"""用户管理业务编排。

**事务边界在本层**：每个公开方法自行决定何时 commit。
repository 只 flush，事务由这里控制。

设计取舍：

- 删除采用**物理删除**，与「删除即禁用」并不矛盾 —— 后者是对业务方的建议
  （停用账号应走禁用而非删除，以保留审计线索），但需求 2.5.1 明确列了
  「增删改查」，故保留删除能力；`operation_logs` 通过 SET NULL + 冗余 username
  保证删除后仍可追溯
- 不允许删除或禁用**自己** —— 管理员误操作会立刻失去全部管理权限，
  且没有其他账号可以救回来
- 全部写操作经 `audit_service.audit()` 留痕，**成功与失败都记**。摘要需要
  「目标用户名」，故对目标的只读预取放在审计上下文**之前** —— 这样目标
  不存在（NotFound 失败）时也能留下可读的记录
- **响应对象在 commit 之前构造**（`_to_out` 读的是内存中的已加载状态）：
  commit 后再触碰 ORM 对象会因过期而触发额外查询，该查询一旦抛错，
  「已提交成功」的操作会被审计记成失败
"""

import logging

from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import Session

from app.core.constants import (
    ACTION_CREATE,
    ACTION_DELETE,
    ACTION_DISABLE,
    ACTION_ENABLE,
    ACTION_RESET_PASSWORD,
    ACTION_UPDATE,
    MODULE_USER,
    ROLE_ADMIN,
)
from app.core.exceptions import BadRequestError, ForbiddenError, NotFoundError
from app.core.response import PageResult
from app.core.security import hash_password
from app.models import User
from app.repositories import role_repository, user_repository
from app.schemas.role import RoleOut
from app.schemas.user import UserCreateIn, UserOut, UserQuery, UserUpdateIn
from app.services import audit_service
from app.services import authorization_management as auth_management
from app.services.audit_service import AuditRecord, RequestMeta

logger = logging.getLogger(__name__)


def _to_out(user: User) -> UserOut:
    """ORM 对象转响应模型。

    禁止把 ORM 对象直接当 response_model —— 表结构变更会直接泄漏到接口契约上。
    """
    return UserOut(
        id=user.id,
        username=user.username,
        real_name=user.real_name,
        phone=user.phone,
        email=user.email,
        status=user.status,
        roles=user_repository.get_role_codes(user),
        last_login_time=user.last_login_time,
        remark=user.remark,
        create_time=user.create_time,
    )


def list_users(session: Session, query: UserQuery) -> PageResult[UserOut]:
    """分页查询用户列表。"""
    users = user_repository.list_users(session, query)
    total = user_repository.count_users(session, query)
    return PageResult[UserOut](
        records=[_to_out(user) for user in users],
        total=total,
        page_num=query.page_num,
        page_size=query.page_size,
    )


def get_user(session: Session, user_id: int) -> UserOut:
    """查询用户详情。

    :raises NotFoundError: 用户不存在
    """
    user = user_repository.get_by_id(session, user_id)
    if user is None:
        raise NotFoundError("用户不存在")
    return _to_out(user)


def create_user(
    session: Session,
    payload: UserCreateIn,
    *,
    operator: User,
    meta: RequestMeta | None = None,
) -> UserOut:
    """新增用户。

    :raises BadRequestError: 用户名已存在，或角色编码无效/已停用
    """
    with audit_service.audit(
        session,
        operator=operator,
        record=AuditRecord(
            module=MODULE_USER,
            action=ACTION_CREATE,
            summary=f"新增用户 {payload.username}",
            # password 会随字典进入审计管道，由 repository 层的结构化脱敏抹除其值
            request_data=payload.model_dump(exclude_none=True),
        ),
        meta=meta,
    ):
        if user_repository.get_by_username(session, payload.username) is not None:
            raise BadRequestError(f"用户名 {payload.username!r} 已存在")

        policy = auth_management.lock_policy(session, operator)
        roles = _resolve_roles(session, payload.roles)

        user = User(
            username=payload.username,
            password=hash_password(payload.password),
            real_name=payload.real_name,
            phone=payload.phone,
            email=payload.email,
            status=1,
            remark=payload.remark,
        )
        try:
            user_repository.create(session, user)
            user_repository.replace_roles(session, user, roles)
            auth_management.bump(policy, operator)
            out = _to_out(user)
            session.commit()
        except IntegrityError as exc:
            # 先查后写不是原子操作：并发提交同一用户名会撞 uk_users_username。
            # 回滚并把唯一键冲突翻译为可读的 400，而非 500
            session.rollback()
            raise BadRequestError(f"用户名 {payload.username!r} 已存在") from exc

        logger.info("新增用户 | username=%s | roles=%s", payload.username, payload.roles)
        return out


def update_user(
    session: Session,
    user_id: int,
    payload: UserUpdateIn,
    *,
    operator: User,
    meta: RequestMeta | None = None,
) -> UserOut:
    """编辑用户的基本信息与角色。

    **不含用户名与密码**：用户名是审计追溯的锚点；密码走专门的重置接口，
    以免"改资料"顺手改掉密码这类越权操作。

    空串字段（`''`）归一为 None：编辑表单会把未修改的字段以空串提交，
    若原样写入会把库中的 NULL 污染成空串（两类空值语义漂移且不可逆）；
    归一后「清空输入框」= 写回 NULL，语义正确。

    :raises NotFoundError: 用户不存在
    :raises BadRequestError: 角色编码无效或已停用
    """
    user = user_repository.get_by_id(session, user_id)
    with audit_service.audit(
        session,
        operator=operator,
        record=AuditRecord(
            module=MODULE_USER,
            action=ACTION_UPDATE,
            summary=f"修改用户 {user.username if user else f'#{user_id}'}",
            request_data=payload.model_dump(exclude_none=True),
        ),
        meta=meta,
    ):
        if user is None:
            raise NotFoundError("用户不存在")

        if payload.real_name is not None:
            user.real_name = payload.real_name or None
        if payload.phone is not None:
            user.phone = payload.phone or None
        if payload.email is not None:
            user.email = payload.email or None
        if payload.remark is not None:
            user.remark = payload.remark or None

        # 不允许把自己降级掉管理角色，否则改完立刻失去管理权限
        if payload.roles is not None and user_id == operator.id and ROLE_ADMIN not in payload.roles:
            raise ForbiddenError("不能移除自己的管理员角色")

        session.flush()

        if payload.roles is not None:
            policy = auth_management.lock_policy(session, operator)
            auth_management.guard_user_change(session, user, operator, roles=payload.roles)
            roles = _resolve_roles(session, payload.roles)
            user_repository.replace_roles(session, user, roles)
            auth_management.bump(policy, operator)

        out = _to_out(user)
        session.commit()
        logger.info("编辑用户 | user_id=%s | roles=%s", user_id, payload.roles)
        return out


def reset_password(
    session: Session,
    user_id: int,
    new_password: str,
    *,
    operator: User,
    meta: RequestMeta | None = None,
) -> None:
    """重置用户密码。

    同时把 `token_version` 加一，使该用户**已签发的令牌立即失效** ——
    改密后旧令牌仍可用是常见疏漏，这里与「离职即失效」复用同一机制。

    :raises NotFoundError: 用户不存在
    """
    user = user_repository.get_by_id(session, user_id)
    with audit_service.audit(
        session,
        operator=operator,
        record=AuditRecord(
            module=MODULE_USER,
            action=ACTION_RESET_PASSWORD,
            summary=f"重置用户 {user.username if user else f'#{user_id}'} 的密码",
            # 明文进审计管道，由 repository 层的结构化脱敏整体抹除
            request_data={"new_password": new_password},
        ),
        meta=meta,
    ):
        if user is None:
            raise NotFoundError("用户不存在")

        user.password = hash_password(new_password)
        user.token_version += 1
        session.commit()
        logger.info("重置密码 | user_id=%s（令牌版本已提升）", user_id)


def set_status(
    session: Session,
    user_id: int,
    status: int,
    *,
    operator: User,
    meta: RequestMeta | None = None,
) -> UserOut:
    """启用或禁用用户。

    禁用时同样提升 `token_version`，使已签发令牌立即失效 ——
    否则被禁用者仍可凭旧令牌访问直到过期（最长 2 小时）。

    :raises NotFoundError: 用户不存在
    :raises ForbiddenError: 试图禁用自己
    """
    user = user_repository.get_by_id(session, user_id)
    verb = "启用" if status == 1 else "禁用"
    with audit_service.audit(
        session,
        operator=operator,
        record=AuditRecord(
            module=MODULE_USER,
            action=ACTION_ENABLE if status == 1 else ACTION_DISABLE,
            summary=f"{verb}用户 {user.username if user else f'#{user_id}'}",
            request_data={"status": status},
        ),
        meta=meta,
    ):
        if user is None:
            raise NotFoundError("用户不存在")

        if status == 0 and user_id == operator.id:
            raise ForbiddenError("不能禁用自己")

        policy = auth_management.lock_policy(session, operator)
        auth_management.guard_user_change(session, user, operator, status=status)
        user.status = status
        auth_management.bump(policy, operator)
        if status == 0:
            user.token_version += 1
        out = _to_out(user)
        session.commit()
        logger.info("变更用户状态 | user_id=%s | status=%s", user_id, status)
        return out


def delete_user(
    session: Session,
    user_id: int,
    *,
    operator: User,
    meta: RequestMeta | None = None,
) -> None:
    """删除用户。

    物理删除。历史操作日志通过 `user_id` 置空 + 冗余 `username` 保留可追溯性。

    :raises NotFoundError: 用户不存在
    :raises ForbiddenError: 试图删除自己
    """
    user = user_repository.get_by_id(session, user_id)
    with audit_service.audit(
        session,
        operator=operator,
        record=AuditRecord(
            module=MODULE_USER,
            action=ACTION_DELETE,
            summary=f"删除用户 {user.username if user else f'#{user_id}'}",
        ),
        meta=meta,
    ):
        if user is None:
            raise NotFoundError("用户不存在")

        if user_id == operator.id:
            raise ForbiddenError("不能删除自己")

        policy = auth_management.lock_policy(session, operator)
        auth_management.guard_user_change(session, user, operator, deleting=True)
        auth_management.bump(policy, operator)
        username = user.username  # 固化：对象随删除失效
        user_repository.delete(session, user)
        session.commit()
        logger.info("删除用户 | username=%s", username)


def list_roles(session: Session) -> list[RoleOut]:
    """取全部启用角色，供用户表单的角色选择使用。"""
    return [RoleOut.model_validate(role) for role in role_repository.get_all_roles(session)]


def _resolve_roles(session: Session, role_codes: list[str]) -> list:
    """把角色编码解析为角色对象，校验全部存在且**未停用**。

    停用角色不出现在表单下拉中；接口层若不拦截，直接调 API（或使用停用前
    加载的旧选项）仍可绑定，与「停用后不可再分配」的语义矛盾。已绑定停用
    角色的用户需先转为启用角色再保存。

    :raises BadRequestError: 存在无效编码，或角色已停用
    """
    if not role_codes:
        raise BadRequestError("至少需要指定一个角色")
    roles = role_repository.get_roles_by_codes(session, role_codes)
    if len(roles) != len(set(role_codes)):
        valid = {role.role_code for role in roles}
        invalid = sorted(set(role_codes) - valid)
        raise BadRequestError(f"角色编码无效：{invalid}")
    disabled = sorted(role.role_code for role in roles if role.status != 1)
    if disabled:
        raise BadRequestError(f"角色已停用，不可分配：{disabled}")
    return list(roles)