"""Unit tests for the active-section boundary — the authoritative computation
the refinement endpoint uses (client mirrors it only for a visual hint)."""

from app.authoring.sections import active_section, slice_lines

DOC = """## Zweck
Dieser Ablauf beschreibt die Rechnungsstellung.

## Ablauf
Erst exportieren, dann versenden.

## Fallstricke
"""


def _span(md: str, cursor_line: int) -> tuple[int, int]:
    section = active_section(md, cursor_line)
    return section.start_line, section.end_line


def test_cursor_in_a_section_selects_from_its_heading_to_the_next() -> None:
    # Line 5 is "Erst exportieren, dann versenden." under "## Ablauf" (line 4).
    assert _span(DOC, 5) == (4, 5)
    _prefix, section, _suffix = slice_lines(DOC, 4, 5)
    assert section == "## Ablauf\nErst exportieren, dann versenden."


def test_cursor_on_the_heading_selects_that_section() -> None:
    assert _span(DOC, 1) == (1, 2)


def test_trailing_blank_lines_are_excluded() -> None:
    # "## Ablauf" body is followed by a blank line before "## Fallstricke";
    # the blank must not be part of the section.
    start, end = _span(DOC, 4)
    assert (start, end) == (4, 5)


def test_content_before_the_first_heading_is_its_own_section() -> None:
    md = "Eine Einleitung ohne Überschrift.\n\n## Danach\nText."
    assert _span(md, 1) == (1, 1)


def test_a_document_without_headings_is_one_section() -> None:
    md = "Nur Fließtext.\nZweite Zeile."
    assert _span(md, 2) == (1, 2)


def test_nested_headings_stop_at_a_same_or_higher_level() -> None:
    md = "## A\natext\n### A1\nsub\n## B\nbtext"
    # Cursor in "## A" (line 1) spans through its subsection "### A1" up to
    # the line before "## B".
    assert _span(md, 1) == (1, 4)
    # Cursor in the subsection spans only the subsection.
    assert _span(md, 4) == (3, 4)


def test_a_heading_inside_a_code_fence_is_not_a_boundary() -> None:
    md = "## Code\n```\n## nicht echt\n```\nfertig"
    assert _span(md, 3) == (1, 5)


def test_a_large_section_narrows_to_the_paragraph_at_the_cursor() -> None:
    big = "\n\n".join(f"Absatz {i} " + "x" * 400 for i in range(6))
    md = f"## Groß\n{big}"
    start, end = _span(md, 6)  # somewhere deep in the section
    _prefix, section, _suffix = slice_lines(md, start, end)
    # Narrowed: a single paragraph, not the whole oversized section.
    assert "\n\n" not in section
    assert section.startswith("Absatz")