"""IMP-47B u7 — Post-AI source_section_ids coverage invariant tests.

Scope (this slice):
  * Helper ``_check_post_ai_coverage_invariant(units, ai_repair_records)``
    (src/phase_z2_pipeline.py) compares the pre-AI superset (unit
    ``source_section_ids``) to the post-apply superset present on
    gather records. Per the AI isolation contract + dropped 절대 룰
    (``feedback_ai_isolation_contract``), AI repair must not silently
    drop a section.
  * The helper returns a structured dict (``pre_ai_section_ids``,
    ``post_ai_section_ids``, ``dropped_section_ids``, ``status``) so u8
    can surface ``status`` through ``slide_status.ai_repair_status``.

u8 slide_status surfacing and u10 E2E no-text-loss assertion are out
of scope for this unit. The helper is pure (no AI call, no IO) so a
synthetic stub-unit / stub-record fixture exercises it directly.
"""
from __future__ import annotations

from dataclasses import dataclass, field

from src.phase_z2_pipeline import _check_post_ai_coverage_invariant


@dataclass
class _StubUnit:
    source_section_ids: list[str] = field(default_factory=list)


def _record(source_section_ids: list[str]) -> dict:
    """Minimal gather-record stub — only the field u7 reads."""
    return {"source_section_ids": list(source_section_ids)}


# ─── Case 1 : matched coverage → status='ok' ────────────────────────


def test_coverage_invariant_ok_when_records_match_units():
    """Records carry every unit's source_section_ids → no drop, status='ok'."""
    units = [_StubUnit(["MOCK_S1", "MOCK_S2"]), _StubUnit(["MOCK_S3"])]
    records = [_record(["MOCK_S1", "MOCK_S2"]), _record(["MOCK_S3"])]
    result = _check_post_ai_coverage_invariant(units, records)
    assert result["status"] == "ok"
    assert result["dropped_section_ids"] == []
    assert result["pre_ai_section_ids"] == ["MOCK_S1", "MOCK_S2", "MOCK_S3"]
    assert result["post_ai_section_ids"] == ["MOCK_S1", "MOCK_S2", "MOCK_S3"]


# ─── Case 2 : record drops a section → status='violated' ────────────


def test_coverage_invariant_violated_when_record_drops_section():
    """If a record loses a unit's section_id (e.g., apply mutation bug),
    the invariant reports status='violated' + dropped list (dropped 절대 룰).
    """
    units = [_StubUnit(["MOCK_S1", "MOCK_S2"]), _StubUnit(["MOCK_S3"])]
    records = [_record(["MOCK_S1"]), _record(["MOCK_S3"])]  # MOCK_S2 dropped
    result = _check_post_ai_coverage_invariant(units, records)
    assert result["status"] == "violated"
    assert result["dropped_section_ids"] == ["MOCK_S2"]
    assert "MOCK_S2" in result["pre_ai_section_ids"]
    assert "MOCK_S2" not in result["post_ai_section_ids"]


# ─── Case 3 : empty inputs → status='ok' (no false positive) ────────


def test_coverage_invariant_ok_on_empty_units_and_records():
    """Empty pipeline (no units / no records) is a vacuous pass —
    avoids false-positive 'violated' on edge-case shapes (no AI work).
    """
    result = _check_post_ai_coverage_invariant([], [])
    assert result["status"] == "ok"
    assert result["dropped_section_ids"] == []
    assert result["pre_ai_section_ids"] == []
    assert result["post_ai_section_ids"] == []


# ─── Case 4 : multiple drops + dedup ────────────────────────────────


def test_coverage_invariant_lists_all_dropped_sections_sorted_and_deduped():
    """Multiple missing sections → dropped_section_ids is sorted + deduped.
    Duplicate ids across units / records collapse to a set comparison.
    """
    units = [
        _StubUnit(["MOCK_S3", "MOCK_S1"]),
        _StubUnit(["MOCK_S2", "MOCK_S1"]),  # MOCK_S1 duplicate
    ]
    records: list[dict] = []  # full drop — every unit section missing
    result = _check_post_ai_coverage_invariant(units, records)
    assert result["status"] == "violated"
    assert result["dropped_section_ids"] == ["MOCK_S1", "MOCK_S2", "MOCK_S3"]
    assert result["pre_ai_section_ids"] == ["MOCK_S1", "MOCK_S2", "MOCK_S3"]
    assert result["post_ai_section_ids"] == []