{-# LANGUAGE DeriveLift                 #-}
{-# LANGUAGE FlexibleContexts           #-}
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE QuasiQuotes                #-}
{-# LANGUAGE ScopedTypeVariables        #-}
{-# LANGUAGE TemplateHaskell            #-}
{-# LANGUAGE TypeFamilies               #-}

module Hasura.RQL.DDL.Relationship where

import qualified Database.PG.Query          as Q
import           Hasura.RQL.DDL.Deps
import           Hasura.RQL.DDL.Permission  (purgePerm)
import           Hasura.RQL.Types
import           Hasura.SQL.Types
import           Hasura.Prelude

import           Data.Aeson.Casing
import           Data.Aeson.TH
import           Data.Aeson.Types
import qualified Data.HashMap.Strict        as HM
import qualified Data.Map.Strict            as M
import qualified Data.Text                  as T
import           Data.Tuple                 (swap)
import           Instances.TH.Lift          ()
import           Language.Haskell.TH.Syntax (Lift)

data RelDef a
  = RelDef
  { rdName    :: !RelName
  , rdUsing   :: !a
  , rdComment :: !(Maybe T.Text)
  } deriving (Show, Eq, Lift)

$(deriveFromJSON (aesonDrop 2 snakeCase){omitNothingFields=True} ''RelDef)

instance (ToJSON a) => ToJSON (RelDef a) where
  toJSON = object . toAesonPairs

instance (ToJSON a) => ToAesonPairs (RelDef a) where
 toAesonPairs (RelDef rn ru rc) =
  [ "name" .= rn
  , "using" .= ru
  , "comment" .= rc
  ]

data RelManualConfig
  = RelManualConfig
  { rmTable   :: !QualifiedTable
  , rmColumns :: !(M.Map PGCol PGCol)
  } deriving (Show, Eq, Lift)

instance FromJSON RelManualConfig where
  parseJSON (Object v) =
    RelManualConfig
    <$> v .:  "remote_table"
    <*> v .:  "column_mapping"

  parseJSON _ =
    fail "manual_configuration should be an object"

instance ToJSON RelManualConfig where
  toJSON (RelManualConfig qt cm) =
    object [ "remote_table" .= qt
           , "column_mapping" .= cm
           ]

data RelUsing a b
  = RUFKeyOn a
  | RUManual b
  deriving (Show, Eq, Lift)

instance (ToJSON a, ToJSON b) => ToJSON (RelUsing a b) where
  toJSON (RUFKeyOn fkey) =
    object [ "foreign_key_constraint_on" .= fkey ]
  toJSON (RUManual manual) =
    object [ "manual_configuration" .= manual ]

instance (FromJSON a, FromJSON b) => FromJSON (RelUsing a b) where
  parseJSON (Object o) = do
    let fkeyOnM = HM.lookup "foreign_key_constraint_on" o
        manualM = HM.lookup "manual_configuration" o
    let msgFrag = "one of foreign_key_constraint_on/manual_configuration should be present"
    case (fkeyOnM, manualM) of
      (Nothing, Nothing) -> fail $ "atleast " <> msgFrag
      (Just a, Nothing)  -> RUFKeyOn <$> parseJSON a
      (Nothing, Just b)  -> RUManual <$> parseJSON b
      _                  -> fail $ "only " <> msgFrag
  parseJSON _ =
    fail "using should be an object"

newtype ObjRelManualConfig =
  ObjRelManualConfig { getObjRelMapping :: RelManualConfig }
  deriving (Show, Eq, FromJSON, ToJSON, Lift)

validateManualConfig
  :: (QErrM m, CacheRM m)
  => FieldInfoMap
  -> RelManualConfig
  -> m ()
validateManualConfig fim rm = do
  let colMapping = M.toList $ rmColumns rm
      remoteQt = rmTable rm
  remoteTabInfo <- askTabInfo remoteQt
  let remoteFim = tiFieldInfoMap remoteTabInfo
  forM_ colMapping $ \(lCol, rCol) -> do
    assertPGCol fim "" lCol
    assertPGCol remoteFim "" rCol
    -- lColType <- askPGType fim lCol ""
    -- rColType <- askPGType remoteFim rCol ""
    -- when (lColType /= rColType) $
    --   throw400 $ mconcat
    --   [ "the types of columns " <> lCol <<> ", " <>> rCol
    --   , " do not match"
    --   ]

persistRel :: QualifiedTable
           -> RelName
           -> RelType
           -> Value
           -> Maybe T.Text
           -> Q.TxE QErr ()
persistRel (QualifiedTable sn tn) rn relType relDef comment =
  Q.unitQE defaultTxErrorHandler [Q.sql|
           INSERT INTO
                  hdb_catalog.hdb_relationship
                  (table_schema, table_name, rel_name, rel_type, rel_def, comment)
           VALUES ($1, $2, $3, $4, $5 :: jsonb, $6)
                |] (sn, tn, rn, relTypeToTxt relType, Q.AltJ relDef, comment) True

checkForColConfilct
  :: (MonadError QErr m)
  => TableInfo
  -> FieldName
  -> m ()
checkForColConfilct tabInfo f =
  case HM.lookup f (tiFieldInfoMap tabInfo) of
    Just _ -> throw400 AlreadyExists $ mconcat
      [ "column/relationship " <>> f
      , " of table " <>> tiName tabInfo
      , " already exists"
      ]
    Nothing -> return ()

type ObjRelUsing = RelUsing PGCol ObjRelManualConfig
type ObjRelDef = RelDef ObjRelUsing

type CreateObjRel = WithTable ObjRelDef

objRelP1
  :: (QErrM m, CacheRM m)
  => TableInfo
  -> ObjRelDef
  -> m ()
objRelP1 tabInfo (RelDef rn ru _) = do
  checkForColConfilct tabInfo (fromRel rn)
  let fim = tiFieldInfoMap tabInfo
  case ru of
    RUFKeyOn cn                      -> assertPGCol fim "" cn
    RUManual (ObjRelManualConfig rm) -> validateManualConfig fim rm

createObjRelP1
  :: (P1C m)
  => CreateObjRel
  -> m ()
createObjRelP1 (WithTable qt rd) = do
  adminOnly
  tabInfo <- askTabInfo qt
  objRelP1 tabInfo rd

objRelP2Setup :: (P2C m) => QualifiedTable -> RelDef ObjRelUsing -> m ()
objRelP2Setup qt (RelDef rn ru _) = do
  relInfo <- case ru of
    RUManual (ObjRelManualConfig rm) -> do
      let refqt = rmTable rm
          (lCols, rCols) = unzip $ M.toList $ rmColumns rm
          deps  = map (\c -> SchemaDependency (SOTableObj qt $ TOCol c) "lcol") lCols
                  <> map (\c -> SchemaDependency (SOTableObj refqt $ TOCol c) "rcol") rCols
      return $ RelInfo rn ObjRel (zip lCols rCols) refqt deps
    RUFKeyOn cn -> do
      res  <- liftTx $ Q.catchE defaultTxErrorHandler $ fetchFKeyDetail cn
      case mapMaybe processRes res of
        [] -> throw400 ConstraintError
                "no foreign constraint exists on the given column"
        [(consName, refsn, reftn, colMapping)] -> do
          let deps = [ SchemaDependency (SOTableObj qt $ TOCons consName) "fkey"
                     , SchemaDependency (SOTableObj qt $ TOCol cn) "using_col"
                     ]
              refqt = QualifiedTable refsn reftn
          void $ askTabInfo refqt
          return $ RelInfo rn ObjRel colMapping refqt deps
        _  -> throw400 ConstraintError
                "more than one foreign key constraint exists on the given column"
  addFldToCache (fromRel rn) (FIRelationship relInfo) qt
  where
    QualifiedTable sn tn = qt
    fetchFKeyDetail cn =
      Q.listQ [Q.sql|
           SELECT constraint_name, ref_table_table_schema, ref_table, column_mapping
             FROM hdb_catalog.hdb_foreign_key_constraint
            WHERE table_schema = $1
              AND table_name = $2
              AND (column_mapping ->> $3) IS NOT NULL
                |] (sn, tn, cn) False
    processRes (consn, refsn, reftn, mapping) =
      case M.toList (Q.getAltJ mapping) of
      m@[_] -> Just (consn, refsn, reftn, m)
      _     -> Nothing

objRelP2 :: (P2C m) => QualifiedTable -> ObjRelDef -> m ()
objRelP2 qt rd@(RelDef rn ru comment) = do
  objRelP2Setup qt rd
  liftTx $ persistRel qt rn ObjRel (toJSON ru) comment

createObjRelP2 :: (P2C m) => CreateObjRel -> m RespBody
createObjRelP2 (WithTable qt rd) = do
  objRelP2 qt rd
  return successMsg

instance HDBQuery CreateObjRel where

  type Phase1Res CreateObjRel = ()
  phaseOne = createObjRelP1

  phaseTwo cor _ = createObjRelP2 cor

  schemaCachePolicy = SCPReload

data ArrRelUsingFKeyOn
  = ArrRelUsingFKeyOn
  { arufTable  :: !QualifiedTable
  , arufColumn :: !PGCol
  } deriving (Show, Eq, Lift)

$(deriveJSON (aesonDrop 4 snakeCase){omitNothingFields=True} ''ArrRelUsingFKeyOn)

newtype ArrRelManualConfig =
  ArrRelManualConfig { getArrRelMapping :: RelManualConfig }
  deriving (Show, Eq, FromJSON, ToJSON, Lift)

type ArrRelUsing = RelUsing ArrRelUsingFKeyOn ArrRelManualConfig
type ArrRelDef = RelDef ArrRelUsing
type CreateArrRel = WithTable ArrRelDef

createArrRelP1 :: (P1C m) => CreateArrRel -> m ()
createArrRelP1 (WithTable qt rd) = do
  adminOnly
  tabInfo    <- askTabInfo qt
  arrRelP1 tabInfo rd

arrRelP1
  :: (QErrM m, CacheRM m)
  => TableInfo -> ArrRelDef -> m ()
arrRelP1 tabInfo (RelDef rn ru _) = do
  checkForColConfilct tabInfo (fromRel rn)
  let fim = tiFieldInfoMap tabInfo
  case ru of
    RUFKeyOn (ArrRelUsingFKeyOn remoteQt rcn) -> do
      remoteTabInfo <- askTabInfo remoteQt
      let rfim = tiFieldInfoMap remoteTabInfo
      -- Check if 'using' column exists
      assertPGCol rfim "" rcn
    RUManual (ArrRelManualConfig rm) ->
      validateManualConfig fim rm

arrRelP2Setup :: (P2C m) => QualifiedTable -> ArrRelDef -> m ()
arrRelP2Setup qt (RelDef rn ru _) = do
  relInfo <- case ru of
    RUManual (ArrRelManualConfig rm) -> do
      let refqt = rmTable rm
          (lCols, rCols) = unzip $ M.toList $ rmColumns rm
          deps  = map (\c -> SchemaDependency (SOTableObj qt $ TOCol c) "lcol") lCols
                  <> map (\c -> SchemaDependency (SOTableObj refqt $ TOCol c) "rcol") rCols
      return $ RelInfo rn ArrRel (zip lCols rCols) refqt deps
    RUFKeyOn (ArrRelUsingFKeyOn refqt refCol) -> do
      let QualifiedTable refSn refTn = refqt
      res <- liftTx $ Q.catchE defaultTxErrorHandler $
        fetchFKeyDetail refSn refTn refCol
      case mapMaybe processRes res of
        [] -> throw400 ConstraintError
                "no foreign constraint exists on the given column"
        [(consName, mapping)] -> do
          let deps = [ SchemaDependency (SOTableObj refqt $ TOCons consName) "remote_fkey"
                     , SchemaDependency (SOTableObj refqt $ TOCol refCol) "using_col"
                     ]
          return $ RelInfo rn ArrRel (map swap mapping) refqt deps
        _  -> throw400 ConstraintError
                "more than one foreign key constraint exists on the given column"
  addFldToCache (fromRel rn) (FIRelationship relInfo) qt
  where
    QualifiedTable sn tn = qt
    fetchFKeyDetail refsn reftn refcn = Q.listQ [Q.sql|
           SELECT constraint_name, column_mapping
             FROM hdb_catalog.hdb_foreign_key_constraint
            WHERE table_schema = $1
              AND table_name = $2
              AND (column_mapping -> $3) IS NOT NULL
              AND ref_table_table_schema = $4
              AND ref_table = $5
                |] (refsn, reftn, refcn, sn, tn) False
    processRes (consn, mapping) =
      case M.toList (Q.getAltJ mapping) of
      m@[_] -> Just (consn, m)
      _     -> Nothing

arrRelP2 :: (P2C m) => QualifiedTable -> ArrRelDef -> m ()
arrRelP2 qt rd@(RelDef rn u comment) = do
  arrRelP2Setup qt rd
  liftTx $ persistRel qt rn ArrRel (toJSON u) comment

createArrRelP2 :: (P2C m) => CreateArrRel -> m RespBody
createArrRelP2 (WithTable qt rd) = do
  arrRelP2 qt rd
  return successMsg

instance HDBQuery CreateArrRel where

  type Phase1Res CreateArrRel = ()
  phaseOne = createArrRelP1

  phaseTwo car _ = createArrRelP2 car

  schemaCachePolicy = SCPReload

data DropRel
  = DropRel
  { drTable        :: !QualifiedTable
  , drRelationship :: !RelName
  , drCascade      :: !(Maybe Bool)
  } deriving (Show, Eq, Lift)

$(deriveJSON (aesonDrop 2 snakeCase){omitNothingFields=True} ''DropRel)

dropRelP1 :: (P1C m) => DropRel -> m [SchemaObjId]
dropRelP1 (DropRel qt rn cascade) = do
  adminOnly
  tabInfo <- askTabInfo qt
  _       <- askRelType (tiFieldInfoMap tabInfo) rn ""
  sc      <- askSchemaCache
  let depObjs = getDependentObjs sc relObjId
  when (depObjs /= [] && not (or cascade)) $ reportDeps depObjs
  return depObjs
  where
    relObjId = SOTableObj qt $ TORel rn

purgeRelDep :: (P2C m) => SchemaObjId -> m ()
purgeRelDep (SOTableObj tn (TOPerm rn pt)) =
  purgePerm tn rn pt
purgeRelDep d = throw500 $ "unexpected dependency of relationship : "
                <> reportSchemaObj d

dropRelP2 :: (P2C m) => DropRel -> [SchemaObjId] -> m RespBody
dropRelP2 (DropRel qt rn _) depObjs = do
  mapM_ purgeRelDep depObjs
  delFldFromCache (fromRel rn) qt
  liftTx $ delRelFromCatalog qt rn
  return successMsg

instance HDBQuery DropRel where

  type Phase1Res DropRel = [SchemaObjId]
  phaseOne = dropRelP1

  phaseTwo = dropRelP2

  schemaCachePolicy = SCPReload

delRelFromCatalog :: QualifiedTable
                  -> RelName
                  -> Q.TxE QErr ()
delRelFromCatalog (QualifiedTable 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

data SetRelComment
  = SetRelComment
  { arTable        :: !QualifiedTable
  , arRelationship :: !RelName
  , arComment      :: !(Maybe T.Text)
  } deriving (Show, Eq, Lift)

$(deriveJSON (aesonDrop 2 snakeCase){omitNothingFields=True} ''SetRelComment)

setRelCommentP1 :: (P1C m) => SetRelComment -> m ()
setRelCommentP1 (SetRelComment qt rn _) = do
  adminOnly
  tabInfo <- askTabInfo qt
  void $ askRelType (tiFieldInfoMap tabInfo) rn ""

setRelCommentP2 :: (P2C m) => SetRelComment -> m RespBody
setRelCommentP2 arc = do
  liftTx $ setRelComment arc
  return successMsg

instance HDBQuery SetRelComment where

  type Phase1Res SetRelComment = ()
  phaseOne = setRelCommentP1

  phaseTwo q _ = setRelCommentP2 q

  schemaCachePolicy = SCPNoChange

setRelComment :: SetRelComment
              -> Q.TxE QErr ()
setRelComment (SetRelComment (QualifiedTable 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