Implement path utility functions

[AliiiBenn]

Implement path validation and manipulation utilities.

Requirements

Path validation

const PATH_SEPARATOR = '/'
const MAX_PATH_LENGTH = 4096

// Validation checks:
- No null bytes in path
- No traversal beyond root (../../etc/passwd)
- No invalid characters
- Not exceeds MAX_PATH_LENGTH
- Resolved path stays within allowed roots
- Windows: handle drive letters, backslashes

Path utilities

const resolve = (path: string): string
const join = (...parts: string[]): string
const dirname = (path: string): string
const basename = (path: string): string
const extname = (path: string): string
const normalize = (path: string): string
const isAbsolute = (path: string): boolean

Usage examples

Basic manipulation

join('src', 'utils', 'helpers.ts')
// → 'src/utils/helpers.ts'

basename('/src/utils/helpers.ts')
// → 'helpers.ts'

dirname('/src/utils/helpers.ts')
// → '/src/utils'

extname('/src/utils/helpers.ts')
// → '.ts'

normalize('/src/../src/utils/./helpers.ts')
// → '/src/utils/helpers.ts'

isAbsolute('/src/utils')
// → true

isAbsolute('src/utils')
// → false

Resolution

resolve('/project', 'src/main.ts')
// → '/project/src/main.ts'

resolve('/project', '../package.json')
// → '/package.json' (blocked by validation!)

Validation

// These should be rejected:
validate('/../../../etc/passwd')  // traversal attack
validate('/path/with/\x00/null')  // null byte
validate('a'.repeat(5000))       // too long

Goals

• Security against path traversal attacks
• Works in both Node.js and browser environments