two-p-set

(no submodules)

Purpose

Provides TwoPSet<T>, a Two-Phase Set CRDT. Elements can be added and removed exactly once; removed elements can never be re-added. The set value is the difference between the add-set and the remove-set. This guarantees eventual consistency at the cost of restricting re-addition.

Features

add(element) — adds to the A-set; throws OPERATION_INVALID if element was previously removed
remove(element) — moves element to the R-set; no-op if not in A-set
has(element) — true if in A-set but not R-set
value() — returns a Set<T> of live elements
merge(state) — union-merges both A-set and R-set
toJSON() / fromJSON() — serialization round-trip
clone() — deep copy

Usage: Basic Example

import { TwoPSet } from "@suaveplan/crdt";

const set = new TwoPSet<string>();
set.add("alice");
set.remove("alice");
console.log(set.has("alice")); // false

Usage: Advanced Example

import { TwoPSet } from "@suaveplan/crdt";

const a = new TwoPSet<number>();
a.add(1);
const b = new TwoPSet<number>();
b.add(2);
a.merge(b.state());
console.log([...a.value()]); // [1, 2]

API Reference

`TwoPSet<T>`

add(element) — throws OPERATION_INVALID if previously removed
remove(element) — no-op if element not in A-set
has(element): boolean
value(): Set<T>
merge(state: TwoPSetState<T>): void

Implementation Notes

Elements are serialised to JSON for key comparison, enabling support for object elements with structural equality. The restriction that removed elements cannot be re-added is a fundamental invariant of 2P-Set that enables simple merge logic.

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