"""CJK bigram matching in QUERY-mode searches.

The bigram fields exist so CJK runs are matchable at all (the default
analyzers keep a whitespace-free CJK run as one indivisible token), but
matching them must not widen the query beyond what the user asked for: a
CJK term the query excludes, or restricts to one field, must not come back
through them.
"""

from __future__ import annotations

from typing import TYPE_CHECKING

import pytest

if TYPE_CHECKING:
    from collections.abc import Callable

    from pytest_django.fixtures import SettingsWrapper

    from documents.models import Document


pytestmark = [pytest.mark.search, pytest.mark.django_db]


class TestCjkParseFailureDegradesGracefully:
    def test_a_cjk_run_tantivy_cannot_parse_drops_the_clause_only(self) -> None:
        """
        GIVEN:
            - A CJK run and an index-like object whose parse_query is
              forced to raise
        WHEN:
            - _parse_cjk_text is called
        THEN:
            - It returns None instead of propagating, so a CJK run tantivy
              cannot parse only drops the bigram clause rather than
              failing the whole query. Broad on purpose (bare except
              Exception), unlike the fuzzy blend's narrower ValueError
              guard: a CJK run is not filtered to a guaranteed-safe token
              set the way the fuzzy blend's word string is, so the exact
              failure mode tantivy could raise here is not pinned down
        """
        from documents.search._query import _parse_cjk_text

        class _RaisingIndex:
            def parse_query(self, *args: object, **kwargs: object) -> object:
                raise RuntimeError("synthetic parse failure")

        assert _parse_cjk_text(_RaisingIndex(), "東京", ["bigram_content"]) is None

    def test_no_cjk_text_at_all_returns_none_without_parsing(self) -> None:
        """
        GIVEN:
            - A raw query string with no CJK characters at all
        WHEN:
            - _build_cjk_query (the simple TEXT/TITLE-mode builder) is
              called directly
        THEN:
            - It returns None without ever attempting to parse anything.
              The only real caller already guards this with _has_cjk(),
              so this is defensive: it keeps the function safe to call on
              its own, not a path a real search currently reaches
        """
        from documents.search._query import _build_cjk_query

        assert _build_cjk_query(None, "invoice total due", ["bigram_content"]) is None


class TestCjkClauseFollowsTheParsedQuery:
    def test_negated_cjk_term_is_excluded(
        self,
        index_document: Callable[..., Document],
        matched_ids: Callable[[str], set[int]],
    ) -> None:
        """
        GIVEN:
            - Two documents both matching "invoice", one whose content
              also contains 漢字
        WHEN:
            - "invoice NOT 漢字" is searched
        THEN:
            - Only the document without 漢字 matches; 'invoice NOT 漢字'
              must not return the document containing 漢字
        """
        with_cjk = index_document(
            title="Invoice A",
            content="invoice total 漢字",
        )
        without_cjk = index_document(
            title="Invoice B",
            content="invoice total only",
        )

        assert matched_ids("invoice") == {with_cjk.pk, without_cjk.pk}
        assert matched_ids("invoice NOT 漢字") == {without_cjk.pk}

    @pytest.mark.parametrize(
        ("threshold", "expected"),
        [
            pytest.param(None, {"titled"}, id="fuzzy_off"),
            pytest.param(0.0, {"titled"}, id="fuzzy_on"),
        ],
    )
    def test_fielded_cjk_term_searches_only_that_field(
        self,
        index_document: Callable[..., Document],
        matched_ids: Callable[[str], set[int]],
        settings: SettingsWrapper,
        threshold: float | None,
        expected: set[str],
    ) -> None:
        """
        GIVEN:
            - One document with 東京 in its title, another with 東京 only
              in its content, and ADVANCED_FUZZY_SEARCH_THRESHOLD either
              off or on
        WHEN:
            - "title:東京" is searched
        THEN:
            - Only the titled document matches, whether fuzzy is on or
              off: both the CJK alternative and the fuzzy alternative are
              widened in place on the fielded leaf, so 'title:東京' still
              must not match a document whose 東京 is only in the content
        """
        settings.ADVANCED_FUZZY_SEARCH_THRESHOLD = threshold
        content_only = index_document(
            title="Tokyo report",
            content="東京都の人口は約1400万人です",
        )
        titled = index_document(
            title="東京都の報告書",
            content="an english summary",
        )
        pks = {"titled": titled.pk, "content_only": content_only.pk}

        assert matched_ids("東京") == set(pks.values())
        assert matched_ids("title:東京") == {pks[label] for label in expected}

    def test_cjk_on_a_non_default_field_is_not_widened(
        self,
        index_document: Callable[..., Document],
        matched_ids: Callable[[str], set[int]],
    ) -> None:
        """
        GIVEN:
            - A document with 東京 in its content
        WHEN:
            - "notes:東京" is searched (a field outside the default
              search fields)
        THEN:
            - Nothing matches; a CJK term restricted to a field outside
              the default search fields has no bigram companion to widen
              to, so it must not fall back to matching 東京 in the
              content
        """
        index_document(
            title="Tokyo report",
            content="東京都の人口は約1400万人です",
        )

        assert matched_ids("notes:東京") == set()

    def test_bare_cjk_term_still_matches_every_default_field(
        self,
        index_document: Callable[..., Document],
        matched_ids: Callable[[str], set[int]],
    ) -> None:
        """
        GIVEN:
            - One document with 重要 in its content, another with 重要 in
              its title
        WHEN:
            - "重要" and "重要 OR report" are each searched unfielded
        THEN:
            - Both documents match either way; bigram matching exists
              so that an unfielded CJK run matches wherever it is
              indexed, and does so alongside a latin term
        """
        in_content = index_document(
            title="report",
            content="本文に重要な情報",
        )
        in_title = index_document(
            title="重要な報告書",
            content="english only",
        )

        assert matched_ids("重要") == {in_content.pk, in_title.pk}
        assert matched_ids("重要 OR report") == {
            in_content.pk,
            in_title.pk,
        }