"""No character stands BETWEEN two concepts, or after the last one.

Round 7 closed the text ABOVE the first concept (`--first-span-from-zero`,
163 804 characters, 79 % of the whole gap) and named the remainder without
opening it: 43 631 characters, 2.51 % of the corpus, over 8 of the 32
documents that get a plan -- 26 041 between entries and 17 590 after the last.

Measured here, the remainder has ONE cause, not the two the shape suggests.
Every rule in `find_candidates` closes a span against the NEXT MARK, and three
separate steps then remove a mark after its neighbour's `end` was already
fixed against it:

* the **orphan check** drops a heading with no body, and the heading line
  itself -- `## 3 Prising\n`, 14 characters -- is what the next candidate no
  longer starts at. Measured with the fold off: **18 527 characters over 15 of
  39 documents**;
* `fold_units` **clause 1** discards a contents run, and the text those
  entries opened goes with them. It accounts for the remaining **7 514**
  characters between entries;
* the same clause discarding the LAST run takes the tail with it. Measured:
  with `unit_fold=False` the tail gap over the corpus is **0**, so all
  **17 590** tail characters are clause 1's.

That is round 6's own principle -- the outline gate filters at ADMISSION,
"before spans close, so the text a removed mark opened is carried by the mark
above" -- not applied to the two steps that remove marks AFTER spans close.
This rule states it once, at the end, where every removal has already
happened: a candidate's span runs to the next candidate's start, and the last
one runs to the end of the text.

It adds NO boundary and removes none. A plan's entry count is identical either
way, which is the same property `--first-span-from-zero` has and the reason
both can be measured by coverage rather than by count.
"""

from __future__ import annotations

from pathlib import Path

from llm_ingestion_okf import cli
from llm_ingestion_okf.propose import find_candidates

ARMS = dict(outline_run=3, table_grid=True, unit_fold=True, first_span_from_zero=True)

#: The orphan check's gap: `## Tom` has no body, so it is dropped -- and the
#: seven characters of its own heading line belong to no segment.
ORPHAN = "## Forste\nInnhold under.\n## Tom\n## Andre\nInnhold under.\n"

#: Clause 1's gap: three page-numbered siblings are read as a contents list
#: and discarded, and the body under them goes too. 130 of 159 characters.
CONTENTS_TAIL = (
    "## Innledning\nBrodtekst her.\n"
    "## Kapittel en 3\nNoe innhold.\n"
    "## Kapittel to 5\nMer innhold.\n"
    "## Kapittel tre 9\nEn avsluttende brodtekst som ingen kandidat dekker.\n"
)

#: The known-negative: nothing is removed, so nothing is carried.
NO_GAP = "## Forste\nInnhold under.\n## Andre\nInnhold under.\n"


def _uncovered(text: str, **kwargs: object) -> int:
    candidates = find_candidates(text, **ARMS, **kwargs)  # type: ignore[arg-type]
    if not candidates:
        return len(text)
    between = sum(
        max(0, candidates[i].start - candidates[i - 1].end) for i in range(1, len(candidates))
    )
    return candidates[0].start + between + max(0, len(text) - candidates[-1].end)


def test_the_default_still_loses_the_orphaned_heading_line() -> None:
    """The defect, kept visible: the dropped mark's own line goes nowhere."""
    assert _uncovered(ORPHAN) == len("## Tom\n")


def test_the_default_still_loses_the_tail_under_a_discarded_contents_run() -> None:
    """82 % of this document is in no segment, and none of it is a listing."""
    assert _uncovered(CONTENTS_TAIL) == 130


def test_no_character_lies_between_two_concepts() -> None:
    assert _uncovered(ORPHAN, close_span_gaps=True) == 0
    candidates = find_candidates(ORPHAN, **ARMS, close_span_gaps=True)
    carried = ORPHAN[candidates[0].start : candidates[0].end]
    assert "## Tom" in carried, "the removed mark's text is carried by the mark ABOVE"


def test_no_character_lies_after_the_last_concept() -> None:
    assert _uncovered(CONTENTS_TAIL, close_span_gaps=True) == 0
    candidates = find_candidates(CONTENTS_TAIL, **ARMS, close_span_gaps=True)
    assert CONTENTS_TAIL[candidates[-1].start : candidates[-1].end].endswith(
        "En avsluttende brodtekst som ingen kandidat dekker.\n"
    )


def test_the_rule_adds_and_removes_no_boundary() -> None:
    """Only `end` moves. Titles, rules and starts are identical."""
    for text in (ORPHAN, CONTENTS_TAIL, NO_GAP):
        plain = find_candidates(text, **ARMS)
        closed = find_candidates(text, **ARMS, close_span_gaps=True)
        assert [c.title for c in plain] == [c.title for c in closed]
        assert [c.rule for c in plain] == [c.rule for c in closed]
        assert [c.start for c in plain] == [c.start for c in closed]


def test_a_document_with_no_gap_is_untouched() -> None:
    """The known-negative, as IDENTICAL objects rather than an equal count."""
    before = find_candidates(NO_GAP, **ARMS)
    after = find_candidates(NO_GAP, **ARMS, close_span_gaps=True)
    assert before == after
    assert _uncovered(NO_GAP) == 0


def test_it_is_on_by_default_in_the_build_command() -> None:
    assert cli.DEFAULT_CLOSE_SPAN_GAPS is True


def test_the_parser_carries_the_default_and_an_opt_out() -> None:
    base = ["build", "src", "--bundle", "out", "--bundle-id", "x"]
    assert cli.parse_args(base).close_span_gaps is True
    assert cli.parse_args([*base, "--no-close-span-gaps"]).close_span_gaps is False


def test_the_flag_reaches_the_proposer_from_the_build_command(tmp_path: Path) -> None:
    """The plumbing, and it needs its own test rather than the smoke build.

    Measured 2026-09-11: the operator's five-document folder has a coverage gap
    of ZERO under round 7's default already, so building it with the rule on
    and off gives `diff -rq` 0 differences. That is the rule behaving correctly
    on an input with nothing to carry -- and it means that build proves nothing
    about whether the flag arrives. This one uses a document that HAS a gap.
    """
    inbox = tmp_path / "in"
    inbox.mkdir()
    (inbox / "d.md").write_text(CONTENTS_TAIL, encoding="utf-8")

    def concepts(bundle: Path, **kwargs: object) -> str:
        report = cli.build(
            inbox,
            bundle=bundle,
            bundle_id="t",
            okf_version="0.2",
            ingested_at="1970-01-01T00:00:00Z",
            **kwargs,  # type: ignore[arg-type]
        )
        assert report.codes == ()
        return "".join(path.read_text(encoding="utf-8") for path in sorted(bundle.rglob("*.md")))

    on = concepts(tmp_path / "on")
    off = concepts(tmp_path / "off", close_span_gaps=False)
    assert "En avsluttende brodtekst som ingen kandidat dekker." in on
    assert "En avsluttende brodtekst som ingen kandidat dekker." not in off