Rename interface

- Fix wrong inheritance in ArchiveModelManager
- Add license headers

osu.Game/Database/IModelDownloader.cs

@@ -0,0 +1,48 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Game.Online.API;
+using System;
+
+namespace osu.Game.Database
+{
+    public interface IModelDownloader<TModel> : IModelManager<TModel>
+        where TModel : class
+    {
+        /// <summary>
+        /// Fired when a <see cref="TModel"/> download begins.
+        /// </summary>
+        event Action<ArchiveDownloadModelRequest<TModel>> DownloadBegan;
+
+        /// <summary>
+        /// Fired when a <see cref="TModel"/> download is interrupted, either due to user cancellation or failure.
+        /// </summary>
+        event Action<ArchiveDownloadModelRequest<TModel>> DownloadFailed;
+
+        bool IsAvailableLocally(TModel model);
+
+        /// <summary>
+        /// Downloads a <see cref="TModel"/>.
+        /// This will post notifications tracking progress.
+        /// </summary>
+        /// <param name="model">The <see cref="TModel"/> to be downloaded.</param>
+        /// <returns>Whether downloading can happen.</returns>
+        bool Download(TModel model);
+
+        /// <summary>
+        /// Downloads a <see cref="TModel"/> with optional parameters for the download request.
+        /// This will post notifications tracking progress.
+        /// </summary>
+        /// <param name="model">The <see cref="TModel"/> to be downloaded.</param>
+        /// <param name="extra">Optional parameters to be used for creating the download request.</param>
+        /// <returns>Whether downloading can happen.</returns>
+        bool Download(TModel model, params object[] extra);
+
+        /// <summary>
+        /// Checks whether a given <see cref="TModel"/> is available in the local store already.
+        /// </summary>
+        /// <param name="model">The <see cref="TModel"/> whose existence needs to be checked.</param>
+        /// <returns>Whether the <see cref="TModel"/> exists locally.</returns>
+        ArchiveDownloadModelRequest<TModel> GetExistingDownload(TModel model);
+    }
+}