gitHubCommitAction: Get error handling to work using `Either`

Get rid of the `fail` and use an `Either` for error handling instead.
This allows us to send back the response string like before, but provide
an additional error message when no data comes back from the database
query.

Remove the old error handling code I had tried to set up previously.

2 files changed, 5 insertions, 8 deletions

diff --git a/src/Plugin/Base.hs b/src/Plugin/Base.hs
index b752fd1..fe3a0f8 100644
--- a/src/Plugin/Base.hs
+++ b/src/Plugin/Base.hs
@@ -9,7 +9,7 @@ import Database.SQLite.Simple
 import Message
 
 -- TODO: Replace Connection with a type class
-type PluginAction = Message -> Connection -> IO String
+type PluginAction = Message -> Connection -> IO (Either String String)
 
 data Plugin = Plugin
     { matchRegex :: String
diff --git a/src/Plugin/GitHubCommit.hs b/src/Plugin/GitHubCommit.hs
index 8c11a12..73b617c 100644
--- a/src/Plugin/GitHubCommit.hs
+++ b/src/Plugin/GitHubCommit.hs
@@ -24,15 +24,12 @@ gitHubCommitAction message dbConn = do
         \ LIMIT 1"
         (Only (M.channel message))
         :: IO [RepoUrlRow]
-    -- return $ response rs
-    respond rs
+    return $ respond rs
   where
-    respond []     = fail "I couldn't find a repo URL for this channel. \
-        \ Try `git remote set origin REPO_URL`"
+    respond []     = Left "I couldn't find a repo URL for this channel. \
+        \Try `git remote set origin REPO_URL`"
     respond ((RepoUrlRow r):rs) =
-        return r ++ "/commits/" ++ M.text message =~ matchRegex gitHubCommit
--- TODO: Make an Either type for plugins to return errors
--- if empty query result, return an empty error, otherwise return the string
+        Right $ r ++ "/commits/" ++ M.text message =~ matchRegex gitHubCommit
 
 type Id = Int