"""truncation.py DTO 单元测试。

覆盖 ``TruncationCandidate`` 与 ``TruncationResult`` 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

import pytest
from yuxi.channels.contract.dtos.truncation import (
    TruncationCandidate,
    TruncationResult,
)
from yuxi.channels.contract.errors import ValidationError

pytestmark = pytest.mark.unit


@pytest.mark.unit
class TestTruncationCandidate:
    """截断候选 DTO 测试。"""

    def test_fields_are_assigned(self):
        # Arrange
        # Act
        candidate = TruncationCandidate(text="hello", source="user_message", length=5)
        # Assert
        assert candidate.text == "hello"
        assert candidate.source == "user_message"
        assert candidate.length == 5

    def test_zero_length_is_valid(self):
        # Arrange
        # Act
        candidate = TruncationCandidate(text="hello", source="user_message", length=0)
        # Assert - length 为 0 是合法的（非负）
        assert candidate.length == 0

    def test_is_frozen(self):
        # Arrange
        candidate = TruncationCandidate(text="hello", source="user_message", length=5)
        # Act / Assert
        with pytest.raises(dataclasses.FrozenInstanceError):
            candidate.text = "other"  # type: ignore[misc]

    def test_empty_text_raises_validation_error(self):
        # Arrange
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            TruncationCandidate(text="", source="user_message", length=5)
        assert exc_info.value.field == "text"

    def test_empty_source_raises_validation_error(self):
        # Arrange
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            TruncationCandidate(text="hello", source="", length=5)
        assert exc_info.value.field == "source"

    def test_negative_length_raises_validation_error(self):
        # Arrange
        # Act / Assert
        with pytest.raises(ValidationError) as exc_info:
            TruncationCandidate(text="hello", source="user_message", length=-1)
        assert exc_info.value.field == "length"


@pytest.mark.unit
class TestTruncationResult:
    """截断结果 DTO 测试。"""

    def test_required_fields_are_assigned(self):
        # Arrange
        # Act
        result = TruncationResult(is_truncated=True)
        # Assert
        assert result.is_truncated is True

    def test_defaults_are_correct(self):
        # Arrange
        # Act
        result = TruncationResult(is_truncated=False)
        # Assert
        assert result.missing_content is None
        assert result.fallback_to_persistent is False
        assert result.completed_text is None
        assert result.original_length is None
        assert result.completed_length is None

    def test_custom_values_are_assigned(self):
        # Arrange
        # Act
        result = TruncationResult(
            is_truncated=True,
            missing_content="missing",
            fallback_to_persistent=True,
            completed_text="completed",
            original_length=100,
            completed_length=150,
        )
        # Assert
        assert result.missing_content == "missing"
        assert result.fallback_to_persistent is True
        assert result.completed_text == "completed"
        assert result.original_length == 100
        assert result.completed_length == 150

    def test_is_frozen(self):
        # Arrange
        result = TruncationResult(is_truncated=True)
        # Act / Assert
        with pytest.raises(dataclasses.FrozenInstanceError):
            result.is_truncated = False  # type: ignore[misc]