class Solution {

    // Solution @ Sergey Leschev, Belarusian State University

    // 468. Validate IP Address
    // Given a string IP, return "IPv4" if IP is a valid IPv4 address, "IPv6" if IP is a valid IPv6 address or "Neither" if IP is not a correct IP of any type.
    // A valid IPv4 address is an IP in the form "x1.x2.x3.x4" where 0 <= xi <= 255 and xi cannot contain leading zeros. For example, "192.168.1.1" and "192.168.1.0" are valid IPv4 addresses but "192.168.01.1", while "192.168.1.00" and "192.168@1.1" are invalid IPv4 addresses.
    // A valid IPv6 address is an IP in the form "x1:x2:x3:x4:x5:x6:x7:x8" where:
    // 1 <= xi.length <= 4
    // xi is a hexadecimal string which may contain digits, lower-case English letter ('a' to 'f') and upper-case English letters ('A' to 'F').
    // Leading zeros are allowed in xi.
    // For example, "2001:0db8:85a3:0000:0000:8a2e:0370:7334" and "2001:db8:85a3:0:0:8A2E:0370:7334" are valid IPv6 addresses, while "2001:0db8:85a3::8A2E:037j:7334" and "02001:0db8:85a3:0000:0000:8a2e:0370:7334" are invalid IPv6 addresses.

    // Example 1:
    // Input: IP = "172.16.254.1"
    // Output: "IPv4"
    // Explanation: This is a valid IPv4 address, return "IPv4".

    // Example 2:
    // Input: IP = "2001:0db8:85a3:0:0:8A2E:0370:7334"
    // Output: "IPv6"
    // Explanation: This is a valid IPv6 address, return "IPv6".

    // Example 3:
    // Input: IP = "256.256.256.256"
    // Output: "Neither"
    // Explanation: This is neither a IPv4 address nor a IPv6 address.

    // Example 4:
    // Input: IP = "2001:0db8:85a3:0:0:8A2E:0370:7334:"
    // Output: "Neither"

    // Example 5:
    // Input: IP = "1e1.4.5.6"
    // Output: "Neither"

    // Constraints:
    // IP consists only of English letters, digits and the characters '.' and ':'.


    enum IPAddressStatus: String {
        case validIPv4 = "IPv4"
        case validIPv6 = "IPv6"
        case neither = "Neither"
    }


    func validIPAddress(_ IP: String) -> String {
        if IP.isEmpty { return IPAddressStatus.neither.rawValue }
        
        if isValidIPv4Address(IP.components(separatedBy: ".")) { return IPAddressStatus.validIPv4.rawValue }
        else if isValidIPv6Address(IP.components(separatedBy: ":")) { return IPAddressStatus.validIPv6.rawValue }
        else { return IPAddressStatus.neither.rawValue }
    }
    
    
    func isValidIPv4Address(_ ipComponents: [String]) -> Bool {
        if ipComponents.count != 4 { return false }
        
        for ipComponent in ipComponents {
            guard let integerIPComponent = Int(ipComponent) else { return false }
            if integerIPComponent < 0 || integerIPComponent > 255 { return false }

            for char in ipComponent {
                if char < "0" || char > "9" { return false }
            }
            
            if integerIPComponent > 0 && ipComponent.first == "0" || integerIPComponent == 0 && ipComponent.count > 1 { return false }
        }
        
        return true
    }
    
    
    func isValidIPv6Address(_ ipComponents: [String]) -> Bool {
        if ipComponents.count != 8 { return false }
        
        for ipComponent in ipComponents {
            if ipComponent.count > 4 || ipComponent.count < 1 { return false }
            
            for char in ipComponent.lowercased() {
                if (char < "0" || char > "9") && (char < "a" || char > "f") { return false }
            }
        }
        
        return true
    }
    
}