diff --git a/app/Main.hs b/app/Main.hs
index 366217a..07f9028 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -6,9 +6,10 @@ import Data.Either (lefts, rights)
 import Data.Text qualified as T
 import Data.Text.Encoding qualified as TE
 import Data.Text.Lazy qualified as TL
-import Data.Time (MonthOfYear, Year, addDays, fromGregorian, getCurrentTime, toGregorian)
+import Data.Time (MonthOfYear, Year, addDays, addUTCTime, fromGregorian, getCurrentTime, secondsToNominalDiffTime, toGregorian)
 import Data.Time.LocalTime
 import Ical
+import Interested qualified
 import Lucid (renderText)
 import Network.HTTP.Simple
 import Network.HTTP.Types (status400)
@@ -16,6 +17,7 @@ import Network.Wai.Middleware.Static
 import Render
 import Text.Printf (printf)
 import Web.Scotty
+import Web.Scotty.Cookie (defaultSetCookie, setCookieExpires, setCookieName, setCookieValue)
 
 getFromUrl :: String -> IO T.Text
 getFromUrl url = do
@@ -82,4 +84,20 @@ main =
                 liftIO $ print errors
 
               html $ renderText $ renderMonthview (year, month) dayToday groupedEvents
+        get "/api/interested/register/:event" $ do
+          event <- pathParam "event"
+          let cookieName = "interested-" <> event
+          returnUri <- queryParam "return"
+          cookie <- getCookie cookieName
+          newCookie <- liftIO $ Interested.register event cookie
+          currentTime <- (liftIO $ getCurrentTime)
+          setCookie
+            ( defaultSetCookie
+                { setCookieName = TE.encodeUtf8 cookieName,
+                  setCookieValue = TE.encodeUtf8 newCookie,
+                  -- TODO: just adding one month of expire which is kind of weird
+                  setCookieExpires = Just (addUTCTime (secondsToNominalDiffTime 60 * 60 * 24 * 30) currentTime)
+                }
+            )
+          redirect returnUri
     )
diff --git a/chipburners-club.cabal b/chipburners-club.cabal
index 9123d54..9e3a036 100644
--- a/chipburners-club.cabal
+++ b/chipburners-club.cabal
@@ -52,6 +52,7 @@ executable chipburners-club
   -- Modules included in this executable, other than Main.
   other-modules:
     Ical
+    Interested
     Render
 
   -- LANGUAGE extensions used by modules in this package.
@@ -62,6 +63,7 @@ executable chipburners-club
 
   -- Other library packages from which modules are imported.
   build-depends:
+    aeson,
     base ^>=4.20.2.0,
     bytestring,
     containers,
@@ -71,6 +73,7 @@ executable chipburners-club
     scotty,
     text,
     time,
+    uuid,
     wai-middleware-static,
 
   -- Directories containing source files.
diff --git a/src/Interested.hs b/src/Interested.hs
new file mode 100644
index 0000000..25a1e12
--- /dev/null
+++ b/src/Interested.hs
@@ -0,0 +1,19 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Interested (register) where
+
+import Data.Text qualified as T
+import Data.UUID qualified as UUID
+import Data.UUID.V4 qualified as UUID.V4
+
+register :: T.Text -> Maybe T.Text -> IO T.Text
+register event identifier = do
+  cookie_uuid <- case ( case identifier of
+                          Just i -> UUID.fromString (T.unpack i)
+                          Nothing -> Nothing
+                      ) of
+    Just i -> pure i
+    Nothing -> UUID.V4.nextRandom
+  appendFile "test.txt" (T.unpack (T.filter (\c -> c /= '\n' && c /= ',') event) <> "," <> (UUID.toString cookie_uuid) <> "\n")
+
+  pure $ (UUID.toText cookie_uuid)