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use super::super::*;

extern crate byteorder;
use self::byteorder::{ByteOrder, BigEndian, ReadBytesExt, WriteBytesExt};

use std::io;

///IEEE 802.1Q VLAN Tagging Header (can be single or double tagged).
pub enum VlanHeader {
    ///IEEE 802.1Q VLAN Tagging Header
    Single(SingleVlanHeader),
    ///IEEE 802.1Q double VLAN Tagging Header
    Double(DoubleVlanHeader)
}

///IEEE 802.1Q VLAN Tagging Header
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct SingleVlanHeader {
    ///A 3 bit number which refers to the IEEE 802.1p class of service and maps to the frame priority level.
    pub priority_code_point: u8,
    ///Indicate that the frame may be dropped under the presence of congestion.
    pub drop_eligible_indicator: bool,
    ///12 bits vland identifier.
    pub vlan_identifier: u16,
    ///"Tag protocol identifier": Type id of content after this header. Refer to the "EtherType" for a list of possible supported values.
    pub ether_type: u16,
}

impl SerializedSize for SingleVlanHeader {
    ///Serialized size of the header in bytes.
    const SERIALIZED_SIZE: usize = 4;
}

impl SingleVlanHeader {
    ///Read a IEEE 802.1Q VLAN tagging header
    pub fn read<T: io::Read + io::Seek + Sized >(reader: &mut T) -> Result<SingleVlanHeader, io::Error> {
        let (priority_code_point, drop_eligible_indicator, vlan_identifier) = {
            let mut buffer: [u8;2] = [0;2];
            reader.read_exact(&mut buffer)?;
            let drop_eligible_indicator = 0 != (buffer[0] & 0x10);
            let priority_code_point = buffer[0] >> 5;
            //mask and read the vlan id
            buffer[0] = buffer[0] & 0xf;
            (priority_code_point, drop_eligible_indicator, BigEndian::read_u16(&buffer))
        };

        Ok(SingleVlanHeader{
            priority_code_point: priority_code_point,
            drop_eligible_indicator: drop_eligible_indicator,
            vlan_identifier: vlan_identifier,
            ether_type: reader.read_u16::<BigEndian>()?
        })
    }

    ///Write the IEEE 802.1Q VLAN tagging header
    pub fn write<T: io::Write + Sized>(&self, writer: &mut T) -> Result<(), WriteError> {
        use ErrorField::*;
        //check value ranges
        max_check_u8(self.priority_code_point, 0x3, VlanTagPriorityCodePoint)?;
        max_check_u16(self.vlan_identifier, 0xfff, VlanTagVlanId)?;
        {
            let mut buffer: [u8;2] = [0;2];
            BigEndian::write_u16(&mut buffer, self.vlan_identifier);
            if self.drop_eligible_indicator {
                buffer[0] = buffer[0] | 0x10;
            }
            buffer[0] = buffer[0] | (self.priority_code_point << 5);
            writer.write_all(&buffer)?;
        }
        writer.write_u16::<BigEndian>(self.ether_type)?;
        Ok(())
    }
}

///IEEE 802.1Q double VLAN Tagging Header
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct DoubleVlanHeader {
    ///The outer vlan tagging header
    pub outer: SingleVlanHeader,
    ///The inner vlan tagging header
    pub inner: SingleVlanHeader
}

impl SerializedSize for DoubleVlanHeader {
    ///Serialized size of the header in bytes.
    const SERIALIZED_SIZE: usize = 8;
}

impl DoubleVlanHeader {
    ///Read a double tagging header from the given source
    pub fn read<T: io::Read + io::Seek + Sized >(reader: &mut T) -> Result<DoubleVlanHeader, ReadError> {
        let outer = SingleVlanHeader::read(reader)?;
        //check that the tagging protocol identifier is correct
        if (EtherType::VlanTaggedFrame as u16) != outer.ether_type {
            use ReadError::*;
            Err(VlanDoubleTaggingUnexpectedOuterTpid(outer.ether_type))
        } else {
            Ok(DoubleVlanHeader{
                outer: outer,
                inner: SingleVlanHeader::read(reader)?
            })
        }
    }

    ///Write the double IEEE 802.1Q VLAN tagging header
    pub fn write<T: io::Write + Sized>(&self, writer: &mut T) -> Result<(), WriteError> {
        self.outer.write(writer)?;
        self.inner.write(writer)
    }
}