支付宝 API 向导（Ruby 版）

gem 'alipay', :github => 'chloerei/alipay'

Alipay.pid = 'YOUR_PID'
Alipay.key = 'YOUR_KEY'
Alipay.seller_email = 'YOUR_SELLER_EMAIL'

class Order
  include Mongoid::Document
  include Mongoid::Timestamps

  # 订单基本信息，我不想处理小数，所以价格字段用 Integer。如果你的交易需要精确到小数位，改用 BigDecimal
  field :plan, :type => Symbol
  field :quantity, :type => Integer
  field :price, :type => Integer, :default => 0
  field :discount, :type => Integer, :default => 0
  filed :trade_no # 支付宝交易号

  # state 字段的取值可以按照自己喜好选择，只要能覆盖支付宝交易状态的类型就行了
  field :state, :default => 'opening'
  STATE = %w(opening pending paid completed canceled)
  validates_inclusion_of :state, :in => STATE

  # 添加 paid? completed? 等方法
  STATE.each do |state|
    define_method "#{state}?" do
      self.state == state
    end
  end

  # 状态迁移方法

  def pend
    if opening?
      update_attribute :state, 'pending'
    end
  end

  # 只在 pending 状态可以 pay
  def pay
    if pending?
      add_plan # 业务逻辑，订单生效
      update_attribute :state, 'paid'
    end
  end

  # 只在 pending 和 paid 状态可以 complete
  def complete
    if pendding? or paid?
      add_plan if pendding? # 如果是 paid 状态，已经执行过 add_plan
      update_attribute :state, 'completed'
    end
  end

  # 只在 pending 和 paid 状态可以 cancel
  def cancel
    if pendding? or paid?
      remove_plan if paid? # 业务逻辑，取消订单
      update_attribute :state, 'canceled'
    end
  end
end

def pay_url
  Alipay::Service.create_partner_trade_by_buyer_url(
    :out_trade_no      => id.to_s,
    :price             => price,
    :quantity          => quantity,
    :discount          => discount,
    :subject           => "Writings.io #{I18n.t "plan.#{plan}"} x #{quantity}",
    :logistics_type    => 'DIRECT',
    :logistics_fee     => '0',
    :logistics_payment => 'SELLER_PAY',
    :return_url        => Rails.application.routes.url_helpers.order_url(self, :host => 'writings.io'),
    :notify_url        => Rails.application.routes.url_helpers.alipay_notify_orders_url(:host => 'writings.io'),
    :receive_name      => 'none', # 这里填写了收货信息，用户就不必填写
    :receive_address   => 'none',
    :receive_zip       => '100000',
    :receive_mobile    => '100000000000'
  )
end

def send_good
  Alipay::Service.send_goods_confirm_by_platform(
    :trade_no => trade_no,
    :logistics_name => 'writings.io',
    :transport_type => 'DIRECT' # 无需物流
  )
end

resources :orders, :only => [:index, :new, :create, :show] do
  collection do
    post :alipay_notify
  end
end

class OrdersController < ApplicationController
  before_filter :require_logined, :except => [:alipay_notify]
  skip_before_filter :verify_authenticity_token, :only => [:alipay_notify]

  # 创建订单
  def create
    @order = current_user.orders.new order_param.merge(:plan => :base, :price => 10)

    # 订单创建成功，将用户重定向到支付页面
    if @order.save
      redirect_to @order.pay_url
    else
      render :new
    end
  end

  # 用户支付完毕后，重定向回来的页面
  def show
    @order = current_user.orders.find params[:id]

    # 友好的提示当前订单的状态
    callback_params = params.except(*request.path_parameters.keys)
    if callback_params.any? && Alipay::Sign.verify?(callback_params)
      if @order.paid? || @order.completed?
        flash.now[:success] = I18n.t('order_paid_message')
      elsif @order.pending?
        flash.now[:info] = I18n.t('order_pendding_message')
      end
    end
  end

  # 支付宝异步消息接口
  def alipay_notify
    notify_params = params.except(*request.path_parameters.keys)
    # 先校验消息的真实性
    if Alipay::Sign.verify?(notify_params) && Alipay::Notify.verify?(notify_params)
      # 获取交易关联的订单
      @order = Order.find params[:out_trade_no]

      case params[:trade_status]
      when 'WAIT_BUYER_PAY'
        # 交易开启
        @order.update_attribute :trade_no, params[:trade_no]
        @order.pend
      when 'WAIT_SELLER_SEND_GOODS'
        # 买家完成支付
        @order.pay
        # 虚拟物品无需发货，所以立即调用发货接口
        @order.send_good
      when 'TRADE_FINISHED'
        # 交易完成
        @order.complete
      when 'TRADE_CLOSED'
        # 交易被关闭
        @order.cancel
      end

      render :text => 'success' # 成功接收消息后，需要返回纯文本的 ‘success’，否则支付宝会定时重发消息，最多重试7次。 
    else
      render :text => 'error'
    end
  end

  private

  def order_param
    params.require(:order).permit(:quantity)
  end
end