"""分片上传路由：建会话 / 查状态 / 传分片 / complete。

complete 成功后创建转写 Task 并交由 scheduler 入队。
"""

from __future__ import annotations

from fastapi import APIRouter, Depends, Request
from starlette.concurrency import run_in_threadpool
from sqlalchemy.orm import Session

from ..database import get_db
from ..schemas.task import (
    ChunkUploadResponse,
    CompleteResponse,
    CreateSessionRequest,
    CreateSessionResponse,
    SessionStatusResponse,
)
from ..services.upload_service import UploadService

router = APIRouter(prefix="/api/tasks/chunk-uploads", tags=["upload"])


def _service(db: Session = Depends(get_db)) -> UploadService:
    return UploadService(db)


@router.post("", response_model=CreateSessionResponse, summary="创建分片上传会话")
def create_session(
    body: CreateSessionRequest,
    service: UploadService = Depends(_service),
) -> CreateSessionResponse:
    return service.create_session(body)


@router.get("/{upload_id}/status", response_model=SessionStatusResponse, summary="查询会话状态（断点续传）")
def session_status(
    upload_id: str,
    service: UploadService = Depends(_service),
) -> SessionStatusResponse:
    return service.get_status(upload_id)


@router.post("/{upload_id}/chunks/{index}", response_model=ChunkUploadResponse, summary="上传单个分片")
async def upload_chunk(
    upload_id: str,
    index: int,
    request: Request,
    service: UploadService = Depends(_service),
) -> ChunkUploadResponse:
    # write_chunk 做文件 fsync + DB commit（阻塞 I/O），必须放到线程池跑，
    # 否则会阻塞 uvicorn 事件循环，导致并发分片上传被串行化、web 请求卡顿。
    body = await request.body()
    uploaded = await run_in_threadpool(service.write_chunk, upload_id, index, body)
    return ChunkUploadResponse(upload_id=upload_id, index=index, uploaded_chunks=uploaded)


@router.post("/{upload_id}/complete", response_model=CompleteResponse, summary="完成拼接并创建转写任务")
def complete_session(
    upload_id: str,
    service: UploadService = Depends(_service),
) -> CompleteResponse:
    """拼接分片 + 创建转写任务 + 入队管线。

    controller 负责编排：service.complete 只管存储（拼接 + 建 Task），
    管线触发由 controller 调用 scheduler（ffmpeg 异步 + GPU 串行调度），service 不依赖
    scheduler（避免循环依赖）。
    """
    resp = service.complete(upload_id)
    # 仅新建任务时入队（幂等 complete 返回的也是同一 task_id，enqueue 幂等无副作用）
    from ..services.scheduler import enqueue_task
    enqueue_task(resp.task_id)
    return resp