scrabble-game/ui/src/lib/dict/generate.parity.test.ts

import { describe, it, expect } from 'vitest';
import { readFileSync } from 'node:fs';
import { Dawg } from './dawg';
import { generateMoves, GenRack, type GenBoard, type Mode } from './generate';
import type { Ruleset } from './validate';

// Conformance gate for the ported move generator: for each committed position it must
// return exactly the ranked play list the real Go solver returns (backend/cmd/movegen).
// The Russian sample reaches alphabet index 32, exercising the 33-letter cross-set.

interface Tile {
  row: number;
  col: number;
  letter: number;
  blank: boolean;
}
interface GenMove {
  dir: number;
  tiles: Tile[];
  score: number;
}
interface Fixture {
  ruleset: {
    size: number;
    cols: number;
    center: number;
    rackSize: number;
    bingo: number;
    values: number[];
    letterMult: number[][];
    wordMult: number[][];
  };
  cases: {
    name: string;
    placed: Tile[] | null;
    rack: { letters: number[]; blanks: number };
    mode: number;
    ignoreCrossWords: boolean;
    moves: GenMove[];
  }[];
}

function load(tag: string): { dawg: Dawg; fx: Fixture } {
  const bytes = new Uint8Array(readFileSync(new URL(`./testdata/sample_${tag}.dawg`, import.meta.url)));
  const fx = JSON.parse(
    readFileSync(new URL(`./testdata/sample_${tag}.gen.json`, import.meta.url), 'utf8'),
  ) as Fixture;
  return { dawg: new Dawg(bytes), fx };
}

function buildBoard(placed: Tile[], cols: number): GenBoard {
  const grid: ({ letter: number; blank: boolean } | null)[] = new Array(cols * cols).fill(null);
  for (const t of placed) grid[t.row * cols + t.col] = { letter: t.letter, blank: t.blank };
  const inBounds = (r: number, c: number): boolean => r >= 0 && r < cols && c >= 0 && c < cols;
  return {
    rows: cols,
    cols,
    inBounds,
    filled: (r, c) => inBounds(r, c) && grid[r * cols + c] !== null,
    cellAt: (r, c) => grid[r * cols + c]!,
    isEmpty: () => placed.length === 0,
  };
}

function rulesetFor(fx: Fixture, ignoreCrossWords: boolean): Ruleset {
  const r = fx.ruleset;
  return {
    cols: r.cols,
    center: r.center,
    rackSize: r.rackSize,
    bingo: r.bingo,
    values: r.values,
    letterMult: (row, col) => r.letterMult[row][col],
    wordMult: (row, col) => r.wordMult[row][col],
    ignoreCrossWords,
  };
}

// sig is an order-stable signature of a move: orientation, score and its placed tiles
// sorted by square — so two lists compare equal iff they rank the same plays the same way.
function sig(m: GenMove): string {
  const ts = m.tiles.slice().sort((a, b) => (a.row !== b.row ? a.row - b.row : a.col - b.col));
  return `${m.dir}#${m.score}#` + ts.map((t) => `${t.row},${t.col},${t.letter}${t.blank ? '*' : ''}`).join(';');
}

for (const tag of ['en', 'ru']) {
  describe(`move generator parity vs Go solver (${tag})`, () => {
    const { dawg, fx } = load(tag);
    for (const c of fx.cases) {
      it(c.name, () => {
        const board = buildBoard(c.placed ?? [], fx.ruleset.cols);
        const rack = GenRack.from(fx.ruleset.size, c.rack.letters, c.rack.blanks);
        const rs = rulesetFor(fx, c.ignoreCrossWords);
        const got = generateMoves(dawg, board, rack, rs, c.mode as Mode);
        expect(got.map(sig)).toEqual(c.moves.map(sig));
      });
    }
  });
}