# api/departments.py
from typing import List

from django.db import IntegrityError
from django.shortcuts import get_object_or_404
from ninja import Router
from ninja.errors import HttpError

from users.models import Department
from users.permission import has_permission, require_permissions
from users.schema import DepartmentOut, DepartmentCreate, DepartmentUpdate

router = Router(tags=['depts'])


@router.get("/", response=List[DepartmentOut], summary="获取部门列表（扁平）")
@require_permissions("dept:list")
def list_departments(request):
    return Department.objects.all()


@router.get("/tree/", response=List[dict], summary="获取部门树形结构")
@require_permissions("dept:list")
def get_department_tree(request):
    depts = Department.objects.all().order_by('order')
    return build_dept_tree(list(depts))


@router.post("/", response=DepartmentOut, summary="创建部门")
@require_permissions("dept:create")
def create_department(request, payload: DepartmentCreate):
    if not has_permission(request.auth.id, "dept:create"):
        raise HttpError(403, "权限不足")

    # 👇 新增：校验根部门唯一性
    if payload.parent_id is None:
        if Department.objects.filter(parent__isnull=True).exists():
            raise HttpError(400, "根部门已存在，无法创建新的根部门")

    data = payload.dict()
    parent_id = data.pop('parent_id', None)
    if parent_id:
        # 可以额外校验 parent_id 是否真实存在
        if not Department.objects.filter(id=parent_id).exists():
            raise HttpError(400, "指定的上级部门不存在")
        data['parent_id'] = parent_id

    try:
        dept = Department.objects.create(**data)
        return dept
    except IntegrityError as e:
        # 捕获数据库层面的唯一性冲突，提供统一错误信息
        if "unique_root_department" in str(e):
            raise HttpError(400, "根部门已存在，无法创建新的根部门")
        else:
            raise HttpError(400, "创建部门失败，请检查数据")


@router.get("/{dept_id}/", response=DepartmentOut, summary="获取部门详情")
@require_permissions("dept:view")
def get_department(request, dept_id: int):
    dept = get_object_or_404(Department, id=dept_id)
    return dept


@router.put("/{dept_id}/", response=DepartmentOut, summary="更新部门")
@require_permissions("dept:update")
def update_department(request, dept_id: int, payload: DepartmentUpdate):
    dept = get_object_or_404(Department, id=dept_id)
    data = payload.dict()
    parent_id = data.pop('parent_id', None)
    if parent_id:
        data['parent_id'] = parent_id
    else:
        data['parent'] = None

    for attr, value in data.items():
        setattr(dept, attr, value)
    dept.save()
    return dept


@router.delete("/{dept_id}/", summary="删除部门")
@require_permissions("dept:delete")
def delete_department(request, dept_id: int):
    dept = get_object_or_404(Department, id=dept_id)
    # 可选：检查是否有子部门或用户
    if dept.user_set.exists() or Department.objects.filter(parent=dept).exists():
        return 400, {"detail": "部门包含用户或子部门，无法删除"}

    dept.delete()
    return {"success": True}


# 工具函数：构建部门树
def build_dept_tree(depts, parent_id=None):
    tree = []
    for dept in depts:
        if dept.parent_id == parent_id:
            node = {
                'id': dept.id,
                'name': dept.name,
                'parent_id': dept.parent_id,
                'order': dept.order,
                'children': build_dept_tree(depts, dept.id) or None
            }
            tree.append(node)
    return tree