import { compileWat, WasmRunner } from "@exercism/wasm-lib";

let wasmModule;
let currentInstance;

beforeAll(async () => {
  try {
    const watPath = new URL("./hello-world.wat", import.meta.url);
    const { buffer } = await compileWat(watPath);
    wasmModule = await WebAssembly.compile(buffer);
  } catch (err) {
    console.log(`Error compiling *.wat: \n${err}`);
    process.exit(1);
  }
});

describe("Hello World", () => {
  beforeEach(async () => {
    currentInstance = null;

    if (!wasmModule) {
      return Promise.reject();
    }
    try {
      currentInstance = await new WasmRunner(wasmModule);
      return Promise.resolve();
    } catch (err) {
      console.log(`Error instantiating WebAssembly module: ${err}`);
      return Promise.reject();
    }
  });

  test("Say Hi!", () => {
    expect(currentInstance).toBeTruthy();
    const [offset, length] = currentInstance.exports.hello();
    expect(length).toBe(13);
    const greeting = currentInstance.get_mem_as_utf8(offset, length);
    expect(greeting).toBe("Hello, World!");
  });
});