callbacks_controller.rb

require 'line/bot'

class CallbacksController < ApplicationController
  def event_handler
    signature = request.env['HTTP_X_LINE_CHANNELSIGNATURE']
    unless client.validate_signature(request.body.read, signature)
      error 400 do 'Bad Request' end
    end

    receive_request = Line::Bot::Receive::Request.new(request.env)

    receive_request.data.each { |message|
      case message.content
      when Line::Bot::Message::Text
        res = client.send_text(
          to_mid: message.from_mid,
          text: "Hola"
        )
      end
    }

    render :nothing => true, status: :ok
  end
  
  def client
    client ||= Line::Bot::Client.new do |config|
      config.channel_id = ENV.fetch('LINE_CHANNEL_ID')
      config.channel_secret = ENV.fetch('LINE_CHANNEL_SECRET')
      config.channel_mid = ENV.fetch('LINE_CHANNEL_MID')
    end
  end
end