using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Firebird2D.EventPipelines
{
    public class EventBus
    {
        private Dictionary<FirebirdEvent, I_Pipeline> pipelines = new();

        private Dictionary<FirebirdEvent, List<Action<I_Pipeline>>> pendingHooks = new();

        public void OnPipelineExists<T>(Action<I_Pipeline> callback, FirebirdEvent type)
        {
            if (callback == null) throw new ArgumentNullException(nameof(callback));

            if (!pendingHooks.TryGetValue(type, out var hookList))
            {
                hookList = new();
                pendingHooks[type] = hookList;
            }

            hookList.Add(callback);
        }

        public I_Pipeline GetOrBuildPipeline(FirebirdEvent type, Type argsType, object master)
        {
            if (pipelines.TryGetValue(type, out var pipeline)) return pipeline;

            var genericPipelineType = typeof(Pipeline<>).MakeGenericType(argsType);
            var pipelineInstance = (I_Pipeline)Activator.CreateInstance(genericPipelineType, master)!;
            pipelines[type] = pipelineInstance;
            return pipelineInstance;
        }

        public I_Pipeline? GetPipeline(FirebirdEvent type, Type argsType)
        {
            if (!pipelines.TryGetValue(type, out var pipeline)) return null;
            return pipeline;
        }

        public void DestroyPipeline(FirebirdEvent type, object master)
        {
            if (!pipelines.ContainsKey(type)) return;
            if (!pipelines[type].PipelineMaster.Equals(master)) throw new InvalidDataException("Only the pipeline master is allowed to delete this pipeline.");
            pipelines.Remove(type);
        }
    }
}