"""Tests for infra.throttler — Throttler, TokenBucketStrategy."""

import time

import pytest

from infra.throttler import Throttler, TokenBucketStrategy


class TestTokenBucketStrategy:
    def test_initial_tokens_equal_capacity(self):
        strategy = TokenBucketStrategy(capacity=5, refill_rate=1.0)
        for _ in range(5):
            success, _ = strategy.try_acquire()
            assert success is True
        success, retry = strategy.try_acquire()
        assert success is False
        assert retry > 0

    def test_single_token_blocks_immediately(self):
        strategy = TokenBucketStrategy(capacity=1, refill_rate=1.0)
        assert strategy.try_acquire() == (True, 0.0)
        success, _ = strategy.try_acquire()
        assert success is False

    def test_refills_over_time(self):
        strategy = TokenBucketStrategy(capacity=1, refill_rate=100.0)
        strategy.try_acquire()  # drain
        time.sleep(0.02)  # 20ms at 100/s = ~2 tokens
        success, _ = strategy.try_acquire()
        assert success is True

    def test_clear_resets_to_capacity(self):
        strategy = TokenBucketStrategy(capacity=3, refill_rate=1.0)
        for _ in range(3):
            strategy.try_acquire()
        strategy.clear()
        success, _ = strategy.try_acquire()
        assert success is True

    def test_invalid_capacity_raises(self):
        with pytest.raises(ValueError, match='capacity'):
            TokenBucketStrategy(capacity=0, refill_rate=1.0)

    def test_invalid_refill_rate_raises(self):
        with pytest.raises(ValueError, match='refill_rate'):
            TokenBucketStrategy(capacity=1, refill_rate=0)


class TestThrottler:
    def test_acquire_blocks_until_available(self):
        strategy = TokenBucketStrategy(capacity=1, refill_rate=100.0)
        throttler = Throttler(strategy)

        throttler.acquire()  # drain first token
        start = time.monotonic()
        throttler.acquire()  # should block briefly
        elapsed = time.monotonic() - start

        assert elapsed < 0.1  # fast refill, should be near-instant

    def test_try_acquire_non_blocking(self):
        strategy = TokenBucketStrategy(capacity=1, refill_rate=0.1)
        throttler = Throttler(strategy)

        assert throttler.try_acquire() is True
        assert throttler.try_acquire() is False

    def test_clear_delegates(self):
        strategy = TokenBucketStrategy(capacity=1, refill_rate=0.1)
        throttler = Throttler(strategy)

        throttler.try_acquire()  # drain
        throttler.clear()
        assert throttler.try_acquire() is True