GoRules.ZenEngine

Open-source Business Rules Engine for .NET. Execute JSON Decision Models (JDM) with native performance powered by Rust.

Installation

dotnet add package GoRules.ZenEngine

Quick Start

using GoRules.ZenEngine;

// Create an engine and evaluate
var engine = new ZenEngine(loader: null, customNode: null);
var decision = engine.CreateDecision(new JsonBuffer(File.ReadAllBytes("my-decision.json")));
var context = new JsonBuffer("""{"input": 42}""");
var response = await decision.Evaluate(context, null);
Console.WriteLine(response.result);

Features

Decision Tables - Rule tables with first/collect hit policies
Expression Language - Built-in ZEN expression language with functions like sum(), filter(), map()
Custom Nodes - Extend the engine with custom node handlers
Tracing - Full execution trace for debugging and auditing
Cross-platform - Native libraries for Windows (x64), macOS (x64/ARM), Linux (x64/ARM)

Tracing

Enable tracing to inspect the execution of each node:

var options = new ZenEvaluateOptions(maxDepth: null, trace: true);
var decided = await decision.Evaluate(context, options);

foreach (var (nodeId, trace) in decided.trace!)
{
    Console.WriteLine($"{trace.name}: {trace.output}");
}

Expression Evaluation

Evaluate expressions directly without a decision file:

// One-off evaluation
var result = ZenUniffiMethods.EvaluateExpression(
    "sum(items) * multiplier",
    new JsonBuffer("{\"items\": [10, 20, 30], \"multiplier\": 2}")
);

// Compiled expression (reusable, better performance)
var expr = ZenExpression.Compile("a + b * 2");
var output = expr.Evaluate(new JsonBuffer("{\"a\": 1, \"b\": 10}"));
Console.WriteLine($"output: {output}");
expr.Dispose();

Custom Nodes

Extend the engine with custom logic:


using var myEngine = new ZenEngine(loader: new FileLoader(), customNode: new MyCustomNode());
var myResponse = await myEngine.Evaluate("custom.json", context, options);
Console.WriteLine(myResponse.result); 

// Custom node handler
class MyCustomNode : ZenCustomNodeCallback
{
    public Task<ZenEngineHandlerResponse> Handle(ZenEngineHandlerRequest request) =>
        Task.FromResult(new ZenEngineHandlerResponse(
            output: new JsonBuffer("""{"result": "custom"}"""),
            traceData: null
        ));
}

// Implement a loader to resolve decision files
class FileLoader : ZenDecisionLoaderCallback
{
    public Task<JsonBuffer?> Load(string key) =>
        Task.FromResult<JsonBuffer?>(new JsonBuffer(File.ReadAllBytes(key)));
}

README.md