"""文件上传 / 列表 / 下载接口。"""

from __future__ import annotations

from pathlib import Path

from fastapi import APIRouter, Depends, File, HTTPException, UploadFile
from fastapi.responses import FileResponse
from sqlalchemy.orm import Session

from ..database import get_db
from ..dao.uploaded_file_dao import UploadedFileDAO
from ..schemas.file import (
    FileListResponse,
    FileUploadResponse,
    SftpRegisterRequest,
    UploadedFileOut,
)
from ..services.upload_service import UploadService

router = APIRouter(prefix="/api/files", tags=["files"])


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


@router.post(
    "/upload",
    response_model=FileUploadResponse,
    summary="上传单个文件（流式，支持大文件）",
    description=(
        "multipart/form-data 上传，按 1 MiB 分片流式落盘，内存占用恒定；"
        "落盘过程中计算 SHA-256 并入库。\n\n"
        "极大或极慢的传输建议改用 SFTP（详见 README），HTTP 链路受 Apache 代理 300s 超时限制。"
    ),
)
async def upload_file(
    file: UploadFile = File(..., description="要上传的文件"),
    service: UploadService = Depends(_service),
) -> FileUploadResponse:
    if not file.filename:
        raise HTTPException(400, "请求缺少 'file' 字段")
    return service.stream_to_disk(file, source="http", uploaded_by="anonymous")


@router.get("", response_model=FileListResponse, summary="列出已上传的文件")
def list_files(
    limit: int = 100,
    offset: int = 0,
    service: UploadService = Depends(_service),
) -> FileListResponse:
    total, items = service.list_files(limit=limit, offset=offset)
    return FileListResponse(total=total, items=items)


@router.get(
    "/exists",
    response_model=UploadedFileOut,
    summary="按 sha256 查询是否已上传",
    description="命中返回 200 + 元数据；未命中返回 404。供客户端在上传前去重。",
)
def file_exists(
    sha256: str,
    service: UploadService = Depends(_service),
) -> UploadedFileOut:
    out = service.find_by_sha256(sha256)
    if out is None:
        raise HTTPException(404, "未找到匹配的 sha256")
    return out


@router.post(
    "/register-sftp",
    response_model=FileUploadResponse,
    summary="登记一个已通过 SFTP 落盘的文件",
    description=(
        "客户端先把文件 SFTP 到 ``incoming/<name>``，再用本接口登记入库。"
        "服务端会计算 sha256（已存在则去重）、把文件原子改名到 ``YYYY/MM/<uuid>.<ext>``、写 DB 行。"
    ),
)
def register_sftp(
    body: SftpRegisterRequest,
    service: UploadService = Depends(_service),
) -> FileUploadResponse:
    return service.register_sftp(
        filename=body.filename,
        original_filename=body.original_filename,
        uploaded_by=body.uploaded_by,
    )


@router.get("/{file_id}", response_model=UploadedFileOut, summary="查询单个文件元数据")
def get_file(file_id: int, service: UploadService = Depends(_service)) -> UploadedFileOut:
    out = service.get_out(file_id)
    if out is None:
        raise HTTPException(404, "文件不存在")
    return out


@router.get("/{file_id}/download", summary="下载文件")
def download_file(file_id: int, service: UploadService = Depends(_service)) -> FileResponse:
    out = service.get_out(file_id)
    if out is None:
        raise HTTPException(404, "文件不存在")
    path: Path | None = service.resolve_disk_path(file_id)
    if path is None or not path.exists():
        raise HTTPException(410, "文件实体已不在磁盘上")
    return FileResponse(
        path=str(path),
        media_type=out.content_type or "application/octet-stream",
        filename=out.original_filename,
    )