# inventory-backend/app/services/permission_service.py

from app.models.system import SysMenu, SysElement, SysRolePermission
from app.extensions import db


class PermissionService:

    @staticmethod
    def get_permission_tree():
        """
        获取完整的权限树（菜单 -> 元素）
        供前端权限配置页面展示
        """
        # 1. 获取所有菜单
        menus = SysMenu.query.order_by(SysMenu.sort_order).all()

        # 2. 获取所有元素
        elements = SysElement.query.all()

        # 3. 组装树结构
        tree_data = []

        for menu in menus:
            menu_dict = menu.to_dict()

            # 找该菜单下的所有元素
            children = []
            for el in elements:
                if el.menu_code == menu.code:
                    children.append(el.to_dict())

            # 如果有子元素，加到 children
            if children:
                menu_dict['children'] = children

            tree_data.append(menu_dict)

        return tree_data

    @staticmethod
    def get_role_permissions(role_code):
        """获取指定角色拥有的所有权限Code"""
        perms = SysRolePermission.query.filter_by(role_code=role_code).all()

        menu_codes = []
        element_codes = []

        for p in perms:
            if p.type == 'menu':
                menu_codes.append(p.target_code)
            else:
                element_codes.append(p.target_code)

        return {
            'menus': menu_codes,
            'elements': element_codes
        }

    @staticmethod
    def assign_permissions(role_code, permission_codes):
        """
        保存角色的权限
        permission_codes: 前端传来的 list，包含 menu_code 和 element_code
        """
        if not role_code:
            raise ValueError("角色代码不能为空")

        try:
            # ========= 1️⃣ 先删除旧权限 =========
            SysRolePermission.query.filter_by(role_code=role_code) \
                .delete(synchronize_session=False)

            # ========= 2️⃣ 去重（关键修复点） =========
            # 防止前端传来重复 code 导致 UNIQUE 冲突
            unique_codes = set(permission_codes) if permission_codes else set()

            # ========= 3️⃣ 批量添加新权限 =========
            if unique_codes:
                # 预先获取所有菜单代码，用于判断类型
                all_menu_codes = {m.code for m in SysMenu.query.all()}

                new_records = []

                for code in unique_codes:
                    if not code:
                        continue

                    # 判断类型
                    p_type = 'menu' if code in all_menu_codes else 'element'

                    new_records.append(SysRolePermission(
                        role_code=role_code,
                        target_code=code,
                        type=p_type
                    ))

                if new_records:
                    db.session.add_all(new_records)

            # ========= 4️⃣ 提交事务 =========
            db.session.commit()
            return True

        except Exception as e:
            # 发生异常时回滚，防止脏事务
            db.session.rollback()
            raise e