[MAF的Agent管道详解-07]利用AIAgent中间件构建Agent管道

1. DelegatingAIAgent

作为AIAgent中间件的一个DelegatingAIAgent类型定义如下。这是一个派生于AIAgent的抽象类，它的核心成员是一个InnerAgent属性，表示被委托的AIAgent对象。我们可以定义DelegatingAIAgent的派生类，通过重写其属性成员和方法来实现对InnerAgent的功能扩展和增强。通过不断地嵌套多个DelegatingAIAgent，我们就可以构建出一个类似于中间件的管道来对AIAgent进行扩展和增强。

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public abstract class DelegatingAIAgent : AIAgent
{
    protected AIAgent InnerAgent { get; }
    protected override string? IdCore => InnerAgent.Id;
    public override string? Name => InnerAgent.Name;
    public override string? Description => InnerAgent.Description;
    protected DelegatingAIAgent(AIAgent innerAgent) =>InnerAgent = innerAgent;

    public override object? GetService(Type serviceType, object? serviceKey = null)
    {
        if (serviceKey != null || !serviceType.IsInstanceOfType(this))
        {
            return InnerAgent.GetService(serviceType, serviceKey);
        }
        return this;
    }

    protected override ValueTask<AgentSession> CreateSessionCoreAsync(
        CancellationToken cancellationToken = default)
    =>InnerAgent.CreateSessionAsync(cancellationToken);

    protected override ValueTask<JsonElement> SerializeSessionCoreAsync(
        AgentSession session, 
        JsonSerializerOptions? jsonSerializerOptions = null, 
        CancellationToken cancellationToken = default)
    =>InnerAgent.SerializeSessionAsync(session, jsonSerializerOptions, cancellationToken);

    protected override ValueTask<AgentSession> DeserializeSessionCoreAsync(
        JsonElement serializedState, 
        JsonSerializerOptions? jsonSerializerOptions = null, 
        CancellationToken cancellationToken = default)
    =>InnerAgent.DeserializeSessionAsync(serializedState, jsonSerializerOptions, cancellationToken);

    protected override Task<AgentResponse> RunCoreAsync(
        IEnumerable<ChatMessage> messages, 
        AgentSession? session = null, 
        AgentRunOptions? options = null, 
        CancellationToken cancellationToken = default)
    => InnerAgent.RunAsync(messages, session, options, cancellationToken);

    protected override IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
        IEnumerable<ChatMessage> messages, 
        AgentSession? session = null, 
        AgentRunOptions? options = null, 
        CancellationToken cancellationToken = default)
    => InnerAgent.RunStreamingAsync(messages, session, options, cancellationToken);
}

多个DelegatingAIAgent和最终的被委托的AIAgent按照顺序组成了一个AIAgent管道，这个管道的结构如下所示。

从定义可以看出，以DelegatingAIAgent形式定义的AIAgent中间件并非专属于ChatClientAgent，理论上它可以用于任何类型的AIAgent对象。所以系统按照ChatClientBuilder一样的模式定义了AIAgentBuilder。我们可以针对一个具体的AIAgent或者创建AIAgent的工厂来构建一个AIAgentBuilder对象，然后通过调用AIAgentBuilder的一系列重载的Use方法来注册不同的AIAgent中间件，最后调用Build方法来构建出一个代表整个管道的AIAgent对象。

2. AIAgentBuilder

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public sealed class AIAgentBuilder
{	
    public AIAgentBuilder(AIAgent innerAgent);
    public AIAgentBuilder(Func<IServiceProvider, AIAgent> innerAgentFactory);

    public AIAgent Build(IServiceProvider? services = null);

    public AIAgentBuilder Use(Func<AIAgent, AIAgent> agentFactory);
    public AIAgentBuilder Use(Func<AIAgent, IServiceProvider, AIAgent> agentFactory);
    public AIAgentBuilder Use(
        Func<IEnumerable<ChatMessage>, AgentSession?, AgentRunOptions?, Func<IEnumerable<ChatMessage>, AgentSession?, AgentRunOptions?, CancellationToken, Task>, CancellationToken, Task> sharedFunc);

    public AIAgentBuilder Use(
        Func<IEnumerable<ChatMessage>, AgentSession?, AgentRunOptions?, AIAgent, CancellationToken, Task<AgentResponse>>? runFunc, 
        Func<IEnumerable<ChatMessage>, AgentSession?, AgentRunOptions?, AIAgent, CancellationToken, IAsyncEnumerable<AgentResponseUpdate>>? runStreamingFunc);
}