/**
 * This Source Code is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright (c) Infonomic Company Limited
 */
/**
 * Copy-to-Locale merge walker.
 *
 * Schema-aware, pure tree merge used by `copyToLocale` to decide, leaf by
 * leaf, whether to take the source locale's value or keep the target's.
 */
import { type FieldSet } from '../../@types/index.js';
/**
 * Result of merging source-locale and target-locale data trees for
 * `copyToLocale`. `data` is the payload to hand to
 * `createDocumentVersion`; `fieldsUpdated` counts every localized leaf
 * the merge rule chose to overwrite (used for UI toasts).
 */
export interface CopyToLocaleMergeResult {
    data: Record<string, any>;
    fieldsUpdated: number;
}
/**
 * Build the payload `copyToLocale` will write into the target locale.
 *
 * Walks `definition.fields` and the two reconstructed data trees in
 * lockstep, applying the merge rule at every leaf:
 *
 *   - **Localized leaf, `overwrite: true`** — take source's value (even
 *     when source is empty; overwriting means overwriting).
 *   - **Localized leaf, `overwrite: false`** — take source's value only
 *     when target is empty AND source is non-empty. Otherwise keep
 *     target's value. Empties under this rule are treated by
 *     `isEmptyLeafValue` — `null` / `undefined` / `''`.
 *   - **Non-localized leaf** — always keep target's value. Non-localized
 *     fields live on `locale: 'all'` rows in storage and would be wiped
 *     by the upcoming write if we did not pass them through verbatim.
 *
 * Structure (number of array items, blocks, etc.) follows the *target*
 * tree — copy-to-locale never restructures the document; it only fills
 * in localized leaves at positions the target already has.
 *
 * Pure: mutates nothing. The returned `data` is a fresh tree suitable
 * to pass to `createDocumentVersion`.
 */
export declare function mergeLocaleData(fields: FieldSet, sourceData: Record<string, any> | null | undefined, targetData: Record<string, any> | null | undefined, overwrite: boolean): CopyToLocaleMergeResult;