// Finds words that can be built from 1-4 distinct tiles in the puzzle pool
// but are missing from our dictionary, using a large reference word list
// (an-array-of-english-words, ~275k words) as the source of truth.
//
// Usage:
//   node scripts/find-missing-combo-words.mjs          # report only
//   node scripts/find-missing-combo-words.mjs --write  # save scripts/combo-words.txt
import fs from 'node:fs';
import { createRequire } from 'node:module';
import { buildWordSet } from './lexicon-sources.mjs';
import { TARGET_WORDS_POOL } from '../src/data/puzzles.js';

const require = createRequire(import.meta.url);
const REFERENCE = require('an-array-of-english-words');
const OUT_FILE = 'scripts/combo-words.txt';

// Every tile that can appear on a board (all puzzles are generated from the pool)
const chunks = new Set();
TARGET_WORDS_POOL.forEach(t => t.tiles.forEach(c => chunks.add(c.toLowerCase())));
const maxChunkLen = Math.max(...[...chunks].map(c => c.length));

// Base dictionary WITHOUT the previously generated combo list, so re-runs are stable
const dictionary = buildWordSet({ includeComboWords: false });

// Can `word` be split into 1-4 distinct pool tiles? Returns the split or null.
function segment(word, start = 0, used = []) {
  if (start === word.length) return used.length ? [...used] : null;
  if (used.length === 4) return null;
  for (let len = 1; len <= maxChunkLen && start + len <= word.length; len++) {
    const piece = word.slice(start, start + len);
    if (!chunks.has(piece) || used.includes(piece)) continue;
    used.push(piece);
    const result = segment(word, start + len, used);
    used.pop();
    if (result) return result;
  }
  return null;
}

const found = [];
for (const raw of REFERENCE) {
  const w = raw.toLowerCase();
  if (w.length < 3 || w.length > 16 || !/^[a-z]+$/.test(w)) continue; // 2-letter words use the fixed allowlist
  if (dictionary.has(w)) continue;
  const split = segment(w);
  if (split) found.push({ word: w, split });
}
found.sort((a, b) => a.word.localeCompare(b.word));

console.log(`Pool tiles: ${chunks.size}`);
console.log(`Missing words buildable from pool tiles: ${found.length}`);
const byTiles = { 1: 0, 2: 0, 3: 0, 4: 0 };
found.forEach(f => byTiles[f.split.length]++);
console.log('By tile count:', byTiles);
console.log('Sample:', found.slice(0, 40).map(f => `${f.word}(${f.split.join('+')})`).join(' '));

if (process.argv.includes('--write')) {
  const header = [
    '# Words buildable from pool tiles that are missing from wordlist-english.',
    '# Generated by scripts/find-missing-combo-words.mjs (source: an-array-of-english-words).',
    '# These are accepted in play but never shown in the 30-word solution lists.',
    '# Delete a line to stop accepting that word.'
  ];
  fs.writeFileSync(OUT_FILE, [...header, ...found.map(f => f.word)].join('\n') + '\n', 'utf8');
  console.log(`Saved ${found.length} words to ${OUT_FILE}`);
}