"""The fusion's tie-break, measured rather than assumed.

`concept_scores` fuses three signals by RRF, and RRF consumes RANKS ONLY. A
rank is therefore produced for every concept in every signal -- including a
signal that does not separate them. The tie-break is declared
(`(-score, concept_id)`), so when a signal gives 269 of 270 concepts the same
score, that signal's contribution to the fusion is the concepts' own ids in
lexicographic order: a UUID, which is noise, weighted exactly as heavily as
the two signals that did the measuring.

MEASURED 2026-09-08 on the N500 bundle (270 concepts, `feae0c8`), for the
question about `vann- og frostsikring` in a subsea tunnel: the document prior
has **two** distinct values over the bundle, and 269 concepts share one of
them. The best covering concept answered **7 of 7** question tokens and led
the body signal at rank 6, and it fused to rank **14** -- outside the cut --
while concepts answering fewer tokens fused ahead of it on nothing but an
earlier id.

This file holds the two halves apart:

- The matcher is CHARACTERISED, not fixed. `normalise` already resolves the
  hyphen-and-`og` coordination, so the alternative that would have widened the
  tokeniser has nothing to widen. That is asserted here so the choice stays
  falsifiable rather than remembered.
- The fusion gets one rule, behind one flag, off by default.
"""

from __future__ import annotations

import sys
from pathlib import Path


PROJECT_ROOT = Path(__file__).resolve().parents[1]
sys.path.insert(0, str(PROJECT_ROOT / "tools"))

import okf_consume  # noqa: E402

QUESTION = "Hvilke krav gjelder vann- og frostsikring i undersjoeisk tunnel?"

_FRONTMATTER = (
    "---\ntype: reference\ntitle: {title}\nsource_file: {slug}.md\n"
    "source_sha256: {digest}\ningested_at: 2026-09-01T00:00:00Z\n"
    "adjudication: proposed\nbundle_id: tie-fixture\n"
    "verified: [{{ by: process:okf-check, at: 2026-09-01T00:00:00Z }}]\n---\n\n"
)


def _tie_bundle(root: Path, *, fillers: int = 30) -> Path:
    """One document, so the document prior cannot separate anything.

    The gold concept's id sorts LAST and the fillers' ids sort first, which is
    what makes the degenerate signal's tie-break work against the concept that
    answers the question. The fillers answer `krav`, `gjelder`, `vann` and
    `tunnel`; only the gold answers `frostsikring` and `undersjoeisk` too.
    """
    (root / "krav").mkdir(parents=True)
    (root / "index.md").write_text(
        "---\nokf_version: 0.2\nbundle_id: tie-fixture\n---\n\n- [krav (index)](krav/index.md)\n",
        encoding="utf-8",
    )
    entries: list[str] = []

    def add(slug: str, title: str, body: str) -> None:
        entries.append(f"- [{title}]({slug}.md) — adjudication: proposed\n")
        (root / "krav" / f"{slug}.md").write_text(
            _FRONTMATTER.format(title=title, slug=slug, digest="1" * 64) + f"## {title}\n\n" + body,
            encoding="utf-8",
        )

    add(
        "zz-gull",
        "Krav om vann- og frostsikring i undersjoeisk tunnel",
        "Kravet gjelder vannsikring og frostsikring i undersjoeisk tunnel.\n" * 4,
    )
    for number in range(1, fillers + 1):
        add(
            f"aa-{number:02d}",
            f"Krav om tunnel og vann {number:02d}",
            "Kravet gjelder tunnel og vann i anlegget.\n" * 4,
        )
    (root / "krav" / "index.md").write_text("".join(entries), encoding="utf-8")
    return root


def _gold_rank(root: Path, *, tie_shared_rank: bool) -> int:
    concepts = [
        okf_consume.read_concept(
            root / f"{concept_id}.md", bundle_root=root, root_bundle_id="tie-fixture"
        )
        for concept_id in okf_consume.enumerate_concepts(root)
    ]
    ranked = okf_consume.concept_scores(
        concepts,
        QUESTION,
        okf_consume.document_scores(root, QUESTION),
        tie_shared_rank=tie_shared_rank,
    )
    for position, (concept, _, _) in enumerate(ranked, start=1):
        if concept.concept_id.endswith("zz-gull"):
            return position
    raise AssertionError("the gold concept is not in the ranking at all")


# --- The half that is characterised, not fixed --------------------------------


def test_the_hyphen_and_og_coordination_is_already_resolved_by_the_tokeniser() -> None:
    # CHARACTERISATION, green on HEAD. This is the measurement that ruled the
    # tokeniser out as the site of the fix: there is no coordination left to
    # resolve, so a rule widening it could not have moved the miss.
    assert okf_consume.normalise("vann- og frostsikring") == ("vann", "frostsikring")
    assert okf_consume.tokens_match("frostsikring", "frostsikringen")
    assert okf_consume.tokens_match("vann", "vannsikring")


def test_a_signal_that_separates_nothing_still_ranks_every_concept(tmp_path: Path) -> None:
    # CHARACTERISATION of the defect's mechanism: one distinct score, and one
    # rank per concept all the same. The second number is the noise.
    root = _tie_bundle(tmp_path / "bundle")
    prior = okf_consume.document_scores(root, QUESTION)
    concepts = okf_consume.enumerate_concepts(root)
    scores = {prior[concept_id.split("/", 1)[0]] for concept_id in concepts}
    assert len(scores) == 1
    assert len(concepts) == 31


# --- The half that gets the rule ----------------------------------------------


def test_shared_rank_lifts_the_concept_the_measuring_signals_lead(tmp_path: Path) -> None:
    root = _tie_bundle(tmp_path / "bundle")
    # Two DIFFERENT numbers, not one predicate two branches share: the concept
    # answering every question token sits at 8 while the degenerate signal
    # orders by id, and at 1 once that signal stops ordering.
    assert _gold_rank(root, tie_shared_rank=False) == 8
    assert _gold_rank(root, tie_shared_rank=True) == 1


def test_the_payload_is_byte_identical_with_the_flag_off(tmp_path: Path) -> None:
    root = _tie_bundle(tmp_path / "bundle")
    without = okf_consume.serialise(okf_consume.build_payload(root, question=QUESTION))
    explicit_off = okf_consume.serialise(
        okf_consume.build_payload(root, question=QUESTION, tie_shared_rank=False)
    )
    assert without == explicit_off


def test_the_flag_changes_the_payload_it_is_meant_to_change(tmp_path: Path) -> None:
    root = _tie_bundle(tmp_path / "bundle")
    off = okf_consume.build_payload(root, question=QUESTION, k=3)
    on = okf_consume.build_payload(root, question=QUESTION, k=3, tie_shared_rank=True)
    delivered_off = [excerpt["concept_id"] for excerpt in off["excerpts"]]  # type: ignore[index]
    delivered_on = [excerpt["concept_id"] for excerpt in on["excerpts"]]  # type: ignore[index]
    assert not any(str(cid).endswith("zz-gull") for cid in delivered_off)
    assert str(delivered_on[0]).endswith("zz-gull")


def test_the_cli_exposes_the_flag_and_defaults_it_off(tmp_path: Path) -> None:
    root = _tie_bundle(tmp_path / "bundle")
    parsed = okf_consume.parse_args([str(root), "--question", QUESTION])
    assert parsed.tie_shared_rank is False
    parsed_on = okf_consume.parse_args([str(root), "--question", QUESTION, "--tie-shared-rank"])
    assert parsed_on.tie_shared_rank is True
    # The other flag this session added, asserted here so "both default off"
    # is one measurement rather than two files' worth of trust.
    assert parsed.withheld_titles is False