"""
测试分页逻辑。
无外部依赖，可离线运行。
"""

from paste.util.pagination import Pagination


class TestPagination:
    """分页功能测试"""

    def test_pages_calculation_exact(self):
        """精确整除的分页计算"""
        p = Pagination(row_count=100)
        pages = p.pages(page_size=20)
        assert pages == 5

    def test_pages_calculation_remainder(self):
        """有余数的分页计算"""
        p = Pagination(row_count=101)
        pages = p.pages(page_size=20)
        assert pages == 6

    def test_pages_calculation_zero_rows(self):
        """零行数据的处理"""
        p = Pagination(row_count=0)
        pages = p.pages(page_size=20)
        assert pages == 1

    def test_page_number_valid(self):
        """页码有效性检测"""
        p = Pagination(row_count=50)
        p.pages(page_size=20)
        assert p.number(1) == 1
        assert p.number(3) == 3  # 超出范围应返回最大页

    def test_page_number_negative(self):
        """负页码处理"""
        p = Pagination(row_count=50)
        p.pages(page_size=20)
        assert p.number(-1) == 1

    def test_offset_calculation(self):
        """偏移量计算"""
        p = Pagination(row_count=100)
        p.pages(page_size=20)
        assert p.offset(1) == 0
        assert p.offset(2) == 20
        assert p.offset(3) == 40

    def test_paging_chain(self):
        """链式调用分页"""
        p = Pagination(row_count=123).paging(page_number=2, page_size=20)
        assert p.page_count == 7
        assert p.page_number == 2
        assert p.offset_size == 20

    def test_page_size_bounds(self):
        """页大小边界: 最小1，最大1000"""
        p = Pagination(row_count=2000)
        assert p.pages(page_size=0) > 0
        assert p.pages(page_size=2000) <= 1000

    def test_large_dataset(self):
        """大数据集分页"""
        p = Pagination(row_count=1000000)
        pages = p.pages(page_size=100)
        assert pages == 10000

    def test_single_row(self):
        """单行数据"""
        p = Pagination(row_count=1)
        assert p.pages(page_size=10) == 1
        p.paging(page_number=1, page_size=10)
        assert p.page_number == 1
        assert p.offset_size == 0

    def test_page_number_upper_bound(self):
        """页码上限处理"""
        p = Pagination(row_count=30).paging(page_number=100, page_size=10)
        assert p.page_number == 3  # 最大只能到3页


# ============================================================
# 以下是从 test_db.py 迁移过来的分页测试
# 原函数 test_pagination() 改为标准的 pytest 测试
# ============================================================


class TestPaginationFromDb:
    """从 test_db.py 迁移的分页测试"""

    def test_pagination_basic(self):
        """基础分页计算"""
        from paste.util.pagination import Pagination
        p = Pagination(row_count=123).paging(page_number=2, page_size=20)
        assert p.page_count == 7
        assert p.page_number == 2
        assert p.offset_size == 20

    def test_pagination_first_page(self):
        """第一页"""
        from paste.util.pagination import Pagination
        p = Pagination(row_count=50).paging(page_number=1, page_size=10)
        assert p.page_number == 1
        assert p.offset_size == 0

    def test_pagination_last_page(self):
        """最后一页"""
        from paste.util.pagination import Pagination
        p = Pagination(row_count=55).paging(page_number=6, page_size=10)
        assert p.page_number == 6
        assert p.offset_size == 50

    def test_pagination_out_of_range(self):
        """超出范围时自动修正"""
        from paste.util.pagination import Pagination
        p = Pagination(row_count=30).paging(page_number=100, page_size=10)
        assert p.page_number == 3  # 只有3页，自动修正