FromSQL.hs

module Data.JSON2.FromSQL where
import Data.JSON2
import qualified Data.Map as Map

-- | Conversion SQL-like JSON array to tree-like JSON object with use column.
groupWithCol :: Json -> Json
groupWithCol (JArray xs) = merges $ map objHT xs where
    merges xs = foldl merge  emptyObj xs
    merge (JObject x) (JObject y) = JObject $ Map.unionWith (jConcat) x y
    jConcat(JArray xs) (JArray ys) = JArray (xs ++ ys)
    objHT (JArray ((JString x):xs)) = singleObj x [xs]
    objHT (JArray (x:xs))           = singleObj (toString x) [xs]
    objHT _                         = emptyObj
groupWithCol _ = emptyObj

-- | Conversion SQL-like JSON array to tree-like JSON object with use columns.
--
--   COMPLEX EXAMPLE :
--
-- > import Database.HDBC
-- > import Database.HDBC.Sqlite3
-- > import Data.JSON2
-- > 
-- > dbName = "..."
-- > selectSql = "SELECT * from test"
-- > 
-- > main = do
-- >     conn <- connectSqlite3 dbName
-- >     stmtSel <- prepare conn selectSql
-- >     execute stmtSel []
-- >     q <- sFetchAllRows stmtSel
-- >     mapM print q
-- >  --   [Just "A",Just "1",Just "Pupkin",Just "1"]
-- >  --   [Just "A",Just "2",Just "Sidorov",Just "2"]
-- >  --   [Just "B",Just "22",Just "Petrov",Just "3"]
-- >  --   [Just "B",Just "22",Just "Ivanov",Just "4"]
-- >  --   [Just "B",Just "22",Just "Golubev",Just "5"]
-- >  --   [Just "B",Just "33",Just "Petrov",Just "6"]
-- >     let json = toJson (q :: [[Maybe String]])
-- >     pprint json
-- >  --   [
-- >  --     ["A", "1", "Pupkin", "1"],
-- >  --     ["A", "2", "Sidorov", "2"],
-- >  --     ["B", "22", "Petrov", "3"],
-- >  --     ["B", "22", "Ivanov", "4"],
-- >  --     ["B", "22", "Golubev", "5"],
-- >  --     ["B", "33", "Petrov", "6"]
-- >  --   ]
-- >     let json' = groupWithNCol 2 json
-- >     pprint json'
-- >  --   {
-- >  --     "A": {
-- >  --       "1": [["Pupkin", "1"]],
-- >  --       "2": [["Sidorov", "2"]]
-- >  --     },
-- >  --     "B": {
-- >  --       "22": [["Petrov", "3"], ["Ivanov", "4"], ["Golubev", "5"]],
-- >  --       "33": [["Petrov", "6"]]
-- >  --     }
-- >  --   }
-- >     disconnect conn

groupWithNCol :: Int -> Json -> Json
groupWithNCol n j | n > 0 = mapj (n - 1) (groupWithCol j) 
                  | otherwise = j
    where
      mapj n j@(JObject xs)
          | n > 0 = JObject ( Map.map  ((mapj (n-1)) . groupWithCol) xs)
          | otherwise = j 
{-
j0 = toJson ["a"]
j1 = toJson ["a", "aa", "aaa"]
j2 = toJson ["a", "ab", "abb"]
j3 = toJson ["a", "aa"]
j4 = toJson ["b", "bb", "bbb"]
j5 = toJson ["c", "87319827"]
j6 = toJson ["a", "ab", "abb"]
j7 = toJson ["a", "ab", "abb"]
-}