Add lenses to listing and use them in the example bot

src/Haboli/Euphoria/ExampleBot.hs

@@ -1,7 +1,13 @@
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TemplateHaskell   #-}
 
 -- | This module contains an example implementation of a small bot. It is a good
 -- starting point if you want to create your own bot.
+--
+-- The example bot uses lenses for its state because they vastly reduce the
+-- amount of code required to update the 'Listing' inside the state. It is
+-- entirely possible to use haboli without lenses though, should you want to do
+-- that.
 
 module Haboli.Euphoria.ExampleBot
   ( exampleBot
@@ -14,15 +20,19 @@ import           Data.List
 import qualified Data.Map.Strict          as Map
 import qualified Data.Text                as T
 import           Data.Time
+import           Lens.Micro
+import           Lens.Micro.TH
 
 import           Haboli.Euphoria
 import           Haboli.Euphoria.Botrulez
 
 data BotState = BotState
-  { botStartTime :: UTCTime
-  , botListing   :: Listing
+  { _botStartTime :: UTCTime
+  , _botListing   :: Listing
   } deriving (Show)
 
+makeLenses ''BotState
+
 -- | A small example bot. Takes a room password as its first argument. You can
 -- run this bot in [&test](https://euphoria.io/room/test) like this:
 --
@@ -33,27 +43,27 @@ exampleBot mPasswd = do
   initialEvents <- untilConnected $
     respondingToBounce mPasswd $
     respondingToPing nextEvent
-  listing <- preferNick "ExampleBot" $ newListing initialEvents
-  stateVar <- liftIO $ newMVar $ BotState startTime listing
+  let initialState = BotState startTime $ newListing initialEvents
+  stateVar <- liftIO $ newMVar initialState
+  preferNickVia botListing stateVar "ExampleBot"
   botMain stateVar
 
 botMain :: MVar BotState -> Client T.Text ()
 botMain stateVar = forever $ do
   event <- respondingToCommands (getCommands stateVar) $
     respondingToPing nextEvent
-  -- Update the listing
-  liftIO $ modifyMVar_ stateVar $ \state ->
-    pure state{botListing = updateFromEvent event $ botListing state}
+  updateFromEventVia botListing stateVar event
 
 getCommands :: MVar BotState -> Client e [Command T.Text]
 getCommands stateVar = do
   state <- liftIO $ readMVar stateVar
-  let name = svNick $ self $ botListing state
+  let name = state ^. botListing . lsSelfL . svNickL
   pure
     [ botrulezPingGeneral
     , botrulezPingSpecific name
-    , botrulezHelpSpecific name "I am an example bot for https://github.com/Garmelon/haboli/."
-    , botrulezUptimeSpecific name $ botStartTime state
+    , botrulezHelpSpecific name
+        "I am an example bot for https://github.com/Garmelon/haboli/."
+    , botrulezUptimeSpecific name $ state ^. botStartTime
     , botrulezKillSpecific name
     , cmdSpecific "hug" name $ \msg -> void $ reply msg "/me hugs back"
     , cmdHello
@@ -68,15 +78,12 @@ cmdHello = cmdGeneral "hello" $ \msg -> do
 
 cmdNick :: MVar BotState -> T.Text -> Command e
 cmdNick stateVar name = cmdSpecificArgs "nick" name $ \msg args -> do
-  -- Update the listing while updating the nick
-  state <- liftIO $ takeMVar stateVar
-  listing' <- preferNick args $ botListing state
-  liftIO $ putMVar stateVar state{botListing = listing'}
+  preferNickVia botListing stateVar args
   void $ reply msg "Is this better?"
 
 cmdWho :: MVar BotState -> Command e
 cmdWho stateVar = cmdGeneral "who" $ \msg -> do
   state <- liftIO $ readMVar stateVar
-  let people = others $ botListing state
+  let people = state ^. botListing . lsOthersL
       nicks = sort $ map svNick $ Map.elems people
   void $ reply msg $ T.intercalate "\n" nicks