DatabaseQueueCollection.cs

using System.Collections.Generic;
using System.Threading.Tasks;
using Waher.Runtime.Inventory;
 
namespace Waher.Persistence.Queues
{
    public class DatabaseQueueCollection : IPersistedQueueCollection
    {
        private static readonly Dictionary<string, IPersistedQueue> queues = new Dictionary<string, IPersistedQueue>();
 
        public DatabaseQueueCollection()
        {
        }
 
        public Grade Supports(IDatabaseProvider Provider)
        {
            return Grade.Barely;    // Slow compared to more efficient queues, so it should only be used if no other is found.
        }
 
        public Task<IPersistedQueue> GetQueue(IDatabaseProvider Provider, string QueueName, 
            bool CanBeNull)
        {
            lock (queues)
            {
                if (!queues.TryGetValue(QueueName, out IPersistedQueue Result))
                {
                    Result = new DatabaseQueue(QueueName);
                    queues[QueueName] = Result;
                }
 
                return Task.FromResult(Result);
            }
        }
 
        public Task<string[]> GetQueues(IDatabaseProvider Provider)
        {
            lock (queues)
            {
                string[] Result = new string[queues.Count];
                queues.Keys.CopyTo(Result, 0);
                return Task.FromResult(Result);
            }
        }
    }
}