Netcatty/application/state/useComposeBarHistory.ts

import { useCallback, useEffect, useLayoutEffect, useRef } from 'react';
import { navigateComposeBarHistory, type ComposeBarHistoryDirection } from '../../domain/composeBarHistory';
import {
  getComposeBarHistory,
  createComposeBarHistoryRecorder,
  subscribeComposeBarHistoryCleared,
} from './composeBarHistoryStore';

export function useComposeBarHistory(sessionId: string, restoreDraft?: (draft: string) => void) {
  const cursor = useRef<{ index: number; draft: string; entries?: readonly string[] }>({ index: Infinity, draft: '' });

  const reset = useCallback(() => {
    cursor.current = { index: Infinity, draft: '' };
  }, []);

  // Keep the existing textarea draft when workspace focus changes, but begin
  // a fresh history walk in the newly focused session.
  useLayoutEffect(() => {
    if (cursor.current.entries) restoreDraft?.(cursor.current.draft);
    reset();
  }, [reset, restoreDraft, sessionId]);

  /**
   * Restore the pre-walk draft and drop the cached history walk.
   *
   * While the user is in an ArrowUp walk the textarea shows the recalled
   * command, so resetting the cursor alone would leave a deleted command ready
   * for Enter. Put the saved draft back first, exactly like the session-change
   * path above.
   */
  const handleHistoryCleared = useCallback(() => {
    if (cursor.current.entries) restoreDraft?.(cursor.current.draft);
    reset();
  }, [reset, restoreDraft]);

  useEffect(
    () => subscribeComposeBarHistoryCleared(handleHistoryCleared),
    [handleHistoryCleared],
  );

  const prepareRecord = useCallback(() => createComposeBarHistoryRecorder(sessionId), [sessionId]);

  const navigate = useCallback((currentValue: string, direction: ComposeBarHistoryDirection) => {
    // A late send can evict old entries. Keep one walk stable until the user
    // returns to the draft or edits, then pick up the latest history.
    const entries = cursor.current.entries ?? getComposeBarHistory(sessionId);
    const result = navigateComposeBarHistory({
      ...cursor.current,
      entries,
      currentValue,
    }, direction);
    if (result) {
      cursor.current = {
        index: result.index === entries.length ? Infinity : result.index,
        draft: result.draft,
        entries: result.index === entries.length ? undefined : entries,
      };
    }
    return result?.value;
  }, [sessionId]);

  return { prepareRecord, navigate, reset };
}