1 files changed, 55 insertions, 0 deletions
diff --git a/aoc2017-gleam/src/helpers/state.gleam b/aoc2017-gleam/src/helpers/state.gleam
new file mode 100644
index 0000000..cbbad81
--- /dev/null
+++ b/aoc2017-gleam/src/helpers/state.gleam
@@ -0,0 +1,55 @@
+import gleam/erlang/process.{type Subject, Normal}
+import gleam/option.{None}
+import gleam/otp/actor.{type Next, Continue, Stop}
+import gleam/set.{type Set}
+
+const timeout = 1000
+
+pub type Message(k) {
+  Shutdown
+  Check(key: k, client: Subject(Bool))
+  Add(key: k)
+  Drop(key: k)
+  Pop(client: Subject(Result(k, Nil)))
+}
+
+fn handle_message(message: Message(k), set: Set(k)) -> Next(Message(k), Set(k)) {
+  case message {
+    Shutdown -> Stop(Normal)
+    Check(key, client) -> {
+      process.send(client, set.contains(set, key))
+      Continue(set, None)
+    }
+    Add(key) -> Continue(set.insert(set, key), None)
+    Drop(key) -> Continue(set.delete(set, key), None)
+    Pop(client) -> {
+      case set.to_list(set) {
+        [next, ..] -> {
+          process.send(client, Ok(next))
+          Continue(set.delete(set, next), None)
+        }
+        [] -> {
+          process.send(client, Error(Nil))
+          Stop(Normal)
+        }
+      }
+    }
+  }
+}
+
+pub fn start_actor(with: Set(a)) {
+  let assert Ok(actor) = actor.start(with, handle_message)
+  actor
+}
+
+pub fn pop(actor) {
+  process.call(actor, Pop, timeout)
+}
+
+pub fn check(actor, value) {
+  process.call(actor, Check(value, _), timeout)
+}
+
+pub fn drop(actor, value) {
+  process.send(actor, Drop(value))
+}