using System;

namespace FlowScope.Resources
{
    public sealed class ResourceHandle<T> : IResourceHandle<T> where T : class
    {
        private readonly ResourceEntry _entry;
        private readonly Action<string, object> _release;
        private T _asset;

        internal ResourceHandle(ResourceEntry entry)
        {
            _entry = entry ?? throw new ArgumentNullException(nameof(entry));
            Key = entry.Key;
            _asset = (T)entry.Asset;
        }

        public ResourceHandle(string key, T asset, Action<string, object> release)
        {
            Key = string.IsNullOrWhiteSpace(key)
                ? throw new ArgumentException("Resource key is required.", nameof(key))
                : key;
            _asset = asset ?? throw new ArgumentNullException(nameof(asset));
            _release = release ?? throw new ArgumentNullException(nameof(release));
        }

        public string Key { get; }
        public T Asset => IsDisposed ? null : _asset;
        public bool IsDisposed { get; private set; }

        public void Dispose()
        {
            if (IsDisposed)
            {
                return;
            }

            IsDisposed = true;
            var asset = _asset;
            _asset = null;

            if (_entry != null)
            {
                _entry.ReleaseHandle();
                return;
            }

            _release(Key, asset);
        }
    }
}