"""Global daily cost circuit breaker (架构文档 §13 三道成本闸门).

The requirement is enforcement, not alerting: once the platform-wide daily
spend crosses the threshold, non-critical AI calls are rejected.
"""

from __future__ import annotations

from datetime import UTC, datetime
from decimal import Decimal

import pytest

from packages.llm.budget import DailyBudgetGuard, InMemoryCostCounter
from packages.llm.errors import DailyBudgetExceededError


def make_guard(
    budget: str = "100", *, enabled: bool = True, now: datetime | None = None
) -> tuple[DailyBudgetGuard, InMemoryCostCounter]:
    counter = InMemoryCostCounter()
    guard = DailyBudgetGuard(
        counter,
        daily_budget_cents=Decimal(budget),
        enabled=enabled,
        clock=(lambda: now) if now else None,
    )
    return guard, counter


async def test_allows_calls_below_the_threshold() -> None:
    guard, _ = make_guard("100")
    await guard.add_cost(Decimal("99.9"))
    await guard.ensure_within_budget(scene="agent_chat")


async def test_rejects_non_critical_scenes_once_the_budget_is_reached() -> None:
    guard, _ = make_guard("100")
    await guard.add_cost(Decimal("100"))
    with pytest.raises(DailyBudgetExceededError) as excinfo:
        await guard.ensure_within_budget(scene="agent_chat")
    assert "agent_chat" in str(excinfo.value)


async def test_critical_scenes_bypass_the_breaker() -> None:
    guard, _ = make_guard("100")
    await guard.add_cost(Decimal("500"))
    # Degrade the product, do not break it: 意图识别/越界拒答 must keep working.
    await guard.ensure_within_budget(scene="intent_classify", critical=True)


async def test_disabled_guard_never_blocks_and_never_counts() -> None:
    guard, counter = make_guard("1", enabled=False)
    await guard.add_cost(Decimal("999"))
    await guard.ensure_within_budget(scene="agent_chat")
    assert await counter.get(guard.current_key()) == Decimal("0")


async def test_cost_accumulates_across_calls() -> None:
    guard, _ = make_guard("100")
    await guard.add_cost(Decimal("1.5"))
    await guard.add_cost(Decimal("2.25"))
    assert await guard.spent_today() == Decimal("3.75")


async def test_zero_cost_is_not_counted() -> None:
    guard, _ = make_guard("100")
    await guard.add_cost(Decimal("0"))
    assert await guard.spent_today() == Decimal("0")


async def test_budget_day_boundary_follows_utc_plus_8() -> None:
    """FR-BILL-01: 跨时区按 UTC+8 统一。17:00Z already belongs to the next day."""
    guard, _ = make_guard(now=datetime(2026, 8, 13, 17, 0, tzinfo=UTC))
    assert guard.current_key().endswith("2026-08-14")

    guard_before, _ = make_guard(now=datetime(2026, 8, 13, 15, 0, tzinfo=UTC))
    assert guard_before.current_key().endswith("2026-08-13")


async def test_budget_properties_are_exposed_for_dashboards() -> None:
    guard, _ = make_guard("42")
    assert guard.enabled is True
    assert guard.budget_cents == Decimal("42")