approval-engine/tests/test_claim_contract.py

import json
from pathlib import Path

from approval_engine.binding import binding_digest
from tests.conftest import approve, binding, validity

ROOT = Path(__file__).resolve().parents[1]


def test_schema_forbids_decision_keys():
    schema = json.loads((ROOT / "schemas/approval_claim.schema.json").read_text())
    assert "not" in schema
    kinds = [item["required"][0] for item in schema["not"]["anyOf"]]
    assert set(kinds) >= {"effect", "decision", "allow", "deny"}


def test_claim_has_issuer_digest_freshness(engine):
    obj = approve(engine)
    claim = engine.claim(obj.id)
    assert claim["kind"] == "approval-claim"
    assert claim["issuer"] == "approval-engine"
    assert claim["approval_id"] == obj.id
    assert claim["valid_now"] is True
    assert claim["reason_code"] == "ok"
    assert claim["binding"]["digest"] == binding_digest(binding())
    assert claim["freshness"]["ttl_seconds"] == 30
    assert claim["freshness"]["not_after"] == "2026-08-29T12:00:30+00:00"
    assert "effect" not in claim
    assert "decision" not in claim
    assert "yields_to" in claim


def test_wrong_target_changes_digest():
    a = binding()
    b = binding(target={"id": "other-lane", "stage": "prod"})
    assert binding_digest(a) != binding_digest(b)


def test_wrong_action_changes_digest():
    assert binding_digest(binding()) != binding_digest(binding(action="secrets.kv.read"))


def test_pdp_digest_is_recorded_not_recomputed(engine):
    pdp = "sha256:" + "ab" * 32
    obj = approve(engine, pdp_digest=pdp)
    claim = engine.claim(obj.id)
    assert claim["binding"]["pdp_digest"] == pdp
    assert claim["binding"]["digest"] == binding_digest(binding())
    assert claim["binding"]["digest"] != pdp


def test_examples_are_claim_shaped():
    for name in ("claim.valid.json", "claim.revoked.json"):
        data = json.loads((ROOT / "examples" / name).read_text())
        assert data["kind"] == "approval-claim"
        assert data["issuer"] == "approval-engine"
        for forbidden in ("effect", "decision", "allow", "deny"):
            assert forbidden not in data


def test_presentation_changes_cannot_change_the_approved_act(engine):
    """GH-DEC-2026-015: presentation cannot enter the native digest preimage."""
    act = binding()
    original = approve(engine, extra_binding=act)
    original_claim = engine.claim(original.id)
    presentation = {
        "view_hash": "sha256:" + "12" * 32,
        "brief": "First explanation",
        "packet": {"sections": ["summary"]},
        "highlights": ["target"],
        "locale": "de-DE",
        "ui_release": "surface-v1",
        "presentation": {"binding_digest": original_claim["binding"]["digest"]},
    }
    first = approve(engine, extra_binding={**act, **presentation})
    changed = {key: {"changed": value} for key, value in presentation.items()}
    second = approve(engine, extra_binding={**act, **changed})
    for obj in (first, second):
        assert engine.claim(obj.id)["binding"]["digest"] == original_claim["binding"]["digest"]
        assert obj.binding == original.binding

    # The invariant is about presentation, not permission to ignore act changes.
    for field, replacement in {
        "action": "secrets.kv.read",
        "actor": "different-agent",
        "principal": "different-principal",
        "purpose": "different-purpose",
        "target": {"id": "different-lane", "stage": "prod"},
    }.items():
        other = approve(engine, extra_binding={**act, **presentation, field: replacement})
        assert engine.claim(other.id)["binding"]["digest"] != original_claim["binding"]["digest"]


def test_approver_identity_is_not_in_the_act_digest(engine):
    """`binding.principal` is the party on whose behalf, never the approver.

    Answers `informed-decision`'s `principal_role_overlap` question. The
    approver is recorded as an entry, so two approvals of the same act bound by
    different people share one digest — which is why a presentation hash that
    must commit to *who was shown this* cannot get that from our digest.
    """
    act = binding()
    first = engine.create(act, validity(), required_count=1)
    first = engine.add_entry(first.id, "user:approver-a")
    second = engine.create(act, validity(), required_count=1)
    second = engine.add_entry(second.id, "user:approver-b")

    expected = binding_digest(act)
    assert engine.claim(first.id)["binding"]["digest"] == expected
    assert engine.claim(second.id)["binding"]["digest"] == expected

    # The approver is still distinguishable — recorded, not hashed into the act.
    assert [e["subject_id"] for e in first.entries] == ["user:approver-a"]
    assert [e["subject_id"] for e in second.entries] == ["user:approver-b"]

    # And changing who the act is *for* does change the digest.
    assert binding_digest(binding(principal="someone-else")) != expected