{-# LANGUAGE GADTs, OverloadedStrings #-}
-- | SQL AST and pretty-printing.
module Database.Selda.SQL where
import Database.Selda.Column
import Database.Selda.SqlType
import Database.Selda.Types (TableName)
import Data.Monoid

-- | A source for an SQL query.
data SqlSource
 = TableName !TableName
 | Product ![SQL]
 | LeftJoin !(Exp Bool) !SQL !SQL

-- | AST for SQL queries.
data SQL = SQL
  { cols      :: ![SomeCol]
  , source    :: !SqlSource
  , restricts :: ![Exp Bool]
  , groups    :: ![SomeCol]
  , ordering  :: ![(Order, SomeCol)]
  , limits    :: !(Maybe (Int, Int))
  }

-- | The order in which to sort result rows.
data Order = Asc | Desc
  deriving (Show, Ord, Eq)

-- | A parameter to a prepared SQL statement.
data Param where
  Param :: !(Lit a) -> Param

instance Show Param where
  show (Param l) = "Param " <> show l

instance Eq Param where
  Param a == Param b = compLit a b == EQ
instance Ord Param where
  compare (Param a) (Param b) = compLit a b