from __future__ import annotations

from dataclasses import dataclass

from sqlalchemy import func, select
from sqlalchemy.orm import Session, selectinload

from app.core.config import get_settings
from app.core.logging import get_logger
from app.core.security import verify_password
from app.models.employee import Employee
from app.schemas.auth import AuthUserRead, LoginRequest, LoginResponse
from app.services.employee import EmployeeService
from app.services.employee_seed import ROLE_DISPLAY_ORDER
from app.services.settings import SettingsService

logger = get_logger("app.services.auth")

ROLE_LABELS = {
    "manager": "管理员",
    "finance": "财务人员",
    "executive": "高级管理人员",
    "approver": "审批负责人",
    "auditor": "审计观察员",
    "user": "使用者",
}


@dataclass(slots=True)
class AuthenticatedUser:
    username: str
    name: str
    role: str
    position: str
    grade: str
    role_codes: list[str]
    email: str
    avatar: str
    is_admin: bool = False


class AuthService:
    def __init__(self, db: Session) -> None:
        self.db = db
        self.settings = get_settings()

    def login(self, payload: LoginRequest) -> LoginResponse:
        identifier = payload.username.strip()
        password = payload.password

        admin_user = self._authenticate_admin(identifier, password)
        if admin_user is not None:
            logger.info("Admin login succeeded identifier=%s", identifier)
            return LoginResponse(user=self._serialize_user(admin_user))

        employee_user = self._authenticate_employee(identifier, password)
        if employee_user is not None:
            logger.info(
                "Employee login succeeded identifier=%s role_codes=%s",
                identifier,
                ",".join(employee_user.role_codes),
            )
            return LoginResponse(user=self._serialize_user(employee_user))

        logger.warning("Login failed identifier=%s", identifier)
        raise ValueError("账号或密码错误。")

    def _authenticate_admin(self, identifier: str, password: str) -> AuthenticatedUser | None:
        record = SettingsService(self.db).verify_admin_login(identifier, password)
        if record is None:
            return None

        admin_username = record.account.strip()
        admin_email = record.email.strip()
        display_name = admin_username or admin_email or "系统管理员"

        return AuthenticatedUser(
            username=admin_username or admin_email,
            name=display_name,
            role="管理员",
            position="系统管理员",
            grade="",
            role_codes=["manager"],
            email=admin_email or f"{admin_username}@local",
            avatar=display_name[:1].upper(),
            is_admin=True,
        )

    def _authenticate_employee(self, identifier: str, password: str) -> AuthenticatedUser | None:
        if not self.settings.setup_completed:
            return None

        EmployeeService(self.db).ensure_directory_ready()

        stmt = (
            select(Employee)
            .options(selectinload(Employee.roles))
            .where(func.lower(Employee.email) == identifier.lower())
        )
        employee = self.db.execute(stmt).scalars().first()

        if employee is None or not employee.password_hash:
            return None

        if employee.employment_status == "停用":
            logger.warning("Disabled employee login blocked identifier=%s", identifier)
            return None

        if not verify_password(password, employee.password_hash):
            return None

        sorted_roles = sorted(
            list(employee.roles),
            key=lambda item: (ROLE_DISPLAY_ORDER.get(item.role_code, 999), item.name),
        )
        role_codes = [role.role_code for role in sorted_roles]
        primary_role_code = role_codes[0] if role_codes else "user"

        return AuthenticatedUser(
            username=employee.email,
            name=employee.name,
            role=ROLE_LABELS.get(primary_role_code, "使用者"),
            position=employee.position,
            grade=employee.grade,
            role_codes=role_codes or ["user"],
            email=employee.email,
            avatar=(employee.name or "?")[:1].upper(),
            is_admin=False,
        )

    @staticmethod
    def _serialize_user(user: AuthenticatedUser) -> AuthUserRead:
        return AuthUserRead(
            username=user.username,
            name=user.name,
            role=user.role,
            position=user.position,
            grade=user.grade,
            roleCodes=user.role_codes,
            email=user.email,
            avatar=user.avatar,
            isAdmin=user.is_admin,
        )