You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
117 lines
2.9 KiB
117 lines
2.9 KiB
-- Necessary:
|
|
{-# LANGUAGE DeriveDataTypeable #-}
|
|
{-# LANGUAGE GADTs #-}
|
|
{-# LANGUAGE MultiParamTypeClasses #-}
|
|
{-# LANGUAGE OverloadedStrings #-}
|
|
{-# LANGUAGE StandaloneDeriving #-}
|
|
{-# LANGUAGE TypeFamilies #-}
|
|
|
|
-- Incidental:
|
|
{-# LANGUAGE FlexibleInstances #-}
|
|
{-# LANGUAGE TypeSynonymInstances #-}
|
|
|
|
module Main where
|
|
|
|
import Control.Monad
|
|
import Data.Hashable
|
|
import Data.List
|
|
import Data.Text (Text)
|
|
import Data.Traversable (for)
|
|
import Data.Typeable
|
|
import Haxl.Core
|
|
import System.Random
|
|
|
|
import qualified Data.Text as Text
|
|
|
|
main :: IO ()
|
|
main = do
|
|
let stateStore = stateSet UserState{} stateEmpty
|
|
env0 <- initEnv stateStore ()
|
|
names <- runHaxl env0 getAllUsernames
|
|
print names
|
|
|
|
-- Data source API.
|
|
|
|
getAllUsernames :: Haxl [Name]
|
|
getAllUsernames = do
|
|
userIds <- getAllUserIds
|
|
for userIds $ \userId -> do
|
|
getUsernameById userId
|
|
|
|
getAllUserIds :: Haxl [Id]
|
|
getAllUserIds = dataFetch GetAllIds
|
|
|
|
getUsernameById :: Id -> Haxl Name
|
|
getUsernameById userId = dataFetch (GetNameById userId)
|
|
|
|
-- Aliases.
|
|
|
|
type Haxl = GenHaxl () ()
|
|
type Id = Int
|
|
type Name = Text
|
|
|
|
-- Data source implementation.
|
|
|
|
data UserReq a where
|
|
GetAllIds :: UserReq [Id]
|
|
GetNameById :: Id -> UserReq Name
|
|
deriving (Typeable)
|
|
|
|
deriving instance Eq (UserReq a)
|
|
instance Hashable (UserReq a) where
|
|
hashWithSalt s GetAllIds = hashWithSalt s (0::Int)
|
|
hashWithSalt s (GetNameById a) = hashWithSalt s (1::Int, a)
|
|
|
|
deriving instance Show (UserReq a)
|
|
instance ShowP UserReq where showp = show
|
|
|
|
instance StateKey UserReq where
|
|
data State UserReq = UserState {}
|
|
|
|
instance DataSourceName UserReq where
|
|
dataSourceName _ = "UserDataSource"
|
|
|
|
instance DataSource u UserReq where
|
|
fetch _state _flags _userEnv = SyncFetch $ \blockedFetches -> do
|
|
let
|
|
allIdVars :: [ResultVar [Id]]
|
|
allIdVars = [r | BlockedFetch GetAllIds r <- blockedFetches]
|
|
|
|
idStrings :: [String]
|
|
idStrings = map show ids
|
|
|
|
ids :: [Id]
|
|
vars :: [ResultVar Name]
|
|
(ids, vars) = unzip
|
|
[(userId, r) | BlockedFetch (GetNameById userId) r <- blockedFetches]
|
|
|
|
unless (null allIdVars) $ do
|
|
allIds <- sql "select id from ids"
|
|
mapM_ (\r -> putSuccess r allIds) allIdVars
|
|
|
|
unless (null ids) $ do
|
|
names <- sql $ unwords
|
|
[ "select name from names where"
|
|
, intercalate " or " $ map ("id = " ++) idStrings
|
|
, "order by find_in_set(id, '" ++ intercalate "," idStrings ++ "')"
|
|
]
|
|
mapM_ (uncurry putSuccess) (zip vars names)
|
|
|
|
-- Mock SQL API.
|
|
|
|
class SQLResult a where
|
|
mockResult :: IO a
|
|
|
|
instance SQLResult a => SQLResult [a] where
|
|
mockResult = replicateM 10 mockResult
|
|
|
|
instance SQLResult Name where
|
|
-- An infinite number of employees, all named Jim.
|
|
mockResult = ("Jim" `Text.append`) . Text.pack . show <$> randomRIO (1::Int, 100)
|
|
|
|
instance SQLResult Id where
|
|
mockResult = randomRIO (1, 100)
|
|
|
|
sql :: SQLResult a => String -> IO a
|
|
sql query = print query >> mockResult
|