# Library IntelliSense Case Sensitivity Fix

## Problem Description

The Library IntelliSense feature had an issue with case sensitivity on Linux systems. When comparing file paths to determine if a directory was already added as a library, the system would not recognize paths that were the same but had different casing.

For example:
- Library already added: `/mnt/Media/Library`
- Browsing path: `/mnt/media/library`

On Linux, these are considered different paths, but they refer to the same directory. The IntelliSense feature would not grey out the already added library because the direct string comparison failed.

## Root Cause

In the IntelliSense API endpoint (`/src/app/api/libraries/intellisense/route.ts`), paths were being compared directly using a Set lookup:

```javascript
const isAlreadyLibrary = libraryPaths.has(entryPath);
```

This approach worked on case-insensitive file systems (Windows, macOS) but failed on case-sensitive systems (Linux) when the same path existed with different casing.

## Solution

Implemented path normalization for case-insensitive comparison:

1. Added a helper function to normalize paths to lowercase:
```typescript
function normalizePathForComparison(filePath: string): string {
  return filePath.toLowerCase();
}
```

2. Modified the library path storage to use normalized paths:
```typescript
const normalizedLibraryPaths = new Set(libraries.map(lib => normalizePathForComparison(lib.path)));
```

3. Updated the path comparison to use normalized paths:
```typescript
const isAlreadyLibrary = normalizedLibraryPaths.has(normalizePathForComparison(entryPath));
```

## Testing

Created a dedicated test script (`tests/diagnostics/test-intellisense-case-sensitivity.mjs`) to verify the fix:

- Tests various case combinations of the same path
- Verifies non-matching paths are correctly identified
- Confirms the normalization works as expected

## Impact

This fix ensures consistent behavior across all operating systems:
- Linux: Now properly recognizes already added libraries regardless of path casing
- Windows/macOS: Continues to work as before (no regression)
- User experience: Libraries are correctly greyed out in the IntelliSense interface

## Files Modified

1. `/src/app/api/libraries/intellisense/route.ts` - Implemented path normalization
2. `/tests/diagnostics/test-intellisense-case-sensitivity.mjs` - Created test script
3. `/tests/README.md` - Updated documentation
4. `/INTELLISENSE_FEATURE_SUMMARY.md` - Updated feature summary

## Verification

The fix has been tested and verified to work correctly across different path casing scenarios while maintaining backward compatibility.