main.py

from fastapi.middleware.cors import CORSMiddleware
from fastapi import FastAPI, Request,  Header, HTTPException, status

import json
import os

from linebot import (
    LineBotApi, WebhookHandler
)
from linebot.exceptions import (
    InvalidSignatureError
)
from linebot.models import (
    MessageEvent, TextMessage, TextSendMessage, ImageSendMessage, AudioMessage
)

app = FastAPI()
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

line_bot_api = LineBotApi(os.environ["line_bot_api"])
line_handler = WebhookHandler(os.environ["line_handler"])

working_status = working_status = os.getenv("DEFALUT_TALKING", default = "true").lower() == "true"

@app.get("/")
def root():
     return {"title": "Echo Bot"}

@app.post("/webhook")
async def webhook(request: Request, x_line_signature: str = Header(None)):
    body = await request.body()
    try:
        line_handler.handle(body.decode("utf-8"), x_line_signature)
    except InvalidSignatureError:
        raise HTTPException(status_code=400, detail="chatbot handle body error.")
    return 'OK'

@line_handler.add(MessageEvent, message=TextMessage)
def handle_message(event):
    global working_status

    if event.message.text == "再見":
        working_status = True
        line_bot_api.reply_message(
            event.reply_token,
            TextSendMessage(text="Bye!"))
        return

    if working_status:
        out = event.message.text
        if not out:
            out = "不懂您的意思!"
        line_bot_api.reply_message(
            event.reply_token,
            TextSendMessage(text=out))