# pdf_qa_loop, condensed
# decide_pipeline_patterns and iterate_with_bound come from the companion notebook.

def pdf_qa_loop(pdf_path, question, *, registry=None, max_iterations=4):
    registry = registry or PatternRegistry.default()
    # 1. Question understanding
    parsed = registry.parse_question(question)
    # 2. Cheap layer-1 parse of the document
    line_df, page_df, toc_df = registry.parse_layer1(pdf_path)
    # 3. Document profile
    doc_profile = registry.detect_document_type(pdf_path)
    # 4. Dispatcher : which patterns fire ?
    activations = decide_pipeline_patterns(parsed, doc_profile)
    # 5-7. Retrieval + generation inside a bounded feedback loop
    state = _State(parsed=parsed, line_df=line_df,
                   page_df=page_df, toc_df=toc_df)
    outcome = iterate_with_bound(
        initial_state=state,
        run_pass=lambda s: _one_pass(s, registry, activations, pdf_path),
        is_satisfactory=lambda a: not _needs_iteration(a),
        adjust=lambda s, a: _adjust_state(s, a, registry,
                                          activations, pdf_path),
        record=_build_record,
        max_iterations=max_iterations,
    )
    return CompositeOutput(answer=outcome.result, activations=activations,
                           history=outcome.history,
                           exhausted=outcome.exhausted)