Dhall configuration

.gitignore

@@ -1 +1,2 @@
 dist/
+config/config.dhall

config/config.dhall.sample

@@ -0,0 +1,8 @@
+{
+  database = {
+      username = "username"
+    , password = "password"
+    , host = "hostname"
+    , database = "ebook"
+  }
+}

config/devel.dhall

@@ -0,0 +1,10 @@
+-- Devel configuration file, with defaults for local testing environment
+-- pre-filled
+{
+  database = {
+      username = "postgres"
+    , password = "devel"
+    , host = "localhost"
+    , database = "postgres"
+  }
+}

docker-compose.yml

@@ -0,0 +1,9 @@
+version: '2'
+
+services:
+  postgres:
+    image: postgres:9.6.1
+    environment:
+      - POSTGRES_PASSWORD=devel
+    ports:
+      - "5432:5432"

ebook-manager.cabal

@@ -18,8 +18,9 @@ cabal-version:       >=1.10
 executable ebook-manager
   main-is:             Main.hs
   other-modules:       Devel.Main
-                     , Server
                      , API
+                     , Configuration
+                     , Server
                      , Types
   -- other-extensions:
   build-depends:       base >=4.10 && <4.11
@@ -45,5 +46,7 @@ executable ebook-manager
                      , dhall
                      , lucid
                      , servant-lucid
+                     , lens
+                     , generic-lens
   hs-source-dirs:      src
   default-language:    Haskell2010

src/Configuration.hs

@@ -0,0 +1,19 @@
+{-# Language NoImplicitPrelude #-}
+{-# Language DeriveGeneric #-}
+{-# Language DuplicateRecordFields #-}
+module Configuration where
+
+import ClassyPrelude
+import Dhall (Interpret)
+
+data Pg = Pg { username :: Text
+             , password :: Text
+             , host :: Text
+             , database :: Text }
+        deriving (Show, Generic)
+
+
+newtype Config = Config { database :: Pg } deriving (Show, Generic)
+
+instance Interpret Pg
+instance Interpret Config

src/Devel/Main.hs

@@ -1,3 +1,4 @@
+{-# Language OverloadedStrings #-}
 module Devel.Main where
 
 import Main (defaultMain)
@@ -6,6 +7,7 @@ import Control.Monad (void)
 import Data.IORef (IORef, newIORef, readIORef, writeIORef)
 import Foreign.Store (Store(..), lookupStore, readStore, storeAction, withStore)
 import GHC.Word (Word32)
+import Dhall (input, auto)
 
 update :: IO ()
 update = do
@@ -23,7 +25,7 @@ update = do
       withStore doneStore takeMVar
       readStore doneStore >>= start
     start :: MVar () -> IO ThreadId
-    start done = forkFinally defaultMain (\_ -> putMVar done ())
+    start done = forkFinally (input auto "./config/devel.dhall" >>= defaultMain) (\_ -> putMVar done ())
 
 modifyStoredIORef :: Store (IORef a) -> (a -> IO a) -> IO ()
 modifyStoredIORef store f = withStore store $ \ref -> do

src/Main.hs

@@ -1,11 +1,16 @@
+{-# Language OverloadedStrings #-}
 module Main where
 
 import Server (server)
 import Network.Wai.Handler.Warp (run)
 import Types
+import Configuration (Config)
+import Dhall (input, auto)
 
-defaultMain :: IO ()
+defaultMain :: Config -> IO ()
-defaultMain = run 8080 (server App)
+defaultMain c = run 8080 (server (App c))
 
 main :: IO ()
-main = defaultMain
+main = do
+  c <- input auto "./config/config.dhall"
+  defaultMain c

src/Types.hs

@@ -3,7 +3,8 @@ module Types where
 
 import ClassyPrelude
 import Control.Monad.Logger
+import Configuration
 
-data App = App
+newtype App = App { config :: Config }
 
 type AppM = LoggingT (ReaderT App IO)