-- | Helper functions for generating the schema of database tables
module Hasura.GraphQL.Schema.Table
  ( getTableGQLName,
    tableSelectColumnsEnum,
    tableUpdateColumnsEnum,
    updateColumnsPlaceholderParser,
    tablePermissions,
    tableSelectPermissions,
    tableSelectFields,
    tableColumns,
    tableSelectColumns,
    tableUpdateColumns,
  )
where

import Data.Has
import Data.HashMap.Strict qualified as Map
import Data.HashSet qualified as Set
import Data.Text.Extended
import Hasura.Base.Error (QErr)
import Hasura.GraphQL.Parser (Kind (..), Parser)
import Hasura.GraphQL.Parser qualified as P
import Hasura.GraphQL.Parser.Constants qualified as G
import Hasura.GraphQL.Schema.Backend
import Hasura.GraphQL.Schema.Common
import Hasura.Prelude
import Hasura.RQL.DML.Internal (getRolePermInfo)
import Hasura.RQL.Types hiding (askTableInfo)
import Hasura.Session (RoleName)
import Language.GraphQL.Draft.Syntax qualified as G

-- | Helper function to get the table GraphQL name. A table may have a
-- custom name configured with it. When the custom name exists, the GraphQL nodes
-- that are generated according to the custom name. For example: Let's say,
-- we have a table called `users address`, the name of the table is not GraphQL
-- compliant so we configure the table with a GraphQL compliant name,
-- say `users_address`
-- The generated top-level nodes of this table will be like `users_address`,
-- `insert_users_address` etc
getTableGQLName ::
  forall b m.
  (Backend b, MonadError QErr m) =>
  TableInfo b ->
  m G.Name
getTableGQLName tableInfo = do
  let coreInfo = _tiCoreInfo tableInfo
      tableName = _tciName coreInfo
      tableCustomName = _tcCustomName $ _tciCustomConfig coreInfo
  tableCustomName
    `onNothing` tableGraphQLName @b tableName
    `onLeft` throwError

-- | Table select columns enum
--
-- Parser for an enum type that matches the columns of the given
-- table. Used as a parameter for "distinct", among others. Maps to
-- the table_select_column object.
--
-- Return Nothing if there's no column the current user has "select"
-- permissions for.
tableSelectColumnsEnum ::
  forall b r m n.
  MonadBuildSchema b r m n =>
  SourceName ->
  TableInfo b ->
  m (Maybe (Parser 'Both n (Column b)))
tableSelectColumnsEnum sourceName tableInfo = do
  tableGQLName <- getTableGQLName @b tableInfo
  columns <- tableSelectColumns sourceName tableInfo
  enumName <- P.mkTypename $ tableGQLName <> G.__select_column
  let description =
        Just $
          G.Description $
            "select columns of table " <>> tableInfoName tableInfo
  pure $
    P.enum enumName description
      <$> nonEmpty
        [ ( define $ ciName column,
            ciColumn column
          )
          | column <- columns
        ]
  where
    define name =
      P.Definition name (Just $ G.Description "column name") P.EnumValueInfo

-- | Table update columns enum
--
-- Parser for an enum type that matches the columns of the given
-- table. Used for conflict resolution in "insert" mutations, among
-- others. Maps to the table_update_column object.
tableUpdateColumnsEnum ::
  forall b r m n.
  MonadBuildSchema b r m n =>
  TableInfo b ->
  m (Maybe (Parser 'Both n (Column b)))
tableUpdateColumnsEnum tableInfo = do
  tableGQLName <- getTableGQLName tableInfo
  columns <- tableUpdateColumns tableInfo
  enumName <- P.mkTypename $ tableGQLName <> G.__update_column
  let tableName = tableInfoName tableInfo
      enumDesc = Just $ G.Description $ "update columns of table " <>> tableName
      enumValues = do
        column <- columns
        pure (define $ ciName column, ciColumn column)
  pure $ P.enum enumName enumDesc <$> nonEmpty enumValues
  where
    define name = P.Definition name (Just $ G.Description "column name") P.EnumValueInfo

-- If there's no column for which the current user has "update"
-- permissions, this functions returns an enum that only contains a
-- placeholder, so as to still allow this type to exist in the schema.
updateColumnsPlaceholderParser ::
  MonadBuildSchema backend r m n =>
  TableInfo backend ->
  m (Parser 'Both n (Maybe (Column backend)))
updateColumnsPlaceholderParser tableInfo = do
  maybeEnum <- tableUpdateColumnsEnum tableInfo
  case maybeEnum of
    Just e -> pure $ Just <$> e
    Nothing -> do
      tableGQLName <- getTableGQLName tableInfo
      enumName <- P.mkTypename $ tableGQLName <> G.__update_column
      pure $
        P.enum enumName (Just $ G.Description $ "placeholder for update columns of table " <> tableInfoName tableInfo <<> " (current role has no relevant permissions)") $
          pure
            ( P.Definition @P.EnumValueInfo G.__PLACEHOLDER (Just $ G.Description "placeholder (do not use)") P.EnumValueInfo,
              Nothing
            )

tablePermissions ::
  forall b r m.
  (MonadReader r m, Has RoleName r) =>
  TableInfo b ->
  m (Maybe (RolePermInfo b))
tablePermissions tableInfo = do
  roleName <- asks getter
  pure $ getRolePermInfo roleName tableInfo

tableSelectPermissions ::
  forall b r m.
  (MonadReader r m, Has RoleName r) =>
  TableInfo b ->
  m (Maybe (SelPermInfo b))
tableSelectPermissions tableInfo = (_permSel =<<) <$> tablePermissions tableInfo

tableSelectFields ::
  forall b r m.
  ( Backend b,
    MonadError QErr m,
    MonadReader r m,
    Has SourceCache r,
    Has RoleName r
  ) =>
  SourceName ->
  TableInfo b ->
  m [FieldInfo b]
tableSelectFields sourceName tableInfo = do
  let tableFields = _tciFieldInfoMap . _tiCoreInfo $ tableInfo
  permissions <- tableSelectPermissions tableInfo
  filterM (canBeSelected permissions) $ Map.elems tableFields
  where
    canBeSelected Nothing _ = pure False
    canBeSelected (Just permissions) (FIColumn columnInfo) =
      pure $ Map.member (ciColumn columnInfo) (spiCols permissions)
    canBeSelected _ (FIRelationship relationshipInfo) = do
      tableInfo' <- askTableInfo sourceName $ riRTable relationshipInfo
      isJust <$> tableSelectPermissions @b tableInfo'
    canBeSelected (Just permissions) (FIComputedField computedFieldInfo) =
      case _cfiReturnType computedFieldInfo of
        CFRScalar _ ->
          pure $ Map.member (_cfiName computedFieldInfo) $ spiScalarComputedFields permissions
        CFRSetofTable tableName -> do
          tableInfo' <- askTableInfo sourceName tableName
          isJust <$> tableSelectPermissions @b tableInfo'
    canBeSelected _ (FIRemoteRelationship _) = pure True

tableColumns ::
  forall b. TableInfo b -> [ColumnInfo b]
tableColumns tableInfo =
  mapMaybe columnInfo . Map.elems . _tciFieldInfoMap . _tiCoreInfo $ tableInfo
  where
    columnInfo (FIColumn ci) = Just ci
    columnInfo _ = Nothing

-- | Get the columns of a table that my be selected under the given select
-- permissions.
tableSelectColumns ::
  forall b r m.
  ( Backend b,
    MonadError QErr m,
    MonadReader r m,
    Has SourceCache r,
    Has RoleName r
  ) =>
  SourceName ->
  TableInfo b ->
  m [ColumnInfo b]
tableSelectColumns sourceName tableInfo =
  mapMaybe columnInfo <$> tableSelectFields sourceName tableInfo
  where
    columnInfo (FIColumn ci) = Just ci
    columnInfo _ = Nothing

-- | Get the columns of a table that my be updated under the given update
-- permissions.
tableUpdateColumns ::
  forall b r m.
  ( Backend b,
    MonadError QErr m,
    MonadReader r m,
    Has RoleName r
  ) =>
  TableInfo b ->
  m [ColumnInfo b]
tableUpdateColumns tableInfo = do
  permissions <- (_permUpd =<<) <$> tablePermissions tableInfo
  pure $ filter (isUpdatable permissions) $ tableColumns tableInfo
  where
    isUpdatable :: Maybe (UpdPermInfo b) -> ColumnInfo b -> Bool
    isUpdatable (Just permissions) columnInfo = columnIsUpdatable && columnIsPermitted && columnHasNoPreset
      where
        columnIsUpdatable = _cmIsUpdatable (ciMutability columnInfo)
        columnIsPermitted = Set.member (ciColumn columnInfo) (upiCols permissions)
        columnHasNoPreset = not (Map.member (ciColumn columnInfo) (upiSet permissions))
    isUpdatable Nothing _ = False