tools/eu4_clausewitz/src/registry.mjs

// Registry metadata + the Sugar Proxy API, layered on top of overlay.mjs /
// index.mjs without changing either. Registries are optional enhancement:
// `eu4.dir('history/provinces')` (the zero-config path) keeps working
// exactly as before whether or not anything is registered. All this module
// adds is:
//   1. a declarative shape (`defineRegistry`) for "this directory's records
//      have this key style, these fields may legitimately repeat, and these
//      fields point at that other registry's key-space";
//   2. named accessors (`eu4.provinces()`, `eu4.countries()`, ...) that are
//      just `eu4.dir(registry.path)` with sugar-wrapped nodes;
//   3. the Sugar Proxy itself (`sugar(node, registry)`), so `p.culture`
//      reads like `p.get('culture')` (or `p.all('culture')` for a
//      multi-valued field) and `p.culture = 'x'` writes through to
//      `p.set('culture', 'x')`.
//
// registry.key is NOT consulted to pick an overlay mode — overlay.mjs's own
// MODE_TABLE (keyed by path) already decides that, independently of
// anything declared here. `key` is documentation of what that mode's
// natural key looks like, kept for readability and for tests that want to
// cross-check a registry's declared `key` against `modeFor(registry.path)`.

/**
 * @typedef {Object} RegistryDescriptor
 * @property {string} path - relative directory path, e.g. "history/provinces"
 * @property {string} as - property name to attach on `eu4`, e.g. "provinces"
 * @property {'province-id'|'country-tag'|'filename'} key - documents the natural key style (see header note)
 * @property {string[]} [multi] - field names that may legitimately repeat at top level
 * @property {Object<string,string>} [refs] - field name -> target registry `as` name (or a bare defined-set name like 'countries'/'cultures'/'religions'/'tradegoods')
 */

/**
 * Normalize a registry descriptor. Doesn't validate against the filesystem
 * or against overlay.mjs — just fills in the optional fields so every
 * consumer can assume `multi`/`refs` exist without checking.
 *
 * @param {RegistryDescriptor} descriptor
 * @returns {RegistryDescriptor}
 */
export function defineRegistry(descriptor) {
  if (!descriptor || typeof descriptor.path !== 'string' || typeof descriptor.as !== 'string') {
    throw new Error('defineRegistry: "path" and "as" are required');
  }
  return {
    path: descriptor.path,
    as: descriptor.as,
    key: descriptor.key ?? 'filename',
    multi: descriptor.multi ?? [],
    refs: descriptor.refs ?? {},
  };
}

// Wraps one already-sugared-or-not Node behind a Proxy. Kept separate from
// wrapCollection so it can be reused directly by anything that already has a
// bare Node in hand (e.g. tests).
export function sugar(node, registry) {
  if (!node) return node;
  const multi = registry?.multi ?? [];

  return new Proxy(node, {
    get(target, prop, receiver) {
      if (typeof prop !== 'string') return Reflect.get(target, prop, receiver);
      // `in` walks the prototype chain, so this covers every real method
      // (get/all/has/keys/bareValues/block/blocks/set/add/remove/at/raw/file)
      // AND every own instance field (items/tokens/text/path/layer/session/
      // readonly/...) — none of those are ever shadowed by sugar, on
      // purpose: a field literally named "path" or "keys" in game data must
      // still be reached via .get('path')/.get('keys'), never silently
      // replace the real API.
      if (prop in target) return Reflect.get(target, prop, receiver);

      if (multi.includes(prop)) return target.all(prop);
      const occurrences = target.all(prop);
      if (occurrences.length > 1) return occurrences;
      return target.get(prop); // 0 or 1 occurrence — safe, never throws
    },
    set(target, prop, value, receiver) {
      if (typeof prop === 'string' && !(prop in target)) {
        target.set(prop, value);
        return true;
      }
      return Reflect.set(target, prop, value, receiver);
    },
  });
}

// Wraps a makeCollection()-shaped collection (get/all/where) so every Node
// it hands back is sugared. `where()` is reimplemented (rather than
// delegated to the inner collection) so a caller's predicate function sees
// SUGARED nodes — `col.where(n => n.culture === 'castillian')` only works
// if `n` is already wrapped by the time the predicate runs.
function wrapCollection(collection, registry) {
  const wrapNode = (node) => sugar(node, registry);
  return {
    async get(key) {
      return wrapNode(await collection.get(key));
    },
    async all() {
      return (await collection.all()).map(wrapNode);
    },
    async where(predicate) {
      const nodes = (await collection.all()).map(wrapNode);
      if (typeof predicate === 'function') return nodes.filter(predicate);
      return nodes.filter((node) => Object.entries(predicate).every(([k, v]) => node.get(k) === v));
    },
  };
}

/**
 * Attach `eu4[registry.as]` for every registry in the list. Each accessor
 * is an async function (matching `eu4.dir`'s own async shape): call it as
 * `await eu4.provinces()` to get a sugar-wrapped collection. Purely
 * additive — never touches `eu4.dir`/`eu4.file`/`eu4.save`.
 *
 * @param {ReturnType<typeof import('../src/index.mjs').load>} eu4
 * @param {RegistryDescriptor[]} registries
 */
export function attachRegistries(eu4, registries) {
  for (const registry of registries) {
    eu4[registry.as] = async () => {
      const collection = await eu4.dir(registry.path);
      return wrapCollection(collection, registry);
    };
  }
  return eu4;
}