create initial POC script generating API

agora-scripts/Data/Cache/Cached.hs

@@ -0,0 +1,41 @@
+{- | Module     : API
+   Maintainer : emi@haskell.fyi
+   Description: API for script exporter.
+
+   API for script exporter.
+-}
+module Data.Cache.Cached (
+  cached,
+  cachedFor,
+) where
+
+import Control.Monad.IO.Class (MonadIO (liftIO))
+import Data.Cache qualified as Cache
+import Data.Functor ((<&>))
+import Data.Hashable (Hashable)
+import System.Clock (TimeSpec)
+
+{- | 'cachedFor' but items last forever.
+
+   Uses a HashMap under the hood.
+-}
+cached :: (Monad m, MonadIO m, Hashable k, Ord k) => (k -> v) -> IO (k -> m v)
+cached = cachedFor Nothing
+
+{- | Create a cached version of a function tainting result with MonadIO context.
+
+   Results are cached dependent on the first argument, @'Maybe' 'TimeSpec'@.
+
+   Uses a HashMap under the hood.
+-}
+cachedFor :: (Monad m, MonadIO m, Hashable k, Ord k) => Maybe TimeSpec -> (k -> v) -> IO (k -> m v)
+cachedFor t f =
+  Cache.newCache t <&> \cache k -> do
+    res <- liftIO $ Cache.lookup cache k
+    case res of
+      Nothing -> do
+        let v = f k
+        liftIO $ Cache.insert cache k v
+        pure v
+      Just v -> do
+        pure v