# How to make a Line chatbot with AWS Lambda

Since I participated Hackathon held by AWS just one week ago, I want to practice how to use AWS services. This side project is just a practice to make a very simple Line chatbot (echo chatbot) using AWS Lambda. I will write another article to explain how to create an AI Line chatbot using AWS bedrock and AWS dynamoDB. Let's get started.


The steps is following:
1. Create a Business Line account and create a Line official account
2. Open webhook feature in Line
3. Copy Channel access token and Channel secert from Line official account, we will use it later.
4. Create AWS account
5. Create a Lambda function
6. Upload required package as layers in AWS lambda
7. Create API in Lambda (without entering API gateway)
8. Put API into Line webhook, and test it.

Since I am lazy, I will start write from step 5. If you want to know about how to create Line business account, you can see in this [link](https://developers.line.biz/en/docs/messaging-api/building-bot/#line-manager-settings).

Also, don't worry about price. AWS Lambda is free if the number of request event is lower than 1 million per month. It is very difficult for a side project.


## Create a Lambda Function
When you get into AWS console, please click Lambda function to enter it, and then click `Create Function`.


After clicking, you can name your function whatever you want, and please change your runtime as `Python 3.12`. Everything else can stay as default, and press `Create Function`.


Put the following code into `Code Source` and press `Deploy`

from linebot.v3 import (
    WebhookHandler
)
from linebot.v3.messaging import (
    Configuration,
    ApiClient,
    MessagingApi,
    TextMessage,
    ReplyMessageRequest
)
from linebot.v3.exceptions import (
    InvalidSignatureError
)
from linebot.v3.webhooks import (
    MessageEvent,
    TextMessageContent
)

import os
import json

configuration = Configuration(access_token=os.environ['Channel_access_token'])
handler = WebhookHandler(os.environ['Channel_secret'])

def lambda_handler(event, context):
    @handler.add(MessageEvent, message=TextMessageContent)
    def handle_message(event):
        with ApiClient(configuration) as api_client:
            line_bot_api = MessagingApi(api_client)
            line_bot_api.reply_message(
                ReplyMessageRequest(
                    reply_token=event.reply_token,
                    messages=[TextMessage(text=event.message.text)]
                )
            )

    signature = event['headers']['x-line-signature']
    body = event['body']

    try:
        handler.handle(body, signature)
    except InvalidSignatureError:
        return {
            'statusCode': 502,
            'body': json.dumps("Invalid signature. Please check your channel access token/channel secret.")
            }
    return {
        'statusCode': 200,
        'body': json.dumps("OK")
        }

## Upload Requirement Package as Layer and Set Environment Variables

First, please find `Configuration` section and find `Environment variables` in side bar. Press `Add variable` and set your **Channel access token** and **Channel secret** from your Line business account.

Next, please use `pip install line-bot-sdk -t target_dir` to download line sdk into your target directory, and zip it as zip file.

Then, click `Layers` on the side bar of AWS Lambda page, and press `Create Layers`. You can name this layer whatever you want, select `Upload a .zip file`, and Upload your zip file mentioned above. Press `Create` at the bottom of this page, and copy the ARN code.


Finally, go to `Functions` at the side bar of Lambda page, and press the name of your function. You can see there is a bar under the logo of Lambda saying that `Layers (0)`. Press it, and press `Add a Layer`. Press `Specify an ARN` and paste ARN code into the bar under the page. Press `Add`, and the layer is done.

If you want to know more about Layers, please check this [link](https://docs.aws.amazon.com/lambda/latest/dg/python-package.html)

## Create API in Lambda
Go to the `Configuration`, press `Trigger` at the side bar, and press `Add Trigger`.
* select `API Gateway`
* select `Create a new API`
* select `REST API`
* select `Open` in Security section.
* Press `Add`


## Put API into Line webhook, and test it.

First, check whether you need to deploy the newest function.

Then, copy `API endpoint` under the `API Gateway` we just created.

Finally, paste `API endpoint` in `Webhook URL` in Line Business account (Please make sure you open `Use webhook` first).

And you can play with your chatbot in Line.

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<a href="https://www.flaticon.com/free-icons/line" title="line icons">Line icons created by Ruslan Babkin - Flaticon</a>