/**
* @license Copyright (c) 2003-2026, CKSource Holding sp. z o.o. All rights reserved.
* For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-licensing-options
*/
/**
* @module engine/model/utils/modifyselection
*/
import { ModelDocumentSelection } from "../documentselection.js";
import { type Model } from "../model.js";
import { type ModelSelection } from "../selection.js";
/**
* Modifies the selection. Currently, the supported modifications are:
*
* * Extending. The selection focus is moved in the specified `options.direction` with a step specified in `options.unit`.
* Possible values for `unit` are:
*  * `'character'` (default) - moves selection by one user-perceived character. In most cases this means moving by one
*  character in `String` sense. However, unicode also defines "combing marks". These are special symbols, that combines
*  with a symbol before it ("base character") to create one user-perceived character. For example, `q̣̇` is a normal
*  letter `q` with two "combining marks": upper dot (`Ux0307`) and lower dot (`Ux0323`). For most actions, i.e. extending
*  selection by one position, it is correct to include both "base character" and all of it's "combining marks". That is
*  why `'character'` value is most natural and common method of modifying selection.
*  * `'codePoint'` - moves selection by one unicode code point. In contrary to, `'character'` unit, this will insert
*  selection between "base character" and "combining mark", because "combining marks" have their own unicode code points.
*  However, for technical reasons, unicode code points with values above `UxFFFF` are represented in native `String` by
*  two characters, called "surrogate pairs". Halves of "surrogate pairs" have a meaning only when placed next to each other.
*  For example `𨭎` is represented in `String` by `\uD862\uDF4E`. Both `\uD862` and `\uDF4E` do not have any meaning
*  outside the pair (are rendered as ? when alone). Position between them would be incorrect. In this case, selection
*  extension will include whole "surrogate pair".
*  * `'word'` - moves selection by a whole word.
*
* **Note:** if you extend a forward selection in a backward direction you will in fact shrink it.
*
* **Note:** Use {@link module:engine/model/model~Model#modifySelection} instead of this function.
* This function is only exposed to be reusable in algorithms
* which change the {@link module:engine/model/model~Model#modifySelection}
* method's behavior.
*
* @param model The model in context of which the selection modification should be performed.
* @param selection The selection to modify.
* @param options.direction The direction in which the selection should be modified. Default 'forward'.
* @param options.unit The unit by which selection should be modified. Default 'character'.
* @param options.treatEmojiAsSingleUnit Whether multi-characer emoji sequences should be handled as single unit.
* @internal
*/
export declare function modifySelection(model: Model, selection: ModelSelection | ModelDocumentSelection, options?: {
	direction?: "forward" | "backward";
	unit?: "character" | "codePoint" | "word";
	treatEmojiAsSingleUnit?: boolean;
}): void;