85 lines
2.6 KiB
Haskell
85 lines
2.6 KiB
Haskell
{-# LANGUAGE OverloadedStrings #-}
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module Main where
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import Control.Applicative
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import Control.Exception (try)
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import Database.HDBC.PostgreSQL (connectPostgreSQL)
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import Database.HDBC.Types (SqlError, seErrorMsg)
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import Network.Wai
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import Network.Wai.Handler.Warp hiding (Connection)
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import Network.HTTP.Types.Status
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import Network.HTTP.Types.Header
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import Network.HTTP.Types.Method
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import Options.Applicative hiding (columns)
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import qualified Data.ByteString.Lazy as BL
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import qualified Data.ByteString.Char8 as BS
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import PgStructure (printTables, printColumns)
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import PgQuery (selectWhere)
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import Data.Maybe (fromMaybe)
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import qualified Data.Text as T
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import Text.Regex.Posix ((=~))
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import Text.Read (readMaybe)
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data AppConfig = AppConfig {
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configDbUri :: String
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, configPort :: Int }
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argParser :: Parser AppConfig
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argParser = AppConfig
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<$> strOption (long "db" <> short 'd' <> metavar "URI"
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<> help "database uri to expose, e.g. postgres://user:pass@host:port/database")
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<*> option (long "port" <> short 'p' <> metavar "NUMBER" <> value 3000
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<> help "port number on which to run HTTP server")
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main :: IO ()
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main = do
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conf <- execParser (info (helper <*> argParser) describe)
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Prelude.putStrLn $ "Listening on port " ++ (show $ configPort conf :: String)
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run (configPort conf) $ app conf
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where
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describe = progDesc "create a REST API to an existing Postgres database"
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app :: AppConfig -> Application
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app config req respond = do
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r <- try $
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case path of
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[] -> responseLBS status200 [json] <$> (printTables ver =<< conn)
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[table] -> responseLBS status200 [json] <$>
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( if verb == methodOptions
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then printColumns table =<< conn
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else selectWhere (T.pack $ show ver) table qq =<< conn )
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_ -> return $ responseLBS status404 [] ""
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respond $ either sqlErrorHandler id r
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where
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path = pathInfo req
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verb = requestMethod req
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json = (hContentType, "application/json")
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conn = connectPostgreSQL $ configDbUri config
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qq = queryString req
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ver = fromMaybe 1 $ requestedVersion (requestHeaders req)
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requestedVersion :: RequestHeaders -> Maybe Int
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requestedVersion hdrs =
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case verStr of
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Just [[_, ver]] -> readMaybe ver
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_ -> Nothing
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where verRegex = "version[ ]*=[ ]*([0-9]+)" :: String
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accept = BS.unpack <$> lookup hAccept hdrs :: Maybe String
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verStr = (=~ verRegex) <$> accept :: Maybe [[String]]
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sqlErrorHandler :: SqlError -> Response
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sqlErrorHandler e =
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responseLBS status400 [] $ BL.fromChunks [BS.pack (seErrorMsg e)]
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