"""
企业版知识库访问控制：RBAC + ABAC（可见性）

规则汇总
--------
- admin   : 全企业范围无限制
- leader  : 管辖「本部门及所有子孙部门」内的用户与文件
- employee: 只能操作自己的资源；可查看同部门 department/enterprise 可见知识库及库内全部文件
- 越级    : 不在管辖子树内的操作一律拒绝
"""
from typing import List, Literal, Optional

import asyncpg

from models.graph_metadata import GraphRecord
from models.knowledge_base import KnowledgeBase
from models.knowledge_base_file import KnowledgeBaseFile
from models.user import User

UserRole = Literal["admin", "leader", "employee"]
KbVisibility = Literal["private", "department", "enterprise"]


# ──────────────────────────────────────────────
# 部门子树查询（方案 A 核心辅助）
# ──────────────────────────────────────────────

async def get_managed_dept_ids(conn: asyncpg.Connection, user: User) -> List[int]:
    """
    返回 user 可管辖的部门 ID 列表。
    - admin  -> 企业全部部门
    - leader -> 本部门及其所有子孙部门（递归 CTE）
    - employee -> 空列表
    """
    if user.enterprise_id is None:
        return []
    if user.role == "admin":
        rows = await conn.fetch(
            "SELECT id FROM department WHERE enterprise_id = $1",
            user.enterprise_id,
        )
        return [r["id"] for r in rows]
    if user.role == "leader" and user.department_id is not None:
        rows = await conn.fetch(
            """
            WITH RECURSIVE sub AS (
                SELECT id FROM department WHERE id = $1
                UNION ALL
                SELECT d.id FROM department d JOIN sub ON d.parent_id = sub.id
            )
            SELECT id FROM sub
            """,
            user.department_id,
        )
        return [r["id"] for r in rows]
    return []


async def is_subordinate(
    conn: asyncpg.Connection, actor: User, target_user_id: int
) -> bool:
    """
    判断 target_user_id 是否在 actor 的管辖范围内。
    - admin 对同企业全员返回 True
    - leader 对子树内（非本人）成员返回 True
    """
    if actor.id == target_user_id:
        return False
    if actor.enterprise_id is None:
        return False
    # 确认被管辖者在同一企业
    row = await conn.fetchrow(
        "SELECT department_id, enterprise_id FROM user_list WHERE id = $1",
        target_user_id,
    )
    if not row or row["enterprise_id"] != actor.enterprise_id:
        return False
    if actor.role == "admin":
        return True
    if actor.role == "leader":
        managed = await get_managed_dept_ids(conn, actor)
        return row["department_id"] in managed if row["department_id"] else False
    return False


# ──────────────────────────────────────────────
# 知识库级权限（同步，无需数据库）
# ──────────────────────────────────────────────

async def can_view_kb(conn: asyncpg.Connection, user: User, kb: KnowledgeBase) -> bool:
    """判断用户是否可查看该知识库。leader 权限覆盖本部门及所有子孙部门。"""
    if user.role == "admin":
        return True
    if kb.creator_id is not None and user.id == kb.creator_id:
        return True
    if user.role == "leader" and user.department_id is not None and kb.department_id is not None:
        managed = await get_managed_dept_ids(conn, user)
        if kb.department_id in managed:
            return True
    vis = kb.visibility or "private"
    if vis == "private":
        return False
    if vis == "department":
        return user.department_id is not None and kb.department_id == user.department_id
    if vis == "enterprise":
        return user.enterprise_id is not None and kb.enterprise_id == user.enterprise_id
    return False


def can_manage_kb(user: User, kb: KnowledgeBase) -> bool:
    """创建者可管理；企业管理员可管理本企业内任意知识库。"""
    if user.role == "admin" and user.enterprise_id is not None and kb.enterprise_id == user.enterprise_id:
        return True
    if kb.creator_id is not None and user.id == kb.creator_id:
        return True
    return False


# ──────────────────────────────────────────────
# 文件级权限（需要异步 DB 查询）
# ──────────────────────────────────────────────

async def can_delete_file(
    conn: asyncpg.Connection,
    user: User,
    file: KnowledgeBaseFile,
    kb: Optional[KnowledgeBase] = None,
) -> bool:
    """
    判断用户是否可删除该文件。
    - 文件上传者本人
    - admin（同企业）
    - leader（下级成员上传的文件，基于子树管辖范围）
    """
    # 本人上传
    if file.user_id == user.id:
        return True
    # admin 可删同企业内任意文件
    if user.role == "admin":
        if kb is not None:
            return kb.enterprise_id == user.enterprise_id
        return True
    # leader 判断上传者是否在子树内
    if user.role == "leader":
        return await is_subordinate(conn, user, file.user_id)
    return False


async def can_upload_to_kb(conn: asyncpg.Connection, user: User, kb: KnowledgeBase) -> bool:
    """
    判断用户是否可向知识库上传文件。
    - 必须能 view KB
    - allow_kb_upload 未被关闭
    - leader 或 admin 也受 allow_kb_upload 约束（管理员初始化时均为 True）
    """
    if not await can_view_kb(conn, user, kb):
        return False
    return bool(user.allow_kb_upload)


# ──────────────────────────────────────────────
# 知识图谱级权限（与知识库规则完全一致）
# ──────────────────────────────────────────────

async def can_view_graph(conn: asyncpg.Connection, user: User, g: GraphRecord) -> bool:
    """判断用户是否可查看该知识图谱。leader 权限覆盖本部门及所有子孙部门（与知识库一致）。"""
    if user.role == "admin":
        return True
    if g.creator_id is not None and user.id == g.creator_id:
        return True
    if user.role == "leader" and user.department_id is not None and g.department_id is not None:
        managed = await get_managed_dept_ids(conn, user)
        if g.department_id in managed:
            return True
    vis = g.visibility or "private"
    if vis == "private":
        return False
    if vis == "department":
        return user.department_id is not None and g.department_id == user.department_id
    if vis == "enterprise":
        return user.enterprise_id is not None and g.enterprise_id == user.enterprise_id
    return False


def can_manage_graph(user: User, g: GraphRecord) -> bool:
    """创建者可删改；企业管理员可管理本企业内任意图谱。"""
    if user.role == "admin" and user.enterprise_id is not None and g.enterprise_id == user.enterprise_id:
        return True
    if g.creator_id is not None and user.id == g.creator_id:
        return True
    return False