module TutorialD.Interpreter.SchemaOperator where
import Text.Megaparsec
import Text.Megaparsec.Text

import ProjectM36.Base
import ProjectM36.IsomorphicSchema
import ProjectM36.Session
import ProjectM36.Client
import ProjectM36.Error
import TutorialD.Interpreter.RelationalExpr
import TutorialD.Interpreter.Base

data SchemaOperator = ModifySchemaExpr SchemaExpr |
                      SetCurrentSchema SchemaName
                      deriving Show
                      
schemaOperatorP :: Parser SchemaOperator                      
schemaOperatorP = (ModifySchemaExpr <$> schemaExprP) <|>
                  setCurrentSchemaP

setCurrentSchemaP :: Parser SchemaOperator
setCurrentSchemaP = do
  reserved ":setschema"
  SetCurrentSchema <$> identifier
  
schemaExprP :: Parser SchemaExpr
schemaExprP = addSubschemaP <|>
              removeSubschemaP
              
addSubschemaP :: Parser SchemaExpr
addSubschemaP = do
  reserved ":addschema"
  AddSubschema <$> identifier <*> parens (sepBy schemaIsomorphP comma)
  
schemaIsomorphP :: Parser SchemaIsomorph  
schemaIsomorphP = isoRestrictP <|> isoUnionP <|> isoRenameP <|> isoPassthrough

removeSubschemaP :: Parser SchemaExpr
removeSubschemaP = do
  reserved ":removeschema"
  RemoveSubschema <$> identifier

isoRestrictP :: Parser SchemaIsomorph
isoRestrictP = do
  reserved "isorestrict"
  relVarIn <- qrelVarP
  relvarsOut <- isoRestrictOutRelVarsP
  IsoRestrict <$> pure relVarIn <*> restrictionPredicateP <*> pure relvarsOut
  
isoRestrictOutRelVarsP :: Parser (RelVarName, RelVarName)  
isoRestrictOutRelVarsP = (,) <$> qrelVarP <*> qrelVarP

qrelVarP :: Parser RelVarName
qrelVarP = quotedString 

isoUnionP :: Parser SchemaIsomorph
isoUnionP = do
  reserved "isounion"
  relVarsIn <- isoUnionInRelVarsP
  relVarsOut <- qrelVarP
  IsoUnion <$> pure relVarsIn <*> restrictionPredicateP <*> pure relVarsOut
  
isoRenameP :: Parser SchemaIsomorph
isoRenameP = do
  reserved "isorename"
  IsoRename <$> qrelVarP <*> qrelVarP
  
isoPassthrough :: Parser SchemaIsomorph  
isoPassthrough = do
  reserved "isopassthrough"
  rv <- qrelVarP
  pure (IsoRename rv rv)
  
isoUnionInRelVarsP :: Parser (RelVarName, RelVarName)  
isoUnionInRelVarsP = (,) <$> qrelVarP <*> qrelVarP
  
evalSchemaOperator :: SessionId -> Connection -> SchemaOperator -> IO (Maybe RelationalError)
evalSchemaOperator sessionId conn (ModifySchemaExpr expr) =  executeSchemaExpr sessionId conn expr
evalSchemaOperator sessionId conn (SetCurrentSchema sname) = setCurrentSchemaName sessionId conn sname