Rework mod enumeration / caching.

- Replaced ModMetadata.AllMods with Game.Mods.
- Store / reference mod Manifest instead of ModMetadata.
- Removes engine dependency on ModContent class.

OpenRA.Game/InstalledMods.cs

@@ -0,0 +1,117 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2016 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using OpenRA.FileSystem;
+using OpenRA.Primitives;
+
+namespace OpenRA
+{
+	public class InstalledMods : IReadOnlyDictionary<string, Manifest>
+	{
+		readonly Dictionary<string, Manifest> mods;
+
+		public InstalledMods()
+		{
+			mods = GetInstalledMods();
+		}
+
+		static IEnumerable<Pair<string, string>> GetCandidateMods()
+		{
+			// Get mods that are in the game folder.
+			var basePath = Platform.ResolvePath(Path.Combine(".", "mods"));
+			var mods = Directory.GetDirectories(basePath)
+				.Select(x => Pair.New(x.Substring(basePath.Length + 1), x))
+				.ToList();
+
+			foreach (var m in Directory.GetFiles(basePath, "*.oramod"))
+				mods.Add(Pair.New(Path.GetFileNameWithoutExtension(m), m));
+
+			// Get mods that are in the support folder.
+			var supportPath = Platform.ResolvePath(Path.Combine("^", "mods"));
+			if (!Directory.Exists(supportPath))
+				return mods;
+
+			foreach (var pair in Directory.GetDirectories(supportPath).ToDictionary(x => x.Substring(supportPath.Length + 1)))
+				mods.Add(Pair.New(pair.Key, pair.Value));
+
+			foreach (var m in Directory.GetFiles(supportPath, "*.oramod"))
+				mods.Add(Pair.New(Path.GetFileNameWithoutExtension(m), m));
+
+			return mods;
+		}
+
+		static Manifest LoadMod(string id, string path)
+		{
+			IReadOnlyPackage package = null;
+			try
+			{
+				if (Directory.Exists(path))
+					package = new Folder(path);
+				else
+				{
+					try
+					{
+						using (var fileStream = File.OpenRead(path))
+							package = new ZipFile(fileStream, path);
+					}
+					catch
+					{
+						throw new InvalidDataException(path + " is not a valid mod package");
+					}
+				}
+
+				if (!package.Contains("mod.yaml"))
+					throw new InvalidDataException(path + " is not a valid mod package");
+
+				// Mods in the support directory and oramod packages (which are listed later
+				// in the CandidateMods list) override mods in the main install.
+				return new Manifest(id, package);
+			}
+			catch (Exception)
+			{
+				if (package != null)
+					package.Dispose();
+
+				return null;
+			}
+		}
+
+		static Dictionary<string, Manifest> GetInstalledMods()
+		{
+			var ret = new Dictionary<string, Manifest>();
+			foreach (var pair in GetCandidateMods())
+			{
+				var mod = LoadMod(pair.First, pair.Second);
+
+				// Mods in the support directory and oramod packages (which are listed later
+				// in the CandidateMods list) override mods in the main install.
+				if (mod != null)
+					ret[pair.First] = mod;
+			}
+
+			return ret;
+		}
+
+		public Manifest this[string key] { get { return mods[key]; } }
+		public int Count { get { return mods.Count; } }
+		public ICollection<string> Keys { get { return mods.Keys; } }
+		public ICollection<Manifest> Values { get { return mods.Values; } }
+		public bool ContainsKey(string key) { return mods.ContainsKey(key); }
+		public IEnumerator<KeyValuePair<string, Manifest>> GetEnumerator() { return mods.GetEnumerator(); }
+		public bool TryGetValue(string key, out Manifest value) { return mods.TryGetValue(key, out value); }
+		IEnumerator IEnumerable.GetEnumerator() { return mods.GetEnumerator(); }
+	}
+}