import { AdvanceDep, EmptyId, EmptyToken, Feature, HeadId, NominalToken, Relation, Sentence, UPOS, XPOS } from ".";
/**
 * The policy to adjust a `head` field that point to a token being merge.
 * Every other tokens will have their head value adjust accordingly but the `head` that point
 * to token being merge may need different treatment depending on user requirement.
 */
export declare enum HeadPolicy {
    /** Update all the `head` pointed to the token within merge range to a merged `ID` */
    Adjust = 0,
    /** Remove any `head` linked to the token within merge range */
    Remove = 1
}
declare type Mergeable = (NominalToken | EmptyToken);
/**
 * A merging policy.
 *
 * It has following attributes:
 * - `headPol` field will determined how all dependants shall be handle.
 * The default value is `HeadPolicy.Adjust`
 * - `lemma` field is a callback that takes all tokens being merged as argument and return merged lemma.
 * The default value is every lemma concatenated together or undefined.
 * - `upos` field is a callback that takes all tokens being merged as argument and return merged part-of-speech.
 * The default value is a part-of-speech of first token being merge.
 * - `xpos` an optional field which is a callback that takes all tokens being merged as argument and return merged language specific part-of-speech.
 * - `feats` field is a callback that takes all tokens being merged as argument and return merged feature(s).
 * The default value is a flatten merge of all unique features from every tokens being merged.
 * - `headRels` field is a callback that takes all tokens being merged as argument and return merged `head` and `deprel` fields.
 * The default is first token being merged head/deprel field if there's no root `Relation` in merging, otherwise, it
 * will become new root.
 * - `deps` field is a callback that takes all tokens being merged as argument and return merged `deps` fields.
 * The default is merged of every unique deps field of tokens being merged.
 * - `misc` field is a callback that takes all tokens being merged as argument and return merged `misc` fields.
 * The default value is all unique of flatten map misc fields of every tokens.
 */
export declare class MergePolicy<X extends XPOS> {
    headPol: HeadPolicy;
    lemma: (tokens: Mergeable[]) => string;
    upos: (tokens: Mergeable[]) => UPOS;
    xpos?: (tokens: Mergeable[]) => X;
    feats: (tokens: Mergeable[]) => Feature[];
    headRels: (tokens: NominalToken[]) => [HeadId, Relation];
    deps: (tokens: Mergeable[]) => AdvanceDep[];
    misc: (tokens: Mergeable[]) => string[];
}
export declare type MergeableId = HeadId | [HeadId, EmptyId];
/**
 * Perform tokens merging.
 * It is an error to merge different types of tokens.
 * For example, you can **not** merge `from` = 0.1 and `to` = 2.
 * If merging token cause a `CompoundToken` that refering to it become invalid,
 * it will automatically remove that `CompoundToken` out.
 *
 * It will result in undefined behavior if `Sentence` being merge is invalid.
 * Caller should ensure that `Sentence` is valid. method `validate` of `Sentence`
 * can be used for such validation.
 *
 * You can merge multiple `EmptyToken`.
 * You can merge multiple `NominalToken`.
 * If there's an `EmptyToken` or a `CompoundToken` between `NominalToken` being merged,
 * it will automatically remove.
 * You can never merge `CompoundToken`.
 *
 * It may end up with invalid `EmptyToken` if it any EmptyToken have single dependency that depends on
 * the token being merged. Such invalid `EmptyToken` will be retain. It is user responsibility
 * to fix the dependency for every `EmptyToken` that become invalid.
 *
 * @param sentence An object of Sentence to merge tokens
 * @param from A first token to be merge. It is an `id`, not an `index` of token.
 * @param to An inclusive id of last token to be merged. It is an `id`, not an `index` of token.
 * @param policy Specify how to treat a head that point to any token being merged. The default policy is to `Adjust`
 */
export declare function mergeTokens<X extends XPOS>(sentence: Sentence, from: MergeableId, to: MergeableId, policy: MergePolicy<X>): void;
export {};