Split db functions into separate module

Main.hs

@@ -2,84 +2,17 @@
 
 module Main where
 
-import Data.ByteString.Lazy
-
-import Data.Text
+import Control.Applicative
 
 import Database.PostgreSQL.Simple
-import Database.PostgreSQL.Simple.FromRow
-import Control.Applicative
 
 import Network.Wai
 import Network.Wai.Handler.Warp hiding (Connection)
 import Network.HTTP.Types.Status
 
-import qualified Data.Aeson as JSON
-import Data.Aeson ((.=))
-
 import Options.Applicative hiding (columns)
 
-data Table = Table {
-  tableSchema :: String
-, tableName :: String
-, tableInsertable :: Bool
-} deriving (Show)
-
-instance FromRow Table where
-  fromRow = Table <$> field <*> field <*> fmap toBool field
-
-instance JSON.ToJSON Table where
-  toJSON v = JSON.object [
-      "schema"     .= tableSchema v
-    , "name"       .= tableName v
-    , "insertable" .= tableInsertable v ]
-
-toBool :: String -> Bool
-toBool = (== "YES")
-
-data Column = Column {
-  colSchema :: String
-, colTable :: String
-, colName :: String
-, colPosition :: Int
-, colNullable :: Bool
-, colType :: String
-, colUpdatable :: Bool
-, colMaxLen :: Maybe Int
-, colPrecision :: Maybe Int
-} deriving (Show)
-
-instance FromRow Column where
-  fromRow = Column <$> field <*> field <*> field <*> field <*>
-                       fmap toBool field <*> field <*>
-                       fmap toBool field <*>
-                       field <*> field
-
-instance JSON.ToJSON Column where
-  toJSON c = JSON.object [
-      "schema"    .= colSchema c
-    , "name"      .= colName c
-    , "position"  .= colPosition c
-    , "nullable"  .= colNullable c
-    , "type"      .= colType c
-    , "updatable" .= colUpdatable c
-    , "maxLen"    .= colMaxLen c
-    , "precision" .= colPrecision c ]
-
-tables :: String -> Connection -> IO [Table]
-tables s conn = query conn q $ Only s
-  where q = "select table_schema, table_name,\
-            \       is_insertable_into \
-            \  from information_schema.tables\
-            \ where table_schema = ?"
-
-columns :: Text -> Connection -> IO [Column]
-columns t conn = query conn q $ Only t
-  where q = "select table_schema, table_name, column_name, ordinal_position,\
-            \       is_nullable, data_type, is_updatable,\
-            \       character_maximum_length, numeric_precision\
-            \  from information_schema.columns\
-            \ where table_name = ?"
+import PgStructure (printTables, printColumns)
 
 data AppConfig = AppConfig {
     configDb   :: String
@@ -92,22 +25,17 @@ argParser = AppConfig
   <*> option (long "port" <> short 'p' <> metavar "NUMBER" <> value 3000
     <> help "port number on which to run HTTP server")
 
-exposeDb :: AppConfig -> IO ()
-exposeDb conf = do
-  Prelude.putStrLn $ "Listening on port " ++ show port
-  run port app
-    where
-      port = configPort conf
-
 main :: IO ()
 main = execParser (info (helper <*> argParser) describe) >>= exposeDb
   where describe = progDesc "create a REST API to an existing Postgres database"
 
-printTables :: Connection -> IO ByteString
-printTables conn = JSON.encode <$> tables "base" conn
+exposeDb :: AppConfig -> IO ()
+exposeDb conf = do
+  Prelude.putStrLn $ "Listening on port " ++ show port
+  run port app
 
-printColumns :: Text -> Connection -> IO ByteString
-printColumns table conn = JSON.encode <$> columns table conn
+  where
+    port = configPort conf
 
 app :: Application
 app req respond =

PgStructure.hs

@@ -0,0 +1,82 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module PgStructure where
+
+import Control.Applicative
+
+import Data.Text
+import Data.ByteString.Lazy
+
+import Database.PostgreSQL.Simple
+import Database.PostgreSQL.Simple.FromRow
+
+import qualified Data.Aeson as JSON
+import Data.Aeson ((.=))
+
+data Table = Table {
+  tableSchema :: String
+, tableName :: String
+, tableInsertable :: Bool
+} deriving (Show)
+
+instance FromRow Table where
+  fromRow = Table <$> field <*> field <*> fmap toBool field
+
+instance JSON.ToJSON Table where
+  toJSON v = JSON.object [
+      "schema"     .= tableSchema v
+    , "name"       .= tableName v
+    , "insertable" .= tableInsertable v ]
+
+toBool :: String -> Bool
+toBool = (== "YES")
+
+data Column = Column {
+  colSchema :: String
+, colTable :: String
+, colName :: String
+, colPosition :: Int
+, colNullable :: Bool
+, colType :: String
+, colUpdatable :: Bool
+, colMaxLen :: Maybe Int
+, colPrecision :: Maybe Int
+} deriving (Show)
+
+instance FromRow Column where
+  fromRow = Column <$> field <*> field <*> field <*> field <*>
+                       fmap toBool field <*> field <*>
+                       fmap toBool field <*>
+                       field <*> field
+
+instance JSON.ToJSON Column where
+  toJSON c = JSON.object [
+      "schema"    .= colSchema c
+    , "name"      .= colName c
+    , "position"  .= colPosition c
+    , "nullable"  .= colNullable c
+    , "type"      .= colType c
+    , "updatable" .= colUpdatable c
+    , "maxLen"    .= colMaxLen c
+    , "precision" .= colPrecision c ]
+
+tables :: String -> Connection -> IO [Table]
+tables s conn = query conn q $ Only s
+  where q = "select table_schema, table_name,\
+            \       is_insertable_into \
+            \  from information_schema.tables\
+            \ where table_schema = ?"
+
+columns :: Text -> Connection -> IO [Column]
+columns t conn = query conn q $ Only t
+  where q = "select table_schema, table_name, column_name, ordinal_position,\
+            \       is_nullable, data_type, is_updatable,\
+            \       character_maximum_length, numeric_precision\
+            \  from information_schema.columns\
+            \ where table_name = ?"
+
+printTables :: Connection -> IO ByteString
+printTables conn = JSON.encode <$> tables "base" conn
+
+printColumns :: Text -> Connection -> IO ByteString
+printColumns table conn = JSON.encode <$> columns table conn

dbapi.cabal

@@ -12,7 +12,7 @@ cabal-version:       >=1.10
 
 executable dbapi
   main-is:             Main.hs
-  -- other-modules:       
+  other-modules:       PgStructure
   other-extensions:    OverloadedStrings
   build-depends:       base >=4.6 && <5
                      , postgresql-simple