fix: resolve cross-platform EPERM permissions errors

modManager.js:
- Switch from hardcoded 'junction' to dynamic symlink type based on OS (fixing Linux EPERM).
- Add retry logic for directory removal to handle file locking race conditions.
- Improve broken symlink detection during profile sync.

gameManager.js:
- Implement retry loop (3 attempts) for game directory removal in updateGameFiles to prevent EBUSY/EPERM errors on Windows.

paths.js:
- Prevent fs.mkdirSync failure in getModsPath by pre-checking for broken symbolic links.

backend/core/paths.js

@@ -179,9 +179,18 @@ async function getModsPath(customInstallPath = null) {
     const profilesPath = path.join(userDataPath, 'Profiles');
 
     if (!fs.existsSync(modsPath)) {
+      // Check for broken symlink to avoid EEXIST/EPERM on mkdir
+      let isBrokenLink = false;
+      try {
+        const stats = fs.lstatSync(modsPath);
+        if (stats.isSymbolicLink()) isBrokenLink = true;
+      } catch (e) { /* ignore */ }
+
+      if (!isBrokenLink) {
         // Ensure the Mods directory exists
         fs.mkdirSync(modsPath, { recursive: true });
       }
+    }
     if (!fs.existsSync(disabledModsPath)) {
       fs.mkdirSync(disabledModsPath, { recursive: true });
     }

backend/managers/gameManager.js

@@ -365,7 +365,21 @@ async function updateGameFiles(newVersion, progressCallback, gameDir = GAME_DIR,
 
     if (fs.existsSync(gameDir)) {
       console.log('Removing old game files...');
+      let retries = 3;
+      while (retries > 0) {
+        try {
           fs.rmSync(gameDir, { recursive: true, force: true });
+          break;
+        } catch (err) {
+          if ((err.code === 'EPERM' || err.code === 'EBUSY') && retries > 0) {
+            retries--;
+            console.log(`[UpdateGameFiles] Removal failed with ${err.code}, retrying in 1s... (${retries} retries left)`);
+            await new Promise(resolve => setTimeout(resolve, 1000));
+          } else {
+            throw err;
+          }
+        }
+      }
     }
 
     fs.renameSync(tempUpdateDir, gameDir);

backend/managers/modManager.js

@@ -2,6 +2,7 @@ const fs = require('fs');
 const path = require('path');
 const crypto = require('crypto');
 const axios = require('axios');
+const { getOS } = require('../utils/platformUtils');
 const { getModsPath, getProfilesDir } = require('../core/paths');
 const { saveModsToConfig, loadModsFromConfig } = require('../core/config');
 const profileManager = require('./profileManager');
@@ -307,11 +308,16 @@ async function syncModsForCurrentProfile() {
 
     // 2. Symlink / Migration Logic
     let needsLink = false;
+    let globalStats = null;
     
-    if (fs.existsSync(globalModsPath)) {
+    try {
-      const stats = fs.lstatSync(globalModsPath);
+      globalStats = fs.lstatSync(globalModsPath);
+    } catch (e) {
+      // Path doesn't exist
+    }
 
-      if (stats.isSymbolicLink()) {
+    if (globalStats) {
+      if (globalStats.isSymbolicLink()) {
         const linkTarget = fs.readlinkSync(globalModsPath);
         // Normalize paths for comparison
         if (path.resolve(linkTarget) !== path.resolve(profileModsPath)) {
@@ -319,7 +325,7 @@ async function syncModsForCurrentProfile() {
           fs.unlinkSync(globalModsPath);
           needsLink = true;
         }
-      } else if (stats.isDirectory()) {
+      } else if (globalStats.isDirectory()) {
         // MIGRATION: It's a real directory. Move contents to profile.
         console.log('[ModManager] Migrating global mods folder to profile folder...');
         const files = fs.readdirSync(globalModsPath);
@@ -348,8 +354,21 @@ async function syncModsForCurrentProfile() {
         }
 
         // Remove the directory so we can link it
+        try {
+            let retries = 3;
+            while (retries > 0) {
                 try {
                     fs.rmSync(globalModsPath, { recursive: true, force: true });
+                    break;
+                } catch (err) {
+                    if ((err.code === 'EPERM' || err.code === 'EBUSY') && retries > 0) {
+                        retries--;
+                        await new Promise(resolve => setTimeout(resolve, 500));
+                    } else {
+                        throw err;
+                    }
+                }
+            }
             needsLink = true;
         } catch (e) {
             console.error('Failed to remove global mods dir:', e);
@@ -364,8 +383,8 @@ async function syncModsForCurrentProfile() {
     if (needsLink) {
       console.log(`[ModManager] Creating symlink: ${globalModsPath} -> ${profileModsPath}`);
       try {
-         // 'junction' is key for Windows without admin
+         const symlinkType = getOS() === 'windows' ? 'junction' : 'dir';
-         fs.symlinkSync(profileModsPath, globalModsPath, 'junction'); 
+         fs.symlinkSync(profileModsPath, globalModsPath, symlinkType); 
       } catch (err) {
         // If we can't create the symlink, try creating the directory first
         console.error('[ModManager] Failed to create symlink. Falling back to direct folder mode.');