"""IMP-46 u1 — Frame cache signature builder tests.

Verifies:
  * Determinism — identical inputs yield the same SHA256 digest.
  * Axis-change sensitivity — every one of the 8 declared axes mutates the
    digest when changed in isolation.
  * Public surface — only the 8 declared axes are accepted (no
    sample/section identifier leakage).
  * char_count bucket boundaries (0-50, 51-150, 151-400, 401-1000, 1001+).
  * source_shape enum equivalence (string and SourceShape inputs match).
  * schema_version is part of the hashed payload (digest stable for fixture).
"""
from __future__ import annotations

import inspect

import pytest

from src.phase_z2_ai_fallback.signature import (
    CHAR_COUNT_BUCKET_LABELS,
    SCHEMA_VERSION,
    SourceShape,
    bucket_char_count,
    build_signature,
)


def _base_kwargs() -> dict:
    return dict(
        frame_id="frame_03",
        v4_label="light_edit",
        cardinality=3,
        source_shape=SourceShape.BULLET,
        h3_count=2,
        char_count_bucket="51-150",
        layout_preset="sidebar-right",
        zone_position="top",
    )


def test_schema_version_is_one() -> None:
    assert SCHEMA_VERSION == 1


def test_bucket_labels_match_spec() -> None:
    assert CHAR_COUNT_BUCKET_LABELS == (
        "0-50",
        "51-150",
        "151-400",
        "401-1000",
        "1001+",
    )


def test_signature_is_deterministic() -> None:
    a = build_signature(**_base_kwargs())
    b = build_signature(**_base_kwargs())
    assert a == b
    assert len(a) == 64


@pytest.mark.parametrize(
    "axis, new_value",
    [
        ("frame_id", "frame_04"),
        ("v4_label", "restructure"),
        ("cardinality", 5),
        ("source_shape", SourceShape.PARAGRAPH),
        ("h3_count", 3),
        ("char_count_bucket", "151-400"),
        ("layout_preset", "two-column"),
        ("zone_position", "bottom_l"),
    ],
)
def test_signature_changes_for_each_axis(axis: str, new_value: object) -> None:
    base = build_signature(**_base_kwargs())
    kwargs = _base_kwargs()
    kwargs[axis] = new_value
    assert build_signature(**kwargs) != base


def test_signature_accepts_string_source_shape() -> None:
    enum_sig = build_signature(**_base_kwargs())
    kwargs = _base_kwargs()
    kwargs["source_shape"] = "bullet"
    assert build_signature(**kwargs) == enum_sig


def test_signature_rejects_unknown_source_shape() -> None:
    kwargs = _base_kwargs()
    kwargs["source_shape"] = "nonsense"
    with pytest.raises(ValueError):
        build_signature(**kwargs)


def test_signature_rejects_unknown_char_count_bucket() -> None:
    kwargs = _base_kwargs()
    kwargs["char_count_bucket"] = "999-1234"
    with pytest.raises(ValueError):
        build_signature(**kwargs)


def test_signature_handles_none_cardinality() -> None:
    kwargs = _base_kwargs()
    kwargs["cardinality"] = None
    sig = build_signature(**kwargs)
    assert len(sig) == 64
    kwargs2 = _base_kwargs()
    kwargs2["cardinality"] = 0
    assert build_signature(**kwargs2) != sig


def test_signature_surface_only_8_declared_axes() -> None:
    params = set(inspect.signature(build_signature).parameters)
    expected = {
        "frame_id",
        "v4_label",
        "cardinality",
        "source_shape",
        "h3_count",
        "char_count_bucket",
        "layout_preset",
        "zone_position",
    }
    assert params == expected


def test_bucket_boundaries() -> None:
    assert bucket_char_count(0) == "0-50"
    assert bucket_char_count(50) == "0-50"
    assert bucket_char_count(51) == "51-150"
    assert bucket_char_count(150) == "51-150"
    assert bucket_char_count(151) == "151-400"
    assert bucket_char_count(400) == "151-400"
    assert bucket_char_count(401) == "401-1000"
    assert bucket_char_count(1000) == "401-1000"
    assert bucket_char_count(1001) == "1001+"
    assert bucket_char_count(10_000) == "1001+"


def test_bucket_rejects_negative() -> None:
    with pytest.raises(ValueError):
        bucket_char_count(-1)


def test_bucket_rejects_non_int() -> None:
    with pytest.raises(TypeError):
        bucket_char_count(3.14)  # type: ignore[arg-type]
    with pytest.raises(TypeError):
        bucket_char_count(True)  # type: ignore[arg-type]


def test_signature_stable_known_fixture() -> None:
    """Lock the digest for a known fixture so a silent payload-shape change
    (e.g. a new axis sneaks in, or schema_version drifts) breaks this test.
    """
    sig = build_signature(
        frame_id="frame_03",
        v4_label="light_edit",
        cardinality=3,
        source_shape=SourceShape.BULLET,
        h3_count=2,
        char_count_bucket="51-150",
        layout_preset="sidebar-right",
        zone_position="top",
    )
    import hashlib
    import json

    expected_payload = {
        "schema_version": 1,
        "frame_id": "frame_03",
        "v4_label": "light_edit",
        "cardinality": 3,
        "source_shape": "bullet",
        "h3_count": 2,
        "char_count_bucket": "51-150",
        "layout_preset": "sidebar-right",
        "zone_position": "top",
    }
    expected = hashlib.sha256(
        json.dumps(expected_payload, sort_keys=True, ensure_ascii=False).encode("utf-8")
    ).hexdigest()
    assert sig == expected