main.py

# -*- coding: utf-8 -*-

#  Licensed under the Apache License, Version 2.0 (the "License"); you may
#  not use this file except in compliance with the License. You may obtain
#  a copy of the License at
#
#       https://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#  License for the specific language governing permissions and limitations
#  under the License.

import os
import sys

from fastapi import Request, FastAPI, HTTPException

from linebot.v3.webhook import WebhookParser
from linebot.v3.messaging import (
    AsyncApiClient,
    AsyncMessagingApi,
    Configuration,
    ReplyMessageRequest,
    TextMessage
)
from linebot.v3.exceptions import (
    InvalidSignatureError
)
from linebot.v3.webhooks import (
    MessageEvent,
    TextMessageContent
)


# get channel_secret and channel_access_token from your environment variable
channel_secret = os.getenv('LINE_CHANNEL_SECRET', None)
channel_access_token = os.getenv('LINE_CHANNEL_ACCESS_TOKEN', None)
if channel_secret is None:
    print('Specify LINE_CHANNEL_SECRET as environment variable.')
    sys.exit(1)
if channel_access_token is None:
    print('Specify LINE_CHANNEL_ACCESS_TOKEN as environment variable.')
    sys.exit(1)

configuration = Configuration(
    access_token=channel_access_token
)

app = FastAPI()
async_api_client = AsyncApiClient(configuration)
line_bot_api = AsyncMessagingApi(async_api_client)
parser = WebhookParser(channel_secret)


@app.post("/callback")
async def handle_callback(request: Request):
    signature = request.headers['X-Line-Signature']

    # get request body as text
    body = await request.body()
    body = body.decode()

    try:
        events = parser.parse(body, signature)
    except InvalidSignatureError:
        raise HTTPException(status_code=400, detail="Invalid signature")

    for event in events:
        if not isinstance(event, MessageEvent):
            continue
        if not isinstance(event.message, TextMessageContent):
            continue

        await line_bot_api.reply_message(
            ReplyMessageRequest(
                reply_token=event.reply_token,
                messages=[TextMessage(text=event.message.text)]
            )
        )

    return 'OK'