dex/scripts/build-snapshot.mjs

#!/usr/bin/env node
/**
 * Build a compact, offline-first data snapshot from PokéAPI.
 *
 * The app runs its list, search, sort, filters and game switching entirely
 * off this file — no network until you open a detail page. It carries, per
 * species: name, generation, current + past typings, the six base stats and
 * their total, height, weight, base experience, and species flags
 * (legendary / mythical / baby, capture rate, growth rate, colour, egg
 * groups, gender rate). Plus every regional Pokédex and every version group.
 *
 * Richer detail (abilities, moves, flavour text, evolution, encounters) is
 * fetched on demand by the app and cached by the service worker.
 *
 * Output: src/data/snapshot.json  (imported by src/data/snapshot.js)
 * Usage:  node scripts/build-snapshot.mjs [--force]
 */
import { writeFile, mkdir, stat } from 'node:fs/promises';
import { dirname, resolve } from 'node:path';
import { fileURLToPath } from 'node:url';

const __dirname = dirname(fileURLToPath(import.meta.url));
const OUT = resolve(__dirname, '../src/data/snapshot.json');
const BASE = 'https://pokeapi.co/api/v2';
const MAX_AGE_DAYS = 30;
const FORCE = process.argv.includes('--force');
const CONCURRENCY = 16;

const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
const idFromUrl = (u) => Number(u.replace(/\/$/, '').split('/').pop());
const pretty = (k) => k.replace(/-/g, ' ').replace(/\b\w/g, (c) => c.toUpperCase());

const _cache = new Map();
async function api(path) {
  if (_cache.has(path)) return _cache.get(path);
  const url = path.startsWith('http') ? path : `${BASE}/${path}`;
  let lastErr;
  for (let attempt = 0; attempt < 5; attempt++) {
    try {
      const res = await fetch(url);
      if (res.ok) {
        const json = await res.json();
        _cache.set(path, json);
        return json;
      }
      if (res.status === 404) throw new Error(`404 ${url}`);
      lastErr = new Error(`${res.status} ${url}`);
    } catch (err) {
      lastErr = err;
    }
    await sleep(400 * (attempt + 1));
  }
  throw lastErr;
}

async function mapLimit(items, limit, fn) {
  const out = new Array(items.length);
  let i = 0;
  let done = 0;
  const total = items.length;
  const workers = Array.from({ length: Math.min(limit, total) }, async () => {
    while (i < total) {
      const idx = i++;
      out[idx] = await fn(items[idx], idx);
      if (++done % 200 === 0 || done === total) {
        process.stdout.write(`\r  … ${done}/${total} species`);
      }
    }
  });
  await Promise.all(workers);
  if (total) process.stdout.write('\n');
  return out;
}

async function isFresh() {
  try {
    const s = await stat(OUT);
    return (Date.now() - s.mtimeMs) / 86_400_000 < MAX_AGE_DAYS;
  } catch {
    return false;
  }
}

async function main() {
  if (!FORCE && (await isFresh())) {
    console.log(
      `snapshot.json is fresh (< ${MAX_AGE_DAYS} days old). Use --force to rebuild.`,
    );
    return;
  }

  console.log('Building snapshot from PokéAPI …');
  const t0 = Date.now();

  // ---- Type name list ------------------------------------------------
  const typeIndex = await api('type?limit=100');
  const types = typeIndex.results
    .map((r) => r.name)
    .filter((n) => !['unknown', 'shadow', 'stellar'].includes(n));

  // ---- Generations (for display names / regions) ------------------
  const genIndex = await api('generation?limit=50');
  const generations = [];
  await mapLimit(genIndex.results, 8, async (g) => {
    const data = await api(`generation/${g.name}`);
    generations.push({
      id: data.id,
      name: pretty(data.main_region?.name || g.name),
      region: data.main_region?.name || null,
    });
  });
  generations.sort((a, b) => a.id - b.id);

  // ---- Pokédexes ----------------------------------------------------
  const dexIndex = await api('pokedex?limit=100');
  const pokedexes = [];
  await mapLimit(dexIndex.results, 8, async (d) => {
    const data = await api(`pokedex/${d.name}`);
    pokedexes.push({
      key: data.name,
      name: pretty(data.name),
      region: data.region?.name || null,
      isMainSeries: data.is_main_series,
      versionGroups: data.version_groups.map((v) => v.name),
      entries: data.pokemon_entries
        .map((e) => [idFromUrl(e.pokemon_species.url), e.entry_number])
        .sort((a, b) => a[1] - b[1]),
    });
  });
  pokedexes.sort((a, b) => a.key.localeCompare(b.key));

  // ---- Version groups (the "games") -----------------------------
  const vgIndex = await api('version-group?limit=100');
  const versionGroups = [];
  await mapLimit(vgIndex.results, 8, async (v) => {
    const data = await api(`version-group/${v.name}`);
    versionGroups.push({
      key: data.name,
      name: pretty(data.name),
      generation: idFromUrl(data.generation.url),
      versions: data.versions.map((x) => x.name),
      pokedexKeys: data.pokedexes.map((x) => x.name),
    });
  });
  versionGroups.sort(
    (a, b) => a.generation - b.generation || a.key.localeCompare(b.key),
  );

  // ---- Species: the data-rich part -----------------------------
  const speciesIndex = await api('pokemon-species?limit=100000');
  const ids = speciesIndex.results
    .map((r) => idFromUrl(r.url))
    .sort((a, b) => a - b);

  console.log(`Fetching ${ids.length} species (stats, typings, flags) …`);
  const species = await mapLimit(ids, CONCURRENCY, async (id) => {
    const [pk, sp] = await Promise.all([
      api(`pokemon/${id}`),
      api(`pokemon-species/${id}`),
    ]);
    const s = Object.fromEntries(pk.stats.map((x) => [x.stat.name, x.base_stat]));
    const stats = {
      hp: s.hp ?? 0,
      atk: s.attack ?? 0,
      def: s.defense ?? 0,
      spa: s['special-attack'] ?? 0,
      spd: s['special-defense'] ?? 0,
      spe: s.speed ?? 0,
    };
    return {
      id,
      name: sp.name,
      generation: idFromUrl(sp.generation.url),
      types: pk.types
        .slice()
        .sort((a, b) => a.slot - b.slot)
        .map((t) => t.type.name),
      pastTypes: (pk.past_types || []).map((p) => ({
        gen: idFromUrl(p.generation.url),
        types: p.types.slice().sort((a, b) => a.slot - b.slot).map((t) => t.type.name),
      })),
      stats,
      bst: stats.hp + stats.atk + stats.def + stats.spa + stats.spd + stats.spe,
      height: pk.height,
      weight: pk.weight,
      baseExp: pk.base_experience ?? null,
      isLegendary: sp.is_legendary,
      isMythical: sp.is_mythical,
      isBaby: sp.is_baby,
      captureRate: sp.capture_rate,
      baseHappiness: sp.base_happiness,
      growthRate: sp.growth_rate?.name || null,
      color: sp.color?.name || null,
      eggGroups: sp.egg_groups.map((g) => g.name),
      genderRate: sp.gender_rate,
    };
  });

  // ---- Write ----------------------------------------------------
  const snapshot = {
    meta: {
      generatedAt: new Date().toISOString(),
      source: BASE,
      counts: {
        species: species.length,
        pokedexes: pokedexes.length,
        versionGroups: versionGroups.length,
      },
    },
    types,
    generations,
    species,
    pokedexes,
    versionGroups,
  };

  await mkdir(dirname(OUT), { recursive: true });
  const body = JSON.stringify(snapshot);
  await writeFile(OUT, body);
  console.log(
    `Wrote ${OUT} — ${species.length} species, ${pokedexes.length} pokédexes, ` +
      `${versionGroups.length} version groups (${(body.length / 1024).toFixed(0)} KB) in ` +
      `${((Date.now() - t0) / 1000).toFixed(1)}s`,
  );
}

main().catch((err) => {
  console.error('\nSnapshot build failed:', err.message);
  console.error(
    'If you are offline, commit a previously generated src/data/snapshot.json ' +
      'or retry when you have a connection.',
  );
  process.exit(1);
});