use Error;
use phy::Device;
use wire::{EthernetAddress, EthernetProtocolType, EthernetFrame};
use wire::{ArpPacket, ArpRepr, ArpOperation};
use super::{ProtocolAddress, ArpCache};

/// An Ethernet network interface.
#[derive(Debug)]
pub struct Interface<'a, DeviceT: Device, ArpCacheT: ArpCache> {
    device:         DeviceT,
    arp_cache:      ArpCacheT,
    hardware_addr:  EthernetAddress,
    protocol_addrs: &'a [ProtocolAddress]
}

impl<'a, DeviceT: Device, ArpCacheT: ArpCache> Interface<'a, DeviceT, ArpCacheT> {
    /// Create a network interface using the provided network device.
    ///
    /// The newly created interface uses hardware address `00-00-00-00-00-00` and
    /// has no assigned protocol addresses.
    pub fn new(device: DeviceT, arp_cache: ArpCacheT) -> Interface<'a, DeviceT, ArpCacheT> {
        Interface {
            device:         device,
            arp_cache:      arp_cache,
            hardware_addr:  EthernetAddress([0x00; 6]),
            protocol_addrs: &[]
        }
    }

    /// Get the hardware address of the interface.
    pub fn hardware_addr(&self) -> EthernetAddress {
        self.hardware_addr
    }

    /// Set the hardware address of the interface.
    ///
    /// # Panics
    /// This function panics if the address is not unicast.
    pub fn set_hardware_addr(&mut self, addr: EthernetAddress) {
        if addr.is_multicast() {
            panic!("hardware address {} is not unicast", addr)
        }

        self.hardware_addr = addr
    }

    /// Get the protocol addresses of the interface.
    pub fn protocol_addrs(&self) -> &'a [ProtocolAddress] {
        self.protocol_addrs
    }

    /// Set the protocol addresses of the interface.
    ///
    /// # Panics
    /// This function panics if any of the addresses is not unicast.
    pub fn set_protocol_addrs(&mut self, addrs: &'a [ProtocolAddress]) {
        for addr in addrs {
            if !addr.is_unicast() {
                panic!("protocol address {} is not unicast", addr)
            }
        }

        self.protocol_addrs = addrs
    }

    /// Checks whether the interface has the given protocol address assigned.
    pub fn has_protocol_addr<T: Into<ProtocolAddress>>(&self, addr: T) -> bool {
        let addr = addr.into();
        self.protocol_addrs.iter().any(|&probe| probe == addr)
    }

    /// Receive and process a packet, if available.
    pub fn poll(&mut self) -> Result<(), Error> {
        enum Response {
            Nop,
            Arp(ArpRepr)
        }
        let mut response = Response::Nop;

        let rx_buffer = try!(self.device.receive());
        let frame = try!(EthernetFrame::new(rx_buffer));
        match frame.ethertype() {
            EthernetProtocolType::Arp => {
                let packet = try!(ArpPacket::new(frame.payload()));
                let repr = try!(ArpRepr::parse(&packet));
                match repr {
                    ArpRepr::EthernetIpv4 {
                        operation: ArpOperation::Request,
                        source_hardware_addr, source_protocol_addr,
                        target_protocol_addr, ..
                    } => {
                        if self.has_protocol_addr(target_protocol_addr) {
                            response = Response::Arp(ArpRepr::EthernetIpv4 {
                                operation: ArpOperation::Reply,
                                source_hardware_addr: self.hardware_addr,
                                source_protocol_addr: target_protocol_addr,
                                target_hardware_addr: source_hardware_addr,
                                target_protocol_addr: source_protocol_addr
                            })
                        }
                    },
                    _ => return Err(Error::Unrecognized)
                }
            },
            _ => return Err(Error::Unrecognized)
        }

        match response {
            Response::Nop => Ok(()),
            Response::Arp(repr) => {
                let tx_size = self.device.mtu();
                let tx_buffer = try!(self.device.transmit(tx_size));
                let mut frame = try!(EthernetFrame::new(tx_buffer));
                frame.set_src_addr(self.hardware_addr);
                frame.set_dst_addr(match repr {
                    ArpRepr::EthernetIpv4 { target_hardware_addr, .. } => target_hardware_addr,
                    _ => unreachable!()
                });
                frame.set_ethertype(EthernetProtocolType::Arp);

                let mut packet = try!(ArpPacket::new(frame.payload_mut()));
                repr.emit(&mut packet);

                Ok(())
            }
        }
    }
}