"""Quota three-phase arithmetic (架构文档 §7.4, FR-BILL-01/05/06)."""

from __future__ import annotations

from datetime import UTC, datetime

import pytest

from packages.domain.billing import quota
from packages.domain.errors import QuotaExceededError


def test_period_key_day_uses_utc_plus_8() -> None:
    # 17:00Z is already 01:00 the next day in UTC+8.
    assert quota.period_key(datetime(2026, 8, 13, 17, 0, tzinfo=UTC), "day") == "d:2026-08-14"
    assert quota.period_key(datetime(2026, 8, 13, 15, 0, tzinfo=UTC), "day") == "d:2026-08-13"


def test_period_key_month_and_lifetime() -> None:
    now = datetime(2026, 8, 13, 1, 0, tzinfo=UTC)
    assert quota.period_key(now, "month") == "m:2026-08"
    assert quota.period_key(now, "lifetime") == "life"


def test_unknown_period_type_is_rejected() -> None:
    with pytest.raises(ValueError, match="unknown period_type"):
        quota.period_key(datetime.now(UTC), "weekly")  # type: ignore[arg-type]


def test_period_reset_at_rolls_to_the_next_local_midnight() -> None:
    reset = quota.period_reset_at(datetime(2026, 8, 13, 1, 0, tzinfo=UTC), "day")
    assert reset is not None
    assert reset == datetime(2026, 8, 13, 16, 0, tzinfo=UTC)  # 2026-08-14 00:00 +08


def test_period_reset_at_handles_december_rollover() -> None:
    reset = quota.period_reset_at(datetime(2026, 12, 20, 1, 0, tzinfo=UTC), "month")
    assert reset is not None
    assert reset.year == 2026  # 2027-01-01 00:00 +08 == 2026-12-31 16:00 UTC
    assert reset.month == 12


def test_lifetime_quota_never_resets() -> None:
    assert quota.period_reset_at(datetime.now(UTC), "lifetime") is None


def test_task_bonus_raises_the_effective_limit() -> None:
    state = quota.QuotaState(used=20, base_limit=20, bonus=3)
    assert state.effective_limit == 23
    assert state.remaining == 3
    assert quota.evaluate(state, 1).allowed


def test_reserve_freezes_the_amount() -> None:
    state = quota.reserve(quota.QuotaState(used=0, base_limit=20), 1)
    assert state.used == 1
    assert state.remaining == 19


def test_reserve_beyond_the_limit_is_rejected_server_side() -> None:
    state = quota.QuotaState(used=20, base_limit=20)
    with pytest.raises(QuotaExceededError) as excinfo:
        quota.reserve(state, 1)
    assert excinfo.value.remaining == 0
    assert excinfo.value.required == 1


def test_reserve_rejects_a_batch_that_would_overshoot() -> None:
    with pytest.raises(QuotaExceededError):
        quota.reserve(quota.QuotaState(used=18, base_limit=20), 3)


def test_non_positive_amounts_are_programming_errors() -> None:
    with pytest.raises(ValueError, match="positive"):
        quota.evaluate(quota.QuotaState(used=0, base_limit=1), 0)
    with pytest.raises(ValueError, match="positive"):
        quota.refund(quota.QuotaState(used=1, base_limit=1), -1)


def test_refund_releases_the_reservation() -> None:
    reserved = quota.reserve(quota.QuotaState(used=5, base_limit=20), 1)
    assert quota.refund(reserved, 1).used == 5


def test_refund_never_drives_usage_negative() -> None:
    assert quota.refund(quota.QuotaState(used=0, base_limit=20), 5).used == 0


def test_balance_after_records_remaining_quota() -> None:
    assert quota.balance_after(quota.QuotaState(used=3, base_limit=20)) == 17


def test_refund_key_is_derived_so_a_retry_cannot_double_refund() -> None:
    reserve_key = quota.reserve_idempotency_key(
        user_id=7, quota_key="agent_chat", request_key="req-1"
    )
    assert reserve_key == "rsv:7:agent_chat:req-1"
    assert quota.refund_idempotency_key(reserve_key) == "rfd:rsv:7:agent_chat:req-1"
    assert quota.refund_idempotency_key(reserve_key) == quota.refund_idempotency_key(reserve_key)


def test_ledger_can_recompute_the_balance() -> None:
    """流水是真相，余额是缓存 (架构文档 §6.1 原则 4)."""
    state = quota.QuotaState(used=0, base_limit=20)
    deltas = []
    for _ in range(3):
        state = quota.reserve(state, 1)
        deltas.append(-1)
    state = quota.refund(state, 1)
    deltas.append(1)
    assert state.used == -sum(deltas)


def test_hard_cap_clips_base_plus_bonus() -> None:
    # 产品方案 §3.2：有效额度 = min(base + bonus, hard_cap)
    state = quota.QuotaState(used=0, base_limit=10, bonus=10, hard_cap=40)
    assert state.effective_limit == 20
    clipped = quota.QuotaState(used=0, base_limit=10, bonus=40, hard_cap=40)
    assert clipped.effective_limit == 40
    assert not quota.evaluate(clipped, 41).allowed