use ip::IpAddr;
use std::str::FromStr;

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 {
    pub network_address: IpAddr,
    pub broadcast_addr: IpAddr,
    pub num_hosts: u32,
}

#[derive(Debug)]
#[allow(unused)]
pub struct Subnet {
    pub networks: Vec<Network>,
    pub subnet_mask: IpAddr,
}

impl Network {
    #[allow(unused)]
    /// Function that constucts a network struct.
    ///
    /// ```
    /// //Awaiting implementation before creating doctest
    /// //let network = Network::new(&IpAddr::V4(127, 0, 0, 1), 32);
    /// ```
    fn new(given_address: &IpAddr, broadcast_address: &IpAddr, num_hosts: u32) -> Network {
        Network {
            network_address: given_address.clone(),
            broadcast_addr: broadcast_address.clone(),
            num_hosts,
        }
    }

    /// Function that constucts a subnet, returning a vector of all subnets included
    ///
    /// ```
    /// use subnet_calculator::ip::IpAddr;
    /// use subnet_calculator::Network;
    ///
    /// let subnets = Network::create_subnet(&IpAddr::V4(127, 0, 0, 1), 16).unwrap();
    ///
    /// assert_eq!(subnets.networks.len(), 256);
    /// ```
    pub fn create_subnet(network_address: &IpAddr, cidr: u8) -> Result<Subnet, NetworkingErr> {
        //Get number of host and network bits.
        let network_class = Network::get_network_class(network_address)?;
        let network_address = network_address.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);
        }

        // 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;
        }

        // Remove trailing values from the base network
        let num_borrowed_bits = cidr - network_class as u8;

        // Get the base network and next added address as u32's
        let mut base_addr = u32::from(IpAddr::from_arr(&base_network)?);
        let subnet_mask = u32::from(Network::gen_subnet_mask(cidr)?);
        let addr_increment = u32::pow(2, subnet_mask.trailing_zeros());

        // The number of hosts per network can be determined using the number of remaining
        // bits raised to the second power.
        let num_hosts = u32::pow(2, (32 - network_class as u8 - num_borrowed_bits) as u32);

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

        // The broadcast address will always be 1 less than the next subnet network address
        let mut broadcast_addr = (base_addr + addr_increment) - 1;

        //Create the subnets
        let mut subnet = Subnet::new(
            &IpAddr::from(base_addr),
            &IpAddr::from(broadcast_addr),
            num_hosts,
            cidr,
        )?;

        // Determine the networking gaps
        //If there is only 1 network, returning the base network will be sufficient
        if num_networks > 1 {
            for _ in 0..num_networks - 1 {
                //Increment address and append to list
                base_addr += addr_increment;
                // We can start adding the full subnet range now instead of 1 less
                broadcast_addr += addr_increment;

                subnet.networks.push(Network::new(
                    &IpAddr::from(base_addr),
                    &IpAddr::from(broadcast_addr),
                    num_hosts,
                ));
            }
        }

        Ok(subnet)
    }

    /// Function that is used to determine the class of network that an IP is in.
    ///
    /// ```ignore
    /// use subnet_calculator::Network;
    ///
    /// let network_class = Network::get_network_class(&[127, 0, 0, 1]).unwrap();
    /// assert_eq!(network_class, 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);
    }

    #[allow(unused)]
    /// Function that takes in a u8 CIDR and converts it to an IP address.
    ///
    /// ```ignore
    /// let cidr: u8 = 22;
    /// let subnet_mask: [u8; 4] = gen_subnet_mask(cidr).unwrap();
    ///
    /// assert_eq!(subnet_mask, 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)?)
    }
}

/// Function that takes in a string reference and returns the result of splitting a string into
/// both its Address and CIDR
///
/// ```
/// use subnet_calculator::ip_and_cidr_from_string;
/// use subnet_calculator::ip::IpAddr;
///
/// 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
/// };
///
/// assert_eq!(result, (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));
}

impl Subnet {
    /// Function to return a new subbet struct
    ///
    fn new(
        base_address: &IpAddr,
        broadcast_addr: &IpAddr,
        num_hosts: u32,
        cidr: u8,
    ) -> Result<Subnet, NetworkingErr> {
        Ok(Subnet {
            networks: vec![Network::new(base_address, broadcast_addr, num_hosts)],
            subnet_mask: Network::gen_subnet_mask(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
        );

        let networks = Network::create_subnet(&IpAddr::V4(127, 0, 0, 1), 10).unwrap();
        assert_eq!(networks.networks.len(), 4);

        let networks = Network::create_subnet(&IpAddr::V4(192, 168, 200, 1), 31)
            .unwrap()
            .networks;
        assert_eq!(networks.len(), 128);
        assert_eq!(
            networks.last().unwrap().network_address,
            IpAddr::V4(192, 168, 200, 254)
        );
        assert_eq!(
            networks.last().unwrap().broadcast_addr,
            IpAddr::V4(192, 168, 200, 255)
        );
        assert_eq!(networks.last().unwrap().num_hosts, 2);

        let networks = Network::create_subnet(&IpAddr::V4(127, 0, 0, 0), 8)
            .unwrap()
            .networks;
        assert_eq!(networks.len(), 1);
        assert_eq!(
            networks.last().unwrap().network_address,
            IpAddr::V4(127, 0, 0, 0)
        );
        assert_eq!(
            networks.last().unwrap().broadcast_addr,
            IpAddr::V4(127, 255, 255, 255)
        );
        assert_eq!(networks.last().unwrap().num_hosts, 16_777_216);

        let networks = Network::create_subnet(&IpAddr::V4(127, 0, 0, 0), 9)
            .unwrap()
            .networks;
        assert_eq!(networks.len(), 2);
        assert_eq!(
            networks.first().unwrap().network_address,
            IpAddr::V4(127, 0, 0, 0)
        );
        assert_eq!(
            networks.first().unwrap().broadcast_addr,
            IpAddr::V4(127, 127, 255, 255)
        );

        let networks = Network::create_subnet(&IpAddr::V4(168, 20, 0, 0), 17)
            .unwrap()
            .networks;
        assert_eq!(networks.len(), 2);
        assert_eq!(
            networks.last().unwrap().network_address,
            IpAddr::V4(168, 20, 128, 0)
        );
        assert_eq!(
            networks.last().unwrap().broadcast_addr,
            IpAddr::V4(168, 20, 255, 255)
        );
        assert_eq!(networks.last().unwrap().num_hosts, 32_768);

        let networks = Network::create_subnet(&IpAddr::V4(127, 0, 0, 0), 17)
            .unwrap()
            .networks;
        assert_eq!(networks.len(), 512);
        assert_eq!(
            networks.last().unwrap().network_address,
            IpAddr::V4(127, 255, 128, 0)
        );
    }
}