from fastapi import APIRouter, Depends, HTTPException, BackgroundTasks
from fastapi.responses import FileResponse
from pydantic import BaseModel
from typing import Optional
import os
from pathlib import Path

from apps.api.dependencies.auth import get_api_key, get_current_user_tier
from apps.worker.export_tasks import export_data_task, EXPORT_DIR

router = APIRouter(prefix="/export", tags=["Export"])

class ExportRequest(BaseModel):
    hs_code: Optional[str] = None
    country: Optional[str] = None
    start_date: str
    end_date: str
    email: str

@router.post("/")
async def request_async_export(
    req: ExportRequest, 
    api_key: str = Depends(get_api_key),
    tier: str = Depends(get_current_user_tier)
):
    """
    提交异步导出任务。
    根据用户的层级 (tier)，可以限制导出的数据量或范围。
    """
    if tier == "trial":
        raise HTTPException(status_code=403, detail="Trial users cannot export data. Please upgrade your plan.")
        
    # 将任务推入 Celery 队列
    task = export_data_task.delay(
        query_params={
            "hs_code": req.hs_code,
            "country": req.country,
            "start_date": req.start_date,
            "end_date": req.end_date
        },
        user_email=req.email
    )
    
    return {
        "message": "Export task submitted successfully.",
        "task_id": task.id,
        "tier": tier
    }

@router.get("/status/{task_id}")
async def get_export_status(task_id: str, api_key: str = Depends(get_api_key)):
    """
    查询异步导出任务状态。
    """
    from packages.core.celery_app import celery_app
    task = celery_app.AsyncResult(task_id)
    
    if task.state == 'PENDING':
        return {"task_id": task_id, "status": "Pending"}
    elif task.state == 'SUCCESS':
        return {"task_id": task_id, "status": "Completed", "result": task.result}
    elif task.state == 'FAILURE':
        return {"task_id": task_id, "status": "Failed", "error": str(task.info)}
    else:
        return {"task_id": task_id, "status": task.state}

@router.get("/download/{filename}")
async def download_export_file(
    filename: str,
    api_key: str = Depends(get_api_key)
):
    """
    下载导出文件。
    
    安全检查：
    1. 验证 API Key
    2. 防止路径遍历攻击
    3. 检查文件是否存在
    """
    # 防止路径遍历攻击
    if ".." in filename or "/" in filename or "\\" in filename:
        raise HTTPException(status_code=400, detail="Invalid filename")
    
    # 只允许 CSV 文件
    if not filename.endswith(".csv"):
        raise HTTPException(status_code=400, detail="Only CSV files are allowed")
    
    file_path = Path(EXPORT_DIR) / filename
    
    # 检查文件是否存在
    if not file_path.exists() or not file_path.is_file():
        raise HTTPException(status_code=404, detail="File not found or has expired")
    
    # 返回文件
    return FileResponse(
        path=str(file_path),
        media_type="text/csv",
        filename=filename,
        headers={
            "Content-Disposition": f"attachment; filename={filename}"
        }
    )