{-# LANGUAGE FlexibleInstances #-}

-- |
-- Module      : Database.Relational.Internal.String
-- Copyright   : 2014-2017 Kei Hibino
-- License     : BSD3
--
-- Maintainer  : ex8k.hibino@gmail.com
-- Stability   : experimental
-- Portability : unknown
--
-- This module provides SQL string wrap interfaces.
module Database.Relational.Internal.String (
  StringSQL, stringSQL, showStringSQL,

  rowStringSQL, rowPlaceHolderStringSQL,

  rowConsStringSQL, listStringSQL,

  boolSQL,
  ) where

import Language.SQL.Keyword (Keyword, word, wordShow, fold, (|*|), paren)


-- | String wrap type for SQL strings.
type StringSQL = Keyword

-- | 'StringSQL' from 'String'.
stringSQL :: String -> StringSQL
stringSQL =  word

-- | 'StringSQL' to 'String'.
showStringSQL :: StringSQL -> String
showStringSQL =  wordShow

-- | Row String of SQL values.
rowStringSQL :: [StringSQL] -> StringSQL
rowStringSQL =  d  where
  d []  = error "Record: no columns. empty row is not allowed in SQL."
  d [c] = c
  d cs  = paren $ fold (|*|) cs

-- | Place holder row String of SQL.
rowPlaceHolderStringSQL :: Int -> StringSQL
rowPlaceHolderStringSQL =  rowStringSQL . (`replicate` stringSQL "?")

-- | List String of SQL.
rowConsStringSQL :: [StringSQL] -> StringSQL
rowConsStringSQL =  paren . fold (|*|)

-- | List String of SQL.
listStringSQL :: [StringSQL] -> StringSQL
listStringSQL =  paren . fold (|*|)

-- | SQL expressions for Bool type.
boolSQL :: Bool -> StringSQL
boolSQL =
    stringSQL . d
  where
    d True  = "(0=0)"
    d False = "(0=1)"