"""ContextualChunker — structure preservation for technical corpora."""

from __future__ import annotations

from thicket.chunker import ContextualChunker


def _filler(n: int, tag: str = "w") -> str:
    return " ".join(f"{tag}{i}" for i in range(n))


def test_empty_text_yields_no_chunks():
    assert ContextualChunker().chunk("T", "") == []
    assert ContextualChunker().chunk("T", "\n\n\n") == []


def test_fenced_block_is_atomic_and_verbatim():
    code = "\n".join([
        "```python",
        "def harden(host):",
        "    if host == 'prod':",
        "        sys.exit('no')",
        "",
        "    return True",
        "```",
    ])
    chunks = ContextualChunker(chunk_size=10, overlap=0).chunk("T", code)
    assert len(chunks) == 1
    assert chunks[0].kind == "code"
    assert chunks[0].lang == "python"
    assert "    if host == 'prod':" in chunks[0].text      # indentation kept
    assert "\n\n" in chunks[0].text                         # blank line kept
    assert "| code:python]" in chunks[0].contextual_text


def test_code_never_merges_with_prose():
    doc = "Intro prose here.\n\n```bash\nls -la\n```\n\nOutro prose here."
    chunks = ContextualChunker(chunk_size=100, overlap=0).chunk("T", doc)
    kinds = [c.kind for c in chunks]
    assert kinds.count("code") == 1
    code = next(c for c in chunks if c.kind == "code")
    assert "Intro" not in code.text and "Outro" not in code.text


def test_shebang_and_comments_are_not_headings():
    doc = "#!/usr/bin/env python3\nimport os\n\n#no-space-comment\n\n## Real Heading\n\nBody text."
    chunks = ContextualChunker(chunk_size=100).chunk("T", doc)
    assert chunks[-1].header == "Real Heading"


def test_prose_paragraph_lines_are_preserved():
    doc = "# H\n\nFirst paragraph.\nSecond line of same paragraph."
    chunks = ContextualChunker(chunk_size=100).chunk("T", doc)
    assert "First paragraph.\nSecond line of same paragraph." in chunks[0].text


def test_paragraph_aligned_budget():
    paras = [_filler(40, f"p{i}_") for i in range(6)]     # 6 x 40 words
    doc = "# H\n\n" + "\n\n".join(paras)
    chunks = ContextualChunker(chunk_size=100, overlap=0).chunk("T", doc)
    # No paragraph is ever split: each chunk is 2 paragraphs (80 words).
    assert all(c.text.count("_") >= 40 for c in chunks)
    assert all(len(c.text.split()) <= 100 for c in chunks)
    assert len(chunks) == 3


def test_oversized_code_is_windowed_with_lang_on_every_window():
    lines = [f"x_{i} = {i}  # {'filler ' * 20}" for i in range(60)]
    doc = "```python\n" + "\n".join(lines) + "\n```"
    chunks = ContextualChunker(chunk_size=40, overlap=0).chunk("T", doc)
    assert len(chunks) > 1
    assert all(c.kind == "code" and c.lang == "python" for c in chunks)
    # Window overlap: first line of window N+1 appeared in window N.
    assert any(chunks[i + 1].text.split("\n")[0] in chunks[i].text
               for i in range(len(chunks) - 1))


def test_section_boundaries_do_not_straddle():
    doc = ("# A\n\n" + _filler(30, "a") + "\n\n"
           "# B\n\n" + _filler(30, "b"))
    chunks = ContextualChunker(chunk_size=100, overlap=50).chunk("T", doc)
    assert len(chunks) == 2
    assert chunks[0].header == "A" and chunks[1].header == "B"
    assert "b0" not in chunks[0].text


def test_indented_block_treated_as_code():
    doc = "Prose.\n\n    permit root no\n    retries 3\n\nMore prose."
    chunks = ContextualChunker(chunk_size=100).chunk("T", doc)
    code = [c for c in chunks if c.kind == "code"]
    assert code and "permit root no" in code[0].text


def test_default_header_is_introduction():
    chunks = ContextualChunker(chunk_size=50).chunk("T", _filler(10))
    assert chunks[0].header == "Introduction"


def test_source_provenance_attaches_to_every_chunk():
    doc = "# H\n\nprose\n\n```python\nx = 1\n```"
    chunks = ContextualChunker(chunk_size=100).chunk(
        "T", doc, source_path="sub/deploy.py")
    assert {c.source for c in chunks} == {"sub/deploy.py"}
    assert ContextualChunker().chunk("T", doc)[0].source is None