"""grant_bonus 纯域函数：封顶边界与不变量（FR-BILL-03）."""

from __future__ import annotations

import pytest

from packages.domain.billing import quota


def test_grant_up_to_the_cap_exactly_is_allowed() -> None:
    # bonus + amount == max：恰好到顶，允许。
    decision = quota.grant_bonus(quota.QuotaState(used=0, base_limit=10, bonus=9), 1, 10)
    assert decision.allowed
    assert decision.bonus == 10
    assert decision.effective_limit == 20
    assert decision.remaining == 20


def test_grant_one_over_the_cap_is_rejected_as_a_whole() -> None:
    # bonus + amount == max + 1：整体拒绝，不做部分发放。
    state = quota.QuotaState(used=4, base_limit=10, bonus=9)
    decision = quota.grant_bonus(state, 2, 10)
    assert not decision.allowed
    # 拒绝时保持发放前的值 —— 调用方不得据此落库。
    assert decision.bonus == 9
    assert decision.remaining == state.remaining
    assert decision.effective_limit == state.effective_limit


def test_zero_cap_rejects_every_grant() -> None:
    # hd_export / report_basic 的 task_bonus_max=0：任务奖励一律拒绝。
    decision = quota.grant_bonus(quota.QuotaState(used=0, base_limit=1), 1, 0)
    assert not decision.allowed


def test_grant_rejects_non_positive_amounts() -> None:
    state = quota.QuotaState(used=0, base_limit=10)
    with pytest.raises(ValueError, match="positive"):
        quota.grant_bonus(state, 0, 10)
    with pytest.raises(ValueError, match="positive"):
        quota.grant_bonus(state, -1, 10)


def test_grant_never_touches_used_or_base_limit() -> None:
    # 任务奖励抬高的是额度不是用量：remaining 的增量恰好等于 amount。
    state = quota.QuotaState(used=7, base_limit=10, bonus=2)
    decision = quota.grant_bonus(state, 3, 10)
    assert decision.allowed
    assert decision.remaining - state.remaining == 3
    assert decision.bonus == 5


def test_task_bonus_cap_is_independent_of_hard_cap() -> None:
    # 两道天花板独立生效：task_bonus_max 放行、hard_cap 把 effective_limit 削回来。
    state = quota.QuotaState(used=0, base_limit=3, bonus=3, hard_cap=5)
    decision = quota.grant_bonus(state, 3, 10)
    assert decision.allowed  # bonus 6 <= task_bonus_max 10
    assert decision.effective_limit == 5  # base 3 + bonus 6 被 hard_cap 削到 5
    assert decision.remaining == 5


def test_grant_key_is_derived_per_user_task_and_claim_period() -> None:
    key = quota.grant_idempotency_key(
        user_id=7, task_key="sign_in", claim_period_key="d:2026-08-14"
    )
    assert key == "grant:7:sign_in:d:2026-08-14"
    # 派生键确定：同一周期重复 claim 得到同一个键，唯一约束才能兜底。
    assert key == quota.grant_idempotency_key(
        user_id=7, task_key="sign_in", claim_period_key="d:2026-08-14"
    )
    # 换周期换键：下个周期可以再领。
    assert key != quota.grant_idempotency_key(
        user_id=7, task_key="sign_in", claim_period_key="d:2026-08-15"
    )