restructured OsuLegacyDecoder into LegacyDecoder

Beatmap works, Storyboard not...

osu.Game/Beatmaps/Formats/LegacyDecoder.cs

@@ -0,0 +1,182 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using osu.Game.Beatmaps.Legacy;
+using osu.Game.Storyboards;
+
+namespace osu.Game.Beatmaps.Formats
+{
+    public abstract class LegacyDecoder : BeatmapDecoder
+    {
+        public static void Register()
+        {
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v14");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v13");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v12");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v11");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v10");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v9");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v8");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v7");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v6");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v5");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v4");
+            AddDecoder<LegacyBeatmapDecoder>(@"osu file format v3");
+            // TODO: differences between versions
+        }
+
+        protected Beatmap beatmap;
+        protected Storyboard storyboard;
+
+        protected int beatmapVersion;
+        protected readonly Dictionary<string, string> variables = new Dictionary<string, string>();
+
+        public override Beatmap DecodeBeatmap(StreamReader stream) => new LegacyBeatmap(base.DecodeBeatmap(stream));
+
+        protected override Beatmap ParseBeatmap(StreamReader stream) => new LegacyBeatmap(base.ParseBeatmap(stream));
+
+        protected override void ParseBeatmap(StreamReader stream, Beatmap beatmap)
+        {
+            if (stream == null)
+                throw new ArgumentNullException(nameof(stream));
+            if (beatmap == null)
+                throw new ArgumentNullException(nameof(beatmap));
+
+            this.beatmap = beatmap;
+            this.beatmap.BeatmapInfo.BeatmapVersion = beatmapVersion;
+
+            ParseContent(stream);
+
+            foreach (var hitObject in this.beatmap.HitObjects)
+                hitObject.ApplyDefaults(this.beatmap.ControlPointInfo, this.beatmap.BeatmapInfo.BaseDifficulty);
+        }
+
+        protected override void ParseStoryboard(StreamReader stream, Storyboard storyboard)
+        {
+            if (stream == null)
+                throw new ArgumentNullException(nameof(stream));
+            if (storyboard == null)
+                throw new ArgumentNullException(nameof(storyboard));
+
+            this.storyboard = storyboard;
+
+            ParseContent(stream);
+        }
+
+        protected void ParseContent(StreamReader stream)
+        {
+            Section section = Section.None;
+
+            string line;
+            while ((line = stream.ReadLine()) != null)
+            {
+                if (string.IsNullOrWhiteSpace(line))
+                    continue;
+
+                if (line.StartsWith("//"))
+                    continue;
+
+                if (line.StartsWith(@"osu file format v"))
+                {
+                    beatmap.BeatmapInfo.BeatmapVersion = int.Parse(line.Substring(17));
+                    continue;
+                }
+
+                if (line.StartsWith(@"[") && line.EndsWith(@"]"))
+                {
+                    if (!Enum.TryParse(line.Substring(1, line.Length - 2), out section))
+                        throw new InvalidDataException($@"Unknown osu section {line}");
+                    continue;
+                }
+
+                processSection(section, line);
+            }
+        }
+
+        protected abstract void processSection(Section section, string line);
+
+        /// <summary>
+        /// Decodes any beatmap variables present in a line into their real values.
+        /// </summary>
+        /// <param name="line">The line which may contains variables.</param>
+        protected void decodeVariables(ref string line)
+        {
+            while (line.IndexOf('$') >= 0)
+            {
+                string origLine = line;
+                string[] split = line.Split(',');
+                for (int i = 0; i < split.Length; i++)
+                {
+                    var item = split[i];
+                    if (item.StartsWith("$") && variables.ContainsKey(item))
+                        split[i] = variables[item];
+                }
+
+                line = string.Join(",", split);
+                if (line == origLine)
+                    break;
+            }
+        }
+
+        protected enum Section
+        {
+            None,
+            General,
+            Editor,
+            Metadata,
+            Difficulty,
+            Events,
+            TimingPoints,
+            Colours,
+            HitObjects,
+            Variables,
+        }
+
+        internal enum LegacySampleBank
+        {
+            None = 0,
+            Normal = 1,
+            Soft = 2,
+            Drum = 3
+        }
+
+        internal enum EventType
+        {
+            Background = 0,
+            Video = 1,
+            Break = 2,
+            Colour = 3,
+            Sprite = 4,
+            Sample = 5,
+            Animation = 6
+        }
+
+        internal enum LegacyOrigins
+        {
+            TopLeft,
+            Centre,
+            CentreLeft,
+            TopRight,
+            BottomCentre,
+            TopCentre,
+            Custom,
+            CentreRight,
+            BottomLeft,
+            BottomRight
+        };
+
+        internal enum StoryLayer
+        {
+            Background = 0,
+            Fail = 1,
+            Pass = 2,
+            Foreground = 3
+        }
+    }
+}