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MongoDB Query Document in Haskell(WIP)
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{-# LANGUAGE FlexibleInstances #-} | |
{-# LANGUAGE TypeSynonymInstances #-} | |
module MongoDB.QueryDocument where | |
import Data.List (intercalate) | |
import Data.Monoid | |
import Data.Set | |
import Prelude hiding (map) | |
import qualified Prelude | |
-- | Value in Query Document | |
type Value = String | |
type ArrayValue = [Value] | |
-- | Pair embedded in Query Document | |
data Pair = ExactMatch (String, String) | | |
ArrayExactMatch (String, [String]) | | |
In (String, Set String) | | |
Lt (String, String) | |
deriving (Eq, Show, Ord) | |
-- | Query Document | |
data Document = Empty | | |
Pair Pair | | |
And (Set Document) | | |
Or (Set Document) | |
deriving (Eq, Show, Ord) | |
-- Instances for exact match targets | |
class ExactMatchable a where | |
exactMatch :: String -> a -> Pair | |
instance ExactMatchable Value where | |
exactMatch k v = ExactMatch (k, v) | |
instance ExactMatchable ArrayValue where | |
exactMatch k vs = ArrayExactMatch (k, vs) | |
class Escape a where | |
escape :: a -> a | |
instance Escape Value where | |
escape xs = "\"" ++ inner xs ++ "\"" | |
where | |
inner [] = [] | |
inner ('"':xs) = "\\\"" ++ xs | |
inner (x :xs) = x:inner xs | |
instance Escape ArrayValue where | |
escape = Prelude.map escape | |
-- | Document is a monoid | |
instance Monoid Document where | |
mempty = Empty | |
Empty `mappend` Empty = Empty | |
Empty `mappend` x = x | |
x@(Pair _) `mappend` y@(Pair _) = And $ fromList [x, y] | |
x@(Pair _) `mappend` (And ys) = And $ x `insert` ys | |
x@(Pair _) `mappend` y@(Or _) = And $ fromList [x, y] | |
And xs `mappend` And ys = And $ xs `union` ys | |
Or xs `mappend` Or ys = Or $ xs `union` ys | |
x@(And _) `mappend` y@(Or _) = And $ fromList [x, y] | |
x `mappend` y = y `mappend` x | |
-- | Render Document to a query | |
render :: Document -> String | |
render Empty = "" | |
render (Pair (ExactMatch (k,v))) = "{" ++ k ++ ": " ++ escape v ++ "}" | |
render (Pair (ArrayExactMatch (k,vs))) = "{" ++ k ++ ": " ++ "[ " ++ concatPairs (escape vs) ++ " ] }" | |
render (Pair (Lt (k,v))) = "{" ++ k ++ ": { $lt: " ++ escape v ++ " } }" | |
render (Pair (In (k,vs))) = "{" ++ k ++ ": " ++ "{ $in: [" ++ concatPairs (escape $ toList vs) ++ " ] } }" | |
render (And xs) = "[" ++ concatPairs (toList $ map render xs) ++ "]" | |
render (Or xs) = "{$or: [ " ++ concatPairs (toList $ map render xs) ++ " ] }" | |
-- | | |
concatPairs :: [String] -> String | |
concatPairs = intercalate ", " | |
-- | Disjunction of documents | |
(<||>) :: Document -> Document -> Document | |
Empty <||> y = y | |
x <||> Empty = x | |
x <||> y = Or $ fromList [x, y] | |
infixr 7 <||> | |
-- | Conjunction of documents | |
(<&&>) :: Document -> Document -> Document | |
(<&&>) = mappend | |
infixr 7 <&&> | |
-- | Builder of exact match document | |
(==>) :: ExactMatchable a => String -> a -> Document | |
x ==> y = Pair $ exactMatch x y | |
infixr 8 ==> | |
-- | Builder of $in document | |
in' :: String -> [String] -> Document | |
x `in'` ys = Pair $ In (x, fromList ys) | |
-- | Builder of $lt document | |
lt :: String -> String -> Document | |
x `lt` y = Pair $ Lt (x, y) | |
main :: IO () | |
main = do | |
let a = "a" ==> "1" | |
b = "b" ==> "2" <||> "b" ==> "0" | |
c = "c" ==> "3" <&&> "d" ==> "foo\"bar" | |
d = "d" `in'` [ "3", "4", "5", "6"] | |
e = "e" `lt` "8" | |
f = "c" ==> ["3", "5", "7"] | |
g = Empty <||> Empty <||> a | |
putStrLn $ render $ (a <&&> b) <&&> c | |
putStrLn $ render $ a <&&> (b <&&> c) | |
putStrLn $ render $ d <&&> e | |
putStrLn $ render $ f <&&> a | |
putStrLn $ render $ b <||> f | |
putStrLn $ render $ g <&&> a |
Author
fujimura
commented
Mar 21, 2014
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