123 lines
3.5 KiB
Haskell
123 lines
3.5 KiB
Haskell
{-# LANGUAGE OverloadedStrings #-}
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module Main where
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import Data.ByteString.Lazy
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import Data.Text
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import Database.PostgreSQL.Simple
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import Database.PostgreSQL.Simple.FromRow
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import Control.Applicative
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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 qualified Data.Aeson as JSON
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import Data.Aeson ((.=))
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import Options.Applicative hiding (columns)
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data Table = Table {
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tableSchema :: String
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, tableName :: String
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, tableInsertable :: Bool
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} deriving (Show)
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instance FromRow Table where
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fromRow = Table <$> field <*> field <*> fmap toBool field
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instance JSON.ToJSON Table where
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toJSON v = JSON.object [
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"schema" .= tableSchema v
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, "name" .= tableName v
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, "insertable" .= tableInsertable v ]
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toBool :: String -> Bool
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toBool = (== "YES")
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data Column = Column {
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colSchema :: String
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, colTable :: String
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, colName :: String
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, colPosition :: Int
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, colNullable :: Bool
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, colType :: String
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, colUpdatable :: Bool
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, colMaxLen :: Maybe Int
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, colPrecision :: Maybe Int
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} deriving (Show)
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instance FromRow Column where
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fromRow = Column <$> field <*> field <*> field <*> field <*>
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fmap toBool field <*> field <*>
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fmap toBool field <*>
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field <*> field
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instance JSON.ToJSON Column where
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toJSON c = JSON.object [
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"schema" .= colSchema c
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, "name" .= colName c
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, "position" .= colPosition c
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, "nullable" .= colNullable c
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, "type" .= colType c
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, "updatable" .= colUpdatable c
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, "maxLen" .= colMaxLen c
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, "precision" .= colPrecision c ]
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tables :: String -> Connection -> IO [Table]
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tables s conn = query conn q $ Only s
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where q = "select table_schema, table_name,\
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\ is_insertable_into \
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\ from information_schema.tables\
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\ where table_schema = ?"
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columns :: Text -> Connection -> IO [Column]
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columns t conn = query conn q $ Only t
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where q = "select table_schema, table_name, column_name, ordinal_position,\
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\ is_nullable, data_type, is_updatable,\
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\ character_maximum_length, numeric_precision\
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\ from information_schema.columns\
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\ where table_name = ?"
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data AppConfig = AppConfig {
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configDb :: 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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exposeDb :: AppConfig -> IO ()
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exposeDb conf = do
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Prelude.putStrLn $ "Listening on port " ++ show port
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run port app
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where
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port = configPort conf
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main :: IO ()
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main = execParser (info (helper <*> argParser) describe) >>= exposeDb
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where describe = progDesc "create a REST API to an existing Postgres database"
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printTables :: Connection -> IO ByteString
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printTables conn = JSON.encode <$> tables "base" conn
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printColumns :: Text -> Connection -> IO ByteString
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printColumns table conn = JSON.encode <$> columns table conn
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app :: Application
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app req respond =
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case path of
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[] -> respond =<< responseLBS status200 [] <$> (printTables =<< conn)
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[table] -> respond =<< responseLBS status200 [] <$> (printColumns table =<< conn)
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_ -> respond $ responseLBS status404 [] ""
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where
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path = pathInfo req
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conn = connect defaultConnectInfo {
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connectDatabase = "dbapi_test"
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}
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