Add dedupeBatch: collapse outbound calls per target

src/AFRP.hs

@@ -52,7 +52,7 @@ data Request = Request
   { requestTime :: !UTCTime
   , requestTimeZone :: !TimeZone
   , requestTraceId :: !UUID
-  } deriving Show
+  } deriving (Show, Eq)
 
 -- | The set of entity ids an arrow subscribes to. Static: it does not
 -- change as the machine steps, so the runtime can read it once to build

src/HomeAssistant/Controller.hs

@@ -39,7 +39,7 @@ import qualified Data.Text.Lens as TL
 import Data.Bool (bool)
 
 data Target = EntityId !T.Text | AreaId !T.Text
-  deriving (Show,Eq)
+  deriving (Show,Eq,Ord)
 
 data Service = Service
   { serviceDomain :: T.Text

src/HomeAssistant/Runtime/Connection.hs

@@ -5,6 +5,7 @@ module HomeAssistant.Runtime.Connection
   ( readerAction
   , writerAction
   , encodeService
+  , dedupeBatch
   ) where
 
 import Control.Concurrent.STM
@@ -23,6 +24,8 @@ import Control.Lens ((^?))
 import Control.Monad (forever, forM_)
 import Data.Aeson (Value, eitherDecode, encode, object, (.=))
 import Data.Aeson.Lens (key, _String)
+import Data.List (sort)
+import qualified Data.Map.Strict as M
 import qualified Data.Set as S
 import qualified Data.Text as T
 import Data.Void (Void)
@@ -119,6 +122,18 @@ encodeService callId Service{..} = object $
   , "target"  .= targetObject serviceTarget
   ] <> maybe [] (\d -> ["service_data" .= d]) serviceData
 
+-- | Collapse a drained batch of outbound calls: the newest call per
+-- `(domain, service, sorted-targets)` survives; older duplicates are
+-- dropped. `serviceData` is not part of the key, so a newer `turn_on`
+-- with different brightness supersedes an older one to the same target.
+dedupeBatch :: [(Request, Service)] -> [(Request, Service)]
+dedupeBatch = M.elems . foldl' ins M.empty
+  where
+    ins m (req, svc) = M.insert (dedupeKey svc) (req, svc) m
+
+dedupeKey :: Service -> (T.Text, T.Text, [Target])
+dedupeKey Service{..} = (serviceDomain, serviceName, sort serviceTarget)
+
 -- | A single target encodes as a scalar; multiple encode as a list. Empty
 -- lists are omitted so Home Assistant receives only populated keys.
 targetObject :: [Target] -> Value