osu/osu.Game/IO/WrappedStorage.cs

// 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 System;
using System.Collections.Generic;
using System.IO;
using osu.Framework.Platform;

namespace osu.Game.IO
{
    /// <summary>
    /// A storage which wraps another storage and delegates implementation, potentially mutating the lookup path.
    /// </summary>
    public class WrappedStorage : Storage
    {
        protected Storage UnderlyingStorage { get; private set; }

        private readonly string subPath;

        public WrappedStorage(Storage underlyingStorage, string subPath = null)
            : base(string.Empty)
        {
            ChangeTargetStorage(underlyingStorage);

            this.subPath = subPath;
        }

        protected virtual string MutatePath(string path)
        {
            if (path == null)
                return null;

            return !string.IsNullOrEmpty(subPath) ? Path.Combine(subPath, path) : path;
        }

        protected virtual void ChangeTargetStorage(Storage newStorage)
        {
            UnderlyingStorage = newStorage;
        }

        public override string GetFullPath(string path, bool createIfNotExisting = false) =>
            UnderlyingStorage.GetFullPath(MutatePath(path), createIfNotExisting);

        public override bool Exists(string path) =>
            UnderlyingStorage.Exists(MutatePath(path));

        public override bool ExistsDirectory(string path) =>
            UnderlyingStorage.ExistsDirectory(MutatePath(path));

        public override void DeleteDirectory(string path) =>
            UnderlyingStorage.DeleteDirectory(MutatePath(path));

        public override void Delete(string path) =>
            UnderlyingStorage.Delete(MutatePath(path));

        public override IEnumerable<string> GetDirectories(string path) =>
            ToLocalRelative(UnderlyingStorage.GetDirectories(MutatePath(path)));

        public IEnumerable<string> ToLocalRelative(IEnumerable<string> paths)
        {
            string localRoot = GetFullPath(string.Empty);

            foreach (string path in paths)
                yield return Path.GetRelativePath(localRoot, UnderlyingStorage.GetFullPath(path));
        }

        public override IEnumerable<string> GetFiles(string path, string pattern = "*") =>
            ToLocalRelative(UnderlyingStorage.GetFiles(MutatePath(path), pattern));

        public override Stream GetStream(string path, FileAccess access = FileAccess.Read, FileMode mode = FileMode.OpenOrCreate) =>
            UnderlyingStorage.GetStream(MutatePath(path), access, mode);

        public override void Move(string from, string to) => UnderlyingStorage.Move(MutatePath(from), MutatePath(to));

        public override bool OpenFileExternally(string filename) => UnderlyingStorage.OpenFileExternally(MutatePath(filename));

        public override bool PresentFileExternally(string filename) => UnderlyingStorage.PresentFileExternally(MutatePath(filename));

        public override Storage GetStorageForDirectory(string path)
        {
            if (string.IsNullOrEmpty(path))
                throw new ArgumentException("Must be non-null and not empty string", nameof(path));

            if (!path.EndsWith(Path.DirectorySeparatorChar))
                path += Path.DirectorySeparatorChar;

            // create non-existing path.
            GetFullPath(path, true);

            return new WrappedStorage(this, path);
        }
    }
}