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scrabble-game/ui/src/lib/dict/dawg.cursor.test.ts
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Ilia Denisov c334a9d7b7
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feat(offline): port DAWG cursor + move generator to TS (parity-pinned)
First engine-first step of PWA offline mode (Phase A): the client-side move
generator — the "robot brain" a local vs_ai game will run on-device — with no
runtime wiring yet (Phase B).

- dawg.ts: add the step-by-step cursor (root/final/next/arcs), a faithful port
  of dafsa traverse.go over the reader's existing bitstream.
- generate.ts: the Appel-Jacobson generator (leftPart/extendRight + cross-sets +
  counts-rack + board transpose + moveKey ranking), reusing the cursor and
  validate.ts evaluate/connected. A cross-set LetterSet is a Uint8Array, so the
  33-letter Russian alphabet (index 32) is exact under JS bit ops.
- validate.ts: export connected for the generator's connectivity filter.
- backend/cmd/movegen: dev tool building small sample dictionaries and emitting
  golden move-generation fixtures from the real Go solver (EN + RU).
- tests: dawg.cursor.test.ts (enumeration bijection vs indexOf) and
  generate.parity.test.ts (7/7 vs the Go solver: empty board, mid-game, blank,
  single-word rule, Russian index-32 cross-set). The committed EN sample also
  unblocks the existing skipped dawg.parity.test.ts once wired with DICT_* in CI.

Pure additive library code; no runtime behavior change.
2026-07-06 01:35:11 +02:00

69 lines
2.4 KiB
TypeScript

import { describe, it, expect } from 'vitest';
import { readFileSync } from 'node:fs';
import { Dawg } from './dawg';
// The step-by-step DAWG cursor (root/final/next/arcs) is the primitive the move
// generator walks. These fast unit tests pin it against a small committed sample
// dictionary (backend/cmd/movegen); the full parity vs the Go solver lands with
// the generator's conformance fixtures.
const bytes = new Uint8Array(readFileSync(new URL('./testdata/sample_en.dawg', import.meta.url)));
const fixture = JSON.parse(
readFileSync(new URL('./testdata/sample_en.words.json', import.meta.url), 'utf8'),
) as { numAdded: number; words: string[]; indexes: number[][] };
const key = (w: number[]): string => w.join(',');
// enumerateWords walks the whole automaton depth-first, collecting the index path
// at every accepting node — i.e. every stored word.
function enumerateWords(d: Dawg): number[][] {
const out: number[][] = [];
const path: number[] = [];
const visit = (node: number): void => {
d.arcs(node, (label, dest, final) => {
path.push(label);
if (final) out.push(path.slice());
visit(dest);
path.pop();
return true;
});
};
if (d.final(d.root())) out.push([]);
visit(d.root());
return out;
}
describe('dawg cursor', () => {
it('parses the sample fixture', () => {
const d = new Dawg(bytes);
expect(d.numAdded).toBe(fixture.numAdded);
});
it('root is not an accepting state (the sample has no empty word)', () => {
const d = new Dawg(bytes);
expect(d.final(d.root())).toBe(false);
});
it('enumerates exactly the stored words', () => {
const d = new Dawg(bytes);
const got = enumerateWords(d).map(key).sort();
const want = fixture.indexes.map(key).sort();
expect(got).toEqual(want);
});
it('next walks a stored word to an accepting node and rejects a non-edge', () => {
const d = new Dawg(bytes);
let node = d.root();
for (const ch of [2, 0, 17, 4, 3]) {
// "cared"
node = d.next(node, ch);
expect(node).toBeGreaterThanOrEqual(0);
}
expect(d.final(node)).toBe(true);
// "care" (index [2,0,17,4]) is an internal accepting node on the way to "cared".
const care = [2, 0, 17, 4].reduce((n, ch) => d.next(n, ch), d.root());
expect(d.final(care)).toBe(true);
// No stored word starts with 'z' (index 25).
expect(d.next(d.root(), 25)).toBe(-1);
});
});