ServiceBusTriggerBackoffBinding.cs

using System.Collections.Concurrent;

namespace ServiceBus.Extensions.Bindings.MessageActions;

/// <summary>
/// Runs on every request and passes the function context (e.g. Http request and host configuration) to a value provider.
/// </summary>
public class MessageActionsExtendedBinding : IBinding
{
    private static ConcurrentDictionary<string, string> _functionNameWithQueueOrTopicNameCache = new ConcurrentDictionary<string, string>();

    private static string GetQueueOrTopicNameFromServicebusTrigger(string functionName)
    {
        if (_functionNameWithQueueOrTopicNameCache.TryGetValue(functionName, out var queueOrTopicName))
        {
            return queueOrTopicName;
        }

        var funcMethodInfo = AppDomain.CurrentDomain
            .GetAssemblies()
            .SelectMany(x => x.GetTypes())
            .SelectMany(t => t.GetMethods())
            .FirstOrDefault(m => m.GetCustomAttributes<FunctionNameAttribute>(false).Any(a => a.Name == functionName));

        if (funcMethodInfo == null)
        {
            throw new InvalidOperationException("Could not match functionName with a trigger.");
        }

        queueOrTopicName = funcMethodInfo 
                .GetParameters()
                .SelectMany(p => p.GetCustomAttributes<ServiceBusTriggerAttribute>(false))
                .Select(a => a.QueueName ?? a.TopicName)
                .FirstOrDefault(q => !string.IsNullOrWhiteSpace(q));

        if (string.IsNullOrEmpty(queueOrTopicName))
        {
            throw new InvalidOperationException("Could not find a servicebustrigger for the function.");
        }

        _functionNameWithQueueOrTopicNameCache.TryAdd(functionName, queueOrTopicName);

        return queueOrTopicName;
    }

    public Task<IValueProvider> BindAsync(BindingContext context)
    {
        var queueOrTopicName = GetQueueOrTopicNameFromServicebusTrigger(context.ValueContext.FunctionContext.MethodName);

        // Get the HTTP request
        var actions = context.BindingData["MessageActions"] as ServiceBusMessageActions;
        var client = context.BindingData["Client"] as ServiceBusClient;

        return Task.FromResult((IValueProvider)new MessageActionsExtendedValueProvider(actions, client, queueOrTopicName));
    }

    public bool FromAttribute => true;

    public Task<IValueProvider> BindAsync(object value, ValueBindingContext context)
    {
        return null;
    }

    public ParameterDescriptor ToParameterDescriptor() => new ParameterDescriptor();
}