"""Before/after effectiveness tests (WP-0009 T02)."""

import os
import sys

sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

from session_memory.measure.effect import effectiveness, split_by_date  # noqa: E402


def _digest(ts, tools=None, errors=0, outcome="success"):
    return {
        "started_at": ts, "outcome": outcome,
        "cost": {"input_tokens": 100, "output_tokens": 0},
        "tool_histogram": tools or {"Bash": 10},
        "error_snippets": [{"fingerprint": f"e{i}", "count": 1} for i in range(errors)],
    }


def test_split_by_date():
    digs = [_digest("2026-06-01"), _digest("2026-06-05"), _digest("2026-06-10")]
    before, after = split_by_date(digs, "2026-06-05")
    assert len(before) == 1 and len(after) == 2  # >= applied_at goes to after


def test_effectiveness_detects_improvement():
    # before: lots of errors + hub overhead; after: clean
    before = [_digest("2026-06-01", tools={"mcp__state-hub__x": 8, "Bash": 2}, errors=3)
              for _ in range(3)]
    after = [_digest("2026-06-10", tools={"Bash": 10}, errors=0) for _ in range(3)]
    e = effectiveness(before + after, "2026-06-05", label="read-before-edit")
    assert not e["insufficient_data"]
    assert e["n_before"] == 3 and e["n_after"] == 3
    assert e["deltas"]["error_rate"]["improved"] is True
    assert e["deltas"]["infra_overhead_share_median"]["improved"] is True
    assert e["deltas"]["error_rate"]["change"] < 0


def test_effectiveness_insufficient_data():
    e = effectiveness([_digest("2026-06-01")], "2026-06-05")
    assert e["insufficient_data"] is True
    assert e["deltas"] == {}


def test_success_rate_higher_is_better():
    before = [_digest("2026-06-01", outcome="fail") for _ in range(2)]
    after = [_digest("2026-06-10", outcome="success") for _ in range(2)]
    e = effectiveness(before + after, "2026-06-05")
    assert e["deltas"]["success_rate"]["improved"] is True