import type { Channel, ChannelMessage, JsonValue } from "@berry/api";
import { token } from "./client.ts";

/** Open a channel to `path`: its first message authorizes it and carries `args`; what `send` is given before then waits. */
export function openChannel(path: string, args: JsonValue | undefined): Channel {
  const scheme = location.protocol === "https:" ? "wss:" : "ws:";
  const socket = new WebSocket(`${scheme}//${location.host}${path}`);
  socket.binaryType = "arraybuffer";
  const waiting: ChannelMessage[] = [];
  const encode = (message: ChannelMessage) =>
    message instanceof Uint8Array ? message : JSON.stringify(message);
  let incoming!: ReadableStreamDefaultController<ChannelMessage>;
  const messages = new ReadableStream<ChannelMessage>({
    start: (controller) => void (incoming = controller),
    cancel: () => socket.close(1000),
  });
  socket.addEventListener("open", () => {
    socket.send(JSON.stringify({ token: token.get(), args: args ?? {} }));
    for (const message of waiting.splice(0)) socket.send(encode(message));
  });
  socket.addEventListener("message", (event) => {
    incoming.enqueue(
      typeof event.data === "string" ? JSON.parse(event.data) : new Uint8Array(event.data),
    );
  });
  socket.addEventListener("close", ({ code, reason }) => {
    try {
      // closed as asked, by either end; anything else is a failure, such as a restart or a refusal
      if (code === 1000) incoming.close();
      else incoming.error(new Error(reason || `the channel closed (${code})`));
    } catch {
      // already ended
    }
  });
  return {
    send(message) {
      if (socket.readyState === WebSocket.CONNECTING) waiting.push(message);
      else if (socket.readyState === WebSocket.OPEN) socket.send(encode(message));
    },
    messages,
    close: () => socket.close(1000),
  };
}