# app/services/authentication.py
from app.db.errors import EntityDoesNotExist
from app.db.repositories.users import UsersRepository


async def check_username_is_taken(repo: UsersRepository, username: str) -> bool:
    """
    返回 True 表示用户名已被占用
    """
    try:
        await repo.get_user_by_username(username=username)
    except EntityDoesNotExist:
        return False
    return True


async def check_email_is_taken(repo: UsersRepository, email: str) -> bool:
    """
    返回 True 表示邮箱已被占用
    """
    try:
        await repo.get_user_by_email(email=email)
    except EntityDoesNotExist:
        return False
    return True


def assert_passwords_match(password: str, confirm_password: str) -> None:
    """
    两次密码一致性校验，不一致抛 ValueError
    """
    if password != confirm_password:
        raise ValueError("Passwords do not match")


async def make_unique_username(repo: UsersRepository, email: str) -> str:
    """
    由邮箱前缀自动生成唯一 username，例如:
      - 先用 local-part: foo
      - 若被占用，则 foo1、foo2…直到找到可用
    """
    base = (email.split("@", 1)[0] or "user").strip().lower()
    # 兜底：避免空前缀
    if not base:
        base = "user"

    candidate = base
    suffix = 0
    while await check_username_is_taken(repo, candidate):
        suffix += 1
        candidate = f"{base}{suffix}"
    return candidate