"""fence.py DTO 单元测试。

覆盖 ``FenceVerdict`` / ``FenceGeneration`` / ``FenceContext`` 的字段赋值、
默认值、不可变语义与 ``__post_init__`` 校验逻辑。
"""

from __future__ import annotations

import dataclasses
from datetime import datetime

import pytest
from yuxi.channels.contract.dtos.fence import (
    FenceContext,
    FenceGeneration,
    FenceVerdict,
)
from yuxi.channels.contract.errors import ValidationError

pytestmark = pytest.mark.unit


@pytest.mark.unit
class TestFenceVerdict:
    """栅栏裁决 DTO 测试。"""

    def test_fields_are_assigned(self):
        # Arrange
        # Act
        verdict = FenceVerdict(is_stale=True, current_generation=3, stale_generation=1)
        # Assert
        assert verdict.is_stale is True
        assert verdict.current_generation == 3
        assert verdict.stale_generation == 1

    def test_stale_generation_defaults_to_none(self):
        # Arrange
        # Act
        verdict = FenceVerdict(is_stale=False, current_generation=2)
        # Assert
        assert verdict.stale_generation is None

    def test_is_frozen(self):
        # Arrange
        verdict = FenceVerdict(is_stale=False, current_generation=0)
        # Act / Assert
        with pytest.raises(dataclasses.FrozenInstanceError):
            verdict.is_stale = True  # type: ignore[misc]


@pytest.mark.unit
class TestFenceGeneration:
    """栅栏代际 DTO 测试。"""

    def test_fields_are_assigned(self):
        # Arrange
        # Act
        gen = FenceGeneration(
            conversation_id="conv-1",
            current_generation=3,
            visible_generation=2,
        )
        # Assert
        assert gen.conversation_id == "conv-1"
        assert gen.current_generation == 3
        assert gen.visible_generation == 2

    def test_zero_generations_are_valid(self):
        # Arrange
        # Act
        gen = FenceGeneration(
            conversation_id="conv-1",
            current_generation=0,
            visible_generation=0,
        )
        # Assert - 代际为 0 是合法的（非负）
        assert gen.current_generation == 0
        assert gen.visible_generation == 0

    def test_is_frozen(self):
        # Arrange
        gen = FenceGeneration(
            conversation_id="conv-1", current_generation=0, visible_generation=0
        )
        # Act / Assert
        with pytest.raises(dataclasses.FrozenInstanceError):
            gen.current_generation = 1  # type: ignore[misc]

    def test_empty_conversation_id_raises_validation_error(self):
        # Arrange
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            FenceGeneration(conversation_id="", current_generation=0, visible_generation=0)
        assert exc_info.value.field == "conversation_id"

    def test_negative_current_generation_raises_validation_error(self):
        # Arrange
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            FenceGeneration(conversation_id="conv-1", current_generation=-1, visible_generation=0)
        assert exc_info.value.field == "current_generation"

    def test_negative_visible_generation_raises_validation_error(self):
        # Arrange
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            FenceGeneration(conversation_id="conv-1", current_generation=0, visible_generation=-1)
        assert exc_info.value.field == "visible_generation"


@pytest.mark.unit
class TestFenceContext:
    """栅栏上下文 DTO 测试。"""

    def test_fields_are_assigned(self):
        # Arrange
        now = datetime(2026, 1, 1, 12, 0, 0)
        # Act
        ctx = FenceContext(
            conversation_id="conv-1",
            generation=1,
            started_at=now,
        )
        # Assert
        assert ctx.conversation_id == "conv-1"
        assert ctx.generation == 1
        assert ctx.started_at is now
        assert ctx.ttl_seconds == 120

    def test_custom_ttl(self):
        # Arrange
        now = datetime(2026, 1, 1, 12, 0, 0)
        # Act
        ctx = FenceContext(
            conversation_id="conv-1",
            generation=1,
            started_at=now,
            ttl_seconds=300,
        )
        # Assert
        assert ctx.ttl_seconds == 300

    def test_zero_generation_is_valid(self):
        # Arrange
        now = datetime(2026, 1, 1, 12, 0, 0)
        # Act
        ctx = FenceContext(conversation_id="conv-1", generation=0, started_at=now)
        # Assert
        assert ctx.generation == 0

    def test_is_frozen(self):
        # Arrange
        now = datetime(2026, 1, 1, 12, 0, 0)
        ctx = FenceContext(conversation_id="conv-1", generation=0, started_at=now)
        # Act / Assert
        with pytest.raises(dataclasses.FrozenInstanceError):
            ctx.generation = 1  # type: ignore[misc]

    def test_empty_conversation_id_raises_validation_error(self):
        # Arrange
        now = datetime(2026, 1, 1, 12, 0, 0)
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            FenceContext(conversation_id="", generation=0, started_at=now)
        assert exc_info.value.field == "conversation_id"

    def test_negative_generation_raises_validation_error(self):
        # Arrange
        now = datetime(2026, 1, 1, 12, 0, 0)
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            FenceContext(conversation_id="conv-1", generation=-1, started_at=now)
        assert exc_info.value.field == "generation"

    def test_non_positive_ttl_raises_validation_error(self):
        # Arrange
        now = datetime(2026, 1, 1, 12, 0, 0)
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            FenceContext(conversation_id="conv-1", generation=0, started_at=now, ttl_seconds=0)
        assert exc_info.value.field == "ttl_seconds"