"""分片上传接口：创建会话 / 查状态 / 传分片 / 完成拼接。

支持大文件分片上传与断点续传。前端先创建会话拿 upload_id，逐片上传，
可随时查 status 获取已传分片以补传缺失部分，最后 complete 触发拼接入库。
"""

from __future__ import annotations

from fastapi import APIRouter, Depends, Request
from sqlalchemy.orm import Session

from ..database import get_db
from ..dao.upload_session_dao import UploadSessionDAO
from ..dao.uploaded_file_dao import UploadedFileDAO
from ..schemas.chunk import (
    ChunkUploadResponse,
    CreateSessionRequest,
    CreateSessionResponse,
    SessionStatusResponse,
)
from ..schemas.file import FileUploadResponse
from ..services.chunk_upload_service import ChunkUploadService

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


def _service(db: Session = Depends(get_db)) -> ChunkUploadService:
    return ChunkUploadService(UploadSessionDAO(db), UploadedFileDAO(db))


@router.post(
    "",
    response_model=CreateSessionResponse,
    summary="创建分片上传会话",
    description=(
        "客户端把文件切成固定大小的分片后，先调本接口创建会话。"
        "服务端生成 upload_id 返回，后续上传分片、查状态、完成拼接都需要它。"
    ),
)
def create_session(
    body: CreateSessionRequest,
    service: ChunkUploadService = 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）",
    description="返回已上传分片下标集合，前端据此只补传缺失分片。",
)
def session_status(
    upload_id: str,
    service: ChunkUploadService = 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",
    description=(
        "请求体为单个分片的原始二进制。分片可乱序上传，重传同一分片会覆盖。"
        "返回当前已上传的分片下标集合。"
    ),
)
async def upload_chunk(
    upload_id: str,
    index: int,
    request: Request,
    service: ChunkUploadService = Depends(_service),
) -> ChunkUploadResponse:
    uploaded = service.write_chunk(upload_id, index, await request.body())
    return ChunkUploadResponse(upload_id=upload_id, index=index, uploaded_chunks=uploaded)


@router.post(
    "/{upload_id}/complete",
    response_model=FileUploadResponse,
    summary="完成拼接并入库",
    description=(
        "服务端校验分片齐全后，按顺序拼接为完整文件、流式计算 sha256，"
        "按 sha256 去重（命中则返回旧行不重复落盘），最后原子改名入库。"
        "重复调用幂等，返回同一 file_id。"
    ),
)
def complete_session(
    upload_id: str,
    service: ChunkUploadService = Depends(_service),
) -> FileUploadResponse:
    return service.complete(upload_id)