/**
 * Shared machinery for walk-path child stubs (see `hast/child-stub.ts` and
 * `mdast/child-stub.ts`): lightweight stand-ins that carry arena id + type
 * eagerly and defer the full-arena snapshot until a plugin reads a real field.
 * Passthrough children (the common replaceNode shape) thus compile to one-word
 * refs without ever serializing the arena.
 */
/** Stub → materialized arena node, filled on the first real-field read. */
const REAL_NODES = new WeakMap();
/** One shared memoizing getter per field name, so stubs install shared
 *  descriptor templates instead of allocating per-field closures per node. */
const FIELD_GETTERS = new Map();
function fieldGetter(key) {
    let getter = FIELD_GETTERS.get(key);
    if (getter === undefined) {
        getter = function () {
            let real = REAL_NODES.get(this);
            if (real === undefined) {
                real = this._resolver.materializeOne(this._id);
                REAL_NODES.set(this, real);
            }
            const value = real[key];
            Object.defineProperty(this, key, {
                value,
                writable: true,
                enumerable: true,
                configurable: true,
            });
            return value;
        };
        FIELD_GETTERS.set(key, getter);
    }
    return getter;
}
/**
 * Descriptor template for one node type's stub fields. Own enumerable getters
 * so a spread copy carries correct values. `position`/`data` ride on every
 * stub; they may yield `undefined` where a materialized node omits the key —
 * accepted drift, invisible to `toEqual`.
 */
export function stubDescriptors(fields) {
    const map = {};
    for (const key of [...fields, "position", "data"]) {
        map[key] = { get: fieldGetter(key), enumerable: true, configurable: true };
    }
    return map;
}
/** Node tags are dense small ints, so the per-child stub loop indexes flat
 *  arrays instead of paying Map/dictionary lookups. */
export function flatByTag(table) {
    const flat = [];
    for (const tag of Object.keys(table)) {
        const nodeType = Number(tag);
        flat[nodeType] = table[nodeType];
    }
    return flat;
}