import os
import asyncio
from telethon.sync import TelegramClient
from telethon.sessions import StringSession
from fastapi import FastAPI, UploadFile, File, HTTPException
from fastapi.responses import FileResponse
import uvicorn
import tempfile # Import the tempfile module

# --- Configuration from environment variables ---
# Your Telegram session string
SESSION_STRING = os.environ.get('SESSION_STRING')

# You MUST get your own API ID and HASH from my.telegram.org
API_ID = os.environ.get('API_ID')
API_HASH = os.environ.get('API_HASH')

# The Telegram channel you want to upload files to
TARGET_CHANNEL = 'https://t.me/TestNAI01'

# --- FIX: Use the system's temporary directory ---
# This directory is guaranteed to be writable and avoids permission errors.
UPLOAD_DIR = tempfile.gettempdir()

app = FastAPI()

async def upload_to_telegram(file_path: str):
    """
    Uploads a file to the specified Telegram channel using a session string.
    """
    if not all([SESSION_STRING, API_ID, API_HASH]):
        raise ValueError("SESSION_STRING, API_ID, and API_HASH must be set as environment variables.")

    # Initialize the client
    async with TelegramClient(StringSession(SESSION_STRING), API_ID, API_HASH) as client:
        try:
            await client.send_file(TARGET_CHANNEL, file_path)
        except Exception as e:
            raise HTTPException(status_code=500, detail=f"Failed to upload to Telegram: {e}")

@app.post("/v1/upload")
async def upload_file(file: UploadFile = File(...)):
    """
    Receives a file, saves it to the temp directory, and uploads it to the Telegram channel.
    """
    # Create a secure path in the temporary directory
    file_location = os.path.join(UPLOAD_DIR, file.filename)
    try:
        # Save the uploaded file temporarily
        with open(file_location, "wb+") as file_object:
            file_object.write(file.file.read())

        # Upload the file to Telegram
        await upload_to_telegram(file_location)
        return {"message": f"File '{file.filename}' uploaded successfully to Telegram."}
    finally:
        # Clean up the local file after uploading to save space
        if os.path.exists(file_location):
            os.remove(file_location)

@app.get("/v1/download/{filename}")
async def download_file(filename: str):
    """
    Serves a file for download.
    NOTE: This endpoint is for demonstration. It looks for files in the temp
    directory, but files uploaded in previous requests will have been deleted.
    A production system would need a proper way to retrieve files from Telegram.
    """
    file_path = os.path.join(UPLOAD_DIR, filename)
    if os.path.exists(file_path):
        return FileResponse(file_path)
    raise HTTPException(status_code=404, detail="File not found. Files are only stored temporarily during upload.")

if __name__ == "__main__":
    if not all([SESSION_STRING, API_ID, API_HASH]):
        print("FATAL ERROR: The environment variables SESSION_STRING, API_ID, and API_HASH must be set.")
    else:
        uvicorn.run(app, host="0.0.0.0", port=8000)