"""Snowflake ids (架构文档 §6.1 原则 2)."""

from __future__ import annotations

import pytest

from packages.domain.ids import (
    DEFAULT_EPOCH_MS,
    SnowflakeGenerator,
    next_id,
    timestamp_ms_of,
)


def test_ids_are_unique_and_monotonic() -> None:
    generator = SnowflakeGenerator(node_id=1)
    ids = [generator.next_id() for _ in range(5000)]
    assert len(set(ids)) == len(ids)
    assert ids == sorted(ids)


def test_ids_fit_in_a_signed_64_bit_integer() -> None:
    assert 0 < next_id() < 2**63


def test_different_nodes_do_not_collide() -> None:
    a = SnowflakeGenerator(node_id=1)
    b = SnowflakeGenerator(node_id=2)
    assert not {a.next_id() for _ in range(500)} & {b.next_id() for _ in range(500)}


def test_node_id_is_bounded() -> None:
    with pytest.raises(ValueError, match="node_id"):
        SnowflakeGenerator(node_id=1024)


def test_timestamp_is_recoverable_for_partition_pruning() -> None:
    generator = SnowflakeGenerator(node_id=3)
    recovered = timestamp_ms_of(generator.next_id())
    assert recovered > DEFAULT_EPOCH_MS


def test_sequence_rollover_within_one_millisecond() -> None:
    """More than 4096 ids in a single ms must wait, not duplicate."""
    frozen = DEFAULT_EPOCH_MS + 1_000
    calls = {"n": 0}

    def fake_now() -> int:
        calls["n"] += 1
        # Hold the clock for the first 5000 calls, then let it advance.
        return frozen if calls["n"] < 5000 else frozen + 1

    generator = SnowflakeGenerator(node_id=1, clock=fake_now)
    ids = [generator.next_id() for _ in range(4200)]
    assert len(set(ids)) == len(ids)