From 196594e1df8dbf9a988600367e2401cbfaa3bdb4 Mon Sep 17 00:00:00 2001
From: YoshiRulz <OSSYoshiRulz@gmail.com>
Date: Mon, 12 Aug 2019 20:03:40 +1000
Subject: [PATCH] Port TryMakeRelative and IsSubfolder

---
 BizHawk.Client.Common/PathManager.cs | 36 +++++++++++++---------------
 1 file changed, 17 insertions(+), 19 deletions(-)

diff --git a/BizHawk.Client.Common/PathManager.cs b/BizHawk.Client.Common/PathManager.cs
index 14af64ccbb..66ba78f4d2 100644
--- a/BizHawk.Client.Common/PathManager.cs
+++ b/BizHawk.Client.Common/PathManager.cs
@@ -3,6 +3,7 @@ using System.Linq;
 using System.IO;
 using System.Reflection;
 
+using BizHawk.Common;
 using BizHawk.Common.StringExtensions;
 using BizHawk.Emulation.Common;
 using BizHawk.Emulation.Common.IEmulatorExtensions;
@@ -403,16 +404,14 @@ namespace BizHawk.Client.Common
 		/// </summary>
 		public static string TryMakeRelative(string absolutePath, string system = null)
 		{
-			var parentPath = string.IsNullOrWhiteSpace(system) ?
-				GetGlobalBasePathAbsolute() :
-				MakeAbsolutePath(GetPlatformBase(system), system);
+			var parentPath = string.IsNullOrWhiteSpace(system)
+				? GetGlobalBasePathAbsolute()
+				: MakeAbsolutePath(GetPlatformBase(system), system);
+			if (!IsSubfolder(parentPath, absolutePath)) return absolutePath;
 
-			if (IsSubfolder(parentPath, absolutePath))
-			{
-				return absolutePath.Replace(parentPath, ".");
-			}
-
-			return absolutePath;
+			return OSTailoredCode.CurrentOS == OSTailoredCode.DistinctOS.Windows
+				? absolutePath.Replace(parentPath, ".")
+				: "./" + OSTailoredCode.SimpleSubshell("realpath", $"--relative-to=\"{parentPath}\" \"{absolutePath}\"", $"invalid path {absolutePath} or missing realpath binary");
 		}
 
 		public static string MakeRelativeTo(string absolutePath, string basePath)
@@ -425,24 +424,23 @@ namespace BizHawk.Client.Common
 			return absolutePath;
 		}
 
-		// http://stackoverflow.com/questions/3525775/how-to-check-if-directory-1-is-a-subdirectory-of-dir2-and-vice-versa
+		/// <remarks>Algorithm for Windows taken from https://stackoverflow.com/a/7710620/7467292</remarks>
 		private static bool IsSubfolder(string parentPath, string childPath)
 		{
-			var parentUri = new Uri(parentPath);
-
-			var childUri = new DirectoryInfo(childPath).Parent;
-
-			while (childUri != null)
+			if (OSTailoredCode.CurrentOS == OSTailoredCode.DistinctOS.Windows)
 			{
-				if (new Uri(childUri.FullName) == parentUri)
+				var parentUri = new Uri(parentPath);
+
+				for (var childUri = new DirectoryInfo(childPath); childUri != null; childUri = childUri?.Parent)
 				{
-					return true;
+					if (new Uri(childUri.FullName) == parentUri) return true;
 				}
 
-				childUri = childUri.Parent;
+				return false;
 			}
 
-			return false;
+			return OSTailoredCode.SimpleSubshell("realpath", $"-L \"{childPath}\"", $"invalid path {childPath} or missing realpath binary")
+				.StartsWith(OSTailoredCode.SimpleSubshell("realpath", $"-L \"{parentPath}\"", $"invalid path {parentPath} or missing realpath binary"));
 		}
 
 		/// <summary>