portfolio-optimiser-claude/tests/test_ledger_loadbearing.py

"""Savings ledger — LOAD-BEARING (parity rows 2-3; §6-style determinism, §11).

The seam this file keeps alive: realized savings enter the book ONLY through
the fail-closed expert gate (an explicit approved verdict + expert identity +
explicit timestamp), and the sum key is DIMENSION-FREE — the same realized
candidate surfaced via two dimensions lands in ONE slot, never double-counted.
RED when an unapproved verdict's numbers enter the book (detach point 1: the
decision gate in ``realize``), or when the mint key starts carrying the
dimension (detach point 2: dimension exclusion in the sum key).

Ledger semantics are a STACK-LOCAL contract mirrored from the MAF plan's
capability description (typed store, fail-closed realize, dimension-free sum
key) — never from MAF code.
"""

from __future__ import annotations

import math
from pathlib import Path

import pytest
from pydantic import ValidationError

from portfolio_optimiser_claude.contracts import FeedbackContract
from portfolio_optimiser_claude.ledger import LedgerGateError, SavingsLedger

APPROVED = FeedbackContract(decision="approved", rationale="Verified on-site by expert.")
REJECTED = FeedbackContract(decision="rejected", rationale="Numbers did not hold up.")
TIMESTAMP = "2026-07-17T03:00:00Z"
EXPERT = "persona:expert-reviewer"


def _realize(
    ledger: SavingsLedger,
    *,
    project: str = "bygg-energi-mikro",
    measure_type: str = "led-retrofit",
    affected_codes: frozenset[str] = frozenset({"E01"}),
    amount_nok: float = 25000.0,
    verdict: FeedbackContract = APPROVED,
    expert: str = EXPERT,
    timestamp: str = TIMESTAMP,
    dimension: str | None = None,
) -> object:
    return ledger.realize(
        project=project,
        measure_type=measure_type,
        affected_codes=affected_codes,
        amount_nok=amount_nok,
        verdict=verdict,
        expert=expert,
        timestamp=timestamp,
        dimension=dimension,
    )


class TestExpertGate:
    """LOAD-BEARING (§11): only expert-APPROVED savings are realized — fail-closed."""

    def test_rejected_verdict_is_refused_entering_nothing(self) -> None:
        ledger = SavingsLedger()
        with pytest.raises(LedgerGateError):
            _realize(ledger, verdict=REJECTED)
        assert len(ledger) == 0
        assert ledger.total_realized_nok() == 0.0

    def test_blank_expert_identity_is_refused(self) -> None:
        ledger = SavingsLedger()
        with pytest.raises(LedgerGateError):
            _realize(ledger, expert="   ")
        assert len(ledger) == 0

    def test_expert_is_an_explicit_required_argument(self) -> None:
        # No implicit expert — realization without a named expert is a call error.
        with pytest.raises(TypeError):
            SavingsLedger().realize(  # type: ignore[call-arg]
                project="p",
                measure_type="m",
                affected_codes=frozenset({"E01"}),
                amount_nok=1.0,
                verdict=APPROVED,
                timestamp=TIMESTAMP,
            )

    def test_timestamp_is_an_explicit_required_argument(self) -> None:
        # No wall-clock default — realization is deterministic and reproducible (§6-style).
        with pytest.raises(TypeError):
            SavingsLedger().realize(  # type: ignore[call-arg]
                project="p",
                measure_type="m",
                affected_codes=frozenset({"E01"}),
                amount_nok=1.0,
                verdict=APPROVED,
                expert=EXPERT,
            )

    @pytest.mark.parametrize("amount", [0.0, -25000.0, math.inf, math.nan])
    def test_non_positive_or_non_finite_amounts_are_refused(self, amount: float) -> None:
        ledger = SavingsLedger()
        with pytest.raises(ValidationError):
            _realize(ledger, amount_nok=amount)
        assert len(ledger) == 0


class TestDimensionFreeSumKey:
    """LOAD-BEARING (§11): the sum key excludes the dimension — no double counting."""

    def test_same_candidate_under_two_dimensions_is_one_slot(self) -> None:
        # Key assumption (K1 plan): the same realized saving surfaced via two
        # dimensions in the same project must NOT be counted twice.
        ledger = SavingsLedger()
        first = _realize(ledger, dimension="energi")
        second = _realize(ledger, dimension="vedlikehold")
        assert len(ledger) == 1
        assert ledger.total_realized_nok() == 25000.0
        assert second == first  # first-write-wins, §4.2-style idempotence

    def test_distinct_candidates_in_the_same_project_both_count(self) -> None:
        ledger = SavingsLedger()
        _realize(ledger, measure_type="led-retrofit", amount_nok=25000.0)
        _realize(ledger, measure_type="heat-recovery", amount_nok=40000.0)
        assert len(ledger) == 2
        assert ledger.total_realized_nok() == 65000.0

    def test_same_candidate_across_projects_both_count(self) -> None:
        ledger = SavingsLedger()
        _realize(ledger, project="prosjekt-a")
        _realize(ledger, project="prosjekt-b")
        assert len(ledger) == 2
        assert ledger.total_realized_nok() == 50000.0


class TestDeterministicPersistence:
    """Deterministic JSON persistence: sort_keys, indent 2, LF, trailing newline."""

    def _populated(self) -> SavingsLedger:
        ledger = SavingsLedger()
        _realize(ledger, project="prosjekt-b", amount_nok=40000.0)
        _realize(ledger, project="prosjekt-a", amount_nok=25000.0)
        return ledger

    def test_identical_sequences_persist_byte_identically(self, tmp_path: Path) -> None:
        path_a = tmp_path / "a.json"
        path_b = tmp_path / "b.json"
        self._populated().save(path_a)
        self._populated().save(path_b)
        assert path_a.read_bytes() == path_b.read_bytes()

    def test_file_is_lf_only_with_trailing_newline(self, tmp_path: Path) -> None:
        path = tmp_path / "ledger.json"
        self._populated().save(path)
        data = path.read_bytes()
        assert b"\r" not in data
        assert data.endswith(b"\n")

    def test_round_trip_is_byte_identical_and_sum_preserving(self, tmp_path: Path) -> None:
        original = tmp_path / "original.json"
        rewritten = tmp_path / "rewritten.json"
        ledger = self._populated()
        ledger.save(original)
        loaded = SavingsLedger.load(original)
        loaded.save(rewritten)
        assert rewritten.read_bytes() == original.read_bytes()
        assert loaded.total_realized_nok() == ledger.total_realized_nok()

    def test_load_fails_fast_on_a_malformed_entry(self, tmp_path: Path) -> None:
        path = tmp_path / "ledger.json"
        text = self._populated().to_json().replace("25000.0", "-25000.0")
        path.write_text(text, encoding="utf-8")
        with pytest.raises(ValidationError):
            SavingsLedger.load(path)