"""Ranking contract for decide_identity: what a score set is allowed to name.

Moved out of test_observe.py when the legacy session model was deleted; the
ranking rules are the live path's, not the legacy one's.
"""

from __future__ import annotations

import os
import sys
import unittest

current_dir = os.path.dirname(os.path.abspath(__file__))
if current_dir not in sys.path:
    sys.path.insert(0, current_dir)

from identity import (  # noqa: E402
    IDENTITY_ACCEPTED,
    IDENTITY_AMBIGUOUS,
    IDENTITY_REJECTED,
    IDENTITY_UNKNOWN,
    decide_identity,
)


class IdentityRankingTests(unittest.TestCase):
    def test_zero_scores_are_rejected_not_a_sku(self):
        ranked = decide_identity({"sku_a": 0.0, "sku_b": 0.0})
        self.assertEqual(ranked["identity_level"], IDENTITY_REJECTED)
        self.assertIsNone(ranked["best_sku"])
        self.assertEqual(ranked["status"], IDENTITY_REJECTED)

    def test_empty_scores_are_rejected(self):
        ranked = decide_identity({})
        self.assertEqual(ranked["identity_level"], IDENTITY_REJECTED)
        self.assertIsNone(ranked["best_sku"])

    def test_weak_unique_score_is_unknown(self):
        ranked = decide_identity({"sku_a": 0.4, "sku_b": 0.0})
        self.assertEqual(ranked["identity_level"], IDENTITY_UNKNOWN)
        self.assertIsNone(ranked["best_sku"])

    def test_close_scores_are_ambiguous(self):
        ranked = decide_identity({"sku_a": 20.0, "sku_b": 19.5})
        self.assertEqual(ranked["identity_level"], IDENTITY_AMBIGUOUS)
        self.assertIsNone(ranked["best_sku"])

    def test_unique_strong_score_is_accepted(self):
        ranked = decide_identity({"sku_a": 40.0, "sku_b": 5.0})
        self.assertEqual(ranked["identity_level"], IDENTITY_ACCEPTED)
        self.assertEqual(ranked["best_sku"], "sku_a")
        self.assertEqual(ranked["status"], "success")

    def test_van_answers_what_the_gate_would_refuse(self):
        # Van's contract is the baseline the decision is measured against, so it
        # must answer exactly where the shipped gate abstains. A weak score and
        # a close pair are both refused above; here both are named.
        weak = decide_identity({"sku_a": 0.4, "sku_b": 0.0}, scale="van")
        self.assertEqual(weak["identity_level"], IDENTITY_ACCEPTED)
        self.assertEqual(weak["best_sku"], "sku_a")
        close = decide_identity({"sku_a": 20.0, "sku_b": 19.5}, scale="van")
        self.assertEqual(close["best_sku"], "sku_a")

    def test_van_still_rejects_when_there_is_no_evidence(self):
        # Always-argmax is not always-answer: with nothing to rank there is no
        # argmax, and naming a SKU from an empty score set would be a fabrication.
        ranked = decide_identity({}, scale="van")
        self.assertEqual(ranked["identity_level"], IDENTITY_REJECTED)
        self.assertIsNone(ranked["best_sku"])