->
              filter ((/=) (Just argName) . faName) inputArgs
          alsoWithoutSession = case sessionArg of
            Nothing -> withoutTable
            Just (FunctionSessionArgument name _) ->
              filter ((/=) (Just name) . faName) withoutTable
      in alsoWithoutSession

data DropComputedField
  = DropComputedField
  { _dccSource  :: !SourceName
  , _dccTable   :: !QualifiedTable
  , _dccName    :: !ComputedFieldName
  , _dccCascade :: !Bool
  } deriving (Show, Eq)
$(deriveToJSON hasuraJSON ''DropComputedField)

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

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

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

  withNewInconsistentObjsCheck do
    metadataModifiers <- mapM purgeComputedFieldDependency deps
    buildSchemaCache $ MetadataModifier $
      tableMetadataSetter source table
      %~ (dropComputedFieldInMetadata computedField) . foldl' (.) id metadataModifiers
  pure successMsg
  where
    purgeComputedFieldDependency = \case
      (SOSourceObj _ (SOITableObj qt (TOPerm roleName permType))) | qt == table ->
        pure $ dropPermissionInMetadata roleName permType
      d -> throw500 $ "unexpected dependency for computed field "
           <> computedField <<> "; " <> reportSchemaObj d

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