use crate::protocol::codec::Decode;
use crate::protocol::ethernet::EthType;
use nom::bits;
use nom::error::Error;
use nom::sequence;
use nom::IResult;

/******************************************************************************
 * Struct
 ******************************************************************************/

#[derive(Debug, PartialEq)]
pub struct VLANHeader {
    // 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 "EthType" for a list of possible supported values.
    pub ether_type: EthType,
}

/******************************************************************************
 * API
 ******************************************************************************/

fn bit_decode(input: &[u8]) -> IResult<&[u8], (u8, u8, u16)> {
    bits::bits::<_, _, Error<_>, _, _>(sequence::tuple((
        bits::streaming::take(3u8),
        bits::streaming::take(1u8),
        bits::streaming::take(12u8),
    )))(input)
}

impl Decode for VLANHeader {
    type Iterm = VLANHeader;
    fn decode(input: &[u8]) -> IResult<&[u8], VLANHeader> {
        let (input, (priority_code_point, drop_eligible_indicator, vlan_identifier)) =
            bit_decode(input)?;
        let (input, ether_type) = EthType::decode(input)?;
        Ok((
            input,
            VLANHeader {
                priority_code_point,
                drop_eligible_indicator: drop_eligible_indicator == 1,
                vlan_identifier,
                ether_type,
            },
        ))
    }
}

/******************************************************************************
 * TEST
 ******************************************************************************/

#[cfg(test)]
mod tests {
    use super::VLANHeader;
    use crate::protocol::codec::Decode;
    use crate::protocol::ethernet::EthType;
    const LAST_SLICE: &'static [u8] = &[0xff];

    #[test]
    fn vlan_header_decode() {
        /*
         * 802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 32
         *     000. .... .... .... = Priority: Best Effort (default) (0)
         *     ...0 .... .... .... = DEI: Ineligible
         *     .... 0000 0010 0000 = ID: 32
         *     Type: IPv4 (0x0800)
         */
        let bytes = [0x00, 0x20, 0x08, 0x00, 0xff /* Payload */];

        let expectation = VLANHeader {
            priority_code_point: 0,
            drop_eligible_indicator: false,
            vlan_identifier: 32,
            ether_type: EthType::IPv4,
        };

        assert_eq!(VLANHeader::decode(&bytes), Ok((LAST_SLICE, expectation)));

        // example
        let result = VLANHeader::decode(&bytes);
        match result {
            Ok((payload, header)) => {
                println!("OK: {:?}, payload: {}", header, payload.len());
            }
            Err(e) => {
                println!("ERR: {:?}", e);
            }
        }

        // assert_eq!(1, 0);
    }
}