CliOptions: Parse the `language` option into a `Locale`

Instead of parsing `--language` as a string, parse it as a real `Locale`
type. This means the parsing is taken care of for us at the CLI option
handling stage instead of later on.

We can thus use the language value more quickly and easily, passing it
to the `translate` function, which takes a `Locale`.

2 files changed, 13 insertions, 4 deletions

diff --git a/src/CliOptions.hs b/src/CliOptions.hs
index 60f05ad..9d8baf6 100644
--- a/src/CliOptions.hs
+++ b/src/CliOptions.hs
@@ -7,11 +7,20 @@ module CliOptions
 import Data.Semigroup ((<>))
 import Options.Applicative
 
+import I18n (Locale(EN, FR))
+
 data Options = Options
     { slackApiToken :: String
-    , language      :: String
+    , language      :: Locale
     }
 
+-- | Parse the language command line option string into a `Locale` type
+parseLanguage :: ReadM Locale
+parseLanguage = eitherReader $ \s -> case s of
+    "en" -> Right EN
+    "fr" -> Right FR
+    _    -> Left "Unrecognised language code"
+
 options :: Parser Options
 options = Options
     <$> strOption
@@ -19,11 +28,11 @@ options = Options
         <> metavar "TOKEN"
         <> value ""
         <> help "Token to access Slack's real-time messaging API" )
-    <*> strOption
+    <*> option parseLanguage
          ( long "language"
         <> short 'l'
         <> metavar "en"
-        <> value "en"
+        <> value EN
         <> help "Set the language Sorbot will speak in (en | fr)" )
 
 parseOptions :: IO Options
diff --git a/src/I18n.hs b/src/I18n.hs
index 5a74d80..e50ba5b 100644
--- a/src/I18n.hs
+++ b/src/I18n.hs
@@ -9,7 +9,7 @@ module I18n
 
 import qualified Data.Text as T
 
-data Locale = EN | FR
+data Locale = EN | FR deriving (Show)
 
 data Message
     = GitHubCommitRepoURLNotFound