module net

// validate_port checks whether a port is valid and returns the port or an error.
// The valid ports numbers are between 0 and 0xFFFF.
// For TCP, port number 0 is reserved and cannot be used, while for UDP, the source port
// is optional and a value of zero means no port.
// See also https://en.wikipedia.org/wiki/Port_%28computer_networking%29 .
pub fn validate_port(port int) !u16 {
    if port >= 0 && port <= 0xFFFF {
        return u16(port)
    } else {
        return err_port_out_of_range
    }
}

// split_address splits an address into its host name and its port
pub fn split_address(addr string) !(string, u16) {
    if _ := addr.index(']') {
        // ipv6 brackets
        address := addr.all_after('[').all_before_last(']')
        port := addr.all_after_last(']:').int()
        p := validate_port(port)!
        return address, p
    } else if _ := addr.index('::') {
        if addr.count(':') == 2 && addr.all_before_last('::') == '' {
            // ipv6 host only `::1`
            return addr, 0
        } else {
            // addr:port, or `::addr:port`
            address := addr.all_before_last(':')
            port := addr.all_after_last(':').int()
            p := validate_port(port)!
            return address, p
        }
    } else if _ := addr.index(':') {
        // addr:port
        address := addr.all_before_last(':')
        p := validate_port(addr.all_after_last(':').int())!
        return address, p
    } else {
        // addr only
        return addr, 0
    }
}