"""MySQL 字符串比较/模糊匹配时统一排序规则，避免 Illegal mix of collations。"""

_UNICODE_CI = "utf8mb4_unicode_ci"


def unicode_ci(col):
    """将列显式设为 utf8mb4_unicode_ci。"""
    return col.collate(_UNICODE_CI)


def eq_unicode(left, right):
    """跨表字符串等值比较（JOIN / WHERE）时统一为 utf8mb4_unicode_ci。"""
    return unicode_ci(left) == unicode_ci(right)


def like_unicode(col, pattern: str):
    """LIKE 模糊匹配时统一排序规则。"""
    return unicode_ci(col).like(pattern)