using System;
using System.IO;

namespace Umbraco.Core.IO.MediaPathSchemes
{
    /// <summary>
    /// Implements a unique directory media path scheme.
    /// </summary>
    /// <remarks>
    /// <para>This scheme provides deterministic short paths, with potential collisions.</para>
    /// </remarks>
    public class UniqueMediaPathScheme : IMediaPathScheme
    {
        private const int DirectoryLength = 8;

        /// <inheritdoc />
        public string GetFilePath(IMediaFileSystem fileSystem, Guid itemGuid, Guid propertyGuid, string filename, string previous = null)
        {
            var combinedGuid = GuidUtils.Combine(itemGuid, propertyGuid);
            var directory = GuidUtils.ToBase32String(combinedGuid, DirectoryLength);

            return Path.Combine(directory, filename).Replace('\\', '/');
        }

        /// <inheritdoc />
        /// <remarks>
        /// <para>Returning null so that <see cref="MediaFileSystem.DeleteMediaFiles"/> does *not*
        /// delete any directory. This is because the above shortening of the Guid to 8 chars
        /// means we're increasing the risk of collision, and we don't want to delete files
        /// belonging to other media items.</para>
        /// <para>And, at the moment, we cannot delete directory "only if it is empty" because of
        /// race conditions. We'd need to implement locks in <see cref="MediaFileSystem"/> for
        /// this.</para>
        /// </remarks>
        public string GetDeleteDirectory(IMediaFileSystem fileSystem, string filepath) => null;
    }
}