一个简单的规则引擎例子
本例使用的规则引擎包是RulesEngine，关于RulesEngine的介绍，请自行补充，这里只是一个极简单使用场景。
例子大体就是用户有一些优惠券，系统会根据用户订单情况，筛选可以使用的优惠券供用户选择，用户选择后会计算出优惠后金额。
代码相对简单，就不一一介绍了，奉上service中的代码：
using Microsoft.Extensions.Logging;
using RulesEngine.Extensions;
using RulesEngine.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
namespace RulesEngineSample.Services
{
public class CouponService : ICouponService
{
private readonly ILogger<CouponService> _logger;
private readonly List<Coupon> _userCoupons;
private readonly Order _order;
private readonly User _user;
public CouponService(ILogger<CouponService> logger)
{
_logger = logger;
//假装用户用的优惠券
_userCoupons = new List<Coupon>() {
new Coupon
{
ID = 1,
Code="YH01",
Name = "满500减20",
BeginTime = DateTime.Parse("2021-01-01"),
EndTime = DateTime.Parse("2021-06-01"),
Expression = "input1.Details.Sum(s => s.Price * Convert.ToDecimal(s.Quantity))>= 500",
Symbol="-",
Number=20
},
new Coupon
{
ID = 2,
Code="YH02",
Name = "新人5元券",
BeginTime = DateTime.Parse("2021-01-01"),
EndTime = DateTime.Parse("2021-06-01"),
Expression = "input1.Details.Count>0",
Symbol="-",
Number=5
},
new Coupon
{
ID = 3,
Code="YH03",
Name = "商品C五折",
BeginTime = DateTime.Parse("2021-01-01"),
EndTime = DateTime.Parse("2021-06-01"),
Expression = "input1.Details.Where(s=>s.GoodsID==\"SP0000003\").Count()>0",
Symbol="*",
Number=0.5f,
GoodsID="SP0000003"
},
};
//假装当前用户的订单
_order = new Order
{
OrderNo = "NO00000001",
OrderTime = DateTime.Now,
Details = new List<Detail>
{
new Detail{ GoodsID="SP0000001", Name="商品A", Price=12.5m, Quantity=3},
new Detail{ GoodsID="SP0000002", Name="商品B", Price=100m, Quantity=4},
new Detail{ GoodsID="SP0000003", Name="商品C", Price=22.3m, Quantity=5},
}
};
_user = new User { ID = 1, UserName = "zhangsan" };
}
/// <summary>
/// 适配优惠券
/// </summary>
/// <returns></returns>
public async Task<string> SelectCouponAsync()
{
var workRules = new RulesEngine.Models.WorkflowRules();
workRules.WorkflowName = "优惠券";
var rules = new List<Rule>();
foreach (var coupon in _userCoupons.Where(s => s.BeginTime < DateTime.Now && s.EndTime > DateTime.Now))
{
var rule = new Rule
{
RuleName = coupon.Name,
SuccessEvent = coupon.Code,
ErrorMessage = "规则应用失败",
ErrorType = ErrorType.Error,
RuleExpressionType = RuleExpressionType.LambdaExpression,
Expression = coupon.Expression
};
rules.Add(rule);
}
workRules.Rules = rules;
var rulesEngine = new RulesEngine.RulesEngine(new WorkflowRules[] { workRules }, _logger, new ReSettings());
var ruleResults = await rulesEngine.ExecuteAllRulesAsync("优惠券", _order, _user);
// var valueCoupons = new List<string>();
//处理结果
var discountCoupons = new StringBuilder();
foreach (var ruleResult in ruleResults)
{
if (ruleResult.IsSuccess)
{
discountCoupons.AppendLine($"可以使用的优惠券 “{_userCoupons.SingleOrDefault(s => s.Code == ruleResult.Rule.SuccessEvent)?.Name}”, Code是：{ruleResult.Rule.SuccessEvent}");
//valueCoupons.Add(ruleResult.Rule.SuccessEvent);
}
}
//resultList.OnSuccess((eventName) =>
//{
// discountOffered += $"可以使用的优惠券“{userCoupons.SingleOrDefault(s => s.Code == eventName)?.Name}”,Code是：{eventName} ";
//});
ruleResults.OnFail(() =>
{
discountCoupons.AppendLine("您没有适合的优惠券！");
});
return discountCoupons.ToString();
}
/// <summary>
/// 计算订单支付总额
/// </summary>
/// <param name="code"></param>
/// <returns></returns>
public string GetOrderAmount(string code)
{
var selectCoupon = _userCoupons.SingleOrDefault(s => s.Code == code);
var orderAmount = 0m;
switch (selectCoupon.Symbol)
{
case "-":
orderAmount = _order.Details.Sum(s => s.Price * Convert.ToDecimal(s.Quantity)) - Convert.ToDecimal(selectCoupon.Number);
break;
case "*":
if (!string.IsNullOrWhiteSpace(selectCoupon.GoodsID))
{
orderAmount = _order.Details.Sum(s => s.Price * Convert.ToDecimal(s.Quantity));
var detail = _order.Details.SingleOrDefault(s => s.GoodsID == selectCoupon.GoodsID);
if (detail != null)
{
orderAmount -= detail.Price * Convert.ToDecimal(detail.Quantity) * Convert.ToDecimal(1 - selectCoupon.Number);
}
}
else
{
orderAmount = _order.Details.Sum(s => s.Price * Convert.ToDecimal(s.Quantity)) * Convert.ToDecimal(selectCoupon.Number);
}
break;
}
return $"订单总金额：{_order.Details.Sum(s => s.Price * Convert.ToDecimal(s.Quantity)) }，优惠后请支付：{orderAmount}";
}
}
public class Coupon
{
public int ID { get; set; }
public string Code { get; set; }
public string Name { get; set; }
public DateTime BeginTime { get; set; }
public DateTime EndTime { get; set; }
public string Expression { get; set; }
public string Symbol { get; set; }
public float Number { get; set; }
public string GoodsID { get; set; }
}
public class User
{
public int ID { get; set; }
public string UserName { get; set; }
}
public class Order
{
public string OrderNo { get; set; }
public DateTime OrderTime { get; set; }
public List<Detail> Details { get; set; }
}
public class Detail
{
public string GoodsID { get; set; }
public float Quantity { get; set; }
public decimal Price { get; set; }
public string Name { get; set; }
}
}
api /selectcoupon是查询可使用的优惠券
/getamount 按优惠券code，计算本次订单的应付金额：
优惠券YH01
优惠券YH02
优惠券YH03
