import type { FinishReason } from '../types/language-model';
import type { UIMessage } from '../ui/ui-messages';
import type { UIMessageStreamOutcome } from './ui-message-stream-outcome';

export type UIMessageStreamOnEndCallback<UI_MESSAGE extends UIMessage> =
  (event: {
    /**
     * The updated list of UI messages.
     */
    messages: UI_MESSAGE[];

    /**
     * Indicates whether the response message is a continuation of the last original message,
     * or if a new message was created.
     */
    isContinuation: boolean;

    /**
     * Indicates whether the stream was aborted.
     */
    isAborted: boolean;

    /**
     * Indicates that the consumer cancelled the stream before an outcome was
     * declared, for example because the client disconnected.
     *
     * This property is only present when it is `true`.
     */
    isCancelled?: true;

    /**
     * The operation-level outcome of the stream. Fatal stream-processing
     * failures override outcomes declared by the stream owner.
     */
    outcome: UIMessageStreamOutcome;

    /**
     * The message that was sent to the client as a response
     * (including the original message if it was extended).
     */
    responseMessage: UI_MESSAGE;

    /**
     * The reason why the generation finished.
     */
    finishReason?: FinishReason;
  }) => PromiseLike<void> | void;