server.rb

require 'sinatra'
require './models'

get '/customers' do
  Customer.all.to_json
end

get '/customer/:cust_num' do |cust_num|
  @customer = Customer.get(cust_num)
  if @customer
    @customer.to_json
  else
    not_found 'unknown customer'
  end
end

post '/customer' do
  next_id = Customer.last.cust_num + 1
  @customer = Customer.create(params.merge(:cust_num => next_id))
  @customer.to_json
end

put '/customer/:cust_num' do |cust_num|
  @customer = Customer.get(cust_num)
  if @customer
    @customer.destroy && Customer.create(request.params.merge({'cust_num' => cust_num}))
    @customer.to_json
  else
    not_found 'unknown customer'
  end
end

patch '/customer/:cust_num' do |cust_num|
  @customer = Customer.get(cust_num)
  if @customer
    @customer.attributes = request.params.reject{|k,v| k == 'cust_num'}
    @customer.save
    @customer.to_json
  else
    not_found 'unknown customer'
  end
end

delete '/customer/:cust_num' do |cust_num|
  @customer = Customer.get(cust_num)
  if @customer
    @customer.destroy
  else
    not_found 'unknown customer'
  end
end