Improve chown implementation - Address code review recommendations

[fbraza]

Summary

This issue tracks improvements to the chown implementation based on code review recommendations from PR #23. The goal is to enhance code quality, consistency, and robustness.

High Priority Improvements

1. Type Safety - Replace null with Option[String]

Current:

def apply(path: String, owner: String, group: String)(implicit fs: FileSystem): Unit
// Usage: chown("/path", "owner", null)

Proposed:

def apply(path: String, owner: String, group: Option[String] = None)(implicit fs: FileSystem): Unit
// Usage: chown("/path", "owner", Some("group")) or chown("/path", "owner")

2. Input Validation

Current: No validation for null/empty strings
Proposed:

def apply(path: String, owner: String)(implicit fs: FileSystem): Unit = {
  require(path != null && path.nonEmpty, "Path cannot be null or empty")
  require(owner != null && owner.nonEmpty, "Owner cannot be null or empty")
  // ... rest of implementation
}

3. Enhanced Error Handling for chmod

Current:

object chmod {
  def apply(path: String, perm: FsPermission)(implicit fs: FileSystem): Unit = {
    val pathToSet = new Path(path)
    fs.setPermission(pathToSet, perm)
  }
}

Proposed:

object chmod {
  def apply(path: String, perm: FsPermission)(implicit fs: FileSystem): Unit = {
    val pathToSet = new Path(path)
    try {
      if (!fs.exists(pathToSet)) {
        throw new FileNotFoundException(s"Path does not exist: $path")
      }
      fs.setPermission(pathToSet, perm)
    } catch {
      case e: FileNotFoundException => throw e
      case e: IOException => throw new IOException(s"Failed to change permissions for $path: ${e.getMessage}", e)
    }
  }
}

Medium Priority Improvements

4. Additional Test Coverage

Add tests for:

• Null/empty owner and group strings
• Invalid user/group name formats
• Permission denied scenarios
• Symbolic link handling
• Very deep directory structures

5. Complete Documentation

• Complete Perm object documentation
• Add usage examples to Scaladoc
• Document error scenarios and recovery

6. User/Group Name Format Validation

private def isValidUserName(name: String): Boolean = {
  name != null && name.matches("^[a-zA-Z0-9._-]+$")
}

Low Priority Improvements

7. Performance Optimizations

• Consider adding batching for large directory operations
• Add configuration options for recursion limits
• Progress reporting for large operations

8. Enhanced API Features

• Dry-run mode
• Follow symlinks option
• Verbose logging option

Acceptance Criteria

• Replace null with Option[String] for optional group parameter
• Add input validation for all parameters
• Implement proper error handling in chmod object
• Add comprehensive test coverage for edge cases
• Complete all Scaladoc documentation
• All existing tests continue to pass

Files to Modify

• src/main/scala/permOps.scala - Main implementation improvements
• src/test/scala/permOps.scala - Additional test cases

Related Issues

• Complete chown implementation in permOps.scala #12 - Original chown implementation request
• Complete chown implementation in permOps.scala #23 - Pull request with initial implementation

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