"""
Admin-only endpoints for storage-service backend configuration.

GET  /admin/storage-config           — current backend driver + health
PATCH /admin/storage-config          — update backend config (no data migration)
POST /admin/storage-config/migrate   — start migration to a new backend
GET  /admin/storage-config/migrate/status — poll migration progress
DELETE /admin/storage-config/migrate — cancel in-progress migration

All endpoints proxy to storage-service:8020.
"""
import logging

import httpx
from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel

from app.core.config import settings
from app.deps import get_current_admin
from app.models.user import User

router = APIRouter()
logger = logging.getLogger(__name__)

_STORAGE_BASE = settings.STORAGE_SERVICE_URL


class BackendConfigUpdate(BaseModel):
    driver: str
    config: dict = {}


class MigrateRequest(BaseModel):
    driver: str
    config: dict = {}


def _storage_url(path: str) -> str:
    return f"{_STORAGE_BASE}{path}"


async def _proxy_get(path: str) -> dict:
    async with httpx.AsyncClient(timeout=15.0) as client:
        resp = await client.get(_storage_url(path))
        if resp.status_code == 404:
            raise HTTPException(status_code=404, detail="Not found")
        resp.raise_for_status()
        return resp.json()


@router.get("/storage-config")
async def get_storage_config(
    _: User = Depends(get_current_admin),
) -> dict:
    """Return current backend driver and health status."""
    async with httpx.AsyncClient(timeout=10.0) as client:
        resp = await client.get(_storage_url("/health"))
        resp.raise_for_status()
        return resp.json()


@router.patch("/storage-config", status_code=204)
async def update_storage_config(
    body: BackendConfigUpdate,
    _: User = Depends(get_current_admin),
) -> None:
    """
    Reconfigure the active backend without migrating data.
    Use when changing credentials for the same backend type, or reverting to local.
    To move data to a new backend, use POST /admin/storage-config/migrate instead.
    """
    async with httpx.AsyncClient(timeout=15.0) as client:
        resp = await client.patch(
            _storage_url("/backend-config"),
            json={"driver": body.driver, "config": body.config},
        )
        if resp.status_code == 400:
            raise HTTPException(status_code=400, detail=resp.json().get("detail", "Validation failed"))
        if resp.status_code == 409:
            raise HTTPException(status_code=409, detail="Migration in progress — cannot reconfigure now")
        resp.raise_for_status()


@router.post("/storage-config/migrate", status_code=202)
async def start_migration(
    body: MigrateRequest,
    _: User = Depends(get_current_admin),
) -> dict:
    """
    Start an async migration to a new backend.

    Flow: validate new backend → copy all objects → verify → switch → delete old objects.
    The old backend stays active until 100% of objects are verified on the new one.
    Poll GET /admin/storage-config/migrate/status to track progress.
    """
    async with httpx.AsyncClient(timeout=30.0) as client:
        resp = await client.post(
            _storage_url("/migrate"),
            json={"driver": body.driver, "config": body.config},
        )
        if resp.status_code == 400:
            raise HTTPException(status_code=400, detail=resp.json().get("detail", "Validation failed"))
        if resp.status_code == 409:
            raise HTTPException(status_code=409, detail="A migration is already in progress")
        resp.raise_for_status()
        return resp.json()


@router.get("/storage-config/migrate/status")
async def migration_status(
    _: User = Depends(get_current_admin),
) -> dict:
    """Poll migration progress. State: idle → validating → migrating → switching → cleaning → done."""
    return await _proxy_get("/migrate/status")


@router.delete("/storage-config/migrate", status_code=204)
async def cancel_migration(
    _: User = Depends(get_current_admin),
) -> None:
    """Cancel a running migration. The old backend remains active."""
    async with httpx.AsyncClient(timeout=10.0) as client:
        resp = await client.delete(_storage_url("/migrate"))
        if resp.status_code == 409:
            raise HTTPException(status_code=409, detail="No cancellable migration in progress")
        resp.raise_for_status()