Move package configuration to the configuration file

lib/SlackBuilder/Package.hs

@@ -2,15 +2,16 @@
    v. 2.0. If a copy of the MPL was not distributed with this file, You can
    obtain one at https://mozilla.org/MPL/2.0/. -}
 
--- | Contains data describing packages and how they are should be updated,
+-- | Contains data describing packages, methods to update them and to request
+-- information about them.
 module SlackBuilder.Package
-    ( DownloadPlaceholder(..)
-    , Download(..)
+    ( Download(..)
     , DownloadTemplate(..)
     , PackageDescription(..)
     , PackageUpdateData(..)
     , Updater(..)
     , renderDownloadWithVersion
+    , renderTextWithVersion
     ) where
 
 import Data.Text (Text)
@@ -41,18 +42,6 @@ data Download = Download
     , md5sum :: Digest MD5
     } deriving (Eq, Show)
 
--- | Appears in the download URI template and specifies which part of the URI
--- should be replaced with the package version.
-data DownloadPlaceholder
-    = StaticPlaceholder Text
-    | VersionPlaceholder
-    deriving Eq
-
-instance Show DownloadPlaceholder
-  where
-    show (StaticPlaceholder staticPlaceholder) = Text.unpack staticPlaceholder
-    show VersionPlaceholder = "{version}"
-
 -- | List of URI components, including version placeholders.
 newtype DownloadTemplate = DownloadTemplate
     { unDownloadTemplate :: Text
@@ -65,7 +54,11 @@ instance Show DownloadTemplate
 -- | Replaces placeholders in the URL template with the given version.
 renderDownloadWithVersion :: MonadThrow m => DownloadTemplate -> Text -> m URI
 renderDownloadWithVersion (DownloadTemplate template) version =
-    URI.mkURI $ Text.replace "{version}" version template
+    URI.mkURI $ renderTextWithVersion template version
+
+-- | Replaces placeholders in the text with the given version.
+renderTextWithVersion :: Text -> Text -> Text
+renderTextWithVersion template version = Text.replace "{version}" version template
 
 -- | Function used to get the latest version of a source.
 data Updater = Updater