import { once } from "node:events";
import WebSocket, { WebSocketServer } from "ws";
import { TestContext } from "node:test";
import { stringify } from "lossless-json";
import { ActorSnapshot, WEBSOCKET_SUBPROTOCOL } from "../src/protocol";

export const REF = "abcdefghijklmnopqrstu";

export function actor(): ActorSnapshot {
  return {
    actor_ref: REF,
    mailbox_id: 18446744073709551615n,
    implementation_id: "implementation:test",
    incarnation: 1n,
    state: {
      type: "record",
      data: {
        minimum: { type: "integer", data: -9223372036854775808n },
        maximum: { type: "integer", data: 9223372036854775807n },
        reference: { type: "actor_ref", data: REF },
        text: { type: "string", data: `@${REF} "雪"` },
        list: { type: "list", data: [{ type: "null" }, { type: "bool", data: true }] },
      },
    },
    status: { status: "paused" },
    execution: { vm_steps: 20n, instruction_pointer: 12n, call_depth: 1n },
    queued: [{ type: "bool", data: false }],
    reserved: { type: "null" },
  };
}

export function json(value: unknown): string {
  const result = stringify(value);
  if (result === undefined) throw new Error("Cannot encode test fixture");
  return result;
}

export interface TestRequest {
  version: number;
  request_id: string;
  command: { operation: string; parameters?: Record<string, unknown> };
}

export function response(request: TestRequest, reply: unknown): string {
  return json({ version: 4, request_id: request.request_id, result: { Ok: reply } });
}

export async function fakeImage(
  t: TestContext,
  handle: (request: TestRequest, socket: WebSocket) => void,
  protocol = WEBSOCKET_SUBPROTOCOL,
): Promise<string> {
  const server = new WebSocketServer({
    host: "127.0.0.1",
    port: 0,
    handleProtocols: (offered) => (offered.has(protocol) ? protocol : false),
  });
  server.on("connection", (socket) => {
    socket.on("error", () => {
      // Transport-failure tests intentionally close a socket while the fixture is writing.
    });
    socket.on("message", (data) => handle(JSON.parse(data.toString()), socket));
  });
  await once(server, "listening");
  t.after(async () => {
    for (const socket of server.clients) socket.terminate();
    await new Promise<void>((resolve, reject) =>
      server.close((error) => (error ? reject(error) : resolve())),
    );
  });
  const address = server.address();
  if (!address || typeof address === "string") throw new Error("Missing test listener");
  return `127.0.0.1:${address.port}`;
}

export function notification(revision: bigint): string {
  return json({ version: 4, event: { event: "image_changed", data: { revision } } });
}