1 files changed, 57 insertions, 0 deletions
diff --git a/codingquest2024/src/utilities/memo.gleam b/codingquest2024/src/utilities/memo.gleam
new file mode 100644
index 0000000..b06d8fd
--- /dev/null
+++ b/codingquest2024/src/utilities/memo.gleam
@@ -0,0 +1,57 @@
+import gleam/dict.{type Dict}
+import gleam/otp/actor.{type Next, Continue, Stop}
+import gleam/erlang/process.{type Subject, Normal}
+import gleam/option.{None}
+
+const timeout = 1000
+
+type Message(k, v) {
+  Shutdown
+  Get(key: k, client: Subject(Result(v, Nil)))
+  Set(key: k, value: v)
+}
+
+type Server(k, v) =
+  Subject(Message(k, v))
+
+pub opaque type Cache(k, v) {
+  Cache(server: Server(k, v))
+}
+
+fn handle_message(
+  message: Message(k, v),
+  dict: Dict(k, v),
+) -> Next(Message(k, v), Dict(k, v)) {
+  case message {
+    Shutdown -> Stop(Normal)
+    Get(key, client) -> {
+      process.send(client, dict.get(dict, key))
+      Continue(dict, None)
+    }
+    Set(key, value) -> Continue(dict.insert(dict, key, value), None)
+  }
+}
+
+pub fn create(apply fun: fn(Cache(k, v)) -> t) -> t {
+  let assert Ok(server) = actor.start(dict.new(), handle_message)
+  let result = fun(Cache(server))
+  process.send(server, Shutdown)
+  result
+}
+
+pub fn set(in cache: Cache(k, v), for key: k, insert value: v) -> Nil {
+  process.send(cache.server, Set(key, value))
+}
+
+pub fn get(from cache: Cache(k, v), fetch key: k) -> Result(v, Nil) {
+  process.call(cache.server, fn(c) { Get(key, c) }, timeout)
+}
+
+pub fn memoize(with cache: Cache(k, v), this key: k, apply fun: fn() -> v) -> v {
+  let result = case get(from: cache, fetch: key) {
+    Ok(value) -> value
+    Error(Nil) -> fun()
+  }
+  set(in: cache, for: key, insert: result)
+  result
+}