'use strict';

const crypto = require('node:crypto');

class ORSet {

#added;

#removed;

constructor({ added = {}, removed = {} } = {}) {

this.#added = { ...added };

this.#removed = { ...removed };

}

add(item, tag = crypto.randomUUID()) {

if (!this.#added[item]) this.#added[item] = new Set();

this.#added[item].add(tag);

return tag;

}

remove(item) {

if (!this.#added[item]) return;

if (!this.#removed[item]) this.#removed[item] = new Set();

for (const tag of this.#added[item]) {

this.#removed[item].add(tag);

}

}

merge(instance) {

const added = Object.entries(instance.added);

for (const [item, tags] of added) {

if (!this.#added[item]) this.#added[item] = new Set();

for (const tag of tags) {

this.#added[item].add(tag);

}

}

const removed = Object.entries(instance.removed);

for (const [item, tags] of removed) {

if (!this.#removed[item]) this.#removed[item] = new Set();

for (const tag of tags) {

this.#removed[item].add(tag);

}

}

}

get value() {

const result = [];

for (const item of Object.keys(this.#added)) {

const addTags = this.#added[item] || new Set();

const remTags = this.#removed[item] || new Set();

for (const tag of addTags) {

if (!remTags.has(tag)) {

result.push(item);

break;

}

}

}

return result;

}

get added() {

return this.#added;

}

get removed() {

return this.#removed;

}

}

// Usage

console.log('Replica 0');

const set0 = new ORSet();

set0.add('a');

set0.add('b');

set0.remove('a');

console.log({ id0: set0.value });

console.log('Replica 1');

const set1 = new ORSet();

set1.add('b');

set1.add('c');

set1.remove('b');

console.log({ id1: set1.value });

console.log('Sync');

set0.merge(set1);

set1.merge(set0);

console.log({ id0: { added: set0.added, removed: set0.removed } });

console.log({ id1: { added: set1.added, removed: set1.removed } });

console.log('Get value');

console.log({ id0: set0.value });

console.log({ id1: set1.value });