using RadicadeServer.Utils;

namespace RadicadeServer.CDN
{
	/// <summary>
	/// What may be read out of the CDN storage directory and handed to a client, and which file
	/// a requested name actually is.
	///
	/// Two rules live here because every route that serves a stored blob needs both, and a route
	/// that re-implements them gets one of them wrong:
	///
	/// - A request is a single bare file name in that one directory. A name carrying a separator
	///   or <c>..</c> would let a URL read outside it, and a name ending in the admin upload's
	///   <c>.uploading</c> suffix is a half-imported bundle: it must answer as if it does not
	///   exist rather than serve a truncated file, which the client would then fail to load with
	///   no way to tell why.
	/// - A bundle is asked for under two spellings. The subroom's <c>UnityAssetId</c> is stored
	///   both bare and with the <c>.assetbundle</c> suffix an import appends, so a name resolves
	///   to the exact file first and to <c>&lt;name&gt;.assetbundle</c> second.
	/// </summary>
	internal static class CdnStorageNames
	{
		internal static bool IsServable(string? name) =>
			!string.IsNullOrEmpty(name)
			&& name != "."
			&& !AdminUtils.IsUploadPart(name)
			&& !name.Contains('/')
			&& !name.Contains('\\')
			&& !name.Contains("..")
			&& name.IndexOf('\0') < 0;

		/// <summary>
		/// The stored file a requested name is, or null when nothing by either spelling exists.
		/// A name this server must never serve answers null too, so a route that only checks the
		/// result is still safe.
		/// </summary>
		internal static string? Resolve(string? name)
		{
			if (!IsServable(name)) return null;

			if (System.IO.File.Exists(Path.Join(DBConfig.CDNStorage, name))) return name;

			var withExtension = name + ".assetbundle";
			return System.IO.File.Exists(Path.Join(DBConfig.CDNStorage, withExtension)) ? withExtension : null;
		}
	}
}