"""
预览 / 聊天附件上传：写入 LOCAL_FILE_TOOLS_ROOT 下，供 file_read 等工具使用。
"""
from __future__ import annotations

import re
import uuid
import logging
from pathlib import Path

from fastapi import APIRouter, Depends, File, HTTPException, UploadFile, status
from pydantic import BaseModel

from app.api.auth import get_current_user
from app.core.config import settings
from app.models.user import User
from app.services.builtin_tools import _local_file_workspace_root

logger = logging.getLogger(__name__)

router = APIRouter(
    prefix="/api/v1/uploads",
    tags=["uploads"],
)


class PreviewUploadResponse(BaseModel):
    """相对工作区根的路径，与 file_read 约定一致（可用相对路径）。"""

    relative_path: str
    filename: str
    size: int
    content_type: str | None = None


def _safe_filename(name: str) -> str:
    base = Path(name).name.strip()
    if not base:
        return "attachment.bin"
    base = re.sub(r"[^\w.\-\u4e00-\u9fff]+", "_", base, flags=re.UNICODE)
    return base[:180] if len(base) > 180 else base


@router.post(
    "/preview",
    response_model=PreviewUploadResponse,
    status_code=status.HTTP_201_CREATED,
)
async def upload_preview_file(
    file: UploadFile = File(...),
    current_user: User = Depends(get_current_user),
):
    """
    上传单个文件到工作区 `uploads/preview/<user_id>/`，返回相对路径。
    大小上限与 LOCAL_FILE_WRITE_MAX_BYTES 一致。
    """
    max_bytes = max(1024, int(getattr(settings, "LOCAL_FILE_WRITE_MAX_BYTES", 2_097_152) or 2_097_152))
    root = _local_file_workspace_root()
    uid = str(current_user.id)
    dest_dir = root / "uploads" / "preview" / uid
    try:
        dest_dir.mkdir(parents=True, exist_ok=True)
    except OSError as e:
        logger.warning("创建上传目录失败: %s", e)
        raise HTTPException(status_code=500, detail="无法创建上传目录") from e

    raw_name = file.filename or "attachment"
    safe = _safe_filename(raw_name)
    short = uuid.uuid4().hex[:12]
    dest = dest_dir / f"{short}_{safe}"

    total = 0
    chunk_size = 1024 * 256
    try:
        with dest.open("wb") as out:
            while True:
                buf = await file.read(chunk_size)
                if not buf:
                    break
                total += len(buf)
                if total > max_bytes:
                    raise HTTPException(
                        status_code=status.HTTP_413_REQUEST_ENTITY_TOO_LARGE,
                        detail=f"文件超过允许大小（{max_bytes} 字节）",
                    )
                out.write(buf)
    except HTTPException:
        try:
            dest.unlink(missing_ok=True)
        except OSError:
            pass
        raise
    except OSError as e:
        try:
            dest.unlink(missing_ok=True)
        except OSError:
            pass
        logger.warning("写入上传文件失败: %s", e)
        raise HTTPException(status_code=500, detail="保存文件失败") from e

    try:
        rel = dest.relative_to(root).as_posix()
    except ValueError:
        rel = str(dest).replace("\\", "/")

    logger.info("预览上传 user=%s path=%s size=%s", uid, rel, total)
    return PreviewUploadResponse(
        relative_path=rel,
        filename=raw_name,
        size=total,
        content_type=file.content_type,
    )