Function is_valid_handle 

pub fn is_valid_handle(handle: &str) -> Option<String>

Validates and normalizes an AT Protocol handle.

A valid AT Protocol handle must:

• Be a valid hostname (after stripping prefixes)
• Contain at least one period (to distinguish from simple hostnames)
• Follow all hostname validation rules (RFC 1035)

The function automatically strips common prefixes (at:// and @) before validation.

Arguments

• handle - The handle string to validate and normalize

Returns

Some(String) containing the normalized handle if valid, None if invalid

Examples

use atproto_identity::validation::is_valid_handle;

// Valid handles
assert_eq!(is_valid_handle("alice.bsky.social"), Some("alice.bsky.social".to_string()));
assert_eq!(is_valid_handle("@bob.example.com"), Some("bob.example.com".to_string()));
assert_eq!(is_valid_handle("at://charlie.test.com"), Some("charlie.test.com".to_string()));

// Invalid handles
assert_eq!(is_valid_handle("localhost"), None); // No period
assert_eq!(is_valid_handle("192.168.1.1"), None); // IPv4 address
assert_eq!(is_valid_handle("invalid..handle.com"), None); // Double dot