今更ながらLINE BOTのEchoサーバをRails4で簡易的に書いてみる ref: http://qiita.com/kskomori/items/6718babf55a283fe267e

LINEBOT_Echo_rails4.txt

require 'faraday'

class Linebots::BotController < ApplicationController

  protect_from_forgery except: :callback


  def callback
    if request.method != 'POST'
      render text: 'NG', status: 500
    end

    post_text(params[:result][0][:content][:from], params[:result][0][:content][:text])

    render text: ''
  end


private

  def post_text(to, text)
    content = {
      contentType: 1,
      toType: 1,
      text: text
    }

    post_event(to, content)
  end

  def post_event(to, content)
    msg = {
      to: [ to ],
      toChannel: '1383378250',        # 固定値
      eventType: 138311608800106203,  # 固定値
      content: content
    }

    conn = Faraday::Connection.new(url: 'https://trialbot-api.line.me') do |builder|
      builder.request :url_encoded
      builder.response :logger
      builder.adapter Faraday.default_adapter
    end

    res = conn.post '/v1/events' do |req|
      req.headers['Content-type'] = 'application/json; charset=UTF-8'
      req.headers['X-Line-ChannelID'] = 'xxxxxxxxxxxxx'
      req.headers['X-Line-ChannelSecret'] =  'yyyyyyyyyyyyyyyyyyy'
      req.headers['X-Line-Trusted-User-With-ACL'] =  'zzzzzzzzzzzzzzzzzzzzzzzzzzzz'

      req.body = msg.to_json
    end
  end

end