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+{-# Language CPP #-}
+-- | Settings are centralized, as much as possible, into this file. This
+-- includes database connection settings, static file locations, etc.
+-- In addition, you can configure a number of different aspects of Yesod
+-- by overriding methods in the Yesod typeclass. That instance is
+-- declared in the Foundation.hs file.
+module Settings where
+
+import ClassyPrelude.Yesod
+import qualified Control.Exception as Exception
+import Data.Aeson                  (Result (..), fromJSON, withObject, (.!=),
+                                    (.:?))
+import Data.FileEmbed              (embedFile)
+import Data.Yaml                   (decodeEither')
+import Database.Persist.Postgresql (PostgresConf)
+import Language.Haskell.TH.Syntax  (Exp, Q)
+import Network.Wai.Handler.Warp    (HostPreference)
+import Yesod.Default.Config2       (applyEnvValue, configSettingsYml)
+import Yesod.Default.Util          (WidgetFileSettings, widgetFileNoReload,
+                                    widgetFileReload)
+
+#ifdef DEVELOPMENT
+#define DEV_BOOL True
+#else
+#define DEV_BOOL False
+#endif
+
+-- | Runtime settings to configure this application. These settings can be
+-- loaded from various sources: defaults, environment variables, config files,
+-- theoretically even a database.
+data AppSettings = AppSettings
+    { appStaticDir              :: String
+    -- ^ Directory from which to serve static files.
+    , appDatabaseConf           :: PostgresConf
+    -- ^ Configuration settings for accessing the database.
+    , appRoot                   :: Maybe Text
+    -- ^ Base for all generated URLs. If @Nothing@, determined
+    -- from the request headers.
+    , appHost                   :: HostPreference
+    -- ^ Host/interface the server should bind to.
+    , appPort                   :: Int
+    -- ^ Port to listen on
+    , appIpFromHeader           :: Bool
+    -- ^ Get the IP address from the header when logging. Useful when sitting
+    -- behind a reverse proxy.
+
+    , appDetailedRequestLogging :: Bool
+    -- ^ Use detailed request logging system
+    , appShouldLogAll           :: Bool
+    -- ^ Should all log messages be displayed?
+    , appReloadTemplates        :: Bool
+    -- ^ Use the reload version of templates
+    }
+
+instance FromJSON AppSettings where
+    parseJSON = withObject "AppSettings" $ \o -> do
+        let defaultDev = DEV_BOOL
+        appStaticDir              <- o .: "static-dir"
+        appDatabaseConf           <- o .: "database"
+        appRoot                   <- o .:? "approot"
+        appHost                   <- fromString <$> o .: "host"
+        appPort                   <- o .: "port"
+        appIpFromHeader           <- o .: "ip-from-header"
+
+        appDetailedRequestLogging <- o .:? "detailed-logging" .!= defaultDev
+        appShouldLogAll           <- o .:? "should-log-all"   .!= defaultDev
+        appReloadTemplates        <- o .:? "reload-templates" .!= defaultDev
+
+        return AppSettings {..}
+
+-- | Settings for 'widgetFile', such as which template languages to support and
+-- default Hamlet settings.
+--
+-- For more information on modifying behavior, see:
+--
+-- https://github.com/yesodweb/yesod/wiki/Overriding-widgetFile
+widgetFileSettings :: WidgetFileSettings
+widgetFileSettings = def
+
+-- | How static files should be combined.
+combineSettings :: CombineSettings
+combineSettings = def
+
+-- The rest of this file contains settings which rarely need changing by a
+-- user.
+
+widgetFile :: String -> Q Exp
+widgetFile = (if appReloadTemplates compileTimeAppSettings
+                then widgetFileReload
+                else widgetFileNoReload)
+              widgetFileSettings
+
+-- | Raw bytes at compile time of @config/settings.yml@
+configSettingsYmlBS :: ByteString
+configSettingsYmlBS = $(embedFile configSettingsYml)
+
+-- | @config/settings.yml@, parsed to a @Value@.
+configSettingsYmlValue :: Value
+configSettingsYmlValue = either Exception.throw id
+                       $ decodeEither' configSettingsYmlBS
+
+-- | A version of @AppSettings@ parsed at compile time from @config/settings.yml@.
+compileTimeAppSettings :: AppSettings
+compileTimeAppSettings =
+    case fromJSON $ applyEnvValue False mempty configSettingsYmlValue of
+        Error e -> error e
+        Success settings -> settings