{-# LANGUAGE UndecidableInstances #-}

module Hasura.RQL.DDL.RemoteRelationship
  ( CreateFromSourceRelationship (..),
    runCreateRemoteRelationship,
    runDeleteRemoteRelationship,
    runUpdateRemoteRelationship,
    DeleteFromSourceRelationship (..),
    dropRemoteRelationshipInMetadata,
    PartiallyResolvedSource (..),
    buildRemoteFieldInfo,
  )
where

import Data.Aeson (FromJSON (..), ToJSON (..), (.!=), (.:), (.:?), (.=))
import Data.Aeson qualified as J
import Data.HashMap.Strict qualified as Map
import Data.HashMap.Strict.InsOrd qualified as OMap
import Data.Text.Extended ((<<>), (<>>))
import Hasura.Base.Error
  ( Code (NotFound, NotSupported, RemoteSchemaError),
    QErr,
    QErrM,
    runAesonParser,
    throw400,
  )
import Hasura.EncJSON (EncJSON)
import Hasura.Prelude
import Hasura.RQL.DDL.RemoteRelationship.Validate
  ( errorToText,
    validateToSchemaRelationship,
  )
import Hasura.RQL.Types
import Hasura.SQL.AnyBackend qualified as AB

--------------------------------------------------------------------------------
-- Create or update relationship

-- | Argument to the @_create_remote_relationship@ and
-- @_update_remote_relationship@ families of metadata commands.
--
-- For historical reason, this type is also used to represent a db-to-rs schema
-- in the metadata.
data CreateFromSourceRelationship (b :: BackendType) = CreateFromSourceRelationship
  { _crrSource :: SourceName,
    _crrTable :: TableName b,
    _crrName :: RelName,
    _crrDefinition :: RemoteRelationshipDefinition
  }

deriving stock instance (Eq (TableName b)) => Eq (CreateFromSourceRelationship b)

deriving stock instance (Show (TableName b)) => Show (CreateFromSourceRelationship b)

instance Backend b => FromJSON (CreateFromSourceRelationship b) where
  parseJSON = J.withObject "CreateFromSourceRelationship" $ \o -> do
    _crrSource <- o .:? "source" .!= defaultSource
    _crrTable <- o .: "table"
    _crrName <- o .: "name"
    -- In the old format, the definition is inlined; in the new format, the
    -- definition is in the "definition" object, and we don't allow legacy
    -- fields to appear under it.
    remoteSchema :: Maybe J.Value <- o .:? "remote_schema"
    definition <- o .:? "definition"
    _crrDefinition <- case (remoteSchema, definition) of
      -- old format
      (Just {}, Nothing) -> parseRemoteRelationshipDefinition RRPLegacy $ J.Object o
      -- new format
      (Nothing, Just def) -> parseRemoteRelationshipDefinition RRPStrict def
      -- both or neither
      _ -> fail "create_remote_relationship expects exactly one of: remote_schema, definition"
    pure $ CreateFromSourceRelationship {..}

instance (Backend b) => ToJSON (CreateFromSourceRelationship b) where
  toJSON (CreateFromSourceRelationship {..}) =
    -- We need to introspect the definition, to know whether we need to inline
    -- it, or if it needs to be in a distinct "definition" object.
    J.object $ case _crrDefinition of
      -- old format
      RelationshipToSchema RRFOldDBToRemoteSchema _ ->
        case J.toJSON _crrDefinition of
          -- The result of this serialization will be an empty list if this
          -- conversion fails (which it should _never_ do), in which case those
          -- fields will be omitted from the serialized JSON. This could only
          -- happen if the ToJSON instance of RemoteRelationshipDefinition were
          -- changed to return something that isn't an object.
          J.Object obj -> commonFields <> Map.toList obj
          _ -> []
      -- new format
      _ -> ("definition" .= _crrDefinition) : commonFields
    where
      commonFields =
        [ "source" .= _crrSource,
          "table" .= _crrTable,
          "name" .= _crrName
        ]

runCreateRemoteRelationship ::
  forall b m.
  (MonadError QErr m, CacheRWM m, MetadataM m, BackendMetadata b) =>
  CreateFromSourceRelationship b ->
  m EncJSON
runCreateRemoteRelationship CreateFromSourceRelationship {..} = do
  void $ askTabInfo @b _crrSource _crrTable
  let metadataObj =
        MOSourceObjId _crrSource $
          AB.mkAnyBackend $
            SMOTableObj @b _crrTable $
              MTORemoteRelationship _crrName
  buildSchemaCacheFor metadataObj $
    MetadataModifier $
      tableMetadataSetter @b _crrSource _crrTable . tmRemoteRelationships
        %~ OMap.insert _crrName (RemoteRelationship _crrName _crrDefinition)
  pure successMsg

runUpdateRemoteRelationship ::
  forall b m.
  (MonadError QErr m, CacheRWM m, MetadataM m, BackendMetadata b) =>
  CreateFromSourceRelationship b ->
  m EncJSON
runUpdateRemoteRelationship CreateFromSourceRelationship {..} = do
  fieldInfoMap <- askFieldInfoMap @b _crrSource _crrTable
  let metadataObj =
        MOSourceObjId _crrSource $
          AB.mkAnyBackend $
            SMOTableObj @b _crrTable $
              MTORemoteRelationship _crrName
  void $ askRemoteRel fieldInfoMap _crrName
  buildSchemaCacheFor metadataObj $
    MetadataModifier $
      tableMetadataSetter @b _crrSource _crrTable . tmRemoteRelationships
        %~ OMap.insert _crrName (RemoteRelationship _crrName _crrDefinition)
  pure successMsg

--------------------------------------------------------------------------------
-- Drop relationship

-- | Argument to the @_drop_remote_relationship@ family of metadata commands.
data DeleteFromSourceRelationship (b :: BackendType) = DeleteFromSourceRelationship
  { _drrSource :: SourceName,
    _drrTable :: TableName b,
    _drrName :: RelName
  }

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

runDeleteRemoteRelationship ::
  forall b m.
  (BackendMetadata b, MonadError QErr m, CacheRWM m, MetadataM m) =>
  DeleteFromSourceRelationship b ->
  m EncJSON
runDeleteRemoteRelationship (DeleteFromSourceRelationship source table relName) = do
  fieldInfoMap <- askFieldInfoMap @b source table
  void $ askRemoteRel fieldInfoMap relName
  let metadataObj =
        MOSourceObjId source $
          AB.mkAnyBackend $
            SMOTableObj @b table $
              MTORemoteRelationship relName
  buildSchemaCacheFor metadataObj $
    MetadataModifier $
      tableMetadataSetter @b source table %~ dropRemoteRelationshipInMetadata relName
  pure successMsg

--------------------------------------------------------------------------------
-- Schema cache building (TODO: move this elsewere!)

-- | Internal intermediary step.
--
-- We build the output of sources in two steps:
--   1. we first resolve sources, and collect the core info of their tables
--   2. we then build the entire output from the collection of partially resolved sources
--
-- We need this split to be able to resolve cross-source relationships: to process one source's
-- remote relationship, we need to know about the target source's tables core info.
--
-- This data structure is used as an argument to @AnyBackend@ in the backend-agnostic intermediary
-- collection, and used here to build remote field info.
data PartiallyResolvedSource b = PartiallyResolvedSource
  { _prsSourceMetadata :: !(SourceMetadata b),
    _resolvedSource :: !(ResolvedSource b),
    _tableCoreInfoMap :: !(HashMap (TableName b) (TableCoreInfoG b (ColumnInfo b) (ColumnInfo b)))
  }

-- | Builds the schema cache representation of a remote relationship
-- TODO: this is not actually called by the remote relationship DDL API and is only used as part of
-- the schema cache process. Should this be moved elsewhere?
buildRemoteFieldInfo ::
  QErrM m =>
  -- | The entity on which the remote relationship is defined
  LHSIdentifier ->
  -- | join fields provided by the LHS entity
  Map.HashMap FieldName lhsJoinField ->
  -- | definition of remote relationship
  RemoteRelationship ->
  -- | Required context to process cross boundary relationships
  HashMap SourceName (AB.AnyBackend PartiallyResolvedSource) ->
  -- | Required context to process cross boundary relationships
  RemoteSchemaMap ->
  -- | returns
  --   1. schema cache representation of the remote relationships
  --   2. the dependencies on the RHS of the join. The dependencies
  --      on the LHS entities has to be handled by the calling function
  m (RemoteFieldInfo lhsJoinField, [SchemaDependency])
buildRemoteFieldInfo lhsIdentifier lhsJoinFields RemoteRelationship {..} allSources remoteSchemaMap =
  case _rrDefinition of
    RelationshipToSource ToSourceRelationshipDef {..} -> do
      targetTables <-
        Map.lookup _tsrdSource allSources
          `onNothing` throw400 NotFound ("source not found: " <>> _tsrdSource)
      AB.dispatchAnyBackend @Backend targetTables \(partiallyResolvedSource :: PartiallyResolvedSource b') -> do
        let PartiallyResolvedSource _ targetSourceInfo targetTablesInfo = partiallyResolvedSource
        (targetTable :: TableName b') <- runAesonParser J.parseJSON _tsrdTable
        targetColumns <-
          fmap _tciFieldInfoMap $
            onNothing (Map.lookup targetTable targetTablesInfo) $ throwTableDoesNotExist @b' targetTable
        -- TODO: rhs fields should also ideally be DBJoinFields
        columnPairs <- for (Map.toList _tsrdFieldMapping) \(srcFieldName, tgtFieldName) -> do
          lhsJoinField <- askFieldInfo lhsJoinFields srcFieldName
          tgtField <- askFieldInfo targetColumns tgtFieldName
          pure (srcFieldName, lhsJoinField, tgtField)
        mapping <- for columnPairs \(srcFieldName, srcColumn, tgtColumn) -> do
          tgtScalar <- case pgiType tgtColumn of
            ColumnScalar scalarType -> pure scalarType
            ColumnEnumReference _ -> throw400 NotSupported "relationships to enum fields are not supported yet"
          pure (srcFieldName, (srcColumn, tgtScalar, pgiColumn tgtColumn))
        let sourceConfig = _rsConfig targetSourceInfo
            sourceCustomization = _rsCustomization targetSourceInfo
            rsri =
              RemoteSourceFieldInfo _rrName _tsrdRelationshipType _tsrdSource sourceConfig sourceCustomization targetTable $
                fmap (\(_, tgtType, tgtColumn) -> (tgtType, tgtColumn)) $ Map.fromList mapping
            rhsDependencies =
              SchemaDependency (SOSourceObj _tsrdSource $ AB.mkAnyBackend $ SOITable @b' targetTable) DRTable :
              flip map columnPairs \(_, _srcColumn, tgtColumn) ->
                SchemaDependency
                  ( SOSourceObj _tsrdSource $
                      AB.mkAnyBackend $ SOITableObj @b' targetTable $ TOCol @b' $ pgiColumn tgtColumn
                  )
                  DRRemoteRelationship
            requiredLHSJoinFields = fmap (\(srcField, _, _) -> srcField) $ Map.fromList mapping
        pure (RemoteFieldInfo requiredLHSJoinFields $ RFISource $ AB.mkAnyBackend @b' rsri, rhsDependencies)
    RelationshipToSchema _ remoteRelationship@ToSchemaRelationshipDef {..} -> do
      RemoteSchemaCtx {..} <-
        onNothing (Map.lookup _trrdRemoteSchema remoteSchemaMap) $
          throw400 RemoteSchemaError $ "remote schema with name " <> _trrdRemoteSchema <<> " not found"
      (requiredLHSJoinFields, remoteField) <-
        validateToSchemaRelationship remoteRelationship lhsIdentifier _rrName (_rscInfo, _rscIntroOriginal) lhsJoinFields
          `onLeft` (throw400 RemoteSchemaError . errorToText)
      let rhsDependencies = [SchemaDependency (SORemoteSchema _trrdRemoteSchema) DRRemoteSchema]
      pure (RemoteFieldInfo requiredLHSJoinFields $ RFISchema remoteField, rhsDependencies)