refactor(Main): simplify body of main by using ExceptT transformer

src/Main.purs

@@ -1,32 +1,42 @@
 module Main where
 
+import Control.Monad.Except.Trans (ExceptT(..), runExceptT, withExceptT)
 import Data.Either (Either(..))
 import Effect (Effect)
 import HTTP.Server as HTTPServer
 import HTTP.Utils as HTTPUtils
 import Logger as Logger
 import Orchestrator.FS (readFile)
 import Orchestrator.JSON (fromJSON)
-import Orchestrator.Main (makeId, makeSecret, runDefinitionWithIdAndSecret)
+import Orchestrator.Main (Definitions, makeId, makeSecret, runDefinitionWithIdAndSecret)
 import Prelude
 import System.Environment (readEnvInt)
 
+readConfiguration :: ExceptT String Effect String
+readConfiguration =
+ withExceptT
+ (const "Failure reading configuration.json")
+ (ExceptT $ readFile "configuration.json")
+
+parseConfiguration :: String -> ExceptT String Effect Definitions
+parseConfiguration string =
+ withExceptT
+ (\lines -> "Configuration file is not structured properly" <> "\n" <> lines)
+ (ExceptT $ pure $ fromJSON string)
+
+getConfiguration :: Effect (Either String Definitions)
+getConfiguration = runExceptT $ readConfiguration >>= parseConfiguration
+
 main :: Effect Unit
 main = do
  port <- readEnvInt "PORT" 8181
- configuration <- readFile "configuration.json"
+ configuration <- getConfiguration
  case configuration of
- (Left _) -> Logger.error "Failure reading configuration.json"
- (Right contents) -> do
- parsed <- pure $ fromJSON contents
- case parsed of
- (Left error) -> do
- Logger.error "Configuration file is not structured properly"
- Logger.quote error
- (Right definitions) -> do
- HTTPServer.startSync port $ \route -> do
- Logger.info $ "Incoming request " <> route
- when (HTTPUtils.pathname route == "/run") do
- runDefinitionWithIdAndSecret (makeId (HTTPUtils.param "definition" route)) (makeSecret (HTTPUtils.param "secret" route)) definitions
- Logger.log $ "Orchy server is running at http:https://localhost:" <> (show port)
- Logger.line
+ (Left msg) -> Logger.error msg
+ (Right definitions) -> do
+ HTTPServer.startSync port $ \route -> do
+ Logger.info $ "Incoming request " <> route
+ when (HTTPUtils.pathname route == "/run") do
+ runDefinitionWithIdAndSecret (makeId (HTTPUtils.param "definition" route)) (makeSecret (HTTPUtils.param "secret" route)) definitions
+ Logger.log $ "Orchy server is running at http:https://localhost:" <> (show port)
+ Logger.line