from __future__ import annotations

import uuid

from fastapi import APIRouter, Depends, HTTPException, Request, status
from pydantic import BaseModel, field_validator
from sqlalchemy.ext.asyncio import AsyncSession

from db.models import Quota, User
from deps.auth import get_current_admin
from deps.db import get_db
from deps.utils import get_client_ip
from services.audit import write_audit_log
from api.admin.shared import _user_to_dict

router = APIRouter()  # NO prefix — parent __init__.py carries /api/admin (D-04)


# ── Request models ────────────────────────────────────────────────────────────

class QuotaUpdate(BaseModel):
    limit_bytes: int

    @field_validator("limit_bytes")
    @classmethod
    def must_be_positive(cls, v: int) -> int:
        if v <= 0:
            raise ValueError("limit_bytes must be greater than 0")
        return v


# ── Endpoints ─────────────────────────────────────────────────────────────────

@router.get("/users/{user_id}/quota")
async def get_user_quota(
    user_id: uuid.UUID,
    session: AsyncSession = Depends(get_db),
    _admin: User = Depends(get_current_admin),
) -> dict:
    quota = await session.get(Quota, user_id)
    if quota is None:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Quota not found")

    return {
        "user_id": str(quota.user_id),
        "limit_bytes": quota.limit_bytes,
        "used_bytes": quota.used_bytes,
        "limit_mb": quota.limit_bytes // 1048576,
        "used_mb": quota.used_bytes // 1048576,
    }


@router.patch("/users/{user_id}/quota")
async def update_user_quota(
    user_id: uuid.UUID,
    body: QuotaUpdate,
    request: Request,
    session: AsyncSession = Depends(get_db),
    _admin: User = Depends(get_current_admin),
) -> dict:
    quota = await session.get(Quota, user_id)
    if quota is None:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Quota not found")

    warning = body.limit_bytes < quota.used_bytes
    warning_message = (
        "New limit is below current usage. Uploads will be blocked but existing documents are preserved."
        if warning
        else None
    )

    _ip_addr = get_client_ip(request)
    old_limit = quota.limit_bytes
    quota.limit_bytes = body.limit_bytes
    session.add(quota)

    # D-13: quota changed event
    await write_audit_log(
        session,
        event_type="admin.quota_changed",
        user_id=user_id,
        actor_id=_admin.id,
        resource_id=None,
        ip_address=_ip_addr,
        metadata_={"old_bytes": old_limit, "new_bytes": body.limit_bytes},
    )
    await session.commit()

    response: dict = {
        "user_id": str(quota.user_id),
        "limit_bytes": quota.limit_bytes,
        "used_bytes": quota.used_bytes,
        "warning": warning,
    }
    if warning_message:
        response["message"] = warning_message
    return response