Add ability to inject characters into the input

src/mpv/mpv.gleam

@@ -4,13 +4,13 @@ import gleam/otp/actor
 import gleam/result
 import gleam/string
 
-import input/key
+import input/key.{type Key}
 import mpv/control.{type Control}
 import tcp/reason
 import tcp/tcp.{type Socket}
 
-type State(socket, exit) {
-  State(socket: Socket, exit: Subject(Nil))
+type State(socket, inject_input, exit) {
+  State(socket: Socket, inject_input: Subject(Key), exit: Subject(Nil))
 }
 
 pub fn new(exit: Subject(Nil)) -> Result(Nil, String) {
@@ -20,8 +20,14 @@ pub fn new(exit: Subject(Nil)) -> Result(Nil, String) {
   case tcp.connect(socket_path) {
     Error(r) -> Error("Could not connect to mpv: " <> reason.to_string(r))
     Ok(socket) -> {
+      // `inject_input` is created by name to allow the process that
+      // owns `read_input` to be able to register it, while the agent
+      // also have a reference to it to be able to inject input
+      let inject_input_name = process.new_name("inject_input")
+      let inject_input = process.named_subject(inject_input_name)
+
       case
-        actor.new(State(socket, exit))
+        actor.new(State(socket, inject_input, exit))
         |> actor.on_message(handle_message)
         |> actor.start
       {
@@ -30,7 +36,14 @@ pub fn new(exit: Subject(Nil)) -> Result(Nil, String) {
         Ok(actor.Started(data:, ..)) -> {
           echo "waiting for input"
           key.start_raw_shell()
-          process.spawn(fn() { read_input(data) })
+
+          process.spawn(fn() {
+            let assert Ok(_) =
+              process.register(process.self(), inject_input_name)
+
+            read_input(data, inject_input)
+          })
+
           Ok(Nil)
         }
       }
@@ -39,9 +52,9 @@ pub fn new(exit: Subject(Nil)) -> Result(Nil, String) {
 }
 
 fn handle_message(
-  state: State(socket, exit),
+  state: State(socket, inject, exit),
   control: Control,
-) -> actor.Next(State(socket, exit), Control) {
+) -> actor.Next(State(socket, inject, exit), Control) {
   case control {
     control.TogglePlayPause -> {
       echo "toggling play/pause"
@@ -65,14 +78,21 @@ fn handle_message(
   }
 }
 
-fn read_input(subject: Subject(Control)) -> Nil {
-  case
-    key.read_input_until_key([])
-    |> control.from_key
-  {
-    Error(_) -> Nil
-    Ok(control) -> process.send(subject, control)
+/// `read_input` operates by reading from input until a `Key` can be created.
+/// It is possible to create a `Key` without the users input by sending
+/// messages to `inject_input` which will initialize the "input to key" sequence.
+/// This is useful to ultimately create a `Control` without the user having to
+/// input all of the character(s) needed.
+fn read_input(subject: Subject(Control), inject_input: Subject(Key)) -> Nil {
+  let buffer = case process.receive(inject_input, 1) {
+    Ok(key.Continue(buffer)) -> buffer
+    Ok(_) | Error(_) -> []
   }
 
-  read_input(subject)
+  let _ =
+    key.read_input_until_key(buffer)
+    |> control.from_key
+    |> result.map(process.send(subject, _))
+
+  read_input(subject, inject_input)
 }