{-# LANGUAGE UndecidableInstances #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}

-- | Postgres Instances Metadata
--
-- Defines a 'Hasura.RQL.Types.Metadata.Backend.BackendMetadata' type class instance for Postgres.
module Hasura.Backends.Postgres.Instances.Metadata () where

import Data.HashMap.Strict qualified as Map
import Data.Text.Extended
import Hasura.Backends.Postgres.DDL qualified as PG
import Hasura.Backends.Postgres.SQL.Types (QualifiedTable)
import Hasura.Backends.Postgres.Types.CitusExtraTableMetadata
import Hasura.Base.Error
import Hasura.Prelude
import Hasura.RQL.Types.Backend (Backend)
import Hasura.RQL.Types.Metadata.Backend
import Hasura.RQL.Types.Relationships.Local
import Hasura.RQL.Types.Table
import Hasura.SQL.Backend

--------------------------------------------------------------------------------
-- PostgresMetadata

-- | We differentiate the handling of metadata between Citus and Vanilla
-- Postgres because Citus imposes limitations on the types of joins that it
-- permits, which then limits the types of relations that we can track.
class PostgresMetadata (pgKind :: PostgresKind) where
  -- TODO: find a better name
  validateRel ::
    MonadError QErr m =>
    TableCache ('Postgres pgKind) ->
    QualifiedTable ->
    Either (ObjRelDef ('Postgres pgKind)) (ArrRelDef ('Postgres pgKind)) ->
    m ()

instance PostgresMetadata 'Vanilla where
  validateRel _ _ _ = pure ()

instance PostgresMetadata 'Citus where
  validateRel ::
    forall m.
    MonadError QErr m =>
    TableCache ('Postgres 'Citus) ->
    QualifiedTable ->
    Either (ObjRelDef ('Postgres 'Citus)) (ArrRelDef ('Postgres 'Citus)) ->
    m ()
  validateRel tableCache sourceTable relInfo = do
    sourceTableInfo <- lookupTableInfo sourceTable
    case relInfo of
      Left (RelDef _ obj _) ->
        case obj of
          RUFKeyOn (SameTable _) -> pure ()
          RUFKeyOn (RemoteTable targetTable _) -> checkObjectRelationship sourceTableInfo targetTable
          RUManual RelManualConfig {} -> pure ()
      Right (RelDef _ obj _) ->
        case obj of
          RUFKeyOn (ArrRelUsingFKeyOn targetTable _col) -> checkArrayRelationship sourceTableInfo targetTable
          RUManual RelManualConfig {} -> pure ()
    where
      lookupTableInfo tableName =
        Map.lookup tableName tableCache
          `onNothing` throw400 NotFound ("no such table " <>> tableName)

      checkObjectRelationship sourceTableInfo targetTable = do
        targetTableInfo <- lookupTableInfo targetTable
        let notSupported = throwNotSupportedError sourceTableInfo targetTableInfo "object"
        case ( _tciExtraTableMetadata $ _tiCoreInfo sourceTableInfo,
               _tciExtraTableMetadata $ _tiCoreInfo targetTableInfo
             ) of
          (Distributed {}, Local) -> notSupported
          (Distributed {}, Reference) -> pure ()
          (Distributed {}, Distributed {}) -> pure ()
          (_, Distributed {}) -> notSupported
          (_, _) -> pure ()

      checkArrayRelationship sourceTableInfo targetTable = do
        targetTableInfo <- lookupTableInfo targetTable
        let notSupported = throwNotSupportedError sourceTableInfo targetTableInfo "array"
        case ( _tciExtraTableMetadata $ _tiCoreInfo sourceTableInfo,
               _tciExtraTableMetadata $ _tiCoreInfo targetTableInfo
             ) of
          (Distributed {}, Distributed {}) -> pure ()
          (Distributed {}, _) -> notSupported
          (_, Distributed {}) -> notSupported
          (_, _) -> pure ()

      showDistributionType :: ExtraTableMetadata -> Text
      showDistributionType = \case
        Local -> "local"
        Distributed _ -> "distributed"
        Reference -> "reference"

      throwNotSupportedError :: TableInfo ('Postgres 'Citus) -> TableInfo ('Postgres 'Citus) -> Text -> m ()
      throwNotSupportedError sourceTableInfo targetTableInfo t =
        let tciSrc = _tiCoreInfo sourceTableInfo
            tciTgt = _tiCoreInfo targetTableInfo
         in throw400
              NotSupported
              ( showDistributionType (_tciExtraTableMetadata tciSrc)
                  <> " tables ("
                  <> toTxt (_tciName tciSrc)
                  <> ") cannot have an "
                  <> t
                  <> " relationship against a "
                  <> showDistributionType (_tciExtraTableMetadata $ _tiCoreInfo targetTableInfo)
                  <> " table ("
                  <> toTxt (_tciName tciTgt)
                  <> ")"
              )

----------------------------------------------------------------
-- BackendMetadata instance

instance
  ( Backend ('Postgres pgKind),
    PostgresMetadata pgKind,
    PG.ToMetadataFetchQuery pgKind
  ) =>
  BackendMetadata ('Postgres pgKind)
  where
  prepareCatalog = PG.prepareCatalog
  buildComputedFieldInfo = PG.buildComputedFieldInfo
  fetchAndValidateEnumValues = PG.fetchAndValidateEnumValues
  resolveSourceConfig = PG.resolveSourceConfig
  resolveDatabaseMetadata = PG.resolveDatabaseMetadata
  parseBoolExpOperations = PG.parseBoolExpOperations
  buildFunctionInfo = PG.buildFunctionInfo
  updateColumnInEventTrigger = PG.updateColumnInEventTrigger
  parseCollectableType = PG.parseCollectableType
  postDropSourceHook = PG.postDropSourceHook
  validateRelationship = validateRel @pgKind
  buildComputedFieldBooleanExp = PG.buildComputedFieldBooleanExp