app.py

from flask import Flask, request, abort
import os

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

app = Flask(__name__)

line_bot_api = LineBotApi(os.environ.get("LINE_BOT_CHANNEL_TOKEN"))
handler = WebhookHandler(os.environ.get("LINE_BOT_CHANNEL_SECRET"))


@app.route("/", methods=['GET', 'POST'])
def callback():
    if request.method == 'GET':
        return 'Success'
    if request.method == 'POST':
        # get X-Line-Signature header value
        signature = request.headers['X-Line-Signature']

        # get request body as text
        body = request.get_data(as_text=True)
        app.logger.info("Request body: " + body)
        print(body)

        # handle webhook body
        try:
            handler.handle(body, signature)
        except InvalidSignatureError:
            abort(400)

        return 'OK'


@handler.add(MessageEvent, message=TextMessage)
def handle_message(event):
    line_bot_api.reply_message(
        event.reply_token,
        TextSendMessage(text=event.message.text))


if __name__ == "__main__":
    app.run()