using System;

namespace FlowScope.Resources
{
    internal sealed class ResourceEntry
    {
        private readonly Action<string, Type, object> _release;
        private int _referenceCount;
        private bool _released;

        public ResourceEntry(string key, object asset, Action<string, object> release)
            : this(key, asset?.GetType(), asset, (_, _, releasedAsset) => release(key, releasedAsset))
        {
        }

        public ResourceEntry(string key, Type assetType, object asset, Action<string, Type, object> release)
        {
            Key = string.IsNullOrWhiteSpace(key)
                ? throw new ArgumentException("Resource key is required.", nameof(key))
                : key;
            AssetType = assetType ?? throw new ArgumentNullException(nameof(assetType));
            Asset = asset ?? throw new ArgumentNullException(nameof(asset));
            _release = release ?? throw new ArgumentNullException(nameof(release));
        }

        public string Key { get; }
        public Type AssetType { get; }
        public object Asset { get; private set; }
        public int ReferenceCount => _referenceCount;

        public ResourceHandle<T> CreateHandle<T>() where T : class
        {
            if (_released)
            {
                throw new ObjectDisposedException(nameof(ResourceEntry));
            }

            _referenceCount++;
            return new ResourceHandle<T>(this);
        }

        public void ReleaseHandle()
        {
            if (_released)
            {
                return;
            }

            _referenceCount--;
            if (_referenceCount > 0)
            {
                return;
            }

            _released = true;
            var asset = Asset;
            Asset = null;
            _release(Key, AssetType, asset);
        }

        public void ReleaseWithoutHandle()
        {
            if (_released)
            {
                return;
            }

            _released = true;
            var asset = Asset;
            Asset = null;
            _release(Key, AssetType, asset);
        }
    }
}