app.rb

# Sinatra app to demo Bank transactions to AI advice
require "bundler"
Bundler.require
Dotenv.load

require 'erb'
require 'securerandom'
require "sinatra/cookies"

get '/' do
  erb :index
end

get '/institutions' do
  @institutions = nordigen_client.institution.get_institutions("BE")
  erb :institutions
end

post '/init_requisition' do
  ref = SecureRandom.uuid # unique reference
  init = nordigen_client.init_session(
    # redirect url after successful authentication
    redirect_url: "http://127.0.0.1:4567/after_requisition",
    institution_id: params[:institution_id],
    reference_id: ref,
  )
  cookies[:gc_ref] = ref
  cookies[:requisition_id] = init["id"]
  redirect(init["link"])
end

get '/accounts' do
  @accounts = get_accounts(cookies[:requisition_id]).map do |account|
    # details = account.get_details()["account"] # rate limit = 4/day
    # balances = account.get_balances()["balances"] # rate limit = 4/day
    {
      id: account.account_id,
      # iban: details["iban"],
      # currency: details["currency"],
      # balance: balances&.first&.dig("balanceAmount", "acount")
    }
  end

  erb :accounts
end

get '/account' do
  @account_id = params[:account_id]
  erb :account
  # todo: fetch last 30d transactions
  # todo: ask Claude Sonet to give advice
end

get '/after_requisition' do
  redirect to('/')
end

def get_accounts(req_id)
  client = nordigen_client
  requisition_data = client.requisition.get_requisition_by_id(req_id)
  requisition_data["accounts"].map { |account_id| client.account(account_id) }
end

def nordigen_client
  client = Nordigen::NordigenClient.new(
    secret_id: ENV.fetch("GOCARDLESS_SECRET_ID"),
    secret_key: ENV.fetch("GOCARDLESS_SECRET_KEY"),
  )
  token_data = client.generate_token()
  client.set_token(token_data["access"])
  client
end

def anthropic_client
  Anthropic::Client.new(access_token: ENV.fetch("ANTHROPIC_API_KEY"))
end