"""Sidebar-menu override API (菜单管理).

The static sidebar menu tree (icons / routes / adminOnly) is defined in the
frontend code; iframe light-apps are injected into it at render time. This
router persists a **global / shared** set of per-node overrides that the
frontend merges onto that tree: rename (``label``), 停用/启用 (``disabled``),
reorder (``sort_order``) and re-parent (``parent_id``, moving a node's whole
subtree). A node with no override renders exactly as the code defines it.

Reads are open to any authenticated user (the sidebar needs them); the whole
override set is replaced atomically and only by an admin.

Routes (prefix ``/api/menu-overrides``):
    GET ""   list all overrides
    PUT ""   replace the entire override set (admin)
"""

from __future__ import annotations

from datetime import datetime

from fastapi import APIRouter, HTTPException, Request
from pydantic import BaseModel, Field

from app.gateway.deps import get_current_user, get_optional_user_from_request
from deerflow.persistence.menu_overrides import MenuOverrideStore

router = APIRouter(prefix="/api/menu-overrides", tags=["menu-overrides"])

# Hard cap mirroring the sidebar's 一级 → 二级 → 三级 rendering depth.
_MAX_DEPTH = 3


# ── schemas ──────────────────────────────────────────────────────────────


class MenuOverride(BaseModel):
    node_id: str = Field(..., min_length=1, max_length=128)
    parent_id: str | None = Field(default=None, max_length=128)
    sort_order: int = 0
    label: str | None = Field(default=None, max_length=255)
    disabled: bool = False


class MenuOverrideResponse(MenuOverride):
    updated_by: str | None = None
    updated_at: datetime | str | None = None


class MenuOverrideListResponse(BaseModel):
    overrides: list[MenuOverrideResponse]


class MenuOverrideReplaceRequest(BaseModel):
    overrides: list[MenuOverride] = Field(default_factory=list)


# ── helpers ──────────────────────────────────────────────────────────────


def _get_store(request: Request) -> MenuOverrideStore:
    store = getattr(request.app.state, "menu_override_store", None)
    if store is None:
        raise HTTPException(status_code=503, detail="Menu override store not available")
    return store


async def _require_admin(request: Request) -> None:
    """Reject non-admins. Lets the call through when auth is disabled."""
    user = await get_optional_user_from_request(request)
    if user is None:
        return
    if getattr(user, "system_role", None) != "admin":
        raise HTTPException(status_code=403, detail="菜单管理仅限管理员")


def _validate_depth(overrides: list[MenuOverride]) -> None:
    """Reject cycles and any node whose effective depth exceeds 3 levels.

    Only nodes that appear in the override set carry an explicit ``parent_id``;
    a node absent from the set keeps its code-defined parent (which is at most
    3 levels deep by construction). So validating the override graph alone is
    sufficient to stop an admin from pushing a 4th level via re-parenting.
    """
    parent_of = {o.node_id: o.parent_id for o in overrides}

    for node_id in parent_of:
        depth = 1
        seen = {node_id}
        cursor = parent_of[node_id]
        while cursor:
            depth += 1
            if depth > _MAX_DEPTH:
                raise HTTPException(status_code=400, detail=f"菜单「{node_id}」层级超过 {_MAX_DEPTH} 级")
            if cursor in seen:
                raise HTTPException(status_code=400, detail=f"菜单「{node_id}」存在循环引用")
            seen.add(cursor)
            # A parent that is not itself in the override set is a code node at a
            # known depth ≤ 3, so the chain terminates there.
            cursor = parent_of.get(cursor)


# ── routes ───────────────────────────────────────────────────────────────


@router.get("", response_model=MenuOverrideListResponse)
async def list_menu_overrides(request: Request) -> MenuOverrideListResponse:
    store = _get_store(request)
    rows = await store.list_overrides()
    return MenuOverrideListResponse(overrides=[MenuOverrideResponse(**r) for r in rows])


@router.put("", response_model=MenuOverrideListResponse)
async def replace_menu_overrides(request: Request, body: MenuOverrideReplaceRequest) -> MenuOverrideListResponse:
    await _require_admin(request)
    _validate_depth(body.overrides)
    store = _get_store(request)
    user_id = await get_current_user(request)
    rows = await store.replace_all(
        [o.model_dump() for o in body.overrides],
        updated_by=user_id,
    )
    return MenuOverrideListResponse(overrides=[MenuOverrideResponse(**r) for r in rows])