import { OpenHandsEvent } from "#/types/v1/core";
import { isACPToolCallEvent, isObservationEvent } from "#/types/v1/type-guards";

/**
 * Handles adding an event to the UI events array
 * Replaces actions with observations when they arrive (so UI shows observation instead of action)
 * Exception: ThinkAction is NOT replaced because the thought content is in the action, not in the observation
 *
 * ACPToolCallEvent dedup: multiple events share a ``tool_call_id`` as an ACP
 * tool call progresses (in_progress → completed / failed). Collapse them to
 * the latest state at the original position so the card updates in place.
 */
export const handleEventForUI = (
  event: OpenHandsEvent,
  uiEvents: OpenHandsEvent[],
): OpenHandsEvent[] => {
  const newUiEvents = [...uiEvents];

  if (isACPToolCallEvent(event)) {
    const existingIndex = newUiEvents.findIndex(
      (uiEvent) =>
        isACPToolCallEvent(uiEvent) &&
        uiEvent.tool_call_id === event.tool_call_id,
    );
    if (existingIndex !== -1) {
      newUiEvents[existingIndex] = event;
    } else {
      newUiEvents.push(event);
    }
    return newUiEvents;
  }

  if (isObservationEvent(event)) {
    // Don't add ThinkObservation at all - we keep the ThinkAction instead
    // The thought content is in the action, not the observation
    if (event.observation.kind === "ThinkObservation") {
      return newUiEvents;
    }

    // Don't add FinishObservation at all - we keep the FinishAction instead
    // Both contain the same message content, so we only need to display one
    // This also prevents duplicate messages when events arrive out of order due to React batching
    if (event.observation.kind === "FinishObservation") {
      return newUiEvents;
    }

    // Find and replace the corresponding action from uiEvents
    const actionIndex = newUiEvents.findIndex(
      (uiEvent) => uiEvent.id === event.action_id,
    );
    if (actionIndex !== -1) {
      newUiEvents[actionIndex] = event;
    } else {
      // Action not found in uiEvents, just add the observation
      newUiEvents.push(event);
    }
  } else {
    // For non-observation events, just add them to uiEvents
    newUiEvents.push(event);
  }

  return newUiEvents;
};