import mongoose from "mongoose";
import { MongoServerError, MongoErrorLabel } from "mongodb";

console.log("connecting...");

// Connecting to a *ReplicaSet* specifically to make sure that transactions work correctly.
// Nevertheless, whether or not an actual ReplicaSet is used has no effect on the issue.
await mongoose.connect(
  "mongodb://mongo-node1:27017,mongo-node2:27018,mongo-node3:27019/xxx?replicaSet=eof"
);

console.log("connected!");

// Define some schemas...
const subItemSchema = new mongoose.Schema(
  {
    name: { type: String, required: true },
  },
  { _id: false }
);

const itemSchema = new mongoose.Schema(
  {
    name: { type: String, required: true },
    subItems: { type: [subItemSchema], required: true },
  },
  { _id: false }
);

const schema = new mongoose.Schema({
  items: { type: [itemSchema], required: true },
});

// ...and a model
const Model = mongoose.model("MyModel", schema);

// Clear the collection...
await Model.deleteMany({});

// ...and create one document
await Model.create({
  items: [
    { name: "test1", subItems: [{ name: "x1" }] },
    { name: "test2", subItems: [{ name: "x2" }] },
  ],
});

const doc = await Model.findOne();

// Array modification - choose one...
// Works okay, but I guess that's because it's an idempotent operation
doc.items.addToSet({ name: "test3", subItems: [{ name: "x3" }] });
// Adds unexpected extra entries
doc.items.push({ name: "test3", subItems: [{ name: "x3" }] });
// Corrupts the document. It seems that moving this inside the `.transaction()` callback solves the problem
doc.items.pull(doc.items[0]);
// Corrupts the document
doc.items.splice(0, 1);

let attempt = 0;

await mongoose.connection.transaction(async (session) => {
  console.log(`Attempt: ${attempt}`);

  await doc.save({ session });

  // This is the important bit. Uncomment this to trigger a transaction retry.
  // if (attempt === 0) {
  //   attempt += 1;
  //   throw new MongoServerError({
  //     message: "Test transient transaction failures & retries",
  //     errorLabels: [MongoErrorLabel.TransientTransactionError],
  //   });
  // }
});

const updatedDoc = await Model.findOne();

// See the structure here. Depending on the array operation, the structure may be different,
// but it's always wrong.
console.log(updatedDoc.items);

// Bye bye!
await mongoose.disconnect();