/**
 * Merge server-hydrated messages with local rows that are not yet visible in
 * the GET response (in-flight send, outbox retry, failed, or read lag).
 */
import type { ChatMessage } from "../../../utils/globals";
/** Local rows still awaiting server ack or retry. */
export declare function isPendingLocalMessage(message: ChatMessage): boolean;
/** Streaming placeholders must not survive a REST refresh — Ably / GET own them. */
export declare function isEphemeralLocalMessage(message: ChatMessage): boolean;
/**
 * Decide whether a local row should be merged on top of a server GET when its
 * id is absent from the payload.
 */
export declare function shouldRetainLocalMessage(message: ChatMessage): boolean;
/** Collapse duplicate ids in an array, preferring the furthest-along delivery state. */
export declare function dedupeMessagesById(messages: ChatMessage[]): ChatMessage[];
/** First occurrence wins — caller must pass server rows before local rows. */
export declare function dedupeMessagesPreservingOrder(messages: ChatMessage[]): ChatMessage[];
/**
 * Server history first, then retained local rows whose ids are absent from the
 * server payload. Output is chronologically sorted and id-deduplicated (server
 * wins on id collisions).
 */
export declare function mergeHydratedMessages(serverMessages: ChatMessage[], localMessages: ChatMessage[], channelId: string): ChatMessage[];