lattice_text

Plain-text CRDT for Gleam using YATA-style left/right origins.

Use this package when replicas need to edit shared text concurrently and converge without coordination. All operations are grapheme-based, so emoji and combining sequences count as one unit. For a generic list CRDT, use lattice_sequence directly.

Installation

gleam add lattice_text

Quick example

import lattice_core/replica_id
import lattice_text/text

pub fn main() {
  let node_a =
    text.new(replica_id.new("node-a"))
    |> text.insert(0, "Hello world")

  let node_b =
    text.new(replica_id.new("node-b"))
    |> text.append("!")

  let merged = text.merge(node_a, node_b)

  text.value(merged)
  // -> "Hello world!"
}

Modules

Module	Purpose
`lattice_text/text`	Grapheme-based text CRDT with editing, range, and delta operations.

Notes

Editing operations: insert, delete, delete_range, replace_range, move, and append.
Query helpers: value, values, length, substring, and try_substring.
Fallible operations have try_* variants returning Result; the plain variants assert on invalid indexes. Range operations return RangeError when 0 <= start <= end <= length does not hold.
Delta-state variants (*_with_delta) return the updated text plus a delta that can be merged into other replicas, avoiding full-state sync.
Cursor anchors: anchor_at creates a stable position that survives concurrent edits and merges, resolve_anchor maps it back to a current grapheme index, and anchor_to_json/anchor_from_json let anchors travel between replicas (e.g. shared cursors).
merge, to_json, and from_json round-trip the full CRDT state using the canonical sequence JSON envelope.
Backed by lattice_sequence stable item IDs, so concurrent edits converge deterministically on both Erlang and JavaScript targets.

License

MIT