"""
pagination 通用分页器单元测试

覆盖：
- PaginationParams: 默认值/边界/校验/offset/limit
- PaginationMeta: from_params 各种边界场景
- PaginatedResponse: create 工厂方法
- paginate: 内存分页函数
"""

import pytest
from pydantic import ValidationError

from packages.application.common.pagination import (
    PaginatedResponse,
    PaginationMeta,
    PaginationParams,
    paginate,
)

# ============================================================
# PaginationParams
# ============================================================


class TestPaginationParamsDefaults:
    """默认值测试"""

    def test_default_page_is_1(self):
        params = PaginationParams()
        assert params.page == 1

    def test_default_page_size_is_20(self):
        params = PaginationParams()
        assert params.page_size == 20

    def test_default_offset_is_0(self):
        params = PaginationParams()
        assert params.offset == 0

    def test_default_limit_is_20(self):
        params = PaginationParams()
        assert params.limit == 20


class TestPaginationParamsValidation:
    """参数校验"""

    @pytest.mark.parametrize("page", [1, 2, 100, 9999])
    def test_valid_page_values(self, page):
        params = PaginationParams(page=page)
        assert params.page == page

    def test_page_zero_raises(self):
        with pytest.raises(ValidationError):
            PaginationParams(page=0)

    def test_page_negative_raises(self):
        with pytest.raises(ValidationError):
            PaginationParams(page=-1)

    @pytest.mark.parametrize("page_size", [1, 20, 50, 100])
    def test_valid_page_size_values(self, page_size):
        params = PaginationParams(page_size=page_size)
        assert params.page_size == page_size

    def test_page_size_zero_raises(self):
        with pytest.raises(ValidationError):
            PaginationParams(page_size=0)

    def test_page_size_negative_raises(self):
        with pytest.raises(ValidationError):
            PaginationParams(page_size=-5)

    def test_page_size_over_100_raises(self):
        with pytest.raises(ValidationError):
            PaginationParams(page_size=101)

    def test_invalid_page_type_raises(self):
        with pytest.raises(ValidationError):
            PaginationParams(page="abc")

    def test_invalid_page_size_type_raises(self):
        with pytest.raises(ValidationError):
            PaginationParams(page_size="abc")


class TestPaginationParamsOffset:
    """offset 属性计算"""

    def test_page_1_offset_0(self):
        params = PaginationParams(page=1, page_size=20)
        assert params.offset == 0

    def test_page_2_offset_page_size(self):
        params = PaginationParams(page=2, page_size=20)
        assert params.offset == 20

    def test_page_3_offset_2x_page_size(self):
        params = PaginationParams(page=3, page_size=20)
        assert params.offset == 40

    def test_page_5_page_size_10_offset_40(self):
        params = PaginationParams(page=5, page_size=10)
        assert params.offset == 40

    def test_page_1_page_size_100_offset_0(self):
        params = PaginationParams(page=1, page_size=100)
        assert params.offset == 0


class TestPaginationParamsLimit:
    """limit 属性"""

    def test_limit_equals_page_size(self):
        params = PaginationParams(page_size=20)
        assert params.limit == 20

    def test_limit_1(self):
        params = PaginationParams(page_size=1)
        assert params.limit == 1

    def test_limit_100(self):
        params = PaginationParams(page_size=100)
        assert params.limit == 100


# ============================================================
# PaginationMeta.from_params
# ============================================================


class TestPaginationMetaFromParams:
    """from_params 工厂方法"""

    def test_empty_total_zero(self):
        params = PaginationParams(page=1, page_size=20)
        meta = PaginationMeta.from_params(params, total=0)
        assert meta.total == 0
        assert meta.total_pages == 0
        assert meta.has_next is False
        assert meta.has_prev is False

    def test_exactly_one_page(self):
        params = PaginationParams(page=1, page_size=20)
        meta = PaginationMeta.from_params(params, total=20)
        assert meta.total_pages == 1
        assert meta.has_next is False
        assert meta.has_prev is False

    def test_less_than_one_page(self):
        params = PaginationParams(page=1, page_size=20)
        meta = PaginationMeta.from_params(params, total=15)
        assert meta.total_pages == 1
        assert meta.has_next is False
        assert meta.has_prev is False

    def test_multiple_pages_first_page(self):
        params = PaginationParams(page=1, page_size=20)
        meta = PaginationMeta.from_params(params, total=50)
        assert meta.total_pages == 3
        assert meta.has_next is True
        assert meta.has_prev is False

    def test_multiple_pages_middle_page(self):
        params = PaginationParams(page=2, page_size=20)
        meta = PaginationMeta.from_params(params, total=50)
        assert meta.total_pages == 3
        assert meta.has_next is True
        assert meta.has_prev is True

    def test_multiple_pages_last_page(self):
        params = PaginationParams(page=3, page_size=20)
        meta = PaginationMeta.from_params(params, total=50)
        assert meta.total_pages == 3
        assert meta.has_next is False
        assert meta.has_prev is True

    def test_exact_division(self):
        params = PaginationParams(page=2, page_size=20)
        meta = PaginationMeta.from_params(params, total=40)
        assert meta.total_pages == 2
        assert meta.has_next is False
        assert meta.has_prev is True

    def test_non_exact_division_ceil(self):
        params = PaginationParams(page=1, page_size=20)
        meta = PaginationMeta.from_params(params, total=41)
        assert meta.total_pages == 3

    def test_total_1_page_size_20(self):
        params = PaginationParams(page=1, page_size=20)
        meta = PaginationMeta.from_params(params, total=1)
        assert meta.total_pages == 1
        assert meta.has_next is False
        assert meta.has_prev is False

    def test_page_beyond_total_pages(self):
        params = PaginationParams(page=10, page_size=20)
        meta = PaginationMeta.from_params(params, total=50)
        assert meta.total_pages == 3
        assert meta.has_next is False
        assert meta.has_prev is True

    def test_preserves_params_values(self):
        params = PaginationParams(page=3, page_size=15)
        meta = PaginationMeta.from_params(params, total=100)
        assert meta.page == 3
        assert meta.page_size == 15
        assert meta.total == 100


# ============================================================
# PaginatedResponse.create
# ============================================================


class TestPaginatedResponseCreate:
    """create 工厂方法"""

    def test_create_with_data(self):
        params = PaginationParams(page=1, page_size=20)
        data = [1, 2, 3]
        response = PaginatedResponse.create(data, params, total=100)
        assert response.data == data
        assert response.pagination.total == 100
        assert response.pagination.page == 1
        assert response.pagination.page_size == 20

    def test_create_with_empty_data(self):
        params = PaginationParams(page=1, page_size=20)
        response = PaginatedResponse.create([], params, total=0)
        assert response.data == []
        assert response.pagination.total == 0
        assert response.pagination.total_pages == 0

    def test_create_preserves_list_type(self):
        params = PaginationParams(page=1, page_size=20)
        data = ["a", "b", "c"]
        response = PaginatedResponse.create(data, params, total=10)
        assert response.data == ["a", "b", "c"]
        assert len(response.data) == 3


# ============================================================
# paginate 函数
# ============================================================


class TestPaginateFunction:
    """内存分页函数"""

    def test_empty_list(self):
        params = PaginationParams(page=1, page_size=20)
        result = paginate([], params)
        assert result.data == []
        assert result.pagination.total == 0
        assert result.pagination.total_pages == 0

    def test_first_page(self):
        items = list(range(50))
        params = PaginationParams(page=1, page_size=20)
        result = paginate(items, params)
        assert result.data == list(range(20))
        assert result.pagination.total == 50
        assert result.pagination.total_pages == 3
        assert result.pagination.has_next is True
        assert result.pagination.has_prev is False

    def test_middle_page(self):
        items = list(range(50))
        params = PaginationParams(page=2, page_size=20)
        result = paginate(items, params)
        assert result.data == list(range(20, 40))
        assert result.pagination.has_next is True
        assert result.pagination.has_prev is True

    def test_last_page(self):
        items = list(range(50))
        params = PaginationParams(page=3, page_size=20)
        result = paginate(items, params)
        assert result.data == list(range(40, 50))
        assert len(result.data) == 10
        assert result.pagination.has_next is False
        assert result.pagination.has_prev is True

    def test_page_beyond_total(self):
        items = list(range(25))
        params = PaginationParams(page=10, page_size=20)
        result = paginate(items, params)
        assert result.data == []
        assert result.pagination.total == 25
        assert result.pagination.total_pages == 2

    def test_page_size_larger_than_total(self):
        items = list(range(5))
        params = PaginationParams(page=1, page_size=20)
        result = paginate(items, params)
        assert result.data == items
        assert result.pagination.total_pages == 1
        assert result.pagination.has_next is False

    def test_single_item(self):
        items = [42]
        params = PaginationParams(page=1, page_size=20)
        result = paginate(items, params)
        assert result.data == [42]
        assert result.pagination.total == 1

    def test_page_size_1(self):
        items = list(range(5))
        params = PaginationParams(page=3, page_size=1)
        result = paginate(items, params)
        assert result.data == [2]
        assert result.pagination.total_pages == 5

    def test_exact_page_size(self):
        items = list(range(40))
        params = PaginationParams(page=2, page_size=20)
        result = paginate(items, params)
        assert result.data == list(range(20, 40))
        assert result.pagination.total_pages == 2
        assert result.pagination.has_next is False

    def test_string_items(self):
        items = ["a", "b", "c", "d", "e"]
        params = PaginationParams(page=2, page_size=2)
        result = paginate(items, params)
        assert result.data == ["c", "d"]
        assert result.pagination.total == 5

    def test_does_not_mutate_original_list(self):
        items = list(range(10))
        original = items.copy()
        params = PaginationParams(page=1, page_size=3)
        paginate(items, params)
        assert items == original