#!/usr/bin/env python3
"""Unit tests for the trucking same-day coupon A/B/C price test.

Verifies that CAMPAIGN_COUPON_AB_PCTS produces an even, stable per-email split,
that the advertised percent always matches the arm's actual code (so the email
never promises a discount checkout won't honor), and that the off / single-arm
states behave. Pure-function tests, no DB required (psycopg2 is stubbed).

Run: CAMPAIGN_COUPON_AB_PCTS="20,30,40" python3 scripts/tests/test_coupon_ab.py
"""
from __future__ import annotations

import importlib.util
import os
import sys
import types
from collections import Counter
from pathlib import Path

os.environ.setdefault("CAMPAIGN_COUPON_AB_PCTS", "20,30,40")

# Stub the DB driver so the builder imports without a live Postgres.
sys.modules.setdefault("psycopg2", types.ModuleType("psycopg2"))

_SCRIPT = Path(__file__).resolve().parents[1] / "build_trucking_campaigns.py"
_spec = importlib.util.spec_from_file_location("btc", _SCRIPT)
btc = importlib.util.module_from_spec(_spec)
_spec.loader.exec_module(btc)


def test_arms_parsed():
    assert btc.COUPON_AB_PCTS == (20, 30, 40)


def test_even_stable_and_code_matches_pct():
    coupons = {20: "AAAAA", 30: "BBBBB", 40: "CCCCC"}
    emails = [f"user{i}@carrier{i % 500}.com" for i in range(30000)]
    counts: Counter = Counter()
    for e in emails:
        code, pct = btc.pick_coupon_for_email(e, coupons)
        counts[pct] += 1
        # Advertised percent must match the arm's real code.
        assert coupons[int(pct)] == code
        # Stable: same input -> same arm.
        assert btc.pick_coupon_for_email(e, coupons) == (code, pct)
    total = sum(counts.values())
    # Each arm should be within ~2 points of an even third.
    for pct in ("20", "30", "40"):
        share = counts[pct] / total
        assert 0.31 <= share <= 0.353, (pct, share)


def test_off_state():
    assert btc.pick_coupon_for_email("x@y.com", None) == ("", "")
    assert btc.pick_coupon_for_email("x@y.com", {}) == ("", "")


def test_single_arm():
    assert btc.pick_coupon_for_email("a@b.com", {40: "ZZZZZ"}) == ("ZZZZZ", "40")


def test_coupon_attribs_reflects_pct():
    a = btc.coupon_attribs("BBBBB", "30")
    assert a["coupon_code"] == "BBBBB"
    assert a["coupon_pct"] == "30"
    assert btc.coupon_attribs("", "30") == {
        "coupon_code": "", "coupon_pct": "", "coupon_expires": ""
    }


if __name__ == "__main__":
    fns = [v for k, v in sorted(globals().items()) if k.startswith("test_")]
    for fn in fns:
        fn()
        print(f"ok  {fn.__name__}")
    print(f"\nAll {len(fns)} coupon A/B tests passed.")