Verify install and warn user of issues

* Warn if Restock is installed in the wrong place (finds DLL and then goes two directories up, this should be Restock's "root" install directory)
* Warn if some old directories are sitting around from an old version of KSP, since the old part configs break stuff.

Source/Restock/InstallChecker.cs

@@ -0,0 +1,101 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using UnityEngine;
+
+namespace Restock
+{
+    [KSPAddon(KSPAddon.Startup.Instantly, true)]
+    public class InstallChecker : MonoBehaviour
+    {
+        public readonly IEnumerable<string> UNEXPECTED_URLS = Array.AsReadOnly(new[] {
+            "Squad/Parts/FuelTank/fuelTankT100",
+            "Squad/Parts/FuelTank/fuelTankT200",
+            "Squad/Parts/FuelTank/fuelTankT400",
+            "Squad/Parts/FuelTank/fuelTankT800",
+        });
+
+        private void Start()
+        {
+            string[] errorMessages = CheckInstallLocation().Concat(CheckUnexpectedUrls()).ToArray();
+
+            if (errorMessages.Length > 0) CreateWarningDialog(errorMessages);
+        }
+
+        private IEnumerable<string> CheckInstallLocation()
+        {
+            UrlDir gameData = GameDatabase.Instance.root.children.First(dir => dir.type == UrlDir.DirectoryType.GameData);
+            AssemblyLoader.LoadedAssembly loadedAssembly = AssemblyLoader.loadedAssemblies.GetByAssembly(Assembly.GetExecutingAssembly());
+
+            if (loadedAssembly == null)
+            {
+                Debug.LogError("[Restock] Error checking install location - could not find loaded assembly");
+                yield break;
+            }
+
+            UrlDir assemblyDir = GetDirectory(gameData, loadedAssembly.url);
+
+            if (assemblyDir == null)
+            {
+                Debug.LogError("[Restock] Error checking install location - could not find assembly url directory: " + loadedAssembly.url);
+                yield break;
+            }
+
+            string observedInstallPath = Path.GetFullPath(assemblyDir.parent.path);
+            string expectedInstallPath = Path.GetFullPath(Path.Combine(KSPUtil.ApplicationRootPath, Path.Combine("GameData", "ReStock")));
+
+            if (observedInstallPath != expectedInstallPath)
+            {
+                Debug.LogError($"[Restock] Install found at '{observedInstallPath}'");
+                yield return $"Expected Restock to be installed at\n{expectedInstallPath}\nbut actually installed at\n{observedInstallPath}";
+            }
+        }
+
+        private IEnumerable<string> CheckUnexpectedUrls()
+        {
+            UrlDir gameData = GameDatabase.Instance.root.children.First(dir => dir.type == UrlDir.DirectoryType.GameData);
+            foreach (string unexpectedUrl in UNEXPECTED_URLS)
+            {
+                if (!(gameData.GetDirectory(unexpectedUrl) is UrlDir unexpectedDir)) continue;
+                Debug.LogError("[ReStock] Found unexpected directory " + unexpectedDir.path);
+                yield return $"Found unexpected directory, likely left over from an older version of KSP:\n" + unexpectedDir.path;
+            }
+        }
+
+        private void CreateWarningDialog(params string[] allMessages)
+        {
+            PopupDialog.SpawnPopupDialog(new Vector2(0.5f, 0.5f),
+                new Vector2(0.5f, 0.5f),
+                new MultiOptionDialog(
+                    "RestockInstallWarning",
+                    $"Restock has detected installation issues:\n\n{string.Join("\n\n", allMessages)}",
+                    "Restock - installation issues detected",
+                    HighLogic.UISkin,
+                    new Rect(0.5f, 0.5f, 500f, 60f),
+                    new DialogGUIFlexibleSpace(),
+                    new DialogGUIHorizontalLayout(
+                        new DialogGUIFlexibleSpace(),
+                        new DialogGUIButton("OK", delegate () { }, 140.0f, 30.0f, true),
+                        new DialogGUIFlexibleSpace()
+                    )
+                ),
+                true,
+                HighLogic.UISkin);
+        }
+
+        private UrlDir GetDirectory(UrlDir baseUrl, string url)
+        {
+            string[] splitUrl = url.Trim().Split('/');
+
+            UrlDir currentDir = baseUrl;
+            foreach (string dirName in splitUrl)
+            {
+                currentDir = currentDir.children.FirstOrDefault(dir => dir.name == dirName);
+                if (currentDir == null) return null;
+            }
+            return currentDir;
+        }
+    }
+}

Source/Restock/Restock.csproj

@@ -41,6 +41,7 @@
     </Reference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="InstallChecker.cs" />
     <Compile Include="MaterialModifiers\ColorPropertyMaterialModifier.cs" />
     <Compile Include="MaterialModifiers\FloatPropertyMaterialModifier.cs" />
     <Compile Include="MaterialModifiers\IMaterialModifier.cs" />