module Hasura.RQL.DDL.Relationship
  ( runCreateRelationship
  , insertRelationshipToCatalog
  , objRelP2Setup
  , arrRelP2Setup

  , runDropRel
  , delRelFromCatalog

  , runSetRelComment
  )
where

import           Hasura.Prelude

import qualified Data.HashMap.Strict                as HM
import qualified Data.HashSet                       as HS
import qualified Database.PG.Query                  as Q

import           Data.Aeson.Types
import           Data.Tuple                         (swap)
import           Instances.TH.Lift                  ()

import           Hasura.Backends.Postgres.SQL.Types
import           Hasura.EncJSON
import           Hasura.RQL.DDL.Deps
import           Hasura.RQL.DDL.Permission          (purgePerm)
import           Hasura.RQL.Types

runCreateRelationship
  :: (MonadTx m, CacheRWM m, HasSystemDefined m, ToJSON a)
  => RelType -> WithTable (RelDef a) -> m EncJSON
runCreateRelationship relType (WithTable tableName relDef) = do
  insertRelationshipToCatalog tableName relType relDef
  buildSchemaCacheFor $ MOTableObj tableName (MTORel (_rdName relDef) relType)
  pure successMsg

insertRelationshipToCatalog
  :: (MonadTx m, HasSystemDefined m, ToJSON a)
  => QualifiedTable
  -> RelType
  -> RelDef a
  -> m ()
insertRelationshipToCatalog (QualifiedObject schema table) relType (RelDef name using comment) = do
  systemDefined <- askSystemDefined
  let args = (schema, table, name, relTypeToTxt relType, Q.AltJ using, comment, systemDefined)
  liftTx $ Q.unitQE defaultTxErrorHandler query args True
  where
    query = [Q.sql|
      INSERT INTO
        hdb_catalog.hdb_relationship
        (table_schema, table_name, rel_name, rel_type, rel_def, comment, is_system_defined)
      VALUES ($1, $2, $3, $4, $5 :: jsonb, $6, $7) |]

runDropRel :: (MonadTx m, CacheRWM m) => DropRel -> m EncJSON
runDropRel (DropRel qt rn cascade) = do
  depObjs <- collectDependencies
  withNewInconsistentObjsCheck do
    traverse_ purgeRelDep depObjs
    liftTx $ delRelFromCatalog qt rn
    buildSchemaCache
  pure successMsg
  where
    collectDependencies = do
      tabInfo <- askTableCoreInfo qt
      _       <- askRelType (_tciFieldInfoMap tabInfo) rn ""
      sc      <- askSchemaCache
      let depObjs = getDependentObjs sc (SOTableObj qt $ TORel rn)
      when (depObjs /= [] && not cascade) $ reportDeps depObjs
      pure depObjs

delRelFromCatalog
  :: QualifiedTable
  -> RelName
  -> Q.TxE QErr ()
delRelFromCatalog (QualifiedObject sn tn) rn =
  Q.unitQE defaultTxErrorHandler [Q.sql|
           DELETE FROM
                  hdb_catalog.hdb_relationship
           WHERE table_schema =  $1
             AND table_name = $2
             AND rel_name = $3
                |] (sn, tn, rn) True

objRelP2Setup
  :: (QErrM m)
  => QualifiedTable
  -> HashSet ForeignKey
  -> RelDef ObjRelUsing
  -> m (RelInfo, [SchemaDependency])
objRelP2Setup qt foreignKeys (RelDef rn ru _) = case ru of
  RUManual rm -> do
    let refqt = rmTable rm
        (lCols, rCols) = unzip $ HM.toList $ rmColumns rm
        mkDependency tableName reason col = SchemaDependency (SOTableObj tableName $ TOCol col) reason
        dependencies = map (mkDependency qt DRLeftColumn) lCols
                    <> map (mkDependency refqt DRRightColumn) rCols
    pure (RelInfo rn ObjRel (rmColumns rm) refqt True True, dependencies)
  RUFKeyOn columnName -> do
    ForeignKey constraint foreignTable colMap <- getRequiredFkey columnName (HS.toList foreignKeys)
    let dependencies =
          [ SchemaDependency (SOTableObj qt $ TOForeignKey (_cName constraint)) DRFkey
          , SchemaDependency (SOTableObj qt $ TOCol columnName) DRUsingColumn
          -- this needs to be added explicitly to handle the remote table being untracked. In this case,
          -- neither the using_col nor the constraint name will help.
          , SchemaDependency (SOTable foreignTable) DRRemoteTable
          ]
    -- TODO(PDV?): this is too optimistic. Some object relationships are nullable, but
    -- we are marking some as non-nullable here.  This should really be done by
    -- checking nullability in the SQL schema.
    pure (RelInfo rn ObjRel colMap foreignTable False False, dependencies)

arrRelP2Setup
  :: (QErrM m)
  => HashMap QualifiedTable (HashSet ForeignKey)
  -> QualifiedTable
  -> ArrRelDef
  -> m (RelInfo, [SchemaDependency])
arrRelP2Setup foreignKeys qt (RelDef rn ru _) = case ru of
  RUManual rm -> do
    let refqt = rmTable rm
        (lCols, rCols) = unzip $ HM.toList $ rmColumns rm
        deps  = map (\c -> SchemaDependency (SOTableObj qt $ TOCol c) DRLeftColumn) lCols
                <> map (\c -> SchemaDependency (SOTableObj refqt $ TOCol c) DRRightColumn) rCols
    pure (RelInfo rn ArrRel (rmColumns rm) refqt True True, deps)
  RUFKeyOn (ArrRelUsingFKeyOn refqt refCol) -> do
    foreignTableForeignKeys <- getTableInfo refqt foreignKeys
    let keysThatReferenceUs = filter ((== qt) . _fkForeignTable) (HS.toList foreignTableForeignKeys)
    ForeignKey constraint _ colMap <- getRequiredFkey refCol keysThatReferenceUs
    let deps = [ SchemaDependency (SOTableObj refqt $ TOForeignKey (_cName constraint)) DRRemoteFkey
               , SchemaDependency (SOTableObj refqt $ TOCol refCol) DRUsingColumn
               -- we don't need to necessarily track the remote table like we did in
               -- case of obj relationships as the remote table is indirectly
               -- tracked by tracking the constraint name and 'using_col'
               , SchemaDependency (SOTable refqt) DRRemoteTable
               ]
        mapping = HM.fromList $ map swap $ HM.toList colMap
    pure (RelInfo rn ArrRel mapping refqt False False, deps)

purgeRelDep :: (MonadTx m) => SchemaObjId -> m ()
purgeRelDep (SOTableObj tn (TOPerm rn pt)) = purgePerm tn rn pt
purgeRelDep d = throw500 $ "unexpected dependency of relationship : "
                <> reportSchemaObj d

validateRelP1
  :: (UserInfoM m, QErrM m, TableCoreInfoRM m)
  => QualifiedTable -> RelName -> m RelInfo
validateRelP1 qt rn = do
  tabInfo <- askTableCoreInfo qt
  askRelType (_tciFieldInfoMap tabInfo) rn ""

setRelCommentP2
  :: (QErrM m, MonadTx m)
  => SetRelComment -> m EncJSON
setRelCommentP2 arc = do
  liftTx $ setRelComment arc
  return successMsg

runSetRelComment
  :: (QErrM m, CacheRM m, MonadTx m, UserInfoM m)
  => SetRelComment -> m EncJSON
runSetRelComment defn = do
  void $ validateRelP1 qt rn
  setRelCommentP2 defn
  where
    SetRelComment qt rn _ = defn

setRelComment :: SetRelComment
              -> Q.TxE QErr ()
setRelComment (SetRelComment (QualifiedObject sn tn) rn comment) =
  Q.unitQE defaultTxErrorHandler [Q.sql|
           UPDATE hdb_catalog.hdb_relationship
           SET comment = $1
           WHERE table_schema =  $2
             AND table_name = $3
             AND rel_name = $4
                |] (comment, sn, tn, rn) True

getRequiredFkey
  :: (QErrM m)
  => PGCol
  -> [ForeignKey]
  -> m ForeignKey
getRequiredFkey col fkeys =
  case filteredFkeys of
    []  -> throw400 ConstraintError
          "no foreign constraint exists on the given column"
    [k] -> return k
    _   -> throw400 ConstraintError
           "more than one foreign key constraint exists on the given column"
  where
    filteredFkeys = filter ((== [col]) . HM.keys . _fkColumnMapping) fkeys