use std::{str::FromStr, vec};
use ip::IpAddr;

pub mod ip;

#[allow(dead_code)]
#[derive(Debug, Eq, PartialEq)]
pub enum NetworkingErr {
    InvalidCIDRErr,
    InvalidSubnetMask,
    InvalidNetwork,
    InvalidIPErr
}

/// enum to allow the identification of the class of the network
#[derive(Debug, Clone, Copy, Eq, PartialEq)]
enum NetworkClass {
    A = 8,
    B = 16,
    C = 24
}

#[allow(unused)]
#[derive(Debug)]
pub struct Network {
    network_address: IpAddr,
    broadcast_addr: IpAddr,
    num_hosts: u32,
    subnet_mask: Option<IpAddr>
}

impl Network {

    #[allow(unused)]
    /// Function that constucts a network struct.
    /// 
    /// ```
    /// let network = Network::new(&IpAddr::V4(127, 0, 0, 1), 32);
    /// ```
    pub fn new(given_address: &IpAddr, subnet_mask: &IpAddr) -> Network {
        Network { 
            network_address: given_address.clone(), 
            broadcast_addr: given_address.clone(), 
            num_hosts: 0, 
            subnet_mask: Some(subnet_mask.clone())
        }
    }

    /// Function that constucts a subnet, returning a vector of all subnets included
    /// 
    /// ```
    /// let networks = Network::create_subnet(&IpAddr::V4(127, 0, 0, 1), 32);
    /// ```
    pub fn create_subnet(network_address: &IpAddr, cidr: u8) -> Result<Vec<IpAddr>, NetworkingErr> {
        //Get number of host and network bits.
        let network_class = Network::get_network_class(network_address)?;
        let network_address = network_address.to_arr()?;
        //let subnet_mask = Network::gen_subnet_mask(cidr)?.to_arr()?;

        // If the CIDR < class network enum associated value, then there is an invalid subnet.
        if cidr <= network_class as u8 {
            return Err(NetworkingErr::InvalidCIDRErr)
        }
        
        let num_borrowed_bits = cidr - network_class as u8;

        //If no subnetting is required, just return the base address
        if num_borrowed_bits == 0 {
            unimplemented!();
        }

        // Determine the starting network
        let mut base_network = network_address.clone();
        let most_sig_octet: u8 = match network_class {
            NetworkClass::A => 1,
            NetworkClass::B => 2,
            NetworkClass::C => 3
        };

        for i in most_sig_octet..4 {
            base_network[i as usize] = 0;
        }

        // Determine how many networks available
        // We know that this value is >0 at this point
        let num_networks = u8::pow(2, num_borrowed_bits as u32);

        // Determine the networking gaps
        let network_spacing: u8 = u8::pow(2, 8 - num_borrowed_bits as u32);
        
        //Create the subnets
        let mut networks = vec![IpAddr::from_arr(&base_network)?];

        //Add remaming subnets (-1 is because we have already added the first address)
        for _ in 0..(num_networks-1) {
            base_network[most_sig_octet as usize] += network_spacing;
            networks.push(IpAddr::from_arr(&base_network.clone())?);
        }
        println!("{:#?}", networks);
        Ok(networks)
    }

    /// Function that is used to determine the class of network that an IP is in.
    /// 
    /// ```
    /// let network_class = Network::get_network_class(&[127, 0, 0, 1])?;
    /// >>> NetworkClass::A
    /// ```
    fn get_network_class(network_address: &IpAddr) -> Result<NetworkClass, NetworkingErr> {
        let network_address = network_address.to_arr()?;
        if network_address[0] > 224 {
            return Err(NetworkingErr::InvalidIPErr)
        }else if network_address[0] >= 192 {
            return Ok(NetworkClass::C)
        }else if network_address[0] >= 128 {
            return Ok(NetworkClass::B)
        }else if network_address[0] >= 1 {
            return Ok(NetworkClass::A);
        }
        return Err(NetworkingErr::InvalidIPErr)
    }

    /// Function that takes in a u8 CIDR and converts it to an IP address.
    /// 
    /// ```
    /// let cidr: u8 = 22
    /// let subnet_mask: [u8; 4] = gen_subnet_mask(cidr);
    /// 
    /// >> IpAddr::V4(255, 255, 252, 0)
    /// ```
    fn gen_subnet_mask(mut cidr: u8) -> Result<IpAddr, NetworkingErr> {
        if cidr > 32 {
            return Err(NetworkingErr::InvalidCIDRErr)
        }

        let mut oct: [u8; 4] = [0; 4];

        for octet in oct.iter_mut() {
            *octet = if usize::from(cidr) >= 8 {
                cidr -= 8;
                u8::MAX
            }else{
                // Count the number of remaining 1s and convert to binary
                let mut count: u8 = 0;
                for i in ((8-cidr)..8).rev() {
                    count += u8::pow(2, u32::from(i));
                }
                cidr = 0;
                count
            }
        }

        Ok(IpAddr::from_arr(&oct)?)
    }
    //pub fn generate_subnets(self) -> Vec<Network> {}
}

/// Function that takes in a string reference and returns the result of splitting a string into 
/// both its Address and CIDR
/// 
/// ```
/// let ip_string = String::from("192.168.0.1/24");
/// let result = match ip_and_cidr_from_string(&ip_string) {
///     Err(_) => panic!(),
///     Ok(ip_and_cidr) => ip_and_cidr
/// };
/// 
/// >> (IpAddr::V4(192, 168, 0, 1), 24)
/// ```
pub fn ip_and_cidr_from_string(ip_and_cidr: &String) -> Result<(IpAddr, u8), ip::InvalidIPErr>{
    let mut cidr: u8 = Default::default();
    let mut ip: String = Default::default();

    if ip_and_cidr.contains("/") {
        let split_ip_cidr = ip_and_cidr.split("/");
        if split_ip_cidr.clone().count() > 2 {
            return Err(ip::InvalidIPErr);
        }
        ip = split_ip_cidr.clone().into_iter().next().unwrap_or("0.0.0.0").to_owned();
        cidr = match split_ip_cidr.into_iter().last() {
            None => return Err(ip::InvalidIPErr),
            Some(cidr) => match cidr.trim().parse::<u8>() {
                Err(_) => return Err(ip::InvalidIPErr),
                Ok(cidr) => cidr
            }
        };
    }
    
    let ip_address: IpAddr = match IpAddr::from_str(&ip.trim()) {
        Err(_) => return Err(ip::InvalidIPErr),
        Ok(ip) => ip,
    };

    return Ok((ip_address, cidr))
}

mod tests {
    #[cfg(test)]
    #[test]
    fn string_to_ip_cidr_test() {
        use super::*;

        let ip_string = String::from("127.0.0.1/8");
        let result = match ip_and_cidr_from_string(&ip_string) {
            Err(_) => panic!(),
            Ok(ip_and_cidr) => ip_and_cidr
        };
        assert_eq!(result.0, IpAddr::V4(127, 0, 0, 1));
        assert_eq!(result.1, 8);
    }

    #[test]
    fn cidr_to_ip_test() {
        use super::*;

        assert_eq!(Network::gen_subnet_mask(22).unwrap(), IpAddr::V4(255, 255, 252, 0));
        assert_eq!(Network::gen_subnet_mask(24).unwrap(), IpAddr::V4(255, 255, 255, 0));
        assert_eq!(Network::gen_subnet_mask(0).unwrap(), IpAddr::V4(0, 0, 0, 0));
        assert_eq!(Network::gen_subnet_mask(4).unwrap(), IpAddr::V4(240, 0, 0, 0));
        assert_eq!(Network::gen_subnet_mask(35).unwrap_err(), NetworkingErr::InvalidCIDRErr);
    }

    #[test]
    fn network_class_test() {
        use super::*;

        assert_eq!(Network::get_network_class(&IpAddr::V4(127, 0, 0, 1)).unwrap(), NetworkClass::A);
        assert_eq!(Network::get_network_class(&IpAddr::V4(172, 6, 8, 10)).unwrap(), NetworkClass::B);
        assert_eq!(Network::get_network_class(&IpAddr::V4(192, 168, 0, 1)).unwrap(), NetworkClass::C);
        assert_eq!(Network::get_network_class(&IpAddr::V4(10, 6, 8, 10)).unwrap(), NetworkClass::A);
        assert_eq!(Network::get_network_class(&IpAddr::V4(225, 255, 255, 255)).unwrap_err(), NetworkingErr::InvalidIPErr);
        assert_eq!(Network::get_network_class(&IpAddr::V4(225, 0, 0, 0)).unwrap_err(), NetworkingErr::InvalidIPErr);
        assert_eq!(Network::get_network_class(&IpAddr::V4(0, 0, 0, 0)).unwrap_err(), NetworkingErr::InvalidIPErr);
        assert_eq!(Network::get_network_class(&IpAddr::V4(0, 0, 0, 1)).unwrap_err(), NetworkingErr::InvalidIPErr);
    }

    #[test]
    fn subnet_creation_test() {
        use super::*;

        assert_eq!(Network::create_subnet(&IpAddr::V4(192, 168, 0, 1), 23).unwrap_err(), NetworkingErr::InvalidCIDRErr);
    }
}