frontend/src/lib/fork.ts

/**
 * fork.ts — Pure function to fork a SavedResponse into a new ChatState.
 *
 * Extracted from App.tsx handleSelectSavedResponse for testability.
 *
 * Requirements: 7.5
 */

import type { ChatState, SavedResponse } from "../types";

/**
 * Forks a SavedResponse into a new ChatState.
 *
 * The new ChatState:
 * - Has a new conversationId (distinct from source_conversation_id)
 * - messages equals messages_pair from the SavedResponse
 * - history equals history_pair from the SavedResponse
 * - results contains { "1": sr.result }
 * - Streaming state is reset (null/empty/false)
 *
 * @param sr - The SavedResponse to fork
 * @param newConversationId - A new UUID for the forked session
 * @returns A fresh ChatState seeded with the saved response data
 */
export function forkSavedResponse(
  sr: SavedResponse,
  newConversationId: string
): ChatState {
  return {
    conversationId: newConversationId,
    messages: sr.messages_pair,
    history: sr.history_pair,
    results: { "1": sr.result },
    streamingIndex: null,
    streamingContent: "",
    isStreaming: false,
  };
}